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{{Short description|Genus of spinosaurid dinosaur}}
{{Taxobox
{{protection padlock|small=yes|}}
| color = pink
{{Good article}}
| name = ''Spinosaurus''
{{Use American English|date=October 2024}}
| fossil_range = mid ]
{{Use mdy dates|date=October 2024}}
| image = spinosaurus.jpg
{{Automatic taxobox
| image_width = 200px
| fossil_range = ] (]), {{Fossil range|earliest=112|100|94}}
| regnum = ]ia
Possible ] records<ref name="BufOua02" /><ref name="Taquet1998">{{Cite journal |last1=Taquet |first1=P. |last2=and Russell |first2=D.A. |year=1998 |title=New data on spinosaurid dinosaurs from the Early Cretaceous of the Sahara |url=http://lesdinos.free.fr/spi329.pdf |journal=Comptes Rendus de l'Académie des Sciences, Série IIA |volume=327 |issue=5 |pages=347–353 |bibcode=1998CRASE.327..347T |doi=10.1016/S1251-8050(98)80054-2 |access-date=September 22, 2010}}</ref>
| phylum = ]
| image = FSAC-KK-11888.jpg
| classis = ]
| image_upright =
| superordo = ]
| image_caption = Reconstructed skeleton based on the ] specimen FSAC-KK-11888 in swimming posture, ]
| ordo = ]
| taxon = Spinosaurus
| subordo = ]
| authority = ], 1915
| superfamilia = ]
| type_species = {{extinct}}'''''Spinosaurus aegyptiacus'''''
| familia = ]
| type_species_authority = Stromer, 1915
| subfamilia = ]
| genus = '''''Spinosaurus''''' | synonyms = *?'''''Spinosaurus maroccanus''''' <br/><small>], 1996</small>
*?'']'' <br/><small>Russell, 1996</small>
| genus_authority = ], 1915
*?'']'' <br/><small>] ''et al''., ]</small><ref name=Symthetal2020/>
| subdivision_ranks = ]
| subdivision =
*''S. aegyptiacus'' (])
*?''S. marocannus'' <small>Russell, 1996</small>
}} }}


'''''Spinosaurus''''' (meaning "spine lizard") was a ] of ] ] that lived in what is now ], from the ] to early ] ] of the ] ], about 95 to 93&nbsp;] years ago. It is unclear whether there are one or two species. The best known is ''S. aegyptiacus'' from ], though a second species (''S. marocannus'') has been recovered from ]. It was first known from Egyptian remains discovered in the 1910s and described by ] ] ]. The original remains were destroyed in ], but additional skull material has come to light in recent years. '''''Spinosaurus''''' ({{IPAc-en|ˌ|s|p|aɪ|n|ə|ˈ|s|ɔːr|ə|s}}; {{lit|spine lizard}}) is a ] of ] ] that lived in what now is ] during the ] ] of the ] ], about 100 to 94&nbsp;]. The genus was known first from Egyptian remains discovered in 1912 and described by German ] ] in ]. The original remains were destroyed in ], but additional material came to light in the early 21st century. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The ] '''''S. aegyptiacus''''' is mainly known from ] and ]. Although a potential second dubious species, '''''S. maroccanus''''', has been recovered from Morocco, this ] species is likely a junior synonym of ''S. aegyptiacus''. Other possible junior synonyms include '']'' from the ] in Morocco and '']'' from the ] in ], though other researchers propose both genera to be distinct ].


''Spinosaurus'' is the longest known terrestrial ]; other large carnivores comparable to ''Spinosaurus'' include ] such as '']'', '']'' and '']''. The most recent study suggests that previous body size estimates are overestimated, and that ''S. aegyptiacus'' reached {{cvt|14|m|ft}} in length and {{cvt|7.4|MT|ST}} in body mass. The skull of ''Spinosaurus'' was long, low, and narrow, similar to that of a modern ]n, and bore straight conical teeth with no ]. It would have had large, robust forelimbs bearing three-fingered hands, with an enlarged claw on the first ]. The distinctive ] of ''Spinosaurus'', which were long extensions of the ] (or backbones), grew to at least {{cvt|1.65|m|ft}} long and were likely to have had skin connecting them, forming a ], although some authors have suggested that the spines were covered in fat and formed a hump.<ref name="Larramendi">Molina-Pérez & Larramendi 2016. ''Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos'', Larousse. Barcelona, Spain p. 259</ref> The hip bones of ''Spinosaurus'' were reduced, and the legs were very short in proportion to the body. Its long and narrow tail was deepened by tall, thin neural spines and elongated ], forming a flexible fin or paddle-like structure.
The distinctive "spines" of ''Spinosaurus'', which were long extensions of the ]e, grew up to 2&nbsp;]s (6.6&nbsp;]) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that they were covered in muscle and formed a hump or ridge. Multiple functions have been put forward for this structure, including ] and display. According to recent estimates, it is the largest of all known ] ]s, even larger than '']'' and '']''; these estimates suggest that it was 16&nbsp;-&nbsp;18&nbsp;] in length (52.5&nbsp;-&nbsp;59.1&nbsp;]), around 6&nbsp;meters tall (20&nbsp;ft), and 9&nbsp;] (9.9&nbsp;]s) in weight,<ref name="dalsassoetal05">{{cite journal |last=dal Sasso |first=C. |coauthors=Maganuco, S.; Buffetaut, E.; and Mendez, M.A. |year=2005 |title=New information on the skull of the enigmatic theropod ''Spinosaurus'', with remarks on its sizes and affinities |journal=Journal of Vertebrate Paleontology |volume=25 |issue=4 |pages=888-896|url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282005%29025%5B0888%3ANIOTSO%5D2.0.CO%3B2|doi=10.1671/0272-4634(2005)025%5B0888:NIOTSO%5D2.0.CO;2|doilabel=10.1671/0272-4634(2005)0252.0.CO;2}}</ref> although these figures have not been universally accepted.

''Spinosaurus'' is known to have eaten fish and small to medium terrestrial prey as well.<ref name=":1" /> Evidence suggests that it was ]; how capable it was of swimming has been strongly contested. ''Spinosaurus''<nowiki/>'s leg bones had ] (high bone density), allowing for better ] control. Multiple functions have been put forward for the dorsal sail, including ] and ]; either to intimidate rivals or attract mates. It lived in a humid environment of ] and ] forests alongside many other dinosaurs, as well as fish, ], lizards, turtles, ]s, and ].

==Discovery and naming==

===Naming of species===

] (1915) showing ''S. aegyptiacus'' holotype elements]]
Two ] of ''Spinosaurus'' have been named: ''Spinosaurus aegyptiacus'' (meaning "Egyptian spine lizard") and the disputed ''Spinosaurus maroccanus'' (meaning "Moroccan spine lizard").<ref name="Smith06" /><ref name="DAR96" /> The first described remains of ''Spinosaurus'' were found and described in the early 20th century. In 1912, Richard Markgraf discovered a partial skeleton of a giant theropod dinosaur in the ] of western Egypt. In 1915, German paleontologist Ernst Stromer published an article assigning the specimen to a new genus and species, ''Spinosaurus aegyptiacus''.<ref name="Stromer15">{{cite journal|last=Stromer|first=E.|author-link=Ernst Stromer|year=1915|title=Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden ''Spinosaurus aegyptiacus'' nov. gen., nov. spec|journal=Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Klasse|volume=28|issue=3|pages=1–32|language=de|url=http://www.megaupload.com/?d=3KCCC7LS}}{{dead link|date=December 2017|bot=InternetArchiveBot|fix-attempted=yes}}</ref><ref name="Smith06" />

Fragmentary additional remains from Bahariya, including ] and hindlimb bones, were designated by Stromer as "''Spinosaurus B''" in 1934.<ref name="stromer34">{{cite journal|last=Stromer|first=E.|author-link=Ernst Stromer|year=1934|title=Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 13. Dinosauria|journal=Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung |series=Neue Folge|volume=22|pages=1–79|language=de}}</ref> Stromer considered them different enough to belong to another species, and this has been borne out. With the advantage of more expeditions and material, it appears that they pertain either to '']''<ref name="serenoetal98">{{cite journal|last1=Sereno|first1=P.C.|last2=Beck|first2=A.L.|last3=Dutheuil|first3=D.B.|last4=Gado|first4=B.|last5=Larsson|first5=H.C.|last6=Lyon|first6=G.H.|last7=Marcot|first7=J.D.|last8=Rauhut|first8=O.W.M.|last9=Sadleir|first9=R.W.|last10=Sidor|first10=C.A.|last11=Varricchio|first11=D.J.|last12=Wilson|first12=G.P.|last13=Wilson|first13=J.A.|year=1998|title=A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids|journal=Science|volume=282|issue=5392|pages=1298–1302|doi=10.1126/science.282.5392.1298|pmid=9812890|bibcode=1998Sci...282.1298S|doi-access=free}}</ref> or to '']''.<ref name="DAR96">{{cite journal|last=Russell|first=D.A.|author-link=Dale Russell|year=1996|title=Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco|journal=Bulletin du Muséum National d'Histoire Naturelle, Paris, Section C |series=4e série |volume=18|issue=2–3|pages=349–402 |url=https://sciencepress.mnhn.fr/fr/periodiques/bulletin-du-museum-national-d-histoire-naturelle-4eme-serie-section-c-sciences-de-la-terre-paleontologie-geologie-mineralogie/18/2-3/os-isoles-de-dinosaures-du-cretace-moyen-du-tafilalt-maroc}}</ref>

''S. maroccanus'' was originally described by ] in 1996 as a new species based on the length of its neck vertebrae. Specifically, Russell claimed that the ratio of the length of the ] (body of vertebra) to the height of the posterior articular facet was 1.1 in ''S. aegyptiacus'' and 1.5 in ''S. maroccanus''.<ref name="DAR96" /> Later authors have been split on this topic. Some authors note that the length of the vertebrae can vary from individual to individual, that the holotype specimen was destroyed and thus cannot be compared directly with the ''S. maroccanus'' specimen, and that it is unknown which cervical vertebrae the ''S. maroccanus'' specimens represent. Therefore, though some have retained the species as valid without much comment,<ref name="HMC04" /><ref>{{cite journal |last1=Mahler |first1=Luke |title=Record of Abelisauridae (Dinosauria: Theropoda) from the Cenomanian of Morocco |journal=Journal of Vertebrate Paleontology |date=March 11, 2005 |volume=25 |issue=1 |pages=236–239 |doi=10.1671/0272-4634(2005)0252.0.CO;2 |s2cid=4974444 }}</ref><ref name="Hasegawa2010">{{cite journal|last1=Hasegawa|first1=Y.|last2=Tanaka|first2=G.|last3=Takakuwa|first3=Y.|last4=Koike|first4=S.|year=2010|title=Fine sculptures on a tooth of ''Spinosaurus'' (Dinosauria, Theropoda) from Morocco|journal=Bulletin of Gunma Museum of Natural History|volume=14|pages=11–20|url=http://www.gmnh.pref.gunma.jp/research/no_14/bulletin14_2.pdf|access-date=September 11, 2010|archive-date=March 25, 2012|archive-url=https://web.archive.org/web/20120325184537/http://www.gmnh.pref.gunma.jp/research/no_14/bulletin14_2.pdf|url-status=dead}}</ref> most researchers regard ''S. maroccanus'' as a '']'' (dubious name)<ref name="dalsassoetal05">{{cite journal |last=dal Sasso |first=C. |author2=Maganuco, S. |author3=Buffetaut, E. |author4= Mendez, M.A. |year=2005 |title=New information on the skull of the enigmatic theropod ''Spinosaurus'', with remarks on its sizes and affinities |journal=Journal of Vertebrate Paleontology |volume=25 |issue=4 |pages=888–896|doi=10.1671/0272-4634(2005)0252.0.CO;2 |s2cid=85702490 }}</ref><ref name="BufOua02">{{cite journal |last1=Buffetaut |first1=Eric |last2=Ouaja |first2=Mohamed |title=A new specimen of Spinosaurus (Dinosauria, Theropoda) from the Lower Cretaceous of Tunisia, with remarks on the evolutionary history of the Spinosauridae |journal=Bulletin de la Société Géologique de France |date=September 1, 2002 |volume=173 |issue=5 |pages=415–421 |doi=10.2113/173.5.415 |hdl=2042/216 |url=http://doc.rero.ch/record/14728/files/PAL_E1854.pdf }}</ref><ref name="Rauhut03">{{cite book|last=Rauhut|first=O.W.M.|year=2003|title=The interrelationships and evolution of basal theropod dinosaurs|series=Special Papers in Palaeontology|volume=69|pages=1–213|isbn=978-0-901702-79-1}}</ref> or as a junior synonym of ''S. aegyptiacus''.<ref name="serenoetal98" /><ref name="Hendrickxetal"/> Some studies have referred the holotype and other referred specimens of ''S. maroccanus'' (NMC 50791 and MNHN SAM 124–128) as ''S.'' cf. ''aegyptiacus''.<ref>{{cite journal |last1=Bertin |first1=Tor |title=A Catalogue of Material and Review of the Spinosauridae |journal=PalArch's Journal of Vertebrate Palaeontology |date=2010 |volume=7 |issue=4 |pages=01–39 |url=https://archives.palarch.nl/index.php/jvp/article/view/457 }}</ref><ref>{{cite journal|author1=Candeiro, C.R.A.|author2=Gil, L.M.|author3=de Castro, P.E.|year=2018|title=Large-sized theropod Spinosaurus: an important component of the carnivorous dinosaur fauna in southern continents during the Cretaceous|journal=Bulletin de la Société Géologique de France|volume=189|issue=4–6|at=15|doi=10.1051/bsgf/2018010}}</ref> The specimens previously ascribed as paratypes of ''S. maroccanus'' (NMC 41768 and NMC 50790) are reidentified as indeterminate spinosaurid specimens that are currently not identifiable at the generic level.<ref name="Evers 2015" /><ref name=McFeeters>{{cite journal |last=McFeeters |first=Bradley D. |title=New mid-cervical vertebral morphotype of Spinosauridae from the Kem Kem Group of Morocco |journal=Vertebrate Anatomy Morphology Palaeontology |year=2021 |volume=8 |pages=182–193 |doi=10.18435/vamp29370 |s2cid=234104245 |doi-access=free }} {{CC-notice|cc=by4}}</ref>

===Specimens===

] (red), proposed ] (blue), and referred specimens (yellow), according to ] and colleagues]]
Six main partial specimens of ''Spinosaurus'' have been described. BSP 1912 VIII 19, described by Stromer in 1915 from the Bahariya Formation, was the ].<ref name="Stromer15" /><ref name="Smith06" /> The material consisted of the following items, most of which were incomplete: right and left ] and ]s from the lower jaw measuring {{convert|75|cm|in|sp=us}} long; a straight piece of the left ] that was described but not drawn; 20 teeth; 2 ] vertebrae; 7 dorsal (trunk) vertebrae; 3 sacral vertebrae; 1 ] vertebra; 4 thoracic ribs; and ]. Of the nine neural spines whose heights are given, the longest ("i," associated with a dorsal vertebra) was {{convert|1.65|m|ft|sp=us}} in length. Stromer claimed that the specimen was from the early Cenomanian, about 97 million years ago.<ref name="Stromer15" /><ref name="Smith06" />

It was destroyed in ], specifically "during the night of 24/25 April 1944 in a British bombing raid of Munich" that severely damaged the building housing the ] (Bavarian State Collection of Paleontology). However, detailed drawings and descriptions of the specimen remain. Stromer's son donated Stromer's archives to the Paläontologische Staatssammlung München in 1995, and Smith and colleagues analyzed two photographs of the ''Spinosaurus'' holotype specimen BSP 1912 VIII 19 discovered in the archives in 2000. On the basis of a photograph of the lower jaw and a photograph of the entire specimen as mounted, Smith concluded that Stromer's original 1915 drawings were slightly inaccurate.<ref name="Smith06" /> In 2003, Oliver Rauhut suggested that Stromer's ''Spinosaurus'' ] was a ], composed of vertebrae and neural spines from a ] similar to '']'' and a ] from '']'' or '']''.<ref name="Rauhut03" /> The analysis was rejected in at least one subsequent paper.<ref name="dalsassoetal05" />

NMC 50791, held by the ], is a mid-cervical vertebra which is {{convert|19.5|cm|in|sp=us}} long from the ] of ]. It is the holotype of ''Spinosaurus maroccanus,'' as described by Russell in 1996. Other specimens referred to ''S. maroccanus'' in the same paper were two other mid-cervical vertebrae (NMC 41768 and NMC 50790), an anterior dentary fragment (NMC 50832), a mid-dentary fragment (NMC 50833), and an anterior dorsal ] (NMC 50813). Russell stated that "only general locality information could be provided" for the specimen, and therefore it could be dated only "possibly" to the Albian.<ref name="DAR96" />

]

MNHN SAM 124, housed at the ], is a snout (consisting of partial premaxillae, partial maxillae, ]s, and a dentary fragment). Described by Taquet and Russell in 1998, the specimen is {{convert|13.4|to(-)|13.6|cm|in|sp=us}} in width; no length was stated. The specimen was located in Algeria, and "is of Albian age." Taquet and Russell believed that the specimen, along with a premaxilla fragment (SAM 125), two cervical vertebrae (SAM 126–127), and a dorsal neural arch (SAM 128), belonged to ''S. maroccanus''.<ref name="Taquet1998">{{Cite journal |last1=Taquet |first1=P. |last2=and Russell |first2=D.A. |year=1998 |title=New data on spinosaurid dinosaurs from the Early Cretaceous of the Sahara |url=http://lesdinos.free.fr/spi329.pdf |journal=Comptes Rendus de l'Académie des Sciences, Série IIA |volume=327 |issue=5 |pages=347–353 |bibcode=1998CRASE.327..347T |doi=10.1016/S1251-8050(98)80054-2 |access-date=September 22, 2010}}</ref> Although it was originally ascribed to ''S. maroccanus'', based on their examination of this cranial material, the 2016 study considered the difference between the two species to be not taxonomically significant and either ontogenetic or intraspecific, and thus tentatively assigned the specimen to ''S. aegyptiacus''.<ref name="Hendrickxetal"/> The 2017 study considered MNHN SAM 124 to belong to same taxon as MSNM V4047.<ref name="salesschultz"/>

BM231 (in the collection of the Office National des Mines, Tunis) was described by Buffetaut and Ouaja in 2002. It consists of a partial anterior dentary {{convert|11.5|cm|in|sp=us}} in length from an early Albian ] of the ] of ]. The dentary fragment, which included four ] and two partial teeth, was "extremely similar" to existing material of ''S. aegyptiacus''.<ref name="BufOua02" />

UCPC-2 in the ] Paleontological Collection consists mainly of two narrow connected ]s with a fluted (ridged) crest from the region between the eyes. The specimen, which is {{convert|18.0|cm|in|sp=us}} long, was located in an early Cenomanian part of the Moroccan Kem Kem Beds in 1996 and described in the scientific literature in 2005 by ] of the ] in ] and colleagues.<ref name="dalsassoetal05" />

MSNM V4047 (in the ]), described by Dal Sasso and colleagues in 2005 as ''Spinosaurus'' cf. ''S. aegyptiacus'', consists of a snout (premaxillae, partial maxillae, and partial nasals) {{convert|98.8|cm|in|sp=us}} long from the Kem Kem Beds.<ref name="dalsassoetal05" /> An isolated fish vertebra, tentatively referred to '']'', has been associated with the tooth alveolus of this specimen.<ref name="dalsassoetal05" /> Similarly, the dentary fragment of ''Spinosaurus aegyptiacus'', MPDM 31, is associated with the rostral tooth of ''Onchopristis''.<ref name=Ibrahim2020/> Like UCPC-2, it is thought to have come from the early Cenomanian. Arden and colleagues in 2018 tentatively assigned this specimen to ''Sigilmassasaurus brevicollis'' given its size.<ref name="arden2018">{{cite journal|last1=Arden|first1=T.M.S.|last2=Klein|first2=C.G.|last3=Zouhri|first3=S.|last4=Longrich|first4=N.R.|year=2018|title=Aquatic adaptation in the skull of carnivorous dinosaurs (Theropoda: Spinosauridae) and the evolution of aquatic habits in ''Spinosaurus''|journal=Cretaceous Research|volume=93|pages=275–284|doi=10.1016/j.cretres.2018.06.013|s2cid=134735938}}</ref> However, this assignment was later rejected by other researchers who considered the uniqueness of this specimen to be based on misinterpretations and poor preservation of another specimen, NHMUK R16665, another snout stored that is stored in the ].<ref name="Symthetal2020" />

