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Araeoscelidans Temporal range: Carboniferous–Permian 302–275.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Life restoration (top) and skull reconstruction (bottom) of Petrolacosaurus kansensis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Diapsida
Order:	†Araeoscelidia Williston, 1913
Genera
†Spinoaequalis †Petrolacosaurus †Zarcasaurus †Araeoscelis †Aphelosaurus †Kadaliosaurus †Halgaitosaurus

Araeoscelidia or Araeoscelida is a clade of extinct amniotes (traditionally classified as diapsid reptiles) superficially resembling lizards, extending from the Late Carboniferous to the Early Permian. The group contains the genera Araeoscelis, Petrolacosaurus, the possibly aquatic Spinoaequalis, and less well-known genera such as Kadaliosaurus and Zarcasaurus. This clade is usually considered to be the sister group to all (currently known) later diapsids.

Description

Araeoscelidians were small animals (less than one meter in length) looking somewhat like lizards, though they are only distantly related to true lizards. They differ from other, earlier sauropsids by their slender limbs, their elongated tail, and of course by the presence of two temporal openings, the feature defining the diapsid condition. In Araeoscelis, only the upper temporal opening remains, thus resulting in a derived euryapsid condition.

Genera

Araeoscelidia includes well-known genera such as Araeoscelis Williston 1910, Petrolacosaurus Lane 1945 and Spinoaequalis, known from virtually complete skeletons. Zarcasaurus, Aphelosaurus and Kadaliosaurus belong to this clade but are known only from post-cranial remains and a mandible fragment for Zarcasaurus.

The genus Dictybolos has been included in Araeoscelidia by Olson (1970) but this inclusion has been criticized e.g., by Evans (1988), especially since Olson also included distantly related groups such as protorosaurs and mesosaurs.

New specimens have been discovered in the United States state of Oklahoma, but lack a scientific description as of 2023.

Phylogeny

The majority of phylogenetic studies recover araeoscelidians as the most basal group of diapsids; however, Simões et al. (2022) recover them as stem-amniotes instead, as the sister group to the clade including Captorhinidae and Protorothyris archeri.

Stratigraphic and geographic distribution

Araeoscelidia are known from the Late Carboniferous in the United States (Petrolacosaurus, Spinoaequalis) to the Early Permian in France (Aphelosaurus), Germany (Kadaliosaurus) and the United States (Dictybolos, Zarcasaurus, Araeoscelis, Halgaitosaurus). Apart from araeoscelidans, only one other diapsid is known before the Late Permian: Orovenator from the Early Permian of Oklahoma.

References

1. Vaughn 1955
2. Reisz, Berman & Scott 1984
3. Peabody 1952
4. Reisz 1981
5. deBraga & Reisz 1995
6. deBraga & Rieppel 1997
7. Brinkman, Berman & Eberth 1984
8. Gervais 1859
9. Thévenin 1910
10. Falconnet & Steyer 2007
11. Credner 1889
12. Olson 1970
13. Evans 1988
14. May & Hall 2002
15. Swanson & Carlson 2002
16. Simões, T. R.; Kammerer, C. F.; Caldwell, M. W.; Pierce, S. E. (2022). "Successive climate crises in the deep past drove the early evolution and radiation of reptiles". Science Advances. 8 (33): eabq1898. doi:10.1126/sciadv.abq1898. PMC 9390993. PMID 35984885.
17. Henrici, Amy C.; Berman, David S; Sumida, Stuart S.; Huttenlocker, Adam K. (2023-11-15). "Halgaitosaurus gregarius, a New Upper Carboniferous Araeoscelidian (Reptilia: Diapsida) from the Halgaito Formation, Bears Ears National Monument, Utah, USA". Annals of Carnegie Museum. 88 (3). doi:10.2992/007.088.0301. ISSN 0097-4463.
18. Reisz, Modesto & Scott 2011

