Araeoscelidia Fossil range: Carboniferous-Permian
Petrolacosaurus
Conservation status
Fossil
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Subclass:	Diapsida
Genera
Araeoscelis Petrolacosaurus Spinoaequalis Kadaliosaurus Zarcasaurus
Synonyms
Araeoscelida

Araeoscelidia or Araeoscelida is a clade of extinct 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 considered to be the sister group to all (currently known) later diapsids.

Contents 1 Description 2 Genera 3 Phylogeny 4 Stratigraphic and geographic distribution 5 References

[edit] Description

Araeoscelidans 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.

[edit] Genera

Araeoscelida includes well-known genera such as Araeoscelis (Williston, 1910; Vaughn, 1955; Reisz et al., 1984), Petrolacosaurus (Lane, 1945; Peabody, 1952; Reisz, 1981) and Spinoaequalis (deBraga & Reisz, 1995; deBraga & Rieppel, 1997), known from virtually complete skeletons. Zarcasaurus (Brinkman et al., 1984), Aphelosaurus (Gervais, 1859; Thévenin, 1910; Falconnet & Steyer, 2007) and Kadaliosaurus (Credner, 1889) 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 Oklahoma, United States (May & Hall, 2002; Swanson & Carlson, 2002) but so far lack a scientific description.

[edit] Phylogeny

 Araeoscelidia ├─? Dictybolos ├─o Spinoaequalis └─o Araeosceloidea   ├─o Petrolacosauridae   │ └─o Petrolacosaurus   │   └─o Araeoscelidae     ├─o Zarcasaurus     └─o Araeoscelinae       ├─o Kadaliosaurus       └─o         ├─o Araeoscelis         └─o Aphelosaurus 

Phylogenetic relationships after deBraga and Reisz (1995) and Falconnet and Steyer (2007).

[edit] Stratigraphic and geographic distribution

Araeoscelida are known from the Late Carboniferous in the United States (Petrolacosaurus, Spinoaequalis) to the Early Permian in France (Aphelosaurus), Germany (Kadaliasaurus) and the United States (Dictybolos, Zarcasaurus, Araeoscelis). Apart from araeoscelidans, only one other diapsid is known before the Late Permian: Apsisaurus from the Early Permian of Texas (Laurin, 1991).

[edit] References

• Carroll, Robert L. (1988). Vertebrate paleontology and evolution. New York: W.H. Freeman and Co. 
• Benton, Michael J. (2000). Vertebrate paleontology (2nd edition ed.). Oxford: Blackwell Science. 
• 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: 281-354.
• 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. 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 deustchen geologischen Gesellschaft 41: 319-342.
• Evans, S. E. (1988). The early history and relationships of the Diapsida. In: M. J. Benton (ed.), The phylogeny and classification of the tetrapods, Volume 1: Amphibians, Reptiles, Birds. Systematics Association Special Volume 35 A: 221-260. Clarendon Press, Oxford.
• 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 – 2e édition. Bertrand, Paris, 544 pp.
• 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.
• 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 Contribution 10: 1-41.
• 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.
• Swanson, B. A. & Carlson, K J. (2002). Walk, Wade, or Swim? Vertebrate Traces on an Early Permian Lakeshore. Palaios 17: 123-133.
• 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.

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