FSAC-KK 11888 is a partial subadult skeleton recovered from the Kem Kem beds of North Africa. It was described by ] and colleagues in 2014 and designated as the neotype specimen,<ref name="Ibrahim_et_al_2014"/> though Evers and colleagues rejected the neotype designation for FSAC-KK-11888 in 2015.<ref name="Evers 2015" /> It includes cervical vertebrae, dorsal vertebrae, neural spines, a complete sacrum, femora, tibiae, pedal phalanges, caudal vertebra, several dorsal ribs, and fragments of the skull.<ref name="Ibrahim_et_al_2014">{{cite journal |last1=Ibrahim |first1=Nizar |last2=Sereno |first2=Paul C. |last3=Dal Sasso |first3=Cristiano |last4=Maganuco |first4=Simone |last5=Fabbri |first5=Matteo |last6=Martill |first6=David M. |last7=Zouhri |first7=Samir |last8=Myhrvold |first8=Nathan |last9=Iurino |first9=Dawid A. |title=Semiaquatic adaptations in a giant predatory dinosaur |journal=Science |date=September 26, 2014 |volume=345 |issue=6204 |pages=1613–1616 |doi=10.1126/science.1258750 |pmid=25213375 |bibcode=2014Sci...345.1613I |s2cid=34421257 |url=https://researchportal.port.ac.uk/portal/en/publications/semiaquatic-adaptations-in-a-giant-predatory-dinosaur(8f11a1ce-3265-4b3b-8c81-6f576856a87f).html |doi-access=free }} </ref> The body proportions of the specimen have been debated, as the hind limbs are disproportionately shorter in the specimen than in previous reconstructions. However, it has been demonstrated by multiple paleontologists that the specimen is not a chimera, and is indeed a specimen of ''Spinosaurus'' that suggests that the animal had much smaller hind limbs than previously thought.<ref>{{Cite web|url=http://theropoda.blogspot.com/2014/09/spinosaurus-revolution-episodio-iv-una.html|title=Theropoda: Spinosaurus Revolution, Episodio IV: Una soluzione a tutti gli enigmi?|first=Andrea Cau|last=Phd|date=September 20, 2014|access-date=December 20, 2019}}</ref><ref>{{Cite web|url=http://theropoda.blogspot.com/2014/09/spinosaurus-revolution-episodio-v.html|title=Theropoda: Spinosaurus Revolution, Episodio V: Sigilmassasaurus vs Spinosaurus: una battaglia tafonomica|first=Andrea Cau|last=Phd|date=September 21, 2014|access-date=December 20, 2019}}</ref><ref>{{Cite web|url=http://theropoddatabase.blogspot.com/2014/09/spinosaurus-surprise.html|title=The Theropod Database Blog: Spinosaurus surprise|first=Mickey|last=Mortimer|date=September 11, 2014|access-date=December 20, 2019}}</ref>

Other known specimens consist mainly of very fragmentary remains and scattered teeth. These include:

* A 1986 paper described prismatic structures in ] from two ''Spinosaurus'' teeth from Tunisia.<ref>{{Cite journal | last1 = Buffetaut | first1 = E. | last2 = Dauphin | first2 = Y. | last3 = Jaeger | first3 = J.-J. | last4 = Martin | first4 = M. | last5 = Mazin | first5 = J.-M. | last6 = and Tong | first6 = H. | title = Prismatic dental enamel in theropod dinosaurs | journal = Naturwissenschaften | volume = 73 | pages = 326–327 | year = 1986 | doi = 10.1007/BF00451481 | pmid=3748191 | bibcode=1986NW.....73..326B | issue = 6| s2cid = 11701295 }}</ref>
* Buffetaut (1989, 1992) referred three specimens from the Institut und Museum für Geologie und Paläontologie of the ] in Germany to ''Spinosaurus'': a right maxilla fragment IMGP 969–1, a jaw fragment IMGP 969–2, and a tooth IMGP 969–3.<ref name="Buffetaut89">{{Cite journal | last1 = Buffetaut | first1 = E. | title = New remains of the enigmatic dinosaur ''Spinosaurus'' from the Cretaceous of Morocco and the affinities between ''Spinosaurus'' and ''Baryonyx'' | journal = Neues Jahrbuch für Geologie und Paläontologie, Monatshefte | issue = 2 | pages = 79–87 | year = 1989| volume = 1989 | doi = 10.1127/njgpm/1989/1989/79 }}</ref><ref name="Buffetaut92">{{Cite journal | last1 = Buffetaut | first1 = E. | title = Remarks on the Cretaceous theropod dinosaurs ''Spinosaurus'' and ''Baryonyx'' | journal = Neues Jahrbuch für Geologie und Paläontologie, Monatshefte | issue = 2 | pages = 88–96 | year = 1992| volume = 1992 | doi = 10.1127/njgpm/1992/1992/88 }}</ref> These had been found in a Lower Cenomanian or Upper Albian deposit in southeastern Morocco in 1971.<ref name="Buffetaut89" />
* Kellner and Mader (1997) described two unserrated spinosaurid teeth from Morocco (LINHM 001 and 002) that were "highly similar" to the teeth of the ''S. aegyptiacus'' holotype.<ref>{{cite journal |last1= Kellner |first1=A.W.A. |last2= and Mader |first2=B.J. |year= 1997 |title= Archosaur teeth from the Cretaceous of Morocco |journal= Journal of Paleontology |volume= 71 |issue= 3 |pages= 525–527 |jstor= 1306632 |doi=10.1017/S0022336000039548 |bibcode=1997JPal...71..525K |s2cid=132508192 }}</ref>
* Teeth from the Chenini Formation in Tunisia which are "narrow, somewhat rounded in cross-section, and lack the anterior and posterior serrated edges characteristic of theropods and basal ]s" were assigned to ''Spinosaurus'' in 2000.<ref>{{Cite journal | last1 = Benton | first1 = M.J. | last2 = Bouaziz | first2 = S. | last3 = Buffetaut | first3 = E. | last4 = Martill | first4 = D. | last5 = Ouaja | first5 = M. | last6 = Soussi | first6 = M. | last7 = and Trueman | first7 = C. | title = Dinosaurs and other fossil vertebrates from fluvial deposits in the Lower Cretaceous of southern Tunisia | journal = Palaeogeography, Palaeoclimatology, Palaeoecology | volume = 157 | pages = 227–246 | year = 2000 | doi = 10.1016/S0031-0182(99)00167-4 | issue = 3–4| bibcode = 2000PPP...157..227B | url = http://doc.rero.ch/record/14838/files/PAL_E1974.pdf }}</ref>
* Material possibly belonging to ''Spinosaurus'' from the ] of ] has been noted in 2004.<ref name="Weishampel04">{{cite book |last1=Weishampel |first1=David B. |last2=Barrett |first2=Paul M. |last3=Coria |first3=Rodolfo A. |last4=Le Loeuff |first4=Jean |last5=Xing |first5=Xu |last6=Xijin |first6=Zhao |last7=Sanhi |first7=Ashok |last8=Gomani |first8=Elizabeth M. P. |last9=Noto |first9=Christopher R. |chapter=Dinosaur Distribution |pages=517–606 |jstor=10.1525/j.ctt1pn61w.31 |editor1-last=Weishampel |editor1-first=David B. |editor2-last=Dodson |editor2-first=Peter |editor3-last=Osmólska |editor3-first=Halszka |title=The Dinosauria |edition=2nd |date=2004 |publisher=University of California Press |isbn=978-0-520-24209-8 }}</ref>
*Teeth from the ] of ] were tentatively referred to ''Spinosaurus'' in 2007.<ref name="brusatte&sereno2007">{{cite journal |last1=Brusatte |first1=Stephen L. |last2=Sereno |first2=Paul C. |title=A new species of Carcharodontosaurus (Dinosauria: Theropoda) from the Cenomanian of Niger and a revision of the genus |journal=Journal of Vertebrate Paleontology |date=December 12, 2007 |volume=27 |issue=4 |pages=902–916 |doi=10.1671/0272-4634(2007)272.0.CO;2 |s2cid=86202969 }}</ref>
* A partial tooth {{convert|8|cm|in|sp=us}} long purchased at a fossil trade show, reportedly from the Kem Kem Bed of Morocco and attributed to ''Spinosaurus maroccanus'', showed {{convert|1|to|5|mm|in|sp=us}} wide longitudinal striations and micro-structures (irregular ridges) among the striations in a 2010 paper.<ref name="Hasegawa2010" />
* Isolated teeth attributed to ''S. aegyptiacus'' are reported from Algeria in 2015.<ref>{{Cite journal|date=July 1, 2015|title=Overabundance of piscivorous dinosaurs (Theropoda: Spinosauridae) in the mid-Cretaceous of North Africa: The Algerian dilemma|journal=]|language=en|volume=55|pages=44–55|doi=10.1016/j.cretres.2015.02.002|issn=0195-6671|last1=Benyoucef|first1=Madani|last2=Läng|first2=Emilie|last3=Cavin|first3=Lionel|last4=Mebarki|first4=Kaddour|last5=Adaci|first5=Mohammed|last6=Bensalah|first6=Mustapha|bibcode=2015CrRes..55...44B }}</ref>
* Pedal ungual (MSNM V6894), cervical vertebra (FSAC-KK-7280) and dorsal vertebra (FSAC-KK-18118) from the Kem Kem beds are referred to juvenile cf. ''Spinosaurus aegyptiacus''.<ref name=MD2018/><ref name="juvenile"/>
<!-- The following reference (from http://www.museomonfalcone.it/nnonline/natnas11.pdf) was deleted because it did not mention Spinosaurus: <ref name=dallaveccia1995>{{cite journal | last1 = Vecchia | first1 = Dalla | year = 1995 | title = Second record of a site with dinosaur skeletal remains in Libya (northern Africa) | journal = Natura Nascosta | volume = 11 | pages = 16–21 }}</ref> -->

MHNM.KK374, MHNM.KK375, MHNM.KK376, MHNM.KK377, MHNM.KK378 and MSNM V6896 are six isolated quadrates (skull bones) of different sizes that were collected by locals and acquired commercially in the Kem Kem region of southeastern Morocco, provided by François Escuillié and are deposited in the collections of the Muséum d’Histoire Naturelle of Marrakech. Only MHNM.KK376 is assigned to ''Sigilmassasaurus brevicollis'', while the other five specimens are assigned to ''S. aegyptiacus'', since the quadrates show two different morphologies, suggesting the existence of two spinosaurines in Morocco.<ref name="Hendrickxetal">{{cite journal | last1 = Hendrickx | first1 = C. | last2 = Mateus | first2 = O. | last3 = Buffetaut | first3 = E. | year = 2016 | title = Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa | journal = PLOS ONE | volume = 11 | issue = 1| page = e0144695 | doi=10.1371/journal.pone.0144695| pmid = 26734729 | pmc = 4703214 | bibcode = 2016PLoSO..1144695H | doi-access = free }}</ref> However, a 2020 study on variation within ''Spinosaurus'' considers these differences in morphology to be indicative of variation in skull morphology within a single species, as is the case in ''Allosaurus.''<ref name="Symthetal2020" />

===Possible synonyms===
====''Sigilmassasaurus''====
Some scientists have considered the genus ''Sigilmassasaurus'' a junior synonym of ''Spinosaurus''. In Ibrahim and colleagues (2014), the specimens of ''Sigilmassasaurus'' was referred to ''Spinosaurus aegyptiacus'' together with "Spinosaurus B" as the ] and ''Spinosaurus maroccanus'' was considered as a '']'' following the conclusions of the other papers.<ref name="dalsassoetal05" /><ref name="Ibrahim_et_al_2014" /><ref name="serenoetal98" /> A 2015 re-description of ''Sigilmassasaurus'' disputed these conclusions, and considered the genus valid, with inclusion of ''S. maroccanus'' as a synonym of ''Sigilmassasaurus'' instead.<ref name="Evers 2015">{{Cite journal|doi=10.7717/peerj.1323|title=A reappraisal of the morphology and systematic position of the theropod dinosaur ''Sigilmassasaurus'' from the "middle" Cretaceous of Morocco|journal=PeerJ|volume=3|pages=e1323|year=2015|last1=Evers|first1=S. W.|last2=Rauhut|first2=O. W. M.|last3=Milner|first3=A. C.|last4=McFeeters|first4=B.|last5=Allain|first5=R.|pmid=26500829|pmc=4614847 |doi-access=free }}</ref> This conclusion was further supported in 2018 by Arden and colleagues, who consider ''Sigilmassasaurus'' to be a distinct genus, though a very close relative of ''Spinosaurus'', the two unified in the tribe Spinosaurini, coined in the study.<ref name="arden2018" />

The 2020 study indicates synonymy between ''Spinosaurus'' and ''Sigilmassasaurus'', and considered specimens previously referred to ''Sigilmassasaurus'' as those of ''Spinosaurus''.<ref name="Symthetal2020">{{cite journal |last1=Smyth |first1=Robert S.H. |last2=Ibrahim |first2=Nizar |last3=Martill |first3=David M. |date=October 2020 |title=''Sigilmassasaurus'' is ''Spinosaurus'': A reappraisal of African spinosaurines |journal=Cretaceous Research |volume=114 |pages=104520 |doi=10.1016/j.cretres.2020.104520 |bibcode=2020CrRes.11404520S |s2cid=219487346}}</ref> For instance, the referral of an isolated quadrate (specimen MHNM.KK376) to ''Sigilmassasaurus brevicollis'', based on its difference from other specimens assigned to ''Spinosaurus aegyptiacus'',<ref name="Hendrickxetal">{{cite journal | last1 = Hendrickx | first1 = C. | last2 = Mateus | first2 = O. | last3 = Buffetaut | first3 = E. | year = 2016 | title = Morphofunctional Analysis of the Quadrate of Spinosauridae (Dinosauria: Theropoda) and the Presence of Spinosaurus and a Second Spinosaurine Taxon in the Cenomanian of North Africa | journal = PLOS ONE | volume = 11 | issue = 1| page = e0144695 | doi=10.1371/journal.pone.0144695| pmid = 26734729 | pmc = 4703214 | bibcode = 2016PLoSO..1144695H | doi-access = free }}</ref> was rejected by the 2020 study which noted that these differences in morphology are indicative of variation in skull morphology within a single species.<ref name=Symthetal2020/> The 2019 study assigned a juvenile specimen FSAC-KK-18122 to ''Sigilmassasaurus brevicollis'' based on its identical proportion to BSPG 2011 I 115 which was assigned to the taxon in a 2015 study,<ref name="juvenile">{{cite journal |author1=Rebecca J. Lakin |author2=Nicholas R. Longrich |year=2019 |title=Juvenile spinosaurs (Theropoda: Spinosauridae) from the middle Cretaceous of Morocco and implications for spinosaur ecology |journal=Cretaceous Research |volume=93 |pages=129–142 |doi=10.1016/j.cretres.2018.09.012 |bibcode=2019CrRes..93..129L |doi-access=free }}</ref><ref name="Evers 2015" /> but this referral was also rejected in a 2020 study based on the fact that the median tubercle and median suture is present in BSPG 2011 I 115 but absent in FSAC-KK-18122, so the presence or absence of such feature should not be used to taxonomically separate isolated spinosaurid remains.<ref name=Symthetal2020/>

Regardless of the synonymy of ''Sigilmassasaurus'' with ''Spinosaurus'', some authors consider the possibility that there could be a second distinct spinosaurid in North Africa during the Cenomanian age.<ref name=McFeeters/> Additionally, in 2024, a complete posterior cervical vertebra (specimen NHMUK PV R 38358) was assigned to ''Sigilmassasaurus brevicollis''.<ref>{{Cite journal |last1=Lacerda |first1=M. B. S. |last2=Isasmendi |first2=E. |last3=Delcourt |first3=R. |last4=Fernandes |first4=M. A. |last5=Hutchinson |first5=J. R. |year=2024 |title=New theropod dinosaur remains from the Upper Cretaceous of the Kem Kem Group (Eastern Morocco) clarify spinosaurid morphology |journal=Zoological Journal of the Linnean Society |volume=202 |issue=2 |at=zlae109 |doi=10.1093/zoolinnean/zlae109 }}</ref>

====''Oxalaia''====
Since the ] in 2018 engulfed the palace housing the museum,<ref>{{Cite web|url=https://www.theguardian.com/world/2018/sep/03/fire-engulfs-brazil-national-museum-rio|title=Brazil museum fire: 'incalculable' loss as 200-year-old Rio institution gutted|last=Phillips|first=Dom|date=September 2018|website=The Guardian|language=en|access-date=September 3, 2018}}</ref> with specimens of ''Oxalaia'' possibly being destroyed,<ref>{{Cite news|url=https://www1.folha.uol.com.br/cotidiano/2018/09/entenda-a-importancia-do-acervo-do-museu-nacional-destruido-pelas-chamas-no-rj.shtml|title=Entenda a importância do acervo do Museu Nacional, destruído pelas chamas no RJ|last=Lopes|first=Reinaldo José|date=September 2018|work=Folha de S.Paulo|access-date=September 3, 2018|language=pt-BR}}</ref> any classification should remain tentative. In a 2020 paper written by Symth ''et al.'' in assessing spinosaurine specimens from the ] suggested the ]ian spinosaurine ''Oxalaia'' to be a potential junior synonym of ''Spinosaurus aegyptiacus''. This was based on looking at the specimens assigned to ''Oxalaia'', and the supposed autapomorphies of this taxon to be insignificant and fall within the hypodigm of ''Spinosaurus aegyptiacus''. If supported by future studies, this would imply ''Spinosaurus aegyptiacus'' had a wider distribution and supports the faunal exchange between South America and Africa during this time.<ref name="Symthetal2020"/>

However, subsequent studies have rejected the synonymy of ''Oxalaia'' with ''Spinosaurus aegyptiacus'' based on diagnostic features of the holotype (MN 6117-V) and the referred specimen (MN 6119-V). In 2021, Lacerda, Grillo and Romano noted that the anteromedial processes of the holotype maxillae (MN 6117-V) contact medially, a condition not observed in MSNM V4047 which has been referred to as a specimen of ''Spinosaurus'', and thus adding a new possible diagnostic feature of ''Oxalaia''. They also suggested that the premaxilla of ''Oxalaia'' is wider in the posterior portion than that of MSNM V4047, and that the lateral morphology of its rostrum was distinguished from other spinosaurines based on their morphometric analysis.<ref>{{Cite journal|url=https://www.tandfonline.com/doi/abs/10.1080/08912963.2021.2000974?journalCode=ghbi20|doi=10.1080/08912963.2021.2000974|title=Rostral morphology of Spinosauridae (Theropoda, Megalosauroidea): Premaxilla shape variation and a new phylogenetic inference|year=2021|last1=Lacerda|first1=Mauro B.S.|last2=Grillo|first2=Orlando N.|last3=Romano|first3=Pedro S.R.|journal=Historical Biology|volume=34 |issue=11 |pages=2089–2109|s2cid=244418803}}</ref> In 2023, Isasmendi and colleagues considered ''Oxalaia'' as a valid taxon based on the examination of its referred maxilla (MN 6119-V) which suggests that the position of its external naris would have been more anteriorly located, a condition similar to that of '']'' and ]s, differing from African spinosaurines including ''Spinosaurus aegyptiacus''.<ref>{{cite journal| vauthors = Isasmendi E, Navarro-Lorbés P, Sáez-Benito P, Viera LI, Torices A, Pereda-Suberbiola X |title=New contributions to the skull anatomy of spinosaurid theropods: Baryonychinae maxilla from the Early Cretaceous of Igea (La Rioja, Spain) |journal=Historical Biology: An International Journal of Paleobiology |year=2023 |volume=35 |issue=6 |pages=909–923 |doi=10.1080/08912963.2022.2069019 |s2cid=248906462 |doi-access=free |bibcode=2023HBio...35..909I }}</ref>


==Description== ==Description==
=== Size ===
]
]Since its discovery, ''Spinosaurus'' has been a contender for the largest theropod dinosaur.<ref>{{cite web|title='River Monster': 50-Foot Spinosaurus|url=https://video.nationalgeographic.com/video/magazine/140911-ngm-superjaws|archive-url=https://web.archive.org/web/20140913071859/http://video.nationalgeographic.com/video/magazine/140911-ngm-superjaws|url-status=dead|archive-date=September 13, 2014|via=video.nationalgeographic.com}}</ref> Both ] in 1926<ref name="vH26">{{cite journal |last1=Huene |first1=Friedrich von |title=The Carnivorous Saurischia in the Jura and Cretaceous Formations, principally in Europe |journal=Revista del Museo de La Plata |date=1926 |volume=29 |pages=35–167 |url=https://publicaciones.fcnym.unlp.edu.ar/rmlp/article/view/1393 }}</ref> and ] in 1982 listed it as among the most massive theropods in their surveys, at {{cvt|15|m}} in length and upwards of {{cvt|6|MT|ST}} in weight.<ref name="DFG82">{{cite book|last=Glut|first=D.F.|url=https://archive.org/details/newdinosaurdicti00glut/page/226|title=The New Dinosaur Dictionary|publisher=Citadel Press|year=1982|isbn=978-0-8065-0782-8|location=Secaucus, NJ|pages=}}</ref> In 1988, ] also listed it as the longest theropod at {{cvt|15|m}}, but gave a lower mass estimate of {{cvt|4|MT|ST}}.<ref name="GSP88" />
Although ''Spinosaurus'' is well-known to dinosaur enthusiasts due to its size, sail, and elongated skull, it is mostly known from remains that have been destroyed, aside from a few more recently discovered teeth and skull elements. Additionally, so far only the skull and backbone have been described in detail, and limb bones have not been found. Jaw and skull material published in 2005 show that it had one of the longest skulls of any carnivorous dinosaur, estimated at about 1.75&nbsp;meters long (5.7&nbsp;ft). The skull had a narrow snout filled with conical teeth that lacked serrations, not unlike what is seen in other spinosaurids. A small crest was present in front of the eyes.<ref name="dalsassoetal05"/>


In 2005, Dal Sasso and colleagues assumed that ''Spinosaurus'' and the related '']'' had the same body proportions in relation to their skull lengths, and thereby calculated that ''Spinosaurus'' was {{cvt|16|to|18|m}} in length and {{cvt|7|to|9|MT|ST}} in weight.<ref name=dalsassoetal05/> The estimates were criticized because the skull length estimate was uncertain, and (assuming that body mass increases as the cube of body length) scaling ''Suchomimus,'' which was {{cvt|11|m}} long and {{cvt|3.8|MT|ST}} in mass, to the range of estimated lengths of ''Spinosaurus'' would produce an estimated body mass of {{cvt|11.7|to|16.7|MT|ST}}.<ref name="TH07">{{cite journal |last=Therrien |first=F. |author2=Henderson, D.M. |year=2007 |title=My theropod is bigger than yours...or not: estimating body size from skull length in theropods |journal=Journal of Vertebrate Paleontology |volume=27 |issue=1 |pages=108–115 |doi=10.1671/0272-4634(2007)272.0.CO;2 |s2cid=86025320 }}</ref>
The sail of ''Spinosaurus'' is formed of very tall ] growing on the back ]e. These spines are seven to eleven times the height of the vertebrae from which they grow.<ref name=MKD90>{{cite book |last=Molnar |first=Ralph E. |coauthors=Kurzanov, Sergei M.; and Dong Zhiming |year=1990 |chapter=Carnosauria |editors=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.) |title=The Dinosauria |edition=1st |publisher=University of California Press |location=Berkeley |pages=169-209 |isbn=0-520-06727-4}}</ref> The spines are slightly longer front to back at the base than higher up, and are unlike the thin rods seen in the ] finbacks '']'' and '']''.