Further reading

• Carroll, Robert L. (1988). Vertebrate Paleontology and Evolution. New York: W.H. Freeman and Co. ISBN 0-7167-1822-7.
• Benton, Michael J. (2000). Vertebrate Paleontology (2nd ed.). Oxford: Blackwell Science. ISBN 0-632-05614-2.
• deBraga, M. & Reisz, R. R. (1995). "A new diapsid reptile from the uppermost Carboniferous (Stephanian) of Kansas". Palaeontology. 38: 199–212.
• deBraga, M. & Rieppel, O. (1997). "Reptile phylogeny and the interrelationships of turtles". Zoological Journal of the Linnean Society. 120 (3): 281–354. doi:10.1111/j.1096-3642.1997.tb01280.x.
• Brinkman, D. B.; Berman, D. S. & Eberth, D. Z. (1984). "A new araeoscelid reptile, Zarcasaurus tandyderus, from the Culter Formation, (Lower Permian) of north-central New Mexico" (PDF). New Mexico Geology. 6 (2): 34–39.
• Credner, H. (1889). "Die Stegocephalen und Saurier aus dem Rothliegenden des Plauen'schen Grundes bei Dresden. 8 – Kadaliosaurus priscus Cred". Zeitschrift der Deutschen Geologischen Gesellschaft. 41: 319–342.
• Evans, S. E. (1988). "The early history and relationships of the Diapsida". In Benton, M. J. (ed.). The phylogeny and classification of the tetrapods. Vol. 1: Amphibians, Reptiles, Birds. Systematics Association Special Volume 35 A. Oxford: Clarendon Press. pp. 221–260. ISBN 0-19-857705-2.
• Falconnet, J. & Steyer, J.-S. (2007). "Revision, osteology and locomotion of Aphelosaurus, an enigmatic reptile from the Lower Permian of France". Journal of Morphology (abstract of the 8th International Congress of Vertebrate Morphology, Paris, July 2007): 38.
• Gervais, P. (1859). Zoologie et paléontologie française (2nd ed.). Paris: Bertrand.
• Laurin, M. (1991). "The osteology of a Lower Permian eosuchian from Texas and a review of a diapsid phylogeny". Zoological Journal of the Linnean Society. 101: 59–95. doi:10.1111/j.1096-3642.1991.tb00886.x.
• May, W. J. & Hall, J. D. (2002). "Geology and vertebrate fauna of a new site in the Wellington Formation (Lower Permian) of Northern Oklahoma". Oklahoma Geology Notes. 62 (2): 63–66.
• Olson, E. C. (1970). "New and little known genera and species of vertebrates from the Lower Permian of Oklahoma". Fieldiana: Geology. 18: 359–434.
• Peabody, F. E. (1952). "Petrolacosaurus kansensis Lane, a Pennsylvanian reptile from Kansas". University of Kansas Paleontological Contributions. 10: 1–41. hdl:1808/3785.
• Reisz, R. R. (1981). "A diapsid reptile from the Pennsylvanian of Kansas". Special Publication of the Museum of Natural History, University of Kansas. 7: 1–74.
• Reisz, R. R.; Berman, D. S. & Scott, D. (1984). "The anatomy and relationships of the Lower Permian reptile Araeoscelis". Journal of Vertebrate Paleontology. 4 (1): 57–67. doi:10.1080/02724634.1984.10011986.
• Reisz, Robert R.; Modesto, Sean P.; Scott, Diane M. (2011). "A new Early Permian reptile and its significance in early diapsid evolution". Proceedings of the Royal Society B. 278 (1725): 3731–3737. doi:10.1098/rspb.2011.0439. PMC 3203498. PMID 21525061.
• Swanson, B. A. & Carlson, K. J. (2002). "Walk, Wade, or Swim? Vertebrate Traces on an Early Permian Lakeshore" (PDF). PALAIOS. 17 (2): 123–133. Bibcode:2002Palai..17..123S. doi:10.1669/0883-1351(2002)017<0123:WWOSVT>2.0.CO;2. S2CID 130593903.
• Thévenin, A. (1910). "Les plus anciens quadrupèdes de France". Annales de Paléontologie. 5: 1–65.
• Vaughn, P. P. (1955). "The Permian reptile Araeoscelis restudied". Bulletin of the Harvard Museum of Comparative Zoology. 113: 305–467.

