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'''Euthycarcinoidea''' are an enigmatic group of extinct possibly amphibious ]s that ranged from ] to ] times. Fossils are known from Europe, North America, Argentina, Australia and Antarctica. '''Euthycarcinoidea''' are an enigmatic group of extinct possibly amphibious ]s that ranged from ] to ] times. Fossils are known from Europe, North America, Argentina, Australia and ].


==Description== ==Description==
The euthycarcinoid body was divided into a cephalon (head), preabdomen, and ]. The cephalon consisted of two ] and included ], ] and presumed eyes. The preabdomen consisted of five to fourteen ], each having up to three ]. Each somite had in turn a pair of ], segmented legs. The postabdomen was limbless and consisted of up to six segments and a terminal tail spine.<ref name="ReferenceA">{{harvp|Ortega-Hernández|Legg|Tremewan|Braddy|2010|p=195}}</ref> The euthycarcinoid body was divided into a cephalon (head), preabdomen, and ]. The cephalon consisted of two ] and included ], ] and presumed eyes. The preabdomen consisted of five to fourteen ], each having up to three ]. Each somite had in turn a pair of ], segmented legs. The postabdomen was limbless and consisted of up to six segments and a terminal tail spine.<ref name="ReferenceA">{{harvp|Ortega-Hernández|Legg|Tremewan|Braddy|2010|p=195}}</ref>


About 8.5cm long (3.3″), it would have had a similar three-part body plan to other euthycarcinoids – with a head, a limb-bearing ], and a limbless abdomen ending in a tail spine – but its most distinctive feature was a pair of large wing-shaped projections on the sides of its ]. These may have helped to stabilize its body when resting on soft muddy surfaces, spreading out its weight, or they might even have functioned as a ] generating lift while swimming.
==Affinities== ==Affinities==
Due to its particular combination of characteristics, the position of the Euthycarcinoidea within the Arthropoda has been ambiguous; previous authors have allied euthycarcinoids with crustaceans (interpreted as ]s, ]s, or an independent group), with ]s, or the merostomatans (] and ], now an obsolete group<ref>{{Cite journal|last=Lamsdell|first=James C.|date=2012-12-18|title=Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura|journal=Zoological Journal of the Linnean Society|language=en|volume=167|issue=1|pages=1–27|doi=10.1111/j.1096-3642.2012.00874.x|issn=0024-4082|doi-access=free}}</ref>).<ref name="Racheboeuf et al 2008"/> However, due to the general features and the discovery of fossils from this group in Cambrian rocks, a 2010 study suggested that they may have given rise to the mandibulates, the group that includes the ]s (]s, ]s and the like), ]s, and ] (insects, etc.).<ref>{{harvp|Ortega-Hernández|Legg|Tremewan|Braddy|2010|p=196}}</ref> Due to its particular combination of characteristics, the position of the Euthycarcinoidea within the Arthropoda has been ambiguous; previous authors have allied euthycarcinoids with ] (interpreted as ]s, ]s, or an independent group), with ]s, or the merostomatans (] and ], now an obsolete group<ref>{{Cite journal|last=Lamsdell|first=James C.|date=2012-12-18|title=Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura|journal=Zoological Journal of the Linnean Society|language=en|volume=167|issue=1|pages=1–27|doi=10.1111/j.1096-3642.2012.00874.x|issn=0024-4082|doi-access=free}}</ref>).<ref name="Racheboeuf et al 2008"/> However, due to the general features and the discovery of fossils from this group in Cambrian rocks, a 2010 study suggested that they may have given rise to the ], the group that includes the ]s (]s, ]s and the like), ]s, and ] (insects, etc.).<ref>{{harvp|Ortega-Hernández|Legg|Tremewan|Braddy|2010|p=196}}</ref>