]
==Classification==
''Spinosaurus'' gives its name to a ] of dinosaurs, the ], of which other members include '']'' from southern ], '']'' and '']'' (probably synonymous with ''Irritator'') from ], '']'' from ] in central ], and possibly '']'', which is known from fragmentary remains in ]. It is closest to ''Irritator'', which shares its unserrated straight teeth, and the two are included in the ] Spinosaurinae.<ref name=HMC04>{{cite book|title=The Dinosauria (second edition)|year=2004|chapter=Basal Tetanurae|author=Holtz, Jr., T.R., Molnar, R.E, and Currie, P.J.|pages=71-110|publisher=University of California Press|id=ISBN 0-520-24209-2}}</ref> In 2003, Rauhut suggested that Stromer's ''Spinosaurus'' ] was a ], consisting of dorsal vertebrae from a ] similar to '']'' and a dentary from a large theropod similar to '']''.<ref name ="Rauh03">{{cite journal | author = Rauhut, O.W.M. | year = ] | title = The interrelationships and evolution of basal theropod dinosaurs | journal = Special Papers in Palaeontology | volume = 69 | pages = 1-213}}</ref> This analysis, however, has been rejected in recent papers.<ref name=HMC04/><ref name="dalsassoetal05"/>


François Therrien and Donald Henderson, in a 2007 paper using scaling based on skull length, challenged previous estimates of the size of ''Spinosaurus'', finding the length too great and the weight too small. Based on estimated skull lengths of {{cvt|1.5|to|1.75|m}}, their estimates include a body length of {{cvt|12.6|to|14.3|m}} and a body mass of {{cvt|12|to|20.9|MT|ST}}. The lower estimates for ''Spinosaurus'' would imply that the animal was shorter and lighter than ''Carcharodontosaurus'' and ''Giganotosaurus''.<ref name=TH07/> The Therrien and Henderson study has been criticized for the choice of theropods used for comparison (e.g., most of the theropods used to set the initial equations were ]s and ], which have a different build than spinosaurids), and for the assumption that the ''Spinosaurus'' skull could be as little as {{cvt|1.5|m}} in length.<ref>{{cite web|title=Comments on Therrien and Henderson's new paper|url=http://dml.cmnh.org/2007Mar/msg00292.html|last=Mortimer|first=M.|date=March 25, 2007|publisher=Dinosaur Mailing List|access-date=September 22, 2010|archive-date=October 11, 2007|archive-url=https://web.archive.org/web/20071011232449/http://dml.cmnh.org/2007Mar/msg00292.html|url-status=dead}}</ref><ref>{{cite web|title=Re: Comments on Therrien and Henderson's new paper|url=http://dml.cmnh.org/2007Mar/msg00294.html|last=Harris|first=J.D.|date=March 26, 2007|publisher=Dinosaur Mailing List|access-date=September 22, 2010|archive-date=April 14, 2011|archive-url=https://web.archive.org/web/20110414011922/http://dml.cmnh.org/2007Mar/msg00294.html|url-status=dead}}</ref>
==Discovery and species==
The first described remains of ''Spinosaurus'' were found in the ] of ] in 1912, and were named by German paleontologist ] in 1915.<ref name="Stromer15">{{cite journal |last=Stromer |first=E. |authorlink=Ernst Stromer |year=1915 |title=Wirbeltier-Reste der baharije-Stufe (unterstes Cenoman).3. Das Origianl des Theropoden ''Spinosaurus aegyptiacus'' nov. gen. et nov. spec. |journal=Abhandlungen der Königlich Bayerischen Akademie der Wissenschaften Mathematisch-physikalische Klasse Abhandlung |volume=28 |pages=1-32 |language=German}}</ref> Fragmentary additional remains from Bahariya, including vertebrae and hindlimb bones, were designated by Stromer as "''Spinosaurus'' B" in 1934.<ref name=stromer34>{{cite journal |last=Stromer |first=E. |authorlink=Ernst Stromer |year=1934 |title=Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman). 13. Dinosauria |journal=Abhandlungen der Bayerischen Akademie der Wissenschaften Mathematisch-naturwissenschaftliche Abteilung, Neue Folge |volume=22 |pages=1-79 |language=German }}</ref> Stromer considered them different enough to belong to another species, and this has been borne out; they either pertain to '']''<ref name=serenoetal98>{{cite journal |last=Sereno |first=P.C. |authorlink=Paul Sereno |coauthors=Beck, A.L.; Dutheil, D.B.; Gado, B.; Larsson, H.C.E.; Lyon, G.H.; Marcot, J.D.; Rauhut, O.W.M.; Sadleir, R.W.; Sidor, C.A.; Varricchio, D.D.; Wilson, G.P; and Wilson, J.A. |year=1998 |title=A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids |journal=Science |volume=282 |pages=1298-1302 }}</ref> or to '']''.<ref name=DAR96>{{cite journal |last=Russell |first=D.A. |authorlink=Dale Russell |year=1996 |title=Isolated dinosaur bones from the Middle Cretaceous of the Tafilalt, Morocco |Journal=Bulletin du Muséum National d'Histoire Naturelle, Paris, 4e série, section C |volume=18 |issue=2-3 |pages=349-402}}</ref> Some of the ''Spinosaurus'' fossils were damaged during transport back to the ], ], ], and the remaining bones were completely lost due to Allied ] in 1944.


In 2014, Ibrahim and his colleagues suggested that ''Spinosaurus aegyptiacus'' could reach over {{cvt|15|m}} in length.<ref name="Ibrahim_et_al_2014"/> In 2022, however, Paul Sereno and his colleagues suggested that ''Spinosaurus aegyptiacus'' reached a maximum body length of {{cvt|14|m}} and a maximum body mass of {{cvt|7.4|MT|ST}} by constructing a CT-based 3D skeletal model "with the axial column in neutral pose."<ref name="Sereno_et_al_2022"/> They argued that the 2D graphical reconstruction of the aquatic hypothesis by Ibrahim and his colleagues in 2020<ref name=Ibrahim2020>{{cite journal|last1=Ibrahim |first1=N. |last2=Sereno |first2=P.C. |last3=Varrachio |first3=D.J. |last4=Martill |first4=D.M. |last5=Unwin |first5=D.M. |last6=Baidder |first6=L. |last7=Larsson |first7=H.C.E. |last8=Zouhri |first8=S. |last9=Kaoukaya |first9=U. |title=Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco|journal=ZooKeys|year=2020|issue=928|pages=1–216|doi=10.3897/zookeys.928.47517 |pmid=32362741 |pmc=7188693 |bibcode=2020ZooK..928....1I |doi-access=free }}</ref> overestimated the presacral column length by 10%, ribcage depth by 25%, and forelimb length by 30% over dimensions based on CT-scanned fossils; these proportional overestimates shift the center of mass anteriorly when translated to a flesh model, and thus the estimate from Ibrahim and his colleagues cannot be considered a reliable body size estimate.<ref name="Sereno_et_al_2022"/>
Two species of ''Spinosaurus'' have been named: ''Spinosaurus aegyptiacus'' (meaning "Egyptian spine lizard") and ''Spinosaurus marocannus'' (meaning "Moroccan spine lizard"). ''S. marocannus'' was originally described by Russell as a new species based on the length of its neck vertebrae.<ref name=DAR96/> However, several later authors considered the length of the neck vertebrae to be variable from individual to individual and therefore consider ''S. marocannus'' to be a synonym of ''S. aegyptiacus''.<ref name=serenoetal98/><ref name="Mortimer">{{cite web| last =Mortimer| first =M.| authorlink =| coauthors =| title =Megalosauroidea| work =The Theropod Database| publisher =University of Washington| date =2004| url =http://home.myuw.net/eoraptor/Megalosauroidea.htm#Spinosaurusaegyptiacus| format =| doi =| accessdate =2007-07-04}}</ref>


===Skull===
Six partial specimens of ''Spinosaurus'' have been described, the first having been destroyed during ]. However, detailed drawings and descriptions of the specimen remain. The probable size of these individual spinosaurs can be estimated using comparison to known material from other ] dinosaurs. The estimates below are based on the and Dal Sasso ''et al'', 2005.
]


] ]


Its skull had a narrow snout filled with straight conical teeth that lacked serrations. There were six or seven teeth on each side of the very front of the upper jaw, in the ], and another twelve in both ] behind them. The second and third teeth on each side were noticeably larger than the rest of the teeth in the premaxilla, creating a space between them and the large teeth in the front of the maxilla; large teeth in the lower jaw faced this space. The very tip of the snout holding those few large front teeth was expanded, and a small crest was present in front of the eyes. Using the dimensions of three specimens known as MSNM V4047, UCPC-2, and BSP 1912 VIII 19, and assuming that the postorbital part of the skull of MSNM V4047 had a shape similar to the postorbital part of the skull of '']'', Dal Sasso and colleagues (2005) estimated that the skull of ''Spinosaurus'' was {{convert|1.75|m|ft|sp=us}} long,<ref name=dalsassoetal05/> but more recent estimates suggest a length of {{convert|1.6|-|1.68|m|ft|sp=us}}.<ref name=Hendrickxetal/><ref name="Larramendi2">Molina-Pérez & Larramendi 2016. ''Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos'', Larousse. Barcelona, Spain p. 142</ref> The Dal Sasso and colleagues skull length estimate is questioned because skull shapes can vary across spinosaurid species and because MSNM V4047 may not belong to ''Spinosaurus'' itself,<ref name=TH07/><ref name="arden2018" /> though recent studies have reconfirmed it as a specimen of ''Spinosaurus''.<ref name="Sereno_et_al_2022" /><ref name="Symthetal2020" />
'''IPHG 1912 VIII 19''', described by Stromer in 1915,<ref name = "Stromer15"/> and based on a subadult specimen, was destroyed during Allied bombing in WWII. It is estimated to be around 14&nbsp;meters in length and to have weighed about 6.7&nbsp;tons. The material consists of a ] fragment (750&nbsp;mm), an incomplete dentary (the skull is estimated to be 1.45&nbsp;meters long with a mandible approximately 1.34&nbsp;meters long), nineteen teeth (62, 126&nbsp;mm), two incomplete cervical vertebrae, seven dorsal vertebrae (190-210&nbsp;mm), dorsal ribs, gastralia, and eight caudal centra. This is the specimen that Rauhut thought was chimeric.


===Postcranial skeleton===
'''CMN 50791''', described by Russell in 1996, is the ] of ''Spinosaurus marocannus''. The material it is based on includes a mid cervical vertebra which is 195&nbsp;millimeters long, an anterior dorsal neural arch, an anterior dentary, and a mid dentary.


], ], ]]]
'''MNHN SAM 124''', described by Taquet and Russell in 1998, is estimated to be about 14&nbsp;meters long and to have weighed about 6.7&nbsp;tons. The material consists of partial ]e, partial ]e, ]s, and a dentary fragment. (The skull is estimated at approximately 1.42&nbsp;meters long)
As a spinosaurid, ''Spinosaurus'' would have had a long, muscular neck, curved in a ], or S-shape. Its shoulders were prominent, and the forelimbs large and stocky, bearing three clawed ] on each hand. The first finger (or "thumb") would have been the largest. ''Spinosaurus'' had long ] (finger bones), and only somewhat recurved ], suggesting that its hands were longer compared to those of other spinosaurids.<ref name="Ibrahim_et_al_2014" /><ref name="arden2018" /><ref name=":2">{{cite journal |last1=Hone |first1=David William Elliott |last2=Holtz |first2=Thomas Richard |title=A Century of Spinosaurs - A Review and Revision of the Spinosauridae with Comments on Their Ecology |journal=Acta Geologica Sinica - English Edition |date=June 2017 |volume=91 |issue=3 |pages=1120–1132 |doi=10.1111/1755-6724.13328 |bibcode=2017AcGlS..91.1120H |s2cid=90952478 |url=http://qmro.qmul.ac.uk/xmlui/handle/123456789/49404 }}</ref>


Very tall ] growing on the back vertebrae of ''Spinosaurus'' formed the basis of what is usually called the animal's "]". The lengths of the neural spines reached over 10 times the diameters of the ] (vertebral bodies) from which they extended.<ref name="JBB97">{{cite journal |last1=Bailey |first1=Jack Bowman |title=Neural Spine Elongation in Dinosaurs: Sailbacks or Buffalo-Backs? |journal=Journal of Paleontology |date=1997 |volume=71 |issue=6 |pages=1124–1146 |id={{ProQuest|231041667}} |doi=10.1017/S0022336000036076 |jstor=1306608 |bibcode=1997JPal...71.1124B |s2cid=130861276 }}</ref><ref>{{cite journal |last1=Mann |first1=Arjan |last2=Reisz |first2=Robert R. |title=Antiquity of 'Sail-Backed' Neural Spine Hyper-Elongation in Mammal Forerunners |journal=Frontiers in Earth Science |date=2020 |volume=8 |page=83 |doi=10.3389/feart.2020.00083 |bibcode=2020FrEaS...8...83M |doi-access=free }}</ref> The neural spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the ] finbacks '']'' and '']'', contrasting also with the thicker spines in the ]n '']''.<ref name="JBB97" />
'''Office National des Mines nBM231''', described by Buffetaut and Ouaja in 2002, consists of an anterior dentary from Tunisia which is very similar to existing material of ''S. aegyptiacus''.<ref name = "BufOua02">Buffetaut, E & Ouaja, M (2002) A new specimen of ''Spinosaurus'' (Dinosauria, Theropoda) from the Lower Cretaceous of Tunisia, with remarks on the evolutionary history of the Spinosauridae. ''Bulletin de la Société Géologique de France'' '''173''': 415–421. {{DOI|10.2113/173.5.415}}</ref>
]]]
''Spinosaurus'' sails were unusual, although other dinosaurs, namely ''Ouranosaurus'', which lived a few million years earlier in the same general region as ''Spinosaurus'', and the ] South American sauropod ''],'' might have developed similar structural adaptations of their vertebrae. The sail may be an ] of the sail of the ] ] '']'', which lived before the dinosaurs even appeared, produced by ].<ref name="JBB97" />


The structure may also have been more hump-like than sail-like, as noted by Stromer in 1915 ("one might rather think of the existence of a large hump of fat <nowiki>]: ''Fettbuckel''], to which the gave internal support")<ref name="Stromer15" /> and by Jack Bowman Bailey in 1997.<ref name="JBB97" /> In support of his "buffalo-back" hypothesis, Bailey argued that in ''Spinosaurus'', ''Ouranosaurus'', and other dinosaurs with long neural spines, the spines were relatively shorter and thicker than the spines of ]s (which are known to have sails); instead, the dinosaurs' neural spines were similar to the neural spines of extinct hump-backed mammals such as '']'' and '']''.<ref name="JBB97" /><ref>{{cite news |last1=Black |first1=Riley |title=Was Spinosaurus a Bison-Backed Dinosaur? |url=https://www.smithsonianmag.com/science-nature/was-spinosaurus-a-bison-backed-dinosaur-12849430/ |work=Smithsonian Magazine |date=June 6, 2011 }}</ref> In 2014, ] and colleagues instead posited that the spines were covered tightly by skin, similar to a ], given their compactness, sharp edges, and likely poor ].<ref name="Ibrahim_et_al_2014" />
'''MSNM V4047''', described by ] of the Civic Natural History Museum in ] and his colleagues in 2005, is estimated to have been around 16-18&nbsp;meters in length and weighed around 7 to 9&nbsp;tonnes (7.7 to 9.9&nbsp;tons). The massive skull is estimated at 1.75&nbsp;meters long (5.74 ft). The fossils consist of premaxillae, partial maxillae, and partial ]s, which together measure 988&nbsp;]s long (3.24&nbsp;ft).<ref name="dalsassoetal05"/>


''Spinosaurus'' had a significantly smaller ] (hip bone) than that of other giant theropods, with the surface area of the ] (main body of the pelvis) half that of most members of the clade. The hind limbs were short, at just over 25 percent of the total body length, with the ] (calf bone) being longer than the ] (thigh bone). Unlike in other theropods, the hallux (or fourth toe) of ''Spinosaurus'' touched the ground, and the phalanges of the toe bones were unusually long and well-built. At their ends were shallow claws that had flat bottoms. This type of foot ] is also seen in ], indicating that ''Spinosaurus''<nowiki/>'s feet evolved for walking across unstable substrate and that they may have been ].<ref name="Ibrahim_et_al_2014" />
'''UCPC-2''', also described by Dal Sasso ''et al.'' in 2005, which consists of a 'fluted crest'.