v t e Reptiliomorpha (Pan‑Amniota)
Kingdom: Animalia Phylum: Chordata Clade: Osteichthyes Clade: Sarcopterygii Clade: Tetrapoda Tetrapodomorpha see Tetrapodomorpha Reptiliomorpha see below↓ Reptiliomorpha / Pan-Amniota
Reptiliomorpha †Caerorhachis? †Casineria? †Eldeceeon? †Romeriscus †Silvanerpeton? †Solenodonsaurus? †Termonerpeton? †Westlothiana? †Embolomeri? †Gephyrostegidae? †Chroniosuchia? Laosuchus Bystrowianidae Axitectum Bystrowiana Bystrowiella Dromotectum Hassiacoscutum Jiyuanitectum Synesuchus Yumenerpeton Chroniosuchidae Chroniosaurus Chroniosuchus Ingentidens Jarilinus Madygenerpeton Phratochronis Suchonica Uralerpeton †Seymouriamorpha? Ariekanerpeton Biarmica Discosauriscus Enosuchus? Karpinskiosaurus Kotlassia Leptoropha Makowskia Microphon Nyctiboetus Seymouria Spinarerpeton Utegenia Volgerpeton Waggoneria "Microsauria"? see Microsauria possibly includes Lissamphibia Amniota †Diadectomorpha? Limnoscelis? Tseajaia Diadectidae Alveusdectes Ambedus Desmatodon Diadectes Diasparactus Kuwavaatakdectes Orobates Phanerosaurus Stephanospondylus †"Protorothyrididae" Anthracodromeus Brouffia Cephalerpeton Coelostegus Hylonomus Paleothyris Protorothyris Thuringothyris †Araeoscelidia Aphelosaurus Araeoscelis Dictybolos? Halgaitosaurus Kadaliosaurus Petrolacosaurus Spinoaequalis? Zarcasaurus †Captorhinidae Acrodenta Baeotherates Captorhinoides Captorhinus Euconcordia? Labidosauriscus Labidosaurus Opisthodontosaurus? Protocaptorhinus Puercosaurus? Reiszorhinus Rhiodenticulatus Rhodotheratus Riabininus? Romeria Saurorictus Moradisaurinae Balearosaurus Captorhinikos Gansurhinus Gecatogomphius Indosauriscus Kahneria Labidosaurikos Moradisaurus Rothianiscus Sumidadectes Tramuntanasaurus Amniota (crown group) Synapsida (Pan‑Mammalia) see Synapsida includes mammals Sauropsida (Pan‑Reptilia) see Sauropsida includes reptiles and birds
See also: Labyrinthodontia Lepospondyli Anthracosauria Batrachosauria Cotylosauria Eureptilia

v t e Sauropsida (Reptilia sensu lato)
Kingdom: Animalia Phylum: Chordata Superclass: Tetrapoda Clade: Amniota Tetrapodomorpha see Tetrapodomorpha Reptiliomorpha see Reptiliomorpha Sauropsida see below↓
Sauropsida Sauropsida †Australothyris †Erpetonyx †Microleter †Acleistorhinidae Acleistorhinus Carbonodraco Colobomycter Delorhynchus Feeserpeton Karutia Klastomycter †Bolosauridae Belebey Bolosaurus Eudibamus †Mesosauria Brazilosaurus Mesosaurus Stereosternum †Millerettidae Broomia Heleophilus Milleretta Millerosaurus Milleropsis Nanomilleretta †Procolophonia see Procolophonia Diapsida see below↓
Diapsida Diapsida †Adelosaurus? †Claudiosaurus †Cryptovaranoides †Dolerosaurus †Elachistosuchus †Eunotosaurus? †Feralisaurus †Heleosuchus †Kenyasaurus †Kudnu †Lanthanolania †Maiothisavros †Microzemiotes †Orovenator †Palacrodon †Palaeagama †Saurosternon †Sphodrosaurus †Younginidae Galesphyrus Thadeosaurus Youngina †Tangasauridae Acerosodontosaurus? Hovasaurus Tangasaurus †Weigeltisauridae Coelurosauravus Glaurung Rautiania Weigeltisaurus †Drepanosauromorpha Ancistronychus Avicranium Dolabrosaurus Drepanosaurus Hypuronector Kyrgyzsaurus Longisquama? Megalancosaurus Protoavis? Skybalonyx Unguinychus Vallesaurus †Kuehneosauridae Icarosaurus Idiosaura? Kuehneosaurus Kuehneosuchus Pamelina Rhabdopelix? †Choristodera see Choristodera †Ichthyosauromorpha see Ichthyosauromorpha †Sauropterygia see Sauropterygia †Thalattosauria see Thalattosauria Sauria (Crown-Reptilia) Lepidosauromorpha see Lepidosauromorpha Includes Lepidosauria includes rhynchocephalians and squamates Archelosauria Archosauromorpha see Archosauromorpha Includes Archosauria includes birds and crocodilians Pantestudines see Pantestudines Includes Testudines turtles
See also Possible sauropsids Araeoscelidia Captorhinidae Protorothyrididae Recumbirostra Varanopidae Other taxa Anapsida Captorhinida Eureptilia Parareptilia Lanthanosuchoidea Millerosauria Procolophonomorpha Ankyramorpha Neodiapsida Eosuchia Younginiformes Avicephala Eolacertilia Euryapsida
Category

• Araeoscelidians
• Pennsylvanian first appearances
• Cisuralian extinctions
• Taxa named by Samuel Wendell Williston