{{clade {{clade
|1={{clade sequential|]|'''Euthycarcinoidea'''|]|]|]}} |1={{clade sequential|]|'''Euthycarcinoidea'''|]|]|]}}
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However, a 2020 study identified several characters, including ]s and various details of the preoral chamber, that suggested instead a position as the closest relatives of living myriapods.<ref>{{cite journal | doi = 10.1073/pnas.1920733117 | title = Aquatic stem group myriapods close a gap between molecular divergence dates and terrestrial fossil record | journal = Proceedings of the National Academy of Sciences | volume = 117 | issue = 16 | pages = 8966–8972 | year = 2020 | last1 = Edgecombe | first1 = Gregory D. | last2 = Strullu-Derrien | first2 = Christine | last3 = Góral | first3 = Tomasz | last4 = Hetherington | first4 = Alexander J. | last5 = Thompson | first5 = Christine | last6 = Koch | first6 = Marcus | pmid = 32253305 | pmc = 7183169 | s2cid = 215408474 | doi-access = free }}</ref> This would help to close the gap between the earliest body fossils of ] myriapods in the ] and molecular clock data suggesting a divergence from their closest relatives during the ] or ].<ref name="ReferenceA"/> This had already been suggested by the cladogram of a previous study.<ref>{{Cite journal|last1=Vannier|first1=Jean|last2=Aria|first2=Cédric|last3=Taylor|first3=Rod S.|last4=Caron|first4=Jean-Bernard|date=June 2018|title=Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale|journal=Royal Society Open Science|language=en|volume=5|issue=6|pages=172206|doi=10.1098/rsos.172206|issn=2054-5703|pmc=6030330|pmid=30110460}}</ref> However, a 2020 study identified several characters, including ]s and various details of the preoral chamber, that suggested instead a position as the closest relatives of living myriapods.<ref>{{cite journal | doi = 10.1073/pnas.1920733117 | title = Aquatic stem group myriapods close a gap between molecular divergence dates and terrestrial fossil record | journal = Proceedings of the National Academy of Sciences | volume = 117 | issue = 16 | pages = 8966–8972 | year = 2020 | last1 = Edgecombe | first1 = Gregory D. | last2 = Strullu-Derrien | first2 = Christine | last3 = Góral | first3 = Tomasz | last4 = Hetherington | first4 = Alexander J. | last5 = Thompson | first5 = Christine | last6 = Koch | first6 = Marcus | pmid = 32253305 | pmc = 7183169 | s2cid = 215408474 | doi-access = free }}</ref> This would help to close the gap between the earliest body fossils of ] myriapods in the ] and molecular clock data suggesting a divergence from their closest relatives during the ] or ].<ref name="ReferenceA"/> This had already been suggested by the ] of a previous study.<ref>{{Cite journal|last1=Vannier|first1=Jean|last2=Aria|first2=Cédric|last3=Taylor|first3=Rod S.|last4=Caron|first4=Jean-Bernard|date=June 2018|title=Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale|journal=Royal Society Open Science|language=en|volume=5|issue=6|pages=172206|doi=10.1098/rsos.172206|issn=2054-5703|pmc=6030330|pmid=30110460}}</ref>