From the ] vertebrae of the tail projected significantly elongated, thin neural spines, akin to the condition observed in some other spinosaurids,<ref name="arden2018" /> though to a more extreme degree. Coupled with the also elongated ] bones on the underside of the caudals, this resulted in a deep and narrow tail with a paddle or fin-like shape, comparable to the tails of ]s and ]ns.<ref name=":0">{{cite journal |last1=Ibrahim |first1=Nizar |last2=Maganuco |first2=Simone |last3=Dal Sasso |first3=Cristiano |last4=Fabbri |first4=Matteo |last5=Auditore |first5=Marco |last6=Bindellini |first6=Gabriele |last7=Martill |first7=David M. |last8=Zouhri |first8=Samir |last9=Mattarelli |first9=Diego A. |last10=Unwin |first10=David M. |last11=Wiemann |first11=Jasmina |last12=Bonadonna |first12=Davide |last13=Amane |first13=Ayoub |last14=Jakubczak |first14=Juliana |last15=Joger |first15=Ulrich |last16=Lauder |first16=George V. |last17=Pierce |first17=Stephanie E. |title=Tail-propelled aquatic locomotion in a theropod dinosaur |journal=Nature |date=May 7, 2020 |volume=581 |issue=7806 |pages=67–70 |doi=10.1038/s41586-020-2190-3 |pmid=32376955 |bibcode=2020Natur.581...67I |s2cid=216650535 |url=https://researchportal.port.ac.uk/portal/en/publications/tailpropelled-aquatic-locomotion-in-a-theropod-dinosaur(4e40f54e-8974-4a24-878f-d536a3d00115).html |doi-access=free }}</ref>

==Classification==
]
''Spinosaurus'' gives its name to the dinosaur ] ], which includes two subfamilies: ] and Spinosaurinae. Baryonychinae includes '']'' from southern ] and '']'' from ] in central ]. Spinosaurinae includes ''Spinosaurus'', '']'', '']'', '']'', '']'' (which may be synonymous with ''Irritator''), ''Sigilmassasaurus'' and ''Oxalaia'' (both of which may be synonymous with ''Spinosaurus'').<ref name="dalsassoetal05" /><ref name="arden2018" /> The spinosaurines share unserrated straight teeth that are widely spaced (e.g., 12 on one side of the maxilla), as opposed to the baryonychines, which have serrated curved teeth that are numerous (e.g., 30 on one side of the maxilla).<ref name="dalsassoetal05" /><ref name="HMC04">{{cite book |last1=Holtz |first1=Thomas R. |last2=Molnar |first2=Ralph E. |last3=Currie |first3=Philip J. |chapter=Basal Tetanurae |pages=71–110 |jstor=10.1525/j.ctt1pn61w.10 |editor1-last=Weishampel |editor1-first=David B. |editor2-last=Dodson |editor2-first=Peter |editor3-last=Osmólska |editor3-first=Halszka |title=The Dinosauria |edition=2nd |date=2004 |publisher=University of California Press |isbn=978-0-520-24209-8 }}</ref>

An analysis of Spinosauridae by Arden and colleagues (2018) named the clade Spinosaurini and defined it as all spinosaurids closer to ''Spinosaurus aegyptiacus'' than to ''Irritator challengeri'' or ''Oxalaia quilombensis''; it also found ''Siamosaurus suteethorni'' and ''Icthyovenator laosensis'' to be members of Spinosaurinae.<ref name="arden2018" />

=== Phylogeny ===
The subfamily Spinosaurinae was named by Sereno in 1998, and defined by ] and colleagues (2004) as all ] closer to ''Spinosaurus aegyptiacus'' than to ''Baryonyx walkeri''. The subfamily Baryonychinae was named by ] & ] in 1986. They erected both the subfamily and the family Baryonychidae for the newly discovered ''Baryonyx'', before it was referred to Spinosauridae. Their subfamily was defined by Holtz and colleagues in 2004, as the complementary clade of all taxa closer to ''Baryonyx walkeri'' than to ''Spinosaurus aegyptiacus''. Examinations by Marcos Sales, Cesar Schultz, and colleagues (2017) indicate that the South American spinosaurids ''Angaturama'', ''Irritator'', and ''Oxalaia'' were intermediate between Baronychinae and Spinosaurinae based on their craniodental features and cladistic analysis. This indicates that Baryonychinae may in fact be non-monophyletic. Their ] can be seen below.<ref name="salesschultz">{{cite journal|first1=M.A.F. |last1=Sales |first2=C.L. |last2=Schultz |year=2017 |title=Spinosaur taxonomy and evolution of craniodental features: Evidence from Brazil |journal=PLOS ONE |volume=12 |issue=11 |pages=e0187070 |doi=10.1371/journal.pone.0187070 |pmid=29107966 |pmc=5673194 |bibcode=2017PLoSO..1287070S |doi-access=free }}</ref>
] that did not live in the same time or space]]
{{clade| style=font-size:85%; line-height:85%
|label1=]
|1={{clade
|1='']'']
|2='']'' <div style="{{MirrorH}}">]</div>
|3='']'' <div style="{{MirrorH}}">]</div>
|4={{clade
|1='']'' <div style="{{MirrorH}}">]</div>
|2={{clade
|1='']'' <div style="{{MirrorH}}">]</div>
|2=''Spinosaurus'' <div style="{{MirrorH}}">]</div>
}} }} }} }}

The cladogram below depicts the findings of Arden and colleagues (2018):<ref name=arden2018 />

{{clade| style=font-size: 85%; line-height:85%;
|label1=]
|1={{clade
|1=Praia das Aguncheiras taxon
|label2=]
|2={{clade
|1='']'' ]
|2='']'' <div style="{{MirrorH}}">]</div> }}
|label3=]
|3={{clade
|1='']'' <div style="{{MirrorH}}">]</div>
|2={{clade
|1=Eumeralla taxon
|2={{clade
|1='']'' <div style="{{MirrorH}}">]</div>
|2={{clade
|1='']'' <div style="{{MirrorH}}">]</div>
|2='']'' <div style="{{MirrorH}}">]</div>
|label3=]
|3={{clade
|1=Gara Samani taxon
|2='']'' <div style="{{MirrorH}}">]</div>
|3='''''Spinosaurus aegyptiacus''''' <div style="{{MirrorH}}">]</div> }} }} }} }} }} }} }}


==Paleobiology== ==Paleobiology==
''Spinosaurus'' has some unusual features which have been the subject of debate thus far:
===Size===
]
Since its discovery, ''Spinosaurus'' has been a top contender for longest and largest theropod dinosaur, though this fact did not reach the public consciousness until its depiction in the film '']'' and the description of a new specimen in 2005. Both ]<ref name = "vH26">von Huene, F. R. (1926). "The carnivorous saurischia in the Jura and Cretaceous formations principally in Europe." ''Rev. Mus. La Plata'', '''29''', 35-167</ref> and ],<ref name=DFG82>Glut, D.F. (1982). ''The New Dinosaur Dictionary''. Citadel Press, Secaucus, New Jersey, 226-228. ISBN 0-8065-0782-9</ref> decades apart, listed it as among the most massive theropods or the most massive in their surveys, at upwards of 6&nbsp;tons in weight and 15&nbsp;meters (50&nbsp;feet) in length. In 1988, ] also listed it as the longest theropod at 15&nbsp;meters (50&nbsp;feet), but gave a lower mass estimate.<ref name = "Paul88">Paul, G.S. (1988). ''Predatory Dinosaurs of the World.'' New York: Simon and Schuster. 464 pp.</ref> Recent estimates, based on new specimens, list ''Spinosaurus'' at 16&nbsp;-&nbsp;18&nbsp;metres (53.3 to 60&nbsp;feet) long and 7&nbsp;-&nbsp;9&nbsp;tonnes in weight (7.7 to 9.9&nbsp;tons).<ref name="dalsassoetal05"/> At least one unpublished survey, suggested that ''Spinosaurus'' reached sizes of 12&nbsp;-&nbsp;19&nbsp;tonnes in weight. These high-end weight estimates were based on the author's estimated 17.4&nbsp;meter length which was based on comparing the ]'s largest known vertebra (210&nbsp;mm) with the largest known '']'' vertebra. This implied an extremely large overall mass, with an unknown upper bound as apparently the holotype specimens are from animals that weren't fully grown.<ref name=DML1>{{cite web |url=http://dml.cmnh.org/2001Jul/msg00928.html |title=Re: Spinosaurus weight |accessdate=2007-07-04 |last=Mortimer |first=Mickey |date=2001-07-23 |publisher=Dinosaur Mailing List}}</ref><ref name=DML2>{{cite web |url=http://dml.cmnh.org/2003Jul/msg00355.html |title=And the Largest Theropod Is... |accessdate=2007-07-04 |last=Mortimer |first=Mickey |date=2003-07-21 |publisher=Dinosaur Mailing List}}</ref> However, the author of these estimates has recently reduced them to similar sizes suggested by dal Sasso ''et al.''<ref name="Mortimer"/><ref name=DML3>{{cite web |url=http://dml.cmnh.org/2006Dec/msg00421.html |title=Theropod Database Christmas update |accessdate=2007-07-04 |last=Mortimer |first=Mickey |date=2006-12-23 |publisher=Dinosaur Mailing List}}</ref>


===Function of neural spines===
François Therrien and Donald Henderson, in a recent paper using scaling based on skull length, have challenged previous estimates, finding the length too great and the weight too small. Their estimates include a length of 12.6 to 14.3&nbsp;meters (41.3 to 47.0&nbsp;ft) and a mass of 12.0 to 20.9&nbsp;tonnes (13.2 to 23.0 tons).<ref name=TH07>{{cite journal |last=Therrien |first=F. |coauthors= and Henderson, D.M. |year=2007 |title=My theropod is bigger than yours...or not: estimating body size from skull length in theropods |journal=Journal of Vertebrate Paleontology |volume=27 |issue=1 |pages=108-115}}</ref> Their study has been criticized for the choice of large theropods used for comparison (most of the skeletons of large theropods used to set the initial equations are of ]s and ]s, which have a different build than spinosaurids) and for issues relating to their spinosaurid skull reconstructions.<ref name=DML4>{{cite web |url=http://dml.cmnh.org/2007Mar/msg00292.html |title=Comments on Therrien and Henderson's new paper |accessdate=2007-07-04 |last=Mortimer |first=Mickey |date=2007-03-25 |publisher=Dinosaur Mailing List}}</ref> Resolution awaits more complete remains.
]]]
The function of the dinosaur's sail or hump is uncertain; scientists have proposed several ] including heat regulation and display. In addition, such a prominent feature on its back could make it appear even larger than it was, intimidating other animals.<ref name=JBB97/>


The structure may have been used for ]. If the structure contained abundant blood vessels, the animal could have used the sail's large surface area to absorb heat. This would imply that the animal was only partly warm-blooded at best and lived in climates where night-time temperatures were cool or low and the sky usually not cloudy. It is also possible that the structure was used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (]), face far greater problems of dissipating excess heat at higher temperatures than gaining it at lower. Sails of large dinosaurs added considerably to the skin area of their bodies, with minimum increase of volume. Furthermore, if the sail was turned away from the sun, or positioned at a 90 degree angle towards a cooling wind, the animal would quite effectively cool itself in the warm climate of Cretaceous Africa.<ref name="LBH75">{{cite book |last=Halstead |first=L.B.|author-link=Beverly Halstead|year=1975 |title=The Evolution and Ecology of the Dinosaurs |publisher=Eurobook Limited |location=London |pages=1–116 |isbn=978-0-85654-018-9 }}</ref> However, Bailey (1997) was of the opinion that a sail could have absorbed more heat than it radiated. Bailey proposed instead that ''Spinosaurus'' and other dinosaurs with long neural spines had fatty humps on their backs for energy storage, insulation, and shielding from heat.<ref name=JBB97/>
===Sail===
]
''Spinosaurus'' sails were unusual, although other dinosaurs of the same time and area, namely the ] '']'' and the ] ''],'' might have developed a similar structural adaptation of their dorsal vertebrae (however, this is not uncontroversial; see the articles about these animals for more information). The sail is possibly ] (not ]) to that of the ] ], '']'', which lived before the dinosaurs even appeared (these similarities are presumably due to ]). The sail may also have been more hump-like than sail-like; as noted by Jack Bowman Bailey most recently, spinosaur spines are not thin rods but broad front to back, rather like those of some types of ], and so may have supported a thicker, fatty structure as opposed to a skin sail.<ref name=JBB97>{{cite journal |last=Bailey |first=Jack Bowman |year=1997 |title=Neural spine elongation in dinosaurs: sailbacks or buffalo-backs? |journal=Journal of Paleontology |volume=71 |issue=6 |pages=1124-1146}}</ref>


Many elaborate body structures of modern-day animals serve to attract members of the opposite sex during mating. It is possible that the sail of ''Spinosaurus'' was used for courtship, in a way similar to a ]'s tail. Stromer speculated that the size of the neural spines may have differed between males and females.<ref name=Stromer15/>
The function of these sails is uncertain; scientists have proposed several ] including heat regulation and display. In addition, such a prominent feature on its back could also make it appear larger than it was, intimidating other animals.


]]]
If the sail contained abundant blood vessels, the animal could have used the sail's large surface area to absorb heat. This would imply that the animal was only partly warm-blooded at best and lived in climates where nighttime temperatures were cool or low and the sky usually not cloudy. It is thought that ''Spinosaurus'' and ''Ouranosaurus'' both lived in or at the margins of an earlier version of the ], which could explain this. It is also possible that the sail was used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (]), face far greater problems of dissipating excess heat at higher temperatures than gaining it at lower. Sails of these dinosaurs added considerably to the skin area of the body, with minimum increase of volume. Furthermore, if the sail was turned away from the sun, or positioned at a 90 degree angle towards a cooling wind, the animal would quite effectively cool itself in the warm climate of Cretaceous Africa.<ref name=LBH75>{{cite book |last=Halstead |first=L.B. |year=1975 |title=The Evolution and Ecology of the Dinosaurs |publisher=Peter Lowe |location=London |pages=1-116 |isbn=0856540188 }}</ref>
Gimsa and colleagues (2015) suggest that the dorsal sail of ''Spinosaurus'' was analogous to the dorsal fins of ] and served a hydrodynamic purpose.<ref name=Gimsaetal2015>{{cite journal |last1=Gimsa |first1=Jan |last2=Sleigh |first2=Robert |last3=Gimsa |first3=Ulrike |title=The riddle of Spinosaurus aegyptiacus' dorsal sail |journal=Geological Magazine |date=May 2016 |volume=153 |issue=3 |pages=544–547 |doi=10.1017/S0016756815000801 |bibcode=2016GeoM..153..544G |s2cid=51999370 |doi-access=free }}</ref> Gimsa and others point out that more basal, long-legged spinosaurids had otherwise round or crescent-shaped dorsal sails, whereas in ''Spinosaurus'', the dorsal neural spines formed a shape that was roughly rectangular, similar in shape to the dorsal fins of sailfish. They therefore argue that ''Spinosaurus'' used its dorsal neural sail in the same manner as sailfish, and that it also employed its long narrow tail to stun prey like a modern ]. Sailfish employ their dorsal fins for herding schools of fish into a "]" where they cooperate to trap the fish into a certain area where the sailfish can snatch the fish with their bills.
The sail could have possibly reduced yaw rotation by counteracting the lateral force in the direction opposite to the slash as suggested by Gimsa and colleagues (2015).<ref name=Gimsaetal2015/>


''Spinosaurus'' anatomy exhibits another feature that may have a modern analogy: its long tail resembled that of the thresher shark, employed to slap the water to herd and stun shoals of fish before devouring them (Oliver and colleagues, 2013).
Elaborate body structures of many modern-day animals usually serve to attract members of opposite sex during mating. It is quite possible that the sails of these dinosaurs were used for courtship, in a way similar to a ]'s tail. Stromer speculated that ] and ] may have differed in the size of the neural spine. <ref name = "Stromer15">Stromer E (1915) Wirbeltier-Reste der baharije-Stufe (unterstes Cenoman).3. Das Origianl des Theropoden ''Spinosaurus aegyptiacus'' nov. gen. et nov. spec. ''Abhandl. K. Bayer. Akad. Wiss. Math.-phys. Kl.'' '''28''': 1-32</ref> If this was the case, the sails may have been brightly colored, but this is purely speculative.
The strategies that sailfish and thresher sharks employ against shoaling fish are more effective when the shoal is first concentrated into a ‘bait ball’ (Helfman, Collette & Facey, 1997; Oliver and colleagues, 2013; Domenici and colleagues, 2014). Since this is difficult for individual predators to achieve, they cooperate in this effort. When herding a shoal of fish or squid, sailfish also raise their sails to make themselves appear larger. When they slash or wipe their bills through shoaling fish by turning their heads, their dorsal sail and fins are outstretched to stabilize their bodies hydrodynamically (Lauder & Drucker, 2004). Domenici and colleagues (2014) postulate that these fin extensions enhance the accuracy of tapping and slashing. The sail can reduce yaw rotation by counteracting the lateral force in the direction opposite to the slash. This means that prey is less likely to recognize the massive trunk as being part of an approaching predator (Marras and colleagues, 2015; Webb & Weihs 2015).<ref name=Gimsaetal2015/>


''Spinosaurus'' exhibited the anatomical features required to combine all three hunting strategies: a sail for herding prey more efficiently, as well as flexible tail and neck to slap the water for stunning, injuring or killing prey. The submerged dorsal sail would have provided a strong centreboard-like counterforce for powerful sidewards movements of the strong neck and long tail, as performed by sailfish (Domenici and colleagues, 2014) or thresher sharks (Oliver and colleagues, 2013). While smaller dorsal sails or fins make the dorsal water volume better accessible for slashing, it can be speculated that their smaller stabilization effect makes lateral slashing less efficient (e.g. for thresher sharks). Forming a hydrodynamic fulcrum and hydrodynamically stabilizing the trunk along the dorsoventral axis, ''Spinosaurus''’ sail would also have compensated for the inertia of the lateral neck by tail movements and vice versa not only for predation but also for accelerated swimming. This behavior might also have been one reason for ''Spinosaurus''’ muscular chest and neck reported by Ibrahim and colleagues (2014).<ref name=Gimsaetal2015/>
Finally, it is quite possible that the sail combined these functions, acting normally as a heat regulator, becoming a courting aid during the mating season, being used to cool itself and, on occasions, turning into an intimidating device when an animal was feeling threatened.


===Feeding ecology=== ===Diet and feeding===
]
It is unclear whether ''Spinosaurus'' was primarily a terrestrial predator or a fisher, as indicated by its elongated jaws, conical teeth and raised nostrils. The only direct evidence for spinosaur diet comes from related ]an and ]n species. '']'' was found with both fish scales and bones from juvenile '']'' in its stomach, while a tooth embedded in a South American ] bone suggests that spinosaurs occasionally preyed on these flying archosaurs.<ref>Buffetaut, E., D. Martill & F. Escuillié (2004). "Pterosaurs as part of a spinosaur diet." ''Nature'', '''430''': 33. {{doi|10.1038/430033a}}</ref> ''Spinosaurus'' was likely to have been a generalized and opportunistic predator, possibly a Cretaceous equivalent of large ]s, being biased toward fishing, though it undoubtedly scavenged and took many kinds of small-to medium-sized prey.<ref name="Paul88"/>
]
It is unclear whether ''Spinosaurus'' was primarily a terrestrial predator or a ], as indicated by its elongated jaws, conical teeth and raised nostrils. The hypothesis of spinosaurs as specialized fish eaters has been suggested before by A. J. Charig and A. C. Milner for '']''. They base this on the anatomical similarity with crocodilians and the presence of digestive acid-etched fish scales in the rib cage of the ].<ref name=CM97>{{cite journal |last=Charig |first=A.J. |author2=Milner, A.C. |year=1997 |title=''Baryonyx walkeri'', a fish-eating dinosaur from the Wealden of Surrey |journal=Bulletin of the Natural History Museum, Geology Series |volume=53|pages=11–70}}</ref> Large fish are known from the faunas containing other spinosaurids, including the '']'', in the mid-Cretaceous of northern Africa and Brazil. Direct evidence for spinosaur diet comes from related European and South American taxa. ''Baryonyx'' was found with fish scales and bones from juvenile '']'' in its stomach, while a tooth embedded in a South American ] bone suggests that spinosaurs occasionally preyed on pterosaurs,<ref>{{cite journal |last=Buffetaut |first=E. |author2=Martill, D. |author3= Escuillié, F. |year=2004 |title=Pterosaurs as part of a spinosaur diet |journal=Nature |volume=430 |page=33 |doi=10.1038/430033a |pmid=15229562 |issue=6995|bibcode = 2004Natur.429...33B |s2cid=4398855 |doi-access=free }}</ref> but ''Spinosaurus'' was likely to have been a generalized and opportunistic predator, possibly a Cretaceous equivalent of large ]s, being biased toward fishing, though it undoubtedly ] and took many kinds of small or medium-sized prey.<ref name="GSP88">{{cite book |last=Paul |first=G.S. |author-link=Gregory S. Paul |title=Predatory Dinosaurs of the World |year=1988 |publisher=Simon & Schuster |location=New York |isbn=978-0-671-61946-6 |chapter=Family Spinosauridae |pages= |chapter-url=https://archive.org/details/predatorydinosau00paul |url=https://archive.org/details/predatorydinosau00paul/page/271 }}</ref>