{{clade {{clade
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==Environment and life habits== ==Environment and life habits==
Euthycarcinoid fossils have been found in ], ] and freshwater deposits.<ref>{{harvp|Ortega-Hernández|Legg|Tremewan|Braddy|2010|pp=196–197}}</ref> Taxa from the Cambrian are from marine or intertidal sediments, while all specimens from the Ordovician to the Triassic are freshwater or brackish.<ref name="Racheboeuf et al 2008"/> Fossil impressions of euthycarcinoid postabdomens in association with '']'' trackways in Cambrian ]/supratidal deposits also suggest that euthycarcinoids may have been the first arthropods to walk on land.<ref name="Collette_Hagadorn">{{harvp|Collette|Hagadorn|2010}}</ref><ref>{{harvp|Collette|Gass|Hagadorn|2012}}</ref> It has been suggested that the ]s and ] that covered much of the vast ]s during the Cambrian Period in ] may have provided the nourishment that lured these arthropods onto the land.<ref>{{harvp|MacNaughton|Cole|Dalrymple|Braddy|2002|p=394}}</ref> Fossil evidence also suggests the possibility that some euthycarcinoids came onto the land to lay and fertilize their eggs via ], as do the modern horseshoe crabs.<ref>{{harvp|Collette|Gass|Hagadorn|2012|pp=452–453}}</ref> Euthycarcinoid fossils have been found in ], ] and freshwater deposits.<ref>{{harvp|Ortega-Hernández|Legg|Tremewan|Braddy|2010|pp=196–197}}</ref> ] from the Cambrian are from marine or intertidal sediments, while all specimens from the ] to the ] are freshwater or brackish.<ref name="Racheboeuf et al 2008"/> Fossil impressions of euthycarcinoid postabdomens in association with '']'' trackways in Cambrian ]/supratidal deposits also suggest that euthycarcinoids may have been the first arthropods to walk on land.<ref name="Collette_Hagadorn">{{harvp|Collette|Hagadorn|2010}}</ref><ref>{{harvp|Collette|Gass|Hagadorn|2012}}</ref> It has been suggested that the ]s and ] that covered much of the vast ]s during the Cambrian Period in ] may have provided the nourishment that lured these arthropods onto the land.<ref>{{harvp|MacNaughton|Cole|Dalrymple|Braddy|2002|p=394}}</ref> Fossil evidence also suggests the possibility that some euthycarcinoids came onto the land to lay and fertilize their eggs via ], as do the modern horseshoe crabs.<ref>{{harvp|Collette|Gass|Hagadorn|2012|pp=452–453}}</ref>

Most euthycarcinoid species are known from ] and ] climates, but Antarcticarcinus pagoda here hints that these arthropods were much more widespread and diverse than previously thought. Discovered in fossil deposits in the Central Transantarctic Mountains of ], it lived in freshwater lakes during the Early ] (~299-293 million years ago), at a time when the region was in similar polar latitudes to today with a cold icy ] climate.


==Classification== ==Classification==
Line 39: Line 42:


* '']'' * '']''
** ''Antarcticarcinus pagoda'' ] Antarctica, Upper Carboniferous to Lower Permian.<ref>{{Cite journal|last1=Collette|first1=Joseph H.|last2=Isbell|first2=John L.|last3=Miller|first3=Molly F.|date=September 2017|title=A unique winged euthycarcinoid from the Permian of Antarctica|journal=Journal of Paleontology|language=en|volume=91|issue=5|pages=987–993|doi=10.1017/jpa.2017.28|issn=0022-3360|doi-access=free}}</ref> ** ''Antarcticarcinus pagoda'' ] Antarctica, ] to Lower Permian.<ref>{{Cite journal|last1=Collette|first1=Joseph H.|last2=Isbell|first2=John L.|last3=Miller|first3=Molly F.|date=September 2017|title=A unique winged euthycarcinoid from the Permian of Antarctica|journal=Journal of Paleontology|language=en|volume=91|issue=5|pages=987–993|doi=10.1017/jpa.2017.28|issn=0022-3360|doi-access=free}}</ref>


* '']'' (Cambrian), from marine deposits in Argentina * '']'' (]), from marine deposits in ]
* '']'' * '']''
** ''Euthycarcinus ibbenburensis'' (]: ]), from freshwater deposits in Germany ** ''Euthycarcinus ibbenburensis'' (]: ]), from freshwater deposits in ]
** ''Euthycarcinus martensi'' (]), from freshwater deposits in Germany ** ''Euthycarcinus martensi'' (]), from freshwater deposits in Germany
** ''Euthycarcinus kessleri'' (Triassic), from freshwater deposits in France ** ''Euthycarcinus kessleri'' (]), from freshwater deposits in ]
* '']'' (Cambrian), from intertidal deposits in the United States * '']'' (Cambrian), from intertidal deposits in the ]
* '']'' (Cambrian), from intertidal deposits in Canada * '']'' (Cambrian), from intertidal deposits in ]
* '']'' (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United States * '']'' (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United States
* '']'' (Triassic) from freshwater deposits of Australia * '']'' (Triassic) from freshwater deposits of ]
* '']'' (Upper Devonian) * '']'' (])


Family '''Kottixexidae''' <small>Starobogatov, 1988</small> Family '''Kottixexidae''' <small>Starobogatov, 1988</small>
* '']'' (Lower Devonian), from freshwater deposits of the United Kingdom * '']'' (Lower ]), from freshwater deposits of the ]
* '']'' (Ordovician or Late Silurian), from freshwater deposits of Australia (Age and habitat are controversial<ref>{{Cite web |title=Terrestrialization in the Ordovician |url=https://www.lyellcollection.org/doi/10.1144/SP532-2022-92 |access-date=2022-11-14 |website=Geological Society, London, Special Publications |language=en |doi=10.1144/sp532-2022-92}}</ref>) * '']'' (Ordovician or Late ]), from freshwater deposits of Australia (Age and habitat are controversial<ref>{{Cite web |title=Terrestrialization in the Ordovician |url=https://www.lyellcollection.org/doi/10.1144/SP532-2022-92 |access-date=2022-11-14 |website=Geological Society, London, Special Publications |language=en |doi=10.1144/sp532-2022-92}}</ref>)
*'']'' *'']''
** ''Kottixerxes anglicus'' (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United Kingdom ** ''Kottixerxes anglicus'' (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United Kingdom

Revision as of 23:41, 16 December 2023

Extinct order of arthropods

Euthycarcinoidea
Temporal range: Cambrian–Middle Triassic PreꞒ Ꞓ O S D C P T J K Pg N
Life restoration of Apankura
Life restoration of Sottyxerxes
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Clade: Mandibulata
Subclass: †Euthycarcinoidea
Gall & Grauvogel, 1964
Order: †Euthycarcinida
Gall & Grauvogel, 1964
Genera

See text

Euthycarcinoidea are an enigmatic group of extinct possibly amphibious arthropods that ranged from Cambrian to Triassic times. Fossils are known from Europe, North America, Argentina, Australia and Antarctica.

Description

The euthycarcinoid body was divided into a cephalon (head), preabdomen, and postabdomen. The cephalon consisted of two segments and included mandibles, antennae and presumed eyes. The preabdomen consisted of five to fourteen tergites, each having up to three somites. Each somite had in turn a pair of uniramous, segmented legs. The postabdomen was limbless and consisted of up to six segments and a terminal tail spine.

About 8.5cm long (3.3″), it would have had a similar three-part body plan to other euthycarcinoids – with a head, a limb-bearing thorax, and a limbless abdomen ending in a tail spine – but its most distinctive feature was a pair of large wing-shaped projections on the sides of its carapace. These may have helped to stabilize its body when resting on soft muddy surfaces, spreading out its weight, or they might even have functioned as a hydrofoil generating lift while swimming.

Affinities

Due to its particular combination of characteristics, the position of the Euthycarcinoidea within the Arthropoda has been ambiguous; previous authors have allied euthycarcinoids with crustaceans (interpreted as copepods, branchiopods, or an independent group), with trilobites, or the merostomatans (horseshoe crabs and sea scorpions, now an obsolete group). However, due to the general features and the discovery of fossils from this group in Cambrian rocks, a 2010 study suggested that they may have given rise to the mandibulates, the group that includes the myriapods (centipedes, millipedes and the like), crustaceans, and hexapods (insects, etc.).

Euchelicerata

Euthycarcinoidea

Myriapoda

Crustacea

Hexapoda

However, a 2020 study identified several characters, including compound eyes and various details of the preoral chamber, that suggested instead a position as the closest relatives of living myriapods. This would help to close the gap between the earliest body fossils of crown-group myriapods in the Silurian and molecular clock data suggesting a divergence from their closest relatives during the Ediacaran or Cambrian. This had already been suggested by the cladogram of a previous study.

Euchelicerata

Pancrustacea

Myriapoda

Euthycarcinoidea

The Cambrian euthycarcinoid Mosineia macnaughtoni from the Elk Mound Group, Blackberry Hill, central Wisconsin. Cambrian euthycarcinoids such as this one may have been the first animals to walk and survive on land.