] ]]
===Posture===
In 2009, Dal Sasso and colleagues. reported the results of ] of the MSNM V4047 snout. As the ] on the outside all communicated with a space on the inside of the snout, the authors speculated that ''Spinosaurus'' had ] inside the space that allowed it to hold its snout at the surface of the water to detect swimming prey species without seeing them.<ref name="DalSasso20092">{{cite web|title=A neurovascular cavity within the snout of the predatory dinosaur ''Spinosaurus''|url=http://www2.mnhn.fr/hdt203/info/media/navep1/abstracts.pdf|last=Dal Sasso|first=C.|author2=Maganuco, S.|date=May 26, 2009|website=1st International Congress on North African Vertebrate Palaeontology|publisher=Muséum national d'Histoire naturelle|url-status=dead|archive-url=https://web.archive.org/web/20110721013005/http://www2.mnhn.fr/hdt203/info/media/navep1/abstracts.pdf|archive-date=July 21, 2011|access-date=September 22, 2010|author3=Cioffi, A.}}</ref> A 2013 study by Andrew R. Cuff and Emily J. Rayfield concluded that bio-mechanical data suggests that ''Spinosaurus'' was not an ] piscivore and that its diet was more closely associated with each individual's size. The characteristic ] morphology of ''Spinosaurus'' allowed its jaws to resist bending in the vertical direction, but its jaws were poorly adapted with respect to resisting lateral bending compared to other members of this group (''Baryonyx'') and modern alligators. This suggests that ''Spinosaurus'' preyed more regularly on fish than it did on land animals, although considered predators of the former too.<ref name="cuff13">{{Cite journal|last1=Cuff|first1=A. R.|last2=Rayfield|first2=E. J.|year=2013|editor1-last=Farke|editor1-first=Andrew A|title=Feeding Mechanics in Spinosaurid Theropods and Extant Crocodilians|journal=PLOS ONE|volume=8|issue=5|pages=e65295|bibcode=2013PLoSO...865295C|doi=10.1371/journal.pone.0065295|pmc=3665537|pmid=23724135|doi-access=free}}</ref> In 2022, Sakamoto estimated that ''Spinosaurus'' had an anterior bite force of 4,829 newtons and a posterior bite force of 11,936 newtons. Based on this estimate, he asserted that the jaws of ''Spinosaurus'' are adapted for generating relatively faster shutting speeds with less muscle input force, indicating that the animal likely killed its prey with fast-snapping jaws rather than slow-crushing bites, a trait commonly observed in animals which have a semi-aquatic feeding habit.<ref>{{cite journal | doi=10.7717/peerj.13731 | title=Estimating bite force in extinct dinosaurs using phylogenetically predicted physiological cross-sectional areas of jaw adductor muscles | year=2022 | last1=Sakamoto | first1=Manabu | journal=PeerJ | volume=10 | pages=e13731 | pmid=35846881 | pmc=9285543 | doi-access=free }}</ref>
Although traditionally depicted as a ], ''Spinosaurus'' has been suggested as at least an occasional ] since the early 1980s.<ref name=DFG82>{{cite book |last=Glut |first=Donald F. |title=The New Dinosaur Dictionary |year=1982 |publisher=Citadel Press |location=Secaucus, NJ |isbn=0-8065-0782-9 |pages=228 }}</ref> This has been bolstered by the discovery of '']'', a relative with robust arms.<ref name=DFG00>{{cite book |last=Glut |first=Donald F. |authorlink=Donald F. Glut |title=Dinosaurs: The Encyclopedia. 1st Supplement |year=2000 |publisher=McFarland & Company, Inc. |location=Jefferson, North Carolina |isbn=0-7864-0591-0 |pages=329-333 |chapter=Spinosaurus}}</ref> Bailey (1997) was sympathetic to a possible quadrupedal posture,<ref name=JBB97/> leading to new restorations of it as such.<ref name=DFG00/> This ] has fallen out of favor, at least as a typical ]. Spinosaurids may have crouched in a quadrupedal posture, though.<ref name=CM97>{{cite journal |last=Charig |first=Alan J. |coauthors=and Milner, Angela C. |year=1997 |title=''Baryonyx walkeri'', a fish-eating dinosaur from the Wealden of Surrey |journal=Bulletin of the Natural History Museum, Geology Series |volume=53 |issue=1 |pages=11-70}}</ref>


A 2024 paper suggests that Spinosaurus and other spinosaurines in addition to fish also preyed upon small to medium-sized terrestrial vertebrates, and had relatively weak bite forces compared to those of other theropods.<ref name=":1">{{Cite journal |last1=D'Amore |first1=Domenic C. |last2=Johnson-Ransom |first2=Evan |last3=Snively |first3=Eric |last4=Hone |first4=David W. E. |date=August 28, 2024 |title=Prey size and ecological separation in spinosaurid theropods based on heterodonty and rostrum shape |url=https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25563 |journal=The Anatomical Record |language=en |doi=10.1002/ar.25563 |pmid=39205383 |issn=1932-8486}}</ref>
===Paleoenvironment===
The environment inhabited by ''Spinosaurus'' is only partially understood, and covers a great deal of northern Africa. Those that lived in what is now ], for example, may have contended with ]line conditions on ] and channels, living in ] forests alongside similarly large dinosaurian predators '']'' and '']'', giant ] ] '']'', smaller titanosaur '']'', 10 meter long (33 ft) ] '']'', and the ] '']''.<ref name=JSetal01>{{cite journal |last=Smith |first=J.B. |coauthors=Lamanna, M.C.; Lacovara, K.J.; Dodson, P.; Smith, J.R.; Poole, J.C.; Giegengack, R.; and Attia, Y. |year=2001 |title=A Giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt |journal=Science |volume=292 |issue=5522 |pages=1704–1706 |doi=10.1126/science.1060561}}</ref>


==In popular culture== === Aquatic habits ===
]''.]] ] '']'']]
A 2010 ] by Romain Amiot and colleagues found that ] ratios of spinosaurid teeth, including teeth of ''Spinosaurus'', indicate ] lifestyles. Isotope ratios from tooth enamel and from other parts of ''Spinosaurus'' (found in Morocco and Tunisia) and of other predators from the same area such as '']'' were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians. The study found that ''Spinosaurus'' teeth from five of six sampled localities had oxygen isotope ratios closer to those of turtles and crocodilians when compared with other theropod teeth from the same localities. The authors postulated that ''Spinosaurus'' switched between terrestrial and aquatic habitats to compete for food with large crocodilians and other large theropods respectively.<ref name="RMetal10">{{cite journal|last=Amiot|first=R.|author2=Buffetaut, E.|author3=Lécuyer, C.|author4=Wang, X.|author5=Boudad, L.|author6=Ding, Z.|author7=Fourel, F.|author8=Hutt, S.|author9=Martineau, F.|author10=Medeiros, A.|author11=Mo, J.|year=2010|title=Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods|journal=Geology|volume=38|issue=2|pages=139–142|bibcode=2010Geo....38..139A|doi=10.1130/G30402.1|author17=Zhou, Z.|author16=Zhang, F.|author15=Tong, H.|author14=Sweetman, S.|author12=Simon, L.|author13=Suteethorn, V.}}</ref> A 2018 study by Donald Henderson, however, refutes the claim that ''Spinosaurus'' was semiaquatic. By studying the buoyancy in lungs of crocodilians and comparing it to the lung placement in ''Spinosaurus'', it was discovered that ''Spinosaurus'' could not sink or dive below the water surface. It was also capable of keeping its entire head above the water surface while floating, much like other non-aquatic theropods. Furthermore, the study found that ''Spinosaurus'' had to continually paddle its hind legs to prevent itself from tipping over onto its side, something that extant semiaquatic animals do not need to perform. Henderson therefore theorized that ''Spinosaurus'' probably did not hunt completely submerged in water as previously hypothesized, but instead would have spent much of its time on land or in shallow water.<ref>{{cite web|url=https://royaltyrrellmuseum.wordpress.com/2018/08/16/new-research-refutes-claims-that-spinosaurus-was-semi-aquatic/|title=New Research Refutes Claims That Spinosaurus Was Semi-Aquatic|first=Royal Tyrrell Museum of|last=Palaeontology|date=August 16, 2018|website=wordpress.com}}</ref><ref name="Henderson2018">{{cite journal |last1=Henderson |first1=D.M. |title=A buoyancy, balance and stability challenge to the hypothesis of a semi-aquatic Spinosaurus Stromer, 1915 (Dinosauria: Theropoda) |journal=PeerJ |volume=6 |pages=e5409 |date=2018 |doi=10.7717/peerj.5409|pmid=30128195 |pmc=6098948 |doi-access=free }}</ref>
''Spinosaurus'' has long been depicted in popular books about dinosaurs, although only recently has there been enough information about spinosaurids for an accurate depiction to be made. Traditionally, it has been restored as a generalized upright theropod with a sail on its back, after an influential 1955 skeletal reconstruction by Lapparent and Lavocat.<ref name=DFG00/>


Recent studies of the tail vertebrae of ''Spinosaurus'' refute Henderson's proposal that ''Spinosaurus'' mainly inhabited areas of land near and in shallow water and was too buoyant to submerge. Studies of the tail, thanks to fossils recovered and analyzed by Ibrahim, Pierce, Lauder, and Sereno and colleagues in 2018 indicate that ''Spinosaurus'' had a keeled tail that was well adapted to propelling the animal through water. The elongated neural spines and chevrons, which run to the end of the tail on both dorsal and ventral sides, indicate that ''Spinosaurus'' was able to swim in a similar manner to modern crocodilians. Through experimentation by Lauder and Pierce, the tail of ''Spinosaurus'' was found to have eight times as much forward thrust as the tails of terrestrial theropods like '']'' and '']'', as well as being twice as efficient at achieving forward thrust. The discovery indicates that ''Spinosaurus'' may have had a lifestyle comparable to modern alligators and crocodiles, remaining in water for long periods of time while hunting.<ref name=":0" />
''Spinosaurus'' was featured as the main antagonist in the 2001 film '']''. It was portrayed as larger and more powerful than '']'', in a scene depicting a battle between the two resurrected predators where ''Spinosaurus'' emerges victorious by snapping the tyrannosaur's neck. In reality, such a battle could never have taken place while the species were still ], since ''Spinosaurus'' and ''Tyrannosaurus'' lived thousands of miles and millions of years apart.
] study]]
<!--Please do not add in stuff about why the Rex should have won in JP3. We're trying to keep things as objective as possible by not mentioning the Rex's jaw force, seeing as we're just mentioning the facts shown in the movie and don't know how powerful the Spino was . Thanks for leaving it alone.-->
David Hone and ] published a paper in 2021 in which they argue that the anatomy of ''Spinosaurus'' is more consistent with a shoreline generalist lifestyle rather than an active aquatic pursuit predator as suggested by Ibrahim.<ref>{{cite journal |last1=Hone|first11=D.W.E.|last2=Holtz|first2=Thomas R. Jr.|title=Evaluating the ecology of Spinosaurus: Shoreline generalist or aquatic pursuit specialist? |journal=Palaeontologia Electronica |date=2021 |volume=24 |issue=1 |pages=a03|url=https://palaeo-electronica.org/content/2021/3219-the-ecology-of-spinosaurus|doi=10.26879/1110|doi-access=free|hdl=1903/28570|hdl-access=free}}</ref> They highlight the positioning of the nostrils and orbits as one reason why a crocodile-like lifestyle is unlikely: they are ventrally positioned in such a way that the whole head would have to be lifted inefficiently out of the water in order to breathe. Additionally, they argue that the general body shape of ''Spinosaurus'' is poorly adapted for this lifestyle, drawing on the amount of water drag and aquatic instability<ref name="Henderson2018" /> from the sail, as well as the rigid trunk and seemingly scarcely-muscled tail. Animals like crocodilians require a flexible body in order to move through the water and make sharp turns when chasing prey, and this is directly contradicted by Hone and Holtz's findings.


A 2022 study by Fabbri ''et al.'', made comparisons of ''Spinosaurus''{{'}} bone structure and compared it to that of ''Baryonyx'' and ''Suchomimus''. The study revealed that ''Spinosaurus'' and ''Baryonyx'' had dense bones, which allowed them to dive and pursue prey underwater. Compared to these, ''Suchomimus'' had more hollow bones, suggesting it preferred to hunt in shallow water. These findings also suggest that various spinosaurid genera were more ecologically disparate than previously believed, as some were better suited to hunting in subaqueous environments than other, closely related genera.<ref>{{cite journal |last1=Fabbri |first1=Matteo |last2=Navalón |first2=Guillermo |last3=Benson |first3=Roger B. J. |last4=Pol |first4=Diego |last5=O’Connor |first5=Jingmai |last6=Bhullar |first6=Bhart-Anjan S. |last7=Erickson |first7=Gregory M. |last8=Norell |first8=Mark A. |last9=Orkney |first9=Andrew |last10=Lamanna |first10=Matthew C. |last11=Zouhri |first11=Samir |last12=Becker |first12=Justine |last13=Emke |first13=Amanda |last14=Dal Sasso |first14=Cristiano |last15=Bindellini |first15=Gabriele |last16=Maganuco |first16=Simone |last17=Auditore |first17=Marco |last18=Ibrahim |first18=Nizar |title=Subaqueous foraging among carnivorous dinosaurs |journal=Nature |date=March 23, 2022 |volume=603 |issue=7903 |pages=852–857 |doi=10.1038/s41586-022-04528-0 |pmid=35322229 |bibcode=2022Natur.603..852F |s2cid=247630374 |url=https://ora.ox.ac.uk/objects/uuid:264b7ca2-1190-4b76-ab93-074cedf897e1 }}</ref><ref>{{cite news |last1=Greshko |first1=Michael |title=Spinosaurus had penguin-like bones, a sign of hunting underwater |url=https://www.nationalgeographic.com/science/article/spinosaurus-had-penguin-like-bones-a-sign-of-hunting-underwater |archive-url=https://web.archive.org/web/20220323162454/https://www.nationalgeographic.com/science/article/spinosaurus-had-penguin-like-bones-a-sign-of-hunting-underwater |url-status=dead |archive-date=March 23, 2022 |work=National Geographic |date=March 23, 2022 }}</ref><ref>{{cite news |author1=Field Museum |title=Dense bones allowed Spinosaurus to hunt underwater, study shows |url=https://phys.org/news/2022-03-dense-bones-spinosaurus-underwater.html |work=phys.org |date=March 23, 2022 }}</ref>
After appearing in '']'', ''Spinosaurus'' was featured in a wide variety of merchandise related to the ''Jurassic Park'' films, including a number of video games such as '']'' from ]. ''Spinosaurus'' was also featured in the television documentary ''The Lost Dinosaurs of Egypt'', in which it was seen wading through the marshlands of Cretaceous Egypt.


In the same year, contradicting the study by Fabbri and colleagues, Sereno and his colleagues suggested that ''Spinosaurus'' was wholly bipedal on land and an unstable, slow moving surface swimmer in deep water. Their results, taken from reconstructing a CT model of the skeleton, and then adding internal air and muscles. Their results, coupled with fossils from ''Spinosaurus'' that showed it also lived further inland along rivers and lakes, suggest it was a semi-aquatic, ambush piscivore that preferred waterside environments both along the coasts and further inland along rivers and lakes. Simultaneously, they suggested that the large tail fin was probably utilized more for display than swimming, as tails in living animals have the same function when they possess comparably tall neural spines.<ref name="Sereno_et_al_2022">{{cite journal |doi=10.7554/eLife.80092 |doi-access=free |title=Spinosaurus is not an aquatic dinosaur |year=2022 |last1=Sereno |first1=Paul C. |last2=Myhrvold |first2=Nathan |last3=Henderson |first3=Donald M. |last4=Fish |first4=Frank E. |last5=Vidal |first5=Daniel |last6=Baumgart |first6=Stephanie L. |last7=Keillor |first7=Tyler M. |last8=Formoso |first8=Kiersten K. |last9=Conroy |first9=Lauren L. |journal=eLife |volume=11 |pmid=36448670 |pmc=9711522 |at=e80092}} ] Text was copied from this source, which is available under a .</ref>
==References==
{{reflist|2}}


A 2024 paper by Myrhvold ''et al''. also contends that Spinosaurus and Baryonyx were diving pursuit predators. Instead they also argue that ''Spinosaurus'' and ''Baryonyx'' hunted more like ]s instead of diving after prey.<ref>{{Cite journal |last1=Myhrvold |first1=Nathan P. |last2=Baumgart |first2=Stephanie L. |last3=Vidal |first3=Daniel |last4=Fish |first4=Frank E. |last5=Henderson |first5=Donald M. |last6=Saitta |first6=Evan T. |last7=Sereno |first7=Paul C. |date=March 6, 2024 |title=Diving dinosaurs? Caveats on the use of bone compactness and pFDA for inferring lifestyle |journal=PLOS ONE |volume=19 |issue=3 |pages=e0298957 |doi=10.1371/journal.pone.0298957 |doi-access=free |issn=1932-6203 |pmc=10917332 |pmid=38446841|bibcode=2024PLoSO..1998957M }}</ref> Another paper in the same year analyzed the linear measurements of the skull of ''Spinosaurus'', and concluded that the skull morphology and hunting method of ''Spinosaurus'' would likely be the most similar to those of wading birds like ]s, though the authors noted that they're uncertain how beneficial the skull would have been for the diving pursuit predation method.<ref>{{Cite journal |last1=Smart |first1=Sean |last2=Sakamoto |first2=Manabu |date=June 13, 2024 |title=Using linear measurements to diagnose the ecological habitat of ''Spinosaurus'' |journal=PeerJ |language=en |volume=12 |pages=e17544 |doi=10.7717/peerj.17544 |doi-access=free |pmid=38881866 |pmc=11180429 |issn=2167-8359}}</ref>
==External links==

===Locomotion and posture===
]
Although traditionally depicted in the scientific community as a ], ''Spinosaurus'' was occasionally depicted in the mid-20th century as an obligate quadruped akin to '']''.<ref>{{Cite web|title=When Dinosaurs Ruled The Mind #8: Dinosaurs Over The Years: Spinosaurus|url=https://whendinosaursruledthemind.wordpress.com/2014/08/25/when-dinosaurs-ruled-the-mind-8-dinosaurs-over-the-years-spinosaurus/|date=August 25, 2014|website=When Dinosaurs Ruled The Mind|access-date=April 30, 2020}}</ref> Starting in the mid-1970s, it was hypothesized ''Spinosaurus'' was at least an occasional ],<ref name=DFG82/><ref name=LBH75/> bolstered by the discovery of '']'', a relative with robust arms.<ref name="DFG00">{{cite book |last=Glut |first=D.F. |author-link=Donald F. Glut |title=Dinosaurs: The Encyclopedia. 1st Supplement |year=2000 |publisher=McFarland & Company, Inc |location=Jefferson, North Carolina |isbn=978-0-7864-0591-6 |pages=329–333 |chapter=Spinosaurus}}</ref> Because of the mass of the hypothesized fatty dorsal humps of ''Spinosaurus'', Bailey (1997) was open to the possibility of a quadrupedal posture,<ref name=JBB97/> leading to new restorations of it as such.<ref name=DFG00/> Theropods, including spinosaurids, could not pronate their hands (rotate the forearm so the palm faced the ground),<ref name="carpenter2002"/> but a resting position on the side of the hand was possible, as shown by fossil prints from an Early Jurassic theropod.<ref name="AMetal09">{{cite journal |last=Milner |first=A.R.C. |author2=Harris, J.D. |author3=Lockley, M.G. |author4=Kirkland, J.I. |author5= Matthews, N.A. |title=Bird-like anatomy, posture, and behavior revealed by an Early Jurassic theropod dinosaur resting trace|journal=PLOS ONE |year=2009 |volume=4 |issue=3 |page=e4591 |doi=10.1371/journal.pone.0004591|editor1-last=Harpending |editor1-first=Henry |pmid=19259260 |pmc=2645690|bibcode = 2009PLoSO...4.4591M |doi-access=free }}</ref> The hypothesis that ''Spinosaurus'' had a typical quadrupedal gait since fell out of favor, however it was still believed that spinosaurids may have crouched in a quadrupedal posture, due to biological and physiological constraints.<ref name="CM97"/><ref name="carpenter2002">{{Cite journal | doi = 10.1007/BF03043773 | last1 = Carpenter | first1 = K. | year = 2002 | title = Forelimb biomechanics of nonavian theropod dinosaurs in predation | journal = ] | volume = 82 | issue = 1| pages = 59–76 | s2cid = 84702973 }}</ref>

]]]
The possibility of a quadrupedal ''Spinosaurus'' was revived by a 2014 paper by ] and colleagues that described new material of the animal. The paper found that the hind limbs of ''Spinosaurus'' were much shorter than previously believed, and that its center of mass was located in the midpoint of the ] region, as opposed to near the hip as in typical bipedal theropods. It was therefore proposed that ''Spinosaurus'' was poorly adapted for bipedal terrestrial locomotion, and must have been an obligate quadruped on land. The reconstruction used in the study was an extrapolation based on different sized individuals, scaled to what were assumed to be the correct proportions.<ref name=Ibrahim_et_al_2014 /> Paleontologist John Hutchinson of the ] of the University of London has expressed skepticism to the new reconstruction, and cautioned that using different specimens can result in inaccurate chimaeras.<ref>{{Cite journal | doi = 10.1038/nature.2014.15901| title = Swimming dinosaur found in Morocco| journal = Nature| year = 2014| last1 = Witze | first1 = A. | s2cid = 131487243}}</ref> Scott Hartman also expressed criticism because he believed the legs and the pelvis were inaccurately scaled (27% too short) and didn't match the published lengths.<ref name="shartman">{{Cite web|author=Scott Hartman|title=There's something fishy about Spinosaurus|date=September 12, 2014|access-date=September 20, 2014|website=skeletaldrawing.com|url=http://www.skeletaldrawing.com/home/theres-something-fishy-about-spinosaurus9112014}}</ref> However, ] expressed agreement with the proportions reported in the paper.<ref>{{Cite web|author=Mark Witton|title=The Spinosaurus hindlimb controversy: a detailed response from the authors|date=September 22, 2014|access-date=September 22, 2014|website=markwitton-com.blogspot.de|url=http://markwitton-com.blogspot.de/2014/09/the-spinosaurus-hindlimb-controversy.html?spref=tw}}</ref> In their 2015 re-description of '']'', Evers and colleagues argued that ''Sigilmassasaurus'' was in fact a distinct genus from ''Spinosaurus'', and therefore doubted whether the material assigned to ''Spinosaurus'' by Ibrahim ''et al.'' should be assigned to ''Spinosaurus'' or ''Sigilmassasaurus''.<ref name="Evers 2015"/> In 2018, an analysis by Henderson found that ''Spinosaurus'' probably was competent at bipedal terrestrial locomotion; the center of mass was instead found to be close to the hips, allowing ''Spinosaurus'' to stand upright like other bipedal theropods.<ref name="Henderson2018" />

A 2024 article co-authored by Sereno stated that the previous calculations by Sereno that were used to argue quadrupedality for ''Spinosaurus'' had erroneously shifted the center of mass in front of the hips. They instead suggested that the dinosaur fit the criteria of being a graviportal (or slow-moving) biped.<ref name="Diving dinosaurs?">{{cite journal |last1=Myhrvold |first1=Nathan P. |last2=Baumgart |first2=Stephanie L. |last3=Vidal |first3=Daniel |last4=Fish |first4=Frank E. |last5=Henderson |first5=Donald M. |last6=Saitta |first6=Evan T. |last7=Sereno |first7=Paul C. |title=Diving dinosaurs? Caveats on the use of bone compactness and pFDA for inferring lifestyle |journal=PLOS ONE |date=2024 |volume=19 |issue=3 |pages=e0298957 |doi=10.1371/journal.pone.0298957|doi-access=free |pmid=38446841 |pmc=10917332 |bibcode=2024PLoSO..1998957M }}</ref><ref name="NYT-20240306">{{cite news |last=Chang |first=Kenneth |date=March 6, 2024 |title=A Swimming Dinosaur? Maybe Not, Study Says - A new paper challenges the idea that the large, carnivorous Spinosaurus dived after prey rather than wading and plucking it out of the water. |url=https://www.nytimes.com/2024/03/06/science/spinosaurus-dinosaur-fossil-dive.html |url-status=live |archiveurl=https://archive.today/20240306230422/https://www.nytimes.com/2024/03/06/science/spinosaurus-dinosaur-fossil-dive.html |archivedate=March 6, 2024 |work=] |accessdate=March 8, 2024 }}</ref>

===Ontogeny===
An ungual phalanx measuring {{convert|21|mm|in|sp=us}} belonging to a very young juvenile cf. ''S. aegyptiacus'' indicates that the theropod developed its semiaquatic adaptations at a very young age or at birth and maintained them throughout its life. The specimen, found in 1999 and described by Simone Maganuco and Cristiano Dal Sasso and colleagues, is believed to have come from an animal measuring {{convert|1.78|m|ft|sp=us}} (assuming it resembled a smaller version of the adult), making it the smallest specimen of ''Spinosaurus'' currently known.<ref name=MD2018>{{Cite journal|last1=Maganuco|first1=Simone|last2=Dal Sasso|first2=Cristiano|date=May 30, 2018|title=The smallest biggest theropod dinosaur: a tiny pedal ungual of a juvenile ''Spinosaurus'' from the Cretaceous of Morocco|journal=PeerJ|language=en|volume=6|pages=e4785|doi=10.7717/peerj.4785|pmid=29868253|pmc=5984586 |doi-access=free }}</ref>

=== Palaeopathology ===
A cf. ''Spinosaurus'' sp. tooth from the Ifezouane Formation displays enhanced lingual curvature to the tooth's crown, the development of three deep grooves extending from crown root junction in the direction of the crown's apex, an attenuated carina that does not extend apically nor to the base of the tooth, and a wear facet at the tip.<ref>{{Cite journal |last1=Smith |first1=Roy E. |last2=Martill |first2=David M. |date=June 2023 |title=An unusual dental pathology in a tooth of Spinosaurus (Dinosauria, Theropoda) from the mid-Cretaceous of Morocco |url=https://linkinghub.elsevier.com/retrieve/pii/S0195667123000277 |journal=] |language=en |volume=146 |pages=105499 |doi=10.1016/j.cretres.2023.105499 |bibcode=2023CrRes.14605499S |access-date=May 6, 2024 |via=Elsevier Science Direct}}</ref>

== Paleoenvironment ==
]]]

The environment inhabited by ''Spinosaurus'' is only partially understood, and covers a great deal of what is now northern Africa. The region of Africa ''Spinosaurus'' is preserved in dates from 112 to 93.5 million years ago.<ref>{{cite book |title=A Geologic Time Scale 2004 |editor1=Gradstein, F.M. |editor2=Ogg, J.G. |editor3=Smith, A.G. |year=2004 |publisher= Cambridge University Press |location=Cambridge and New York |isbn=978-0-521-78673-7 |page=380}}</ref><ref name="Smith06">{{Cite journal | last1 = Smith | first1 = J.B. | last2 = Lamanna | first2 = M.C. | last3 = Mayr | first3 = H. | last4 = and Lacovara | first4 = K.J. | title = New information regarding the holotype of ''Spinosaurus aegyptiacus'' Stromer, 1915 | journal = Journal of Paleontology | volume = 80 | pages = 400–406 | year = 2006 | doi = 10.1666/0022-3360(2006)0802.0.CO;2 | issue = 2 | s2cid = 130989487 }}</ref><ref>Holtz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' </ref> A potential specimen tentatively referred to as cf. ''Spinosaurus'' has been found in the ] ] of Egypt, but no detailed description of the specimen was provided.<ref>{{Cite journal|journal=Palaeontology |volume=44 |issue=2 |pages=305–323 |doi=10.1111/1475-4983.00181 |year=2001 |last1=Churcher |first1=C. S |title=A new species of Protopterus and a revision of Ceratodus humei (Dipnoi: Ceratodontiformes) from the Late Cretaceous Mut Formation of eastern Dakhleh Oasis, Western Desert of Egypt |last2=De Iuliis |first2=G |bibcode=2001Palgy..44..305C |doi-access=free }}</ref><ref name=Augustin2023>{{cite book|last1=Augustin|first1=F.J.|last2=Hartung|first2=J.|last3=Kampouridis|first3=P.|editor1=Hamimi, Z.|editor2=Khozyem, H.|editor3=Adatte, T.|editor4=Nader, Fadi H.|editor5=Oboh-Ikuenobe, F.|editor6=Zobba, Mohamed K.|editor7=Atfy, Haytham El|year=2023|chapter=Dinosaur Faunas of Egypt—The Terrestrial Late Cretaceous Vertebrate Record|title=The Phanerozoic Geology and Natural Resources of Egypt|pages=253–284|series=Advances in Science, Technology & Innovation|publisher=Springer, Cham|doi=10.1007/978-3-030-95637-0_9|isbn=978-3-030-95636-3}}</ref> A 1996 study concluded from Moroccan fossils that ''Spinosaurus'', '']'', and '']'' "ranged across north Africa during the late Cretaceous (Cenomanian)."<ref name="serenoetal96">{{cite journal | last1 = Sereno | first1 = PC | last2 = Dutheil | first2 = DB | last3 = Iarochene | first3 = M | last4 = Larsson | first4 = HCE | last5 = Lyon | first5 = GH | last6 = Magwene | first6 = PM | last7 = Sidor | first7 = CA | last8 = Varricchio | first8 = DJ | last9 = Wilson | first9 = JA | year = 1996 | title = Predatory dinosaurs from the Sahara and Late Cretaceous faunal differentiation | journal = Science | volume = 272 | issue = 5264| pages = 986–991 | doi=10.1126/science.272.5264.986 | pmid=8662584| bibcode = 1996Sci...272..986S | s2cid = 39658297 | url = http://doc.rero.ch/record/13893/files/PAL_E831.pdf }}</ref> Those ''Spinosaurus'' that lived in the Bahariya Formation of what is now ] may have contended with shoreline conditions on ] and channels, living in ] forests alongside similarly large dinosaurian predators '']'' and ''Carcharodontosaurus'', the ] ] '']'' and '']'', ], bony and cartilaginous fish, turtles, lizards, and ]s.<ref name="JSetal01">{{cite journal |last=Smith |first=J.B. |author2=Lamanna, M.C. |author3=Lacovara, K.J. |author4=Dodson, P. |author5=Smith, J.R. |author6=Poole, J.C. |author7=Giegengack, R. |author8= Attia, Y. |year=2001 |title=A giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt |journal=Science |volume=292 |issue=5522 |pages=1704–1706 |doi=10.1126/science.1060561 |pmid=11387472|bibcode = 2001Sci...292.1704S |s2cid=33454060 |url=http://doc.rero.ch/record/14792/files/PAL_E1924.pdf }}</ref> In the dry season it might have resorted to preying on ]s.<ref name="naish, 2012">{{cite book|last=Naish|first=Darren|title=Planet Dinosaur : The Next Generation of Killer Giants|year=2012|publisher=Firefly Books|isbn=978-1-77085-049-1|pages=|url=https://archive.org/details/planetdinosaurne00scot/page/80}}</ref> This situation resembles that in the Late ] ] of ], which boasts up to five theropod genera over {{Convert|1|MT|short ton}} in weight, as well as several smaller genera (Henderson, 1998; Holtz ''and colleagues'', 2004). Differences in head shape and body size among the large North African theropods may have been enough to allow ] partitioning as seen among the many different predator species found today in the ]n ] (Farlow & Pianka, 2002).

== In popular culture ==
], Barcelona]]
''Spinosaurus'' appeared in the 2001 film '']'', replacing '']'' as the main antagonist.<ref name="variety">{{cite news|title=Jurassic Park III |work=] |url=https://www.variety.com/review/VE1117798505.html?categoryid=31&cs=1 |access-date=July 9, 2007 | first=Derek | last=Elley | date=July 17, 2001}}</ref> The film's consulting paleontologist ] was quoted as saying, "If we base the ferocious factor on the length of the animal, there was nothing that ever lived on this planet that could match this creature . Also my hypothesis is that T-rex was actually a scavenger rather than a killer. ''Spinosaurus'' was really the predatory animal."<ref>{{cite news |title= Spinosaurus makes ''T. Rex'' look like a pussycat: When it comes to Jurassic Park III, size does matter |author= Portman, J. |newspaper= Ottawa Citizen |date= July 11, 2001}}</ref> He has since retracted the statement about ''T. rex'' being a scavenger. In the film, ''Spinosaurus'' was portrayed as larger and more powerful than ''Tyrannosaurus'': in a scene depicting a battle between the two resurrected predators, ''Spinosaurus'' emerges victorious by snapping the ''Tyrannosaurus''{{'}} neck.<ref>{{cite news|last=Chandler|first=G.|title=A bite-size guide to the dinosaurs of the new movie Jurassic Park III|work=National Geographic World|date=August 2001}}</ref> In the fourth film, '']'', there is a nod to this fight where the ''T. rex'' smashes through the skeleton of a ''Spinosaurus'' in the climactic fight near the end of the film.<ref>{{cite news|last=Romano|first=Nick|title=Jurassic World Snuck in A Sweet Nod to Jurassic Park 3|url= https://www.cinemablend.com/new/Jurassic-World-Snuck-Sweet-Nod-Jurassic-Park-3-72074.html| work=CinemaBlend|date=June 2015}}</ref> The Spinosaurus would appear in many Jurassic Park games most notably '']'', and its ]. The same ''Spinosaurus'' from the third film returns in the fourth, and fifth season of '']'', this time battling two ''T. rex''.<ref>{{cite news |last1=Orquiola |first1=John |date=July 23, 2022 |title=Jurassic World Finally Has A Proper T-Rex vs Spinosaurus Rematch |url=https://screenrant.com/jurassic-world-camp-cretaceous-trex-spinosaurus-rematch/ |work=] |access-date=February 7, 2024}}</ref><ref>{{cite news |last1=Matadeen |first1=Renaldo |date=December 9, 2021 |title=Jurassic World: Camp Cretaceous Wastes Its Most Destructive Dinosaur |url=https://www.cbr.com/jurassic-world-camp-cretaceous-wastes-spinosaurus/ |work=] |access-date=February 7, 2024}}</ref>

''Spinosaurus'' has long been depicted in popular books about dinosaurs, although only recently has there been enough information about spinosaurids for an accurate depiction. After an influential 1955 skeletal reconstruction by Lapparent and Lavocat<ref name="Lapparent">Lapparent, A.F. de; and Lavocat, R. (1955). "Dinosauriens." In: Piveteau, J., editor. ''Traité de Paléontologie. Tome V. La Sortie des Eaux. Naissance de la Tétrapodie. L'Exubérance de la Vie Végétative. La Conquête de l'Air. Amphibiens. Reptiles. Oiseaux.'' Paris: Masson et Cie, pp. 785–962.</ref> based on a 1936 diagram by Stromer,<ref name="Stromer36">{{cite journal |last=Stromer |first=E. |author-link=Ernst Stromer |year=1936 |title= Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. VII. Baharije-Kessel und -Stufe mit deren Fauna und Flora. Eine ergänzende Zusammenfassung |journal= Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung |series=Neue Folge |volume=33|pages=1–102 |language=de}}</ref> it has been treated as a generalized upright theropod, with a skull similar to that of other large theropods and a sail on its back, even having four-fingered hands.<ref name="DFG00" />

In addition to films, action figures, video games, and books, ''Spinosaurus'' has been depicted on ]s from countries such as ], ], and ].<ref>{{cite news |title=From the past |author= Khatri, V.S. |date=June 9, 2006 |url=http://www.hindu.com/yw/2006/06/09/stories/2006060900450500.htm |archive-url=https://web.archive.org/web/20060618201148/http://www.hindu.com/yw/2006/06/09/stories/2006060900450500.htm |url-status=dead |archive-date=June 18, 2006 |newspaper=] |access-date=September 12, 2010}}</ref><ref>{{Cite book |editor1-last= Farlow |editor1-first= J.O. |editor2-last= and Walters |editor2-first= R.H |last1= Glut |first1= D.F. |last2= and Brett-Surman |first2= M.K. |chapter= Dinosaurs and the media |chapter-url= http://si-pddr.si.edu/dspace/bitstream/10088/8043/1/paleo_1997e_MBS__part2.pdf |title= The Complete Dinosaur |year= 2000 |publisher= Indiana University Press |location= Bloomington, IN |isbn= 978-0-253-21313-6 |pages= 673–706 |access-date= September 12, 2010 |archive-date= March 27, 2012 |archive-url= https://web.archive.org/web/20120327054521/http://si-pddr.si.edu/dspace/bitstream/10088/8043/1/paleo_1997e_MBS__part2.pdf |url-status= dead }}</ref>

==See also==
{{Portal|Dinosaurs}}
*'']''
*'']''
*'']''
*'']''

== References ==
{{Reflist}}

== Further reading ==
* Glut, D.F. "In search of ''Spinosaurus''." In: ''Jurassic classics: a collection of saurian essays and Mesozoic musings'', pp.&nbsp;77–85. Jefferson, NC: McFarland, 2001. {{ISBN|0-7864-0961-4}}.
* Nothdurft, W.; and Smith, J. ''The Lost Dinosaurs of Egypt.'' New York: Random House, 2002. {{ISBN|0-375-50795-7}}.
*A Tribute to Ernst Stromer: Hundred Years of the Discovery of ''Spinosaurus aegyptiacus'': Saubhik Ghosh

== External links ==
{{Commons}} {{Commons}}
{{wiktionary}}
{{portalpar|Dinosaurs}}
{{Wikiquote|Spinosaurus}}
{{Wikispecies}}
*. Spinosaurus profile by ] at NY Times, April 29, 2020
* Hartman, Scott. ''SkeletalDrawing.com'', 2006.
* Mortimer, Mickey. (List of specimens from The Theropod Database.)
* ].
* Prendergast, John. ''The Pennsylvania Gazette, the Alumni Magazine of the University of Pennsylvania'', July/Aug 2001.


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Latest revision as of 00:15, 25 December 2024

Genus of spinosaurid dinosaur

Spinosaurus
Temporal range: Late Cretaceous (Cenomanian), 100–94 Ma PreꞒ O S D C P T J K Pg N Possible Albian records
Reconstructed skeleton based on the Neotype specimen FSAC-KK-11888 in swimming posture, Field Museum of Natural History
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Spinosauridae
Tribe: Spinosaurini
Genus: Spinosaurus
Stromer, 1915
Type species
Spinosaurus aegyptiacus
Stromer, 1915
Synonyms

Spinosaurus (/ˌspaɪnəˈsɔːrəs/; lit. 'spine lizard') is a genus of spinosaurid dinosaur that lived in what now is North Africa during the Cenomanian stage of the Late Cretaceous period, about 100 to 94 million years ago. The genus was known first from Egyptian remains discovered in 1912 and described by German palaeontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material came to light in the early 21st century. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The type species S. aegyptiacus is mainly known from Egypt and Morocco. Although a potential second dubious species, S. maroccanus, has been recovered from Morocco, this dubious species is likely a junior synonym of S. aegyptiacus. Other possible junior synonyms include Sigilmassasaurus from the Kem Kem beds in Morocco and Oxalaia from the Alcântara Formation in Brazil, though other researchers propose both genera to be distinct taxa.

Spinosaurus is the longest known terrestrial carnivore; other large carnivores comparable to Spinosaurus include theropods such as Tyrannosaurus, Giganotosaurus and Carcharodontosaurus. The most recent study suggests that previous body size estimates are overestimated, and that S. aegyptiacus reached 14 m (46 ft) in length and 7.4 t (8.2 short tons) in body mass. The skull of Spinosaurus was long, low, and narrow, similar to that of a modern crocodilian, and bore straight conical teeth with no serrations. It would have had large, robust forelimbs bearing three-fingered hands, with an enlarged claw on the first digit. The distinctive neural spines of Spinosaurus, which were long extensions of the vertebrae (or backbones), grew to at least 1.65 m (5.4 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that the spines were covered in fat and formed a hump. The hip bones of Spinosaurus were reduced, and the legs were very short in proportion to the body. Its long and narrow tail was deepened by tall, thin neural spines and elongated chevrons, forming a flexible fin or paddle-like structure.

Spinosaurus is known to have eaten fish and small to medium terrestrial prey as well. Evidence suggests that it was semiaquatic; how capable it was of swimming has been strongly contested. Spinosaurus's leg bones had osteosclerosis (high bone density), allowing for better buoyancy control. Multiple functions have been put forward for the dorsal sail, including thermoregulation and display; either to intimidate rivals or attract mates. It lived in a humid environment of tidal flats and mangrove forests alongside many other dinosaurs, as well as fish, crocodylomorphs, lizards, turtles, pterosaurs, and plesiosaurs.

Discovery and naming

Naming of species

Plate I in Stromer (1915) showing S. aegyptiacus holotype elements

Two species of Spinosaurus have been named: Spinosaurus aegyptiacus (meaning "Egyptian spine lizard") and the disputed Spinosaurus maroccanus (meaning "Moroccan spine lizard"). The first described remains of Spinosaurus were found and described in the early 20th century. In 1912, Richard Markgraf discovered a partial skeleton of a giant theropod dinosaur in the Bahariya Formation of western Egypt. In 1915, German paleontologist Ernst Stromer published an article assigning the specimen to a new genus and species, Spinosaurus aegyptiacus.

Fragmentary additional remains from Bahariya, including vertebrae and hindlimb bones, were designated by Stromer as "Spinosaurus B" in 1934. Stromer considered them different enough to belong to another species, and this has been borne out. With the advantage of more expeditions and material, it appears that they pertain either to Carcharodontosaurus or to Sigilmassasaurus.

S. maroccanus was originally described by Dale Russell in 1996 as a new species based on the length of its neck vertebrae. Specifically, Russell claimed that the ratio of the length of the centrum (body of vertebra) to the height of the posterior articular facet was 1.1 in S. aegyptiacus and 1.5 in S. maroccanus. Later authors have been split on this topic. Some authors note that the length of the vertebrae can vary from individual to individual, that the holotype specimen was destroyed and thus cannot be compared directly with the S. maroccanus specimen, and that it is unknown which cervical vertebrae the S. maroccanus specimens represent. Therefore, though some have retained the species as valid without much comment, most researchers regard S. maroccanus as a nomen dubium (dubious name) or as a junior synonym of S. aegyptiacus. Some studies have referred the holotype and other referred specimens of S. maroccanus (NMC 50791 and MNHN SAM 124–128) as S. cf. aegyptiacus. The specimens previously ascribed as paratypes of S. maroccanus (NMC 41768 and NMC 50790) are reidentified as indeterminate spinosaurid specimens that are currently not identifiable at the generic level.

Specimens

Digital skeletal reconstruction of Spinosaurus, showing known bones based on the holotype (red), proposed neotype (blue), and referred specimens (yellow), according to Sereno and colleagues

Six main partial specimens of Spinosaurus have been described. BSP 1912 VIII 19, described by Stromer in 1915 from the Bahariya Formation, was the holotype. The material consisted of the following items, most of which were incomplete: right and left dentaries and splenials from the lower jaw measuring 75 centimeters (30 in) long; a straight piece of the left maxilla that was described but not drawn; 20 teeth; 2 cervical vertebrae; 7 dorsal (trunk) vertebrae; 3 sacral vertebrae; 1 caudal vertebra; 4 thoracic ribs; and gastralia. Of the nine neural spines whose heights are given, the longest ("i," associated with a dorsal vertebra) was 1.65 meters (5.4 ft) in length. Stromer claimed that the specimen was from the early Cenomanian, about 97 million years ago.

It was destroyed in World War II, specifically "during the night of 24/25 April 1944 in a British bombing raid of Munich" that severely damaged the building housing the Paläontologisches Museum München (Bavarian State Collection of Paleontology). However, detailed drawings and descriptions of the specimen remain. Stromer's son donated Stromer's archives to the Paläontologische Staatssammlung München in 1995, and Smith and colleagues analyzed two photographs of the Spinosaurus holotype specimen BSP 1912 VIII 19 discovered in the archives in 2000. On the basis of a photograph of the lower jaw and a photograph of the entire specimen as mounted, Smith concluded that Stromer's original 1915 drawings were slightly inaccurate. In 2003, Oliver Rauhut suggested that Stromer's Spinosaurus holotype was a chimera, composed of vertebrae and neural spines from a carcharodontosaurid similar to Acrocanthosaurus and a dentary from Baryonyx or Suchomimus. The analysis was rejected in at least one subsequent paper.

NMC 50791, held by the Canadian Museum of Nature, is a mid-cervical vertebra which is 19.5 centimeters (7.7 in) long from the Kem Kem Beds of Morocco. It is the holotype of Spinosaurus maroccanus, as described by Russell in 1996. Other specimens referred to S. maroccanus in the same paper were two other mid-cervical vertebrae (NMC 41768 and NMC 50790), an anterior dentary fragment (NMC 50832), a mid-dentary fragment (NMC 50833), and an anterior dorsal neural arch (NMC 50813). Russell stated that "only general locality information could be provided" for the specimen, and therefore it could be dated only "possibly" to the Albian.

Comparison between the snouts MNSM V4047 and MNHN SAM 124

MNHN SAM 124, housed at the Muséum National d'Histoire Naturelle, is a snout (consisting of partial premaxillae, partial maxillae, vomers, and a dentary fragment). Described by Taquet and Russell in 1998, the specimen is 13.4 to 13.6 centimeters (5.3–5.4 in) in width; no length was stated. The specimen was located in Algeria, and "is of Albian age." Taquet and Russell believed that the specimen, along with a premaxilla fragment (SAM 125), two cervical vertebrae (SAM 126–127), and a dorsal neural arch (SAM 128), belonged to S. maroccanus. Although it was originally ascribed to S. maroccanus, based on their examination of this cranial material, the 2016 study considered the difference between the two species to be not taxonomically significant and either ontogenetic or intraspecific, and thus tentatively assigned the specimen to S. aegyptiacus. The 2017 study considered MNHN SAM 124 to belong to same taxon as MSNM V4047.

BM231 (in the collection of the Office National des Mines, Tunis) was described by Buffetaut and Ouaja in 2002. It consists of a partial anterior dentary 11.5 centimeters (4.5 in) in length from an early Albian stratum of the Chenini Formation of Tunisia. The dentary fragment, which included four alveoli and two partial teeth, was "extremely similar" to existing material of S. aegyptiacus.

UCPC-2 in the University of Chicago Paleontological Collection consists mainly of two narrow connected nasals with a fluted (ridged) crest from the region between the eyes. The specimen, which is 18.0 centimeters (7.1 in) long, was located in an early Cenomanian part of the Moroccan Kem Kem Beds in 1996 and described in the scientific literature in 2005 by Cristiano Dal Sasso of the Civic Natural History Museum in Milan and colleagues.

MSNM V4047 (in the Museo di Storia Naturale di Milano), described by Dal Sasso and colleagues in 2005 as Spinosaurus cf. S. aegyptiacus, consists of a snout (premaxillae, partial maxillae, and partial nasals) 98.8 centimeters (38.9 in) long from the Kem Kem Beds. An isolated fish vertebra, tentatively referred to Onchopristis, has been associated with the tooth alveolus of this specimen. Similarly, the dentary fragment of Spinosaurus aegyptiacus, MPDM 31, is associated with the rostral tooth of Onchopristis. Like UCPC-2, it is thought to have come from the early Cenomanian. Arden and colleagues in 2018 tentatively assigned this specimen to Sigilmassasaurus brevicollis given its size. However, this assignment was later rejected by other researchers who considered the uniqueness of this specimen to be based on misinterpretations and poor preservation of another specimen, NHMUK R16665, another snout stored that is stored in the Natural History Museum, London.

FSAC-KK 11888 is a partial subadult skeleton recovered from the Kem Kem beds of North Africa. It was described by Ibrahim and colleagues in 2014 and designated as the neotype specimen, though Evers and colleagues rejected the neotype designation for FSAC-KK-11888 in 2015. It includes cervical vertebrae, dorsal vertebrae, neural spines, a complete sacrum, femora, tibiae, pedal phalanges, caudal vertebra, several dorsal ribs, and fragments of the skull. The body proportions of the specimen have been debated, as the hind limbs are disproportionately shorter in the specimen than in previous reconstructions. However, it has been demonstrated by multiple paleontologists that the specimen is not a chimera, and is indeed a specimen of Spinosaurus that suggests that the animal had much smaller hind limbs than previously thought.

Other known specimens consist mainly of very fragmentary remains and scattered teeth. These include:

  • A 1986 paper described prismatic structures in tooth enamel from two Spinosaurus teeth from Tunisia.
  • Buffetaut (1989, 1992) referred three specimens from the Institut und Museum für Geologie und Paläontologie of the University of Göttingen in Germany to Spinosaurus: a right maxilla fragment IMGP 969–1, a jaw fragment IMGP 969–2, and a tooth IMGP 969–3. These had been found in a Lower Cenomanian or Upper Albian deposit in southeastern Morocco in 1971.
  • Kellner and Mader (1997) described two unserrated spinosaurid teeth from Morocco (LINHM 001 and 002) that were "highly similar" to the teeth of the S. aegyptiacus holotype.
  • Teeth from the Chenini Formation in Tunisia which are "narrow, somewhat rounded in cross-section, and lack the anterior and posterior serrated edges characteristic of theropods and basal archosaurs" were assigned to Spinosaurus in 2000.
  • Material possibly belonging to Spinosaurus from the Turkana Grits of Kenya has been noted in 2004.
  • Teeth from the Echkar Formation of Niger were tentatively referred to Spinosaurus in 2007.
  • A partial tooth 8 centimeters (3.1 in) long purchased at a fossil trade show, reportedly from the Kem Kem Bed of Morocco and attributed to Spinosaurus maroccanus, showed 1 to 5 millimeters (0.039 to 0.197 in) wide longitudinal striations and micro-structures (irregular ridges) among the striations in a 2010 paper.
  • Isolated teeth attributed to S. aegyptiacus are reported from Algeria in 2015.
  • Pedal ungual (MSNM V6894), cervical vertebra (FSAC-KK-7280) and dorsal vertebra (FSAC-KK-18118) from the Kem Kem beds are referred to juvenile cf. Spinosaurus aegyptiacus.

MHNM.KK374, MHNM.KK375, MHNM.KK376, MHNM.KK377, MHNM.KK378 and MSNM V6896 are six isolated quadrates (skull bones) of different sizes that were collected by locals and acquired commercially in the Kem Kem region of southeastern Morocco, provided by François Escuillié and are deposited in the collections of the Muséum d’Histoire Naturelle of Marrakech. Only MHNM.KK376 is assigned to Sigilmassasaurus brevicollis, while the other five specimens are assigned to S. aegyptiacus, since the quadrates show two different morphologies, suggesting the existence of two spinosaurines in Morocco. However, a 2020 study on variation within Spinosaurus considers these differences in morphology to be indicative of variation in skull morphology within a single species, as is the case in Allosaurus.

Possible synonyms

Sigilmassasaurus

Some scientists have considered the genus Sigilmassasaurus a junior synonym of Spinosaurus. In Ibrahim and colleagues (2014), the specimens of Sigilmassasaurus was referred to Spinosaurus aegyptiacus together with "Spinosaurus B" as the neotype and Spinosaurus maroccanus was considered as a nomen dubium following the conclusions of the other papers. A 2015 re-description of Sigilmassasaurus disputed these conclusions, and considered the genus valid, with inclusion of S. maroccanus as a synonym of Sigilmassasaurus instead. This conclusion was further supported in 2018 by Arden and colleagues, who consider Sigilmassasaurus to be a distinct genus, though a very close relative of Spinosaurus, the two unified in the tribe Spinosaurini, coined in the study.

The 2020 study indicates synonymy between Spinosaurus and Sigilmassasaurus, and considered specimens previously referred to Sigilmassasaurus as those of Spinosaurus. For instance, the referral of an isolated quadrate (specimen MHNM.KK376) to Sigilmassasaurus brevicollis, based on its difference from other specimens assigned to Spinosaurus aegyptiacus, was rejected by the 2020 study which noted that these differences in morphology are indicative of variation in skull morphology within a single species. The 2019 study assigned a juvenile specimen FSAC-KK-18122 to Sigilmassasaurus brevicollis based on its identical proportion to BSPG 2011 I 115 which was assigned to the taxon in a 2015 study, but this referral was also rejected in a 2020 study based on the fact that the median tubercle and median suture is present in BSPG 2011 I 115 but absent in FSAC-KK-18122, so the presence or absence of such feature should not be used to taxonomically separate isolated spinosaurid remains.

Regardless of the synonymy of Sigilmassasaurus with Spinosaurus, some authors consider the possibility that there could be a second distinct spinosaurid in North Africa during the Cenomanian age. Additionally, in 2024, a complete posterior cervical vertebra (specimen NHMUK PV R 38358) was assigned to Sigilmassasaurus brevicollis.

Oxalaia

Since the National Museum of Brazil fire in 2018 engulfed the palace housing the museum, with specimens of Oxalaia possibly being destroyed, any classification should remain tentative. In a 2020 paper written by Symth et al. in assessing spinosaurine specimens from the Kem Kem Group suggested the Brazilian spinosaurine Oxalaia to be a potential junior synonym of Spinosaurus aegyptiacus. This was based on looking at the specimens assigned to Oxalaia, and the supposed autapomorphies of this taxon to be insignificant and fall within the hypodigm of Spinosaurus aegyptiacus. If supported by future studies, this would imply Spinosaurus aegyptiacus had a wider distribution and supports the faunal exchange between South America and Africa during this time.

However, subsequent studies have rejected the synonymy of Oxalaia with Spinosaurus aegyptiacus based on diagnostic features of the holotype (MN 6117-V) and the referred specimen (MN 6119-V). In 2021, Lacerda, Grillo and Romano noted that the anteromedial processes of the holotype maxillae (MN 6117-V) contact medially, a condition not observed in MSNM V4047 which has been referred to as a specimen of Spinosaurus, and thus adding a new possible diagnostic feature of Oxalaia. They also suggested that the premaxilla of Oxalaia is wider in the posterior portion than that of MSNM V4047, and that the lateral morphology of its rostrum was distinguished from other spinosaurines based on their morphometric analysis. In 2023, Isasmendi and colleagues considered Oxalaia as a valid taxon based on the examination of its referred maxilla (MN 6119-V) which suggests that the position of its external naris would have been more anteriorly located, a condition similar to that of Irritator and baryonychines, differing from African spinosaurines including Spinosaurus aegyptiacus.

Description

Size

Size comparison of selected giant theropod dinosaurs, S. aegyptiacus in red

Since its discovery, Spinosaurus has been a contender for the largest theropod dinosaur. Both Friedrich von Huene in 1926 and Donald F. Glut in 1982 listed it as among the most massive theropods in their surveys, at 15 m (49 ft) in length and upwards of 6 t (6.6 short tons) in weight. In 1988, Gregory S. Paul also listed it as the longest theropod at 15 m (49 ft), but gave a lower mass estimate of 4 t (4.4 short tons).

In 2005, Dal Sasso and colleagues assumed that Spinosaurus and the related Suchomimus had the same body proportions in relation to their skull lengths, and thereby calculated that Spinosaurus was 16 to 18 m (52 to 59 ft) in length and 7 to 9 t (7.7 to 9.9 short tons) in weight. The estimates were criticized because the skull length estimate was uncertain, and (assuming that body mass increases as the cube of body length) scaling Suchomimus, which was 11 m (36 ft) long and 3.8 t (4.2 short tons) in mass, to the range of estimated lengths of Spinosaurus would produce an estimated body mass of 11.7 to 16.7 t (12.9 to 18.4 short tons).

Estimated size of the largest known, holotype, neotype, and smallest known specimen with a human

François Therrien and Donald Henderson, in a 2007 paper using scaling based on skull length, challenged previous estimates of the size of Spinosaurus, finding the length too great and the weight too small. Based on estimated skull lengths of 1.5 to 1.75 m (4 ft 11 in to 5 ft 9 in), their estimates include a body length of 12.6 to 14.3 m (41 to 47 ft) and a body mass of 12 to 20.9 t (13.2 to 23.0 short tons). The lower estimates for Spinosaurus would imply that the animal was shorter and lighter than Carcharodontosaurus and Giganotosaurus. The Therrien and Henderson study has been criticized for the choice of theropods used for comparison (e.g., most of the theropods used to set the initial equations were tyrannosaurids and carnosaurs, which have a different build than spinosaurids), and for the assumption that the Spinosaurus skull could be as little as 1.5 m (4 ft 11 in) in length.

In 2014, Ibrahim and his colleagues suggested that Spinosaurus aegyptiacus could reach over 15 m (49 ft) in length. In 2022, however, Paul Sereno and his colleagues suggested that Spinosaurus aegyptiacus reached a maximum body length of 14 m (46 ft) and a maximum body mass of 7.4 t (8.2 short tons) by constructing a CT-based 3D skeletal model "with the axial column in neutral pose." They argued that the 2D graphical reconstruction of the aquatic hypothesis by Ibrahim and his colleagues in 2020 overestimated the presacral column length by 10%, ribcage depth by 25%, and forelimb length by 30% over dimensions based on CT-scanned fossils; these proportional overestimates shift the center of mass anteriorly when translated to a flesh model, and thus the estimate from Ibrahim and his colleagues cannot be considered a reliable body size estimate.

Skull

Annotated diagram of the reconstructed skull
Annotated diagram of the reconstructed skull muscles of Spinosaurus

Its skull had a narrow snout filled with straight conical teeth that lacked serrations. There were six or seven teeth on each side of the very front of the upper jaw, in the premaxillae, and another twelve in both maxillae behind them. The second and third teeth on each side were noticeably larger than the rest of the teeth in the premaxilla, creating a space between them and the large teeth in the front of the maxilla; large teeth in the lower jaw faced this space. The very tip of the snout holding those few large front teeth was expanded, and a small crest was present in front of the eyes. Using the dimensions of three specimens known as MSNM V4047, UCPC-2, and BSP 1912 VIII 19, and assuming that the postorbital part of the skull of MSNM V4047 had a shape similar to the postorbital part of the skull of Irritator, Dal Sasso and colleagues (2005) estimated that the skull of Spinosaurus was 1.75 meters (5.7 ft) long, but more recent estimates suggest a length of 1.6–1.68 meters (5.2–5.5 ft). The Dal Sasso and colleagues skull length estimate is questioned because skull shapes can vary across spinosaurid species and because MSNM V4047 may not belong to Spinosaurus itself, though recent studies have reconfirmed it as a specimen of Spinosaurus.

Postcranial skeleton

Reconstructed replicas of the holotype vertebrae, National Geographic Museum, Washington, D. C.

As a spinosaurid, Spinosaurus would have had a long, muscular neck, curved in a sigmoid, or S-shape. Its shoulders were prominent, and the forelimbs large and stocky, bearing three clawed digits on each hand. The first finger (or "thumb") would have been the largest. Spinosaurus had long phalanges (finger bones), and only somewhat recurved claws, suggesting that its hands were longer compared to those of other spinosaurids.

Very tall neural spines growing on the back vertebrae of Spinosaurus formed the basis of what is usually called the animal's "sail". The lengths of the neural spines reached over 10 times the diameters of the centra (vertebral bodies) from which they extended. The neural spines were slightly longer front to back at the base than higher up, and were unlike the thin rods seen in the pelycosaur finbacks Edaphosaurus and Dimetrodon, contrasting also with the thicker spines in the iguanodontian Ouranosaurus.

Life restoration

Spinosaurus sails were unusual, although other dinosaurs, namely Ouranosaurus, which lived a few million years earlier in the same general region as Spinosaurus, and the Early Cretaceous South American sauropod Amargasaurus, might have developed similar structural adaptations of their vertebrae. The sail may be an analog of the sail of the Permian synapsid Dimetrodon, which lived before the dinosaurs even appeared, produced by convergent evolution.

The structure may also have been more hump-like than sail-like, as noted by Stromer in 1915 ("one might rather think of the existence of a large hump of fat , to which the gave internal support") and by Jack Bowman Bailey in 1997. In support of his "buffalo-back" hypothesis, Bailey argued that in Spinosaurus, Ouranosaurus, and other dinosaurs with long neural spines, the spines were relatively shorter and thicker than the spines of pelycosaurs (which are known to have sails); instead, the dinosaurs' neural spines were similar to the neural spines of extinct hump-backed mammals such as Megacerops and Bison latifrons. In 2014, Ibrahim and colleagues instead posited that the spines were covered tightly by skin, similar to a crested chameleon, given their compactness, sharp edges, and likely poor blood flow.

Spinosaurus had a significantly smaller pelvis (hip bone) than that of other giant theropods, with the surface area of the ilium (main body of the pelvis) half that of most members of the clade. The hind limbs were short, at just over 25 percent of the total body length, with the tibia (calf bone) being longer than the femur (thigh bone). Unlike in other theropods, the hallux (or fourth toe) of Spinosaurus touched the ground, and the phalanges of the toe bones were unusually long and well-built. At their ends were shallow claws that had flat bottoms. This type of foot morphology is also seen in shorebirds, indicating that Spinosaurus's feet evolved for walking across unstable substrate and that they may have been webbed.

From the caudal vertebrae of the tail projected significantly elongated, thin neural spines, akin to the condition observed in some other spinosaurids, though to a more extreme degree. Coupled with the also elongated chevron bones on the underside of the caudals, this resulted in a deep and narrow tail with a paddle or fin-like shape, comparable to the tails of newts and crocodilians.

Classification

Specimen MNBH EGA1 which may belong to Spinosaurus

Spinosaurus gives its name to the dinosaur family Spinosauridae, which includes two subfamilies: Baryonychinae and Spinosaurinae. Baryonychinae includes Baryonyx from southern England and Suchomimus from Niger in central Africa. Spinosaurinae includes Spinosaurus, Siamosaurus, Ichthyovenator, Irritator, Angaturama (which may be synonymous with Irritator), Sigilmassasaurus and Oxalaia (both of which may be synonymous with Spinosaurus). The spinosaurines share unserrated straight teeth that are widely spaced (e.g., 12 on one side of the maxilla), as opposed to the baryonychines, which have serrated curved teeth that are numerous (e.g., 30 on one side of the maxilla).

An analysis of Spinosauridae by Arden and colleagues (2018) named the clade Spinosaurini and defined it as all spinosaurids closer to Spinosaurus aegyptiacus than to Irritator challengeri or Oxalaia quilombensis; it also found Siamosaurus suteethorni and Icthyovenator laosensis to be members of Spinosaurinae.

Phylogeny

The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Holtz and colleagues (2004) as all taxa closer to Spinosaurus aegyptiacus than to Baryonyx walkeri. The subfamily Baryonychinae was named by Charig & Milner in 1986. They erected both the subfamily and the family Baryonychidae for the newly discovered Baryonyx, before it was referred to Spinosauridae. Their subfamily was defined by Holtz and colleagues in 2004, as the complementary clade of all taxa closer to Baryonyx walkeri than to Spinosaurus aegyptiacus. Examinations by Marcos Sales, Cesar Schultz, and colleagues (2017) indicate that the South American spinosaurids Angaturama, Irritator, and Oxalaia were intermediate between Baronychinae and Spinosaurinae based on their craniodental features and cladistic analysis. This indicates that Baryonychinae may in fact be non-monophyletic. Their cladogram can be seen below.

Restoration of various spinosaurids that did not live in the same time or space
Spinosauridae

Baryonyx

Cristatusaurus
Suchomimus
Angaturama
Oxalaia
Spinosaurus

The cladogram below depicts the findings of Arden and colleagues (2018):

Spinosauridae

Praia das Aguncheiras taxon

Baryonychinae

Baryonyx walkeri

Suchomimus tenerensis
Spinosaurinae
Siamosaurus suteethorni

Eumeralla taxon

Ichthyovenator laosensis
Irritator challengeri
Oxalaia quilombensis
Spinosaurini

Gara Samani taxon

Sigilmassasaurus brevicollis
Spinosaurus aegyptiacus

Paleobiology

Function of neural spines

1915 illustration of S. aegyptiacus dorsal vertebrae

The function of the dinosaur's sail or hump is uncertain; scientists have proposed several hypotheses including heat regulation and display. In addition, such a prominent feature on its back could make it appear even larger than it was, intimidating other animals.

The structure may have been used for thermoregulation. If the structure contained abundant blood vessels, the animal could have used the sail's large surface area to absorb heat. This would imply that the animal was only partly warm-blooded at best and lived in climates where night-time temperatures were cool or low and the sky usually not cloudy. It is also possible that the structure was used to radiate excess heat from the body, rather than to collect it. Large animals, due to the relatively small ratio of surface area of their body compared to the overall volume (Haldane's principle), face far greater problems of dissipating excess heat at higher temperatures than gaining it at lower. Sails of large dinosaurs added considerably to the skin area of their bodies, with minimum increase of volume. Furthermore, if the sail was turned away from the sun, or positioned at a 90 degree angle towards a cooling wind, the animal would quite effectively cool itself in the warm climate of Cretaceous Africa. However, Bailey (1997) was of the opinion that a sail could have absorbed more heat than it radiated. Bailey proposed instead that Spinosaurus and other dinosaurs with long neural spines had fatty humps on their backs for energy storage, insulation, and shielding from heat.

Many elaborate body structures of modern-day animals serve to attract members of the opposite sex during mating. It is possible that the sail of Spinosaurus was used for courtship, in a way similar to a peacock's tail. Stromer speculated that the size of the neural spines may have differed between males and females.

Reconstructed skeleton in National Geographic Museum

Gimsa and colleagues (2015) suggest that the dorsal sail of Spinosaurus was analogous to the dorsal fins of sailfish and served a hydrodynamic purpose. Gimsa and others point out that more basal, long-legged spinosaurids had otherwise round or crescent-shaped dorsal sails, whereas in Spinosaurus, the dorsal neural spines formed a shape that was roughly rectangular, similar in shape to the dorsal fins of sailfish. They therefore argue that Spinosaurus used its dorsal neural sail in the same manner as sailfish, and that it also employed its long narrow tail to stun prey like a modern thresher shark. Sailfish employ their dorsal fins for herding schools of fish into a "bait ball" where they cooperate to trap the fish into a certain area where the sailfish can snatch the fish with their bills. The sail could have possibly reduced yaw rotation by counteracting the lateral force in the direction opposite to the slash as suggested by Gimsa and colleagues (2015).

Spinosaurus anatomy exhibits another feature that may have a modern analogy: its long tail resembled that of the thresher shark, employed to slap the water to herd and stun shoals of fish before devouring them (Oliver and colleagues, 2013). The strategies that sailfish and thresher sharks employ against shoaling fish are more effective when the shoal is first concentrated into a ‘bait ball’ (Helfman, Collette & Facey, 1997; Oliver and colleagues, 2013; Domenici and colleagues, 2014). Since this is difficult for individual predators to achieve, they cooperate in this effort. When herding a shoal of fish or squid, sailfish also raise their sails to make themselves appear larger. When they slash or wipe their bills through shoaling fish by turning their heads, their dorsal sail and fins are outstretched to stabilize their bodies hydrodynamically (Lauder & Drucker, 2004). Domenici and colleagues (2014) postulate that these fin extensions enhance the accuracy of tapping and slashing. The sail can reduce yaw rotation by counteracting the lateral force in the direction opposite to the slash. This means that prey is less likely to recognize the massive trunk as being part of an approaching predator (Marras and colleagues, 2015; Webb & Weihs 2015).

Spinosaurus exhibited the anatomical features required to combine all three hunting strategies: a sail for herding prey more efficiently, as well as flexible tail and neck to slap the water for stunning, injuring or killing prey. The submerged dorsal sail would have provided a strong centreboard-like counterforce for powerful sidewards movements of the strong neck and long tail, as performed by sailfish (Domenici and colleagues, 2014) or thresher sharks (Oliver and colleagues, 2013). While smaller dorsal sails or fins make the dorsal water volume better accessible for slashing, it can be speculated that their smaller stabilization effect makes lateral slashing less efficient (e.g. for thresher sharks). Forming a hydrodynamic fulcrum and hydrodynamically stabilizing the trunk along the dorsoventral axis, Spinosaurus’ sail would also have compensated for the inertia of the lateral neck by tail movements and vice versa not only for predation but also for accelerated swimming. This behavior might also have been one reason for Spinosaurus’ muscular chest and neck reported by Ibrahim and colleagues (2014).

Diet and feeding

Tooth from Morocco in various views
CT scan of possible Spinosaurus snout NHMUK 16665

It is unclear whether Spinosaurus was primarily a terrestrial predator or a piscivore, as indicated by its elongated jaws, conical teeth and raised nostrils. The hypothesis of spinosaurs as specialized fish eaters has been suggested before by A. J. Charig and A. C. Milner for Baryonyx. They base this on the anatomical similarity with crocodilians and the presence of digestive acid-etched fish scales in the rib cage of the type specimen. Large fish are known from the faunas containing other spinosaurids, including the Mawsonia, in the mid-Cretaceous of northern Africa and Brazil. Direct evidence for spinosaur diet comes from related European and South American taxa. Baryonyx was found with fish scales and bones from juvenile Iguanodon in its stomach, while a tooth embedded in a South American pterosaur bone suggests that spinosaurs occasionally preyed on pterosaurs, but Spinosaurus was likely to have been a generalized and opportunistic predator, possibly a Cretaceous equivalent of large grizzly bears, being biased toward fishing, though it undoubtedly scavenged and took many kinds of small or medium-sized prey.

S. aegyptiacus head based on the 2005 reconstruction by Cristiano Dal Sasso

In 2009, Dal Sasso and colleagues. reported the results of X-ray computed tomography of the MSNM V4047 snout. As the foramina on the outside all communicated with a space on the inside of the snout, the authors speculated that Spinosaurus had pressure receptors inside the space that allowed it to hold its snout at the surface of the water to detect swimming prey species without seeing them. A 2013 study by Andrew R. Cuff and Emily J. Rayfield concluded that bio-mechanical data suggests that Spinosaurus was not an obligate piscivore and that its diet was more closely associated with each individual's size. The characteristic rostral morphology of Spinosaurus allowed its jaws to resist bending in the vertical direction, but its jaws were poorly adapted with respect to resisting lateral bending compared to other members of this group (Baryonyx) and modern alligators. This suggests that Spinosaurus preyed more regularly on fish than it did on land animals, although considered predators of the former too. In 2022, Sakamoto estimated that Spinosaurus had an anterior bite force of 4,829 newtons and a posterior bite force of 11,936 newtons. Based on this estimate, he asserted that the jaws of Spinosaurus are adapted for generating relatively faster shutting speeds with less muscle input force, indicating that the animal likely killed its prey with fast-snapping jaws rather than slow-crushing bites, a trait commonly observed in animals which have a semi-aquatic feeding habit.

A 2024 paper suggests that Spinosaurus and other spinosaurines in addition to fish also preyed upon small to medium-sized terrestrial vertebrates, and had relatively weak bite forces compared to those of other theropods.

Aquatic habits

Restoration of Spinosaurus attacking the sawskate Onchopristis

A 2010 isotope analysis by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid teeth, including teeth of Spinosaurus, indicate semiaquatic lifestyles. Isotope ratios from tooth enamel and from other parts of Spinosaurus (found in Morocco and Tunisia) and of other predators from the same area such as Carcharodontosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians. The study found that Spinosaurus teeth from five of six sampled localities had oxygen isotope ratios closer to those of turtles and crocodilians when compared with other theropod teeth from the same localities. The authors postulated that Spinosaurus switched between terrestrial and aquatic habitats to compete for food with large crocodilians and other large theropods respectively. A 2018 study by Donald Henderson, however, refutes the claim that Spinosaurus was semiaquatic. By studying the buoyancy in lungs of crocodilians and comparing it to the lung placement in Spinosaurus, it was discovered that Spinosaurus could not sink or dive below the water surface. It was also capable of keeping its entire head above the water surface while floating, much like other non-aquatic theropods. Furthermore, the study found that Spinosaurus had to continually paddle its hind legs to prevent itself from tipping over onto its side, something that extant semiaquatic animals do not need to perform. Henderson therefore theorized that Spinosaurus probably did not hunt completely submerged in water as previously hypothesized, but instead would have spent much of its time on land or in shallow water.

Recent studies of the tail vertebrae of Spinosaurus refute Henderson's proposal that Spinosaurus mainly inhabited areas of land near and in shallow water and was too buoyant to submerge. Studies of the tail, thanks to fossils recovered and analyzed by Ibrahim, Pierce, Lauder, and Sereno and colleagues in 2018 indicate that Spinosaurus had a keeled tail that was well adapted to propelling the animal through water. The elongated neural spines and chevrons, which run to the end of the tail on both dorsal and ventral sides, indicate that Spinosaurus was able to swim in a similar manner to modern crocodilians. Through experimentation by Lauder and Pierce, the tail of Spinosaurus was found to have eight times as much forward thrust as the tails of terrestrial theropods like Coelophysis and Allosaurus, as well as being twice as efficient at achieving forward thrust. The discovery indicates that Spinosaurus may have had a lifestyle comparable to modern alligators and crocodiles, remaining in water for long periods of time while hunting.

Flesh model of S. aegyptiacus used for a 2022 buoyancy study

David Hone and Thomas Holtz published a paper in 2021 in which they argue that the anatomy of Spinosaurus is more consistent with a shoreline generalist lifestyle rather than an active aquatic pursuit predator as suggested by Ibrahim. They highlight the positioning of the nostrils and orbits as one reason why a crocodile-like lifestyle is unlikely: they are ventrally positioned in such a way that the whole head would have to be lifted inefficiently out of the water in order to breathe. Additionally, they argue that the general body shape of Spinosaurus is poorly adapted for this lifestyle, drawing on the amount of water drag and aquatic instability from the sail, as well as the rigid trunk and seemingly scarcely-muscled tail. Animals like crocodilians require a flexible body in order to move through the water and make sharp turns when chasing prey, and this is directly contradicted by Hone and Holtz's findings.

A 2022 study by Fabbri et al., made comparisons of Spinosaurus' bone structure and compared it to that of Baryonyx and Suchomimus. The study revealed that Spinosaurus and Baryonyx had dense bones, which allowed them to dive and pursue prey underwater. Compared to these, Suchomimus had more hollow bones, suggesting it preferred to hunt in shallow water. These findings also suggest that various spinosaurid genera were more ecologically disparate than previously believed, as some were better suited to hunting in subaqueous environments than other, closely related genera.

In the same year, contradicting the study by Fabbri and colleagues, Sereno and his colleagues suggested that Spinosaurus was wholly bipedal on land and an unstable, slow moving surface swimmer in deep water. Their results, taken from reconstructing a CT model of the skeleton, and then adding internal air and muscles. Their results, coupled with fossils from Spinosaurus that showed it also lived further inland along rivers and lakes, suggest it was a semi-aquatic, ambush piscivore that preferred waterside environments both along the coasts and further inland along rivers and lakes. Simultaneously, they suggested that the large tail fin was probably utilized more for display than swimming, as tails in living animals have the same function when they possess comparably tall neural spines.

A 2024 paper by Myrhvold et al. also contends that Spinosaurus and Baryonyx were diving pursuit predators. Instead they also argue that Spinosaurus and Baryonyx hunted more like herons instead of diving after prey. Another paper in the same year analyzed the linear measurements of the skull of Spinosaurus, and concluded that the skull morphology and hunting method of Spinosaurus would likely be the most similar to those of wading birds like herons, though the authors noted that they're uncertain how beneficial the skull would have been for the diving pursuit predation method.

Locomotion and posture

Reconstructed skeleton with traditional, long-legged posture

Although traditionally depicted in the scientific community as a biped, Spinosaurus was occasionally depicted in the mid-20th century as an obligate quadruped akin to Dimetrodon. Starting in the mid-1970s, it was hypothesized Spinosaurus was at least an occasional quadruped, bolstered by the discovery of Baryonyx, a relative with robust arms. Because of the mass of the hypothesized fatty dorsal humps of Spinosaurus, Bailey (1997) was open to the possibility of a quadrupedal posture, leading to new restorations of it as such. Theropods, including spinosaurids, could not pronate their hands (rotate the forearm so the palm faced the ground), but a resting position on the side of the hand was possible, as shown by fossil prints from an Early Jurassic theropod. The hypothesis that Spinosaurus had a typical quadrupedal gait since fell out of favor, however it was still believed that spinosaurids may have crouched in a quadrupedal posture, due to biological and physiological constraints.

Reconstructed foot, note straight claws and large hallux

The possibility of a quadrupedal Spinosaurus was revived by a 2014 paper by Ibrahim and colleagues that described new material of the animal. The paper found that the hind limbs of Spinosaurus were much shorter than previously believed, and that its center of mass was located in the midpoint of the torso region, as opposed to near the hip as in typical bipedal theropods. It was therefore proposed that Spinosaurus was poorly adapted for bipedal terrestrial locomotion, and must have been an obligate quadruped on land. The reconstruction used in the study was an extrapolation based on different sized individuals, scaled to what were assumed to be the correct proportions. Paleontologist John Hutchinson of the Royal Veterinary College of the University of London has expressed skepticism to the new reconstruction, and cautioned that using different specimens can result in inaccurate chimaeras. Scott Hartman also expressed criticism because he believed the legs and the pelvis were inaccurately scaled (27% too short) and didn't match the published lengths. However, Mark Witton expressed agreement with the proportions reported in the paper. In their 2015 re-description of Sigilmassasaurus, Evers and colleagues argued that Sigilmassasaurus was in fact a distinct genus from Spinosaurus, and therefore doubted whether the material assigned to Spinosaurus by Ibrahim et al. should be assigned to Spinosaurus or Sigilmassasaurus. In 2018, an analysis by Henderson found that Spinosaurus probably was competent at bipedal terrestrial locomotion; the center of mass was instead found to be close to the hips, allowing Spinosaurus to stand upright like other bipedal theropods.

A 2024 article co-authored by Sereno stated that the previous calculations by Sereno that were used to argue quadrupedality for Spinosaurus had erroneously shifted the center of mass in front of the hips. They instead suggested that the dinosaur fit the criteria of being a graviportal (or slow-moving) biped.

Ontogeny

An ungual phalanx measuring 21 millimeters (0.83 in) belonging to a very young juvenile cf. S. aegyptiacus indicates that the theropod developed its semiaquatic adaptations at a very young age or at birth and maintained them throughout its life. The specimen, found in 1999 and described by Simone Maganuco and Cristiano Dal Sasso and colleagues, is believed to have come from an animal measuring 1.78 meters (5.8 ft) (assuming it resembled a smaller version of the adult), making it the smallest specimen of Spinosaurus currently known.

Palaeopathology

A cf. Spinosaurus sp. tooth from the Ifezouane Formation displays enhanced lingual curvature to the tooth's crown, the development of three deep grooves extending from crown root junction in the direction of the crown's apex, an attenuated carina that does not extend apically nor to the base of the tooth, and a wear facet at the tip.

Paleoenvironment

Restoration of Spinosaurus with contemporaneous animals of the Bahariya Formation

The environment inhabited by Spinosaurus is only partially understood, and covers a great deal of what is now northern Africa. The region of Africa Spinosaurus is preserved in dates from 112 to 93.5 million years ago. A potential specimen tentatively referred to as cf. Spinosaurus has been found in the Campanian Quseir Formation of Egypt, but no detailed description of the specimen was provided. A 1996 study concluded from Moroccan fossils that Spinosaurus, Carcharodontosaurus, and Deltadromeus "ranged across north Africa during the late Cretaceous (Cenomanian)." Those Spinosaurus that lived in the Bahariya Formation of what is now Egypt may have contended with shoreline conditions on tidal flats and channels, living in mangrove forests alongside similarly large dinosaurian predators Bahariasaurus and Carcharodontosaurus, the titanosaur sauropods Paralititan and Aegyptosaurus, crocodylomorphs, bony and cartilaginous fish, turtles, lizards, and plesiosaurs. In the dry season it might have resorted to preying on pterosaurs. This situation resembles that in the Late Jurassic Morrison Formation of North America, which boasts up to five theropod genera over 1 metric ton (1.1 short tons) in weight, as well as several smaller genera (Henderson, 1998; Holtz and colleagues, 2004). Differences in head shape and body size among the large North African theropods may have been enough to allow niche partitioning as seen among the many different predator species found today in the African savanna (Farlow & Pianka, 2002).

In popular culture

Sculpture based on the 2014 reconstruction, prior to the discovery of the paddle-like tail, Museum of Natural Science, Barcelona

Spinosaurus appeared in the 2001 film Jurassic Park III, replacing Tyrannosaurus as the main antagonist. The film's consulting paleontologist John R. Horner was quoted as saying, "If we base the ferocious factor on the length of the animal, there was nothing that ever lived on this planet that could match this creature . Also my hypothesis is that T-rex was actually a scavenger rather than a killer. Spinosaurus was really the predatory animal." He has since retracted the statement about T. rex being a scavenger. In the film, Spinosaurus was portrayed as larger and more powerful than Tyrannosaurus: in a scene depicting a battle between the two resurrected predators, Spinosaurus emerges victorious by snapping the Tyrannosaurus' neck. In the fourth film, Jurassic World, there is a nod to this fight where the T. rex smashes through the skeleton of a Spinosaurus in the climactic fight near the end of the film. The Spinosaurus would appear in many Jurassic Park games most notably Jurassic World Evolution, and its sequel. The same Spinosaurus from the third film returns in the fourth, and fifth season of Jurassic World Camp Cretaceous, this time battling two T. rex.

Spinosaurus has long been depicted in popular books about dinosaurs, although only recently has there been enough information about spinosaurids for an accurate depiction. After an influential 1955 skeletal reconstruction by Lapparent and Lavocat based on a 1936 diagram by Stromer, it has been treated as a generalized upright theropod, with a skull similar to that of other large theropods and a sail on its back, even having four-fingered hands.

In addition to films, action figures, video games, and books, Spinosaurus has been depicted on postage stamps from countries such as Angola, The Gambia, and Tanzania.

See also

References

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Further reading

  • Glut, D.F. "In search of Spinosaurus." In: Jurassic classics: a collection of saurian essays and Mesozoic musings, pp. 77–85. Jefferson, NC: McFarland, 2001. ISBN 0-7864-0961-4.
  • Nothdurft, W.; and Smith, J. The Lost Dinosaurs of Egypt. New York: Random House, 2002. ISBN 0-375-50795-7.
  • A Tribute to Ernst Stromer: Hundred Years of the Discovery of Spinosaurus aegyptiacus: Saubhik Ghosh

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