Environment and life habits

Euthycarcinoid fossils have been found in marine, brackish and freshwater deposits. Taxa from the Cambrian are from marine or intertidal sediments, while all specimens from the Ordovician to the Triassic are freshwater or brackish. Fossil impressions of euthycarcinoid postabdomens in association with Protichnites trackways in Cambrian intertidal/supratidal deposits also suggest that euthycarcinoids may have been the first arthropods to walk on land. It has been suggested that the biofilms and microbial mats that covered much of the vast tidal flats during the Cambrian Period in North America may have provided the nourishment that lured these arthropods onto the land. Fossil evidence also suggests the possibility that some euthycarcinoids came onto the land to lay and fertilize their eggs via amplexus, as do the modern horseshoe crabs.

Most euthycarcinoid species are known from tropical and subtropical climates, but Antarcticarcinus pagoda here hints that these arthropods were much more widespread and diverse than previously thought. Discovered in fossil deposits in the Central Transantarctic Mountains of Antarctica, it lived in freshwater lakes during the Early Permian (~299-293 million years ago), at a time when the region was in similar polar latitudes to today with a cold icy subarctic climate.

Classification

The known species of euthycarcinoids and their distribution were reviewed by Racheboeuf et al. in 2008. Additional species were described by Collette and Hagadorn in 2010.

Family Kottixexidae Starobogatov, 1988

  • Heterocrania rhyniensis (Lower Devonian), from freshwater deposits of the United Kingdom
  • Kalbarria brimmellae (Ordovician or Late Silurian), from freshwater deposits of Australia (Age and habitat are controversial)
  • Kottixerxes
    • Kottixerxes anglicus (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United Kingdom
    • Kottyxerxes gloriosus (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United States
  • Schramixerxes gerem (Late Pennsylvanian: Stephanian stage), from freshwater deposits in France
  • Smithixerxes
    • Smithixerxes juliarum (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United States
    • Smithixerxes pustulosus (Pennsylvanian: Westphalian), from brackish to freshwater deposits of the United Kingdom
  • Sottyxerxes multiplex (Late Pennsylvanian: Stephanian stage), from freshwater deposits in France

References

  1. ^ Ortega-Hernández et al. (2010), p. 195
  2. Lamsdell, James C. (2012-12-18). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi:10.1111/j.1096-3642.2012.00874.x. ISSN 0024-4082.
  3. ^ Racheboeuf et al. (2008)
  4. Ortega-Hernández et al. (2010), p. 196
  5. Edgecombe, Gregory D.; Strullu-Derrien, Christine; Góral, Tomasz; Hetherington, Alexander J.; Thompson, Christine; Koch, Marcus (2020). "Aquatic stem group myriapods close a gap between molecular divergence dates and terrestrial fossil record". Proceedings of the National Academy of Sciences. 117 (16): 8966–8972. doi:10.1073/pnas.1920733117. PMC 7183169. PMID 32253305. S2CID 215408474.
  6. Vannier, Jean; Aria, Cédric; Taylor, Rod S.; Caron, Jean-Bernard (June 2018). "Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale". Royal Society Open Science. 5 (6): 172206. doi:10.1098/rsos.172206. ISSN 2054-5703. PMC 6030330. PMID 30110460.
  7. McNamara & Trewin (1993)
  8. Ortega-Hernández et al. (2010), pp. 196–197
  9. ^ Collette & Hagadorn (2010)
  10. Collette, Gass & Hagadorn (2012)
  11. MacNaughton et al. (2002), p. 394
  12. Collette, Gass & Hagadorn (2012), pp. 452–453
  13. Collette, Joseph H.; Isbell, John L.; Miller, Molly F. (September 2017). "A unique winged euthycarcinoid from the Permian of Antarctica". Journal of Paleontology. 91 (5): 987–993. doi:10.1017/jpa.2017.28. ISSN 0022-3360.
  14. "Terrestrialization in the Ordovician". Geological Society, London, Special Publications. doi:10.1144/sp532-2022-92. Retrieved 2022-11-14.

Bibliography

Taxon identifiers
Euthycarcinoidea
Categories: