Araeoscelidia or Araeoscelida is a clade of extinct (traditionally classified as diapsid reptiles) superficially resembling lizards, extending from the Late Carboniferous to the Early Permian.
The group contains the genus 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
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,
and
Spinoaequalis,
known from virtually complete skeletons.
Zarcasaurus,
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)
New specimens have been discovered in the United States state of Oklahoma,
Phylogeny
The majority of historical phylogenetic studies recovered araeoscelidians as the most basal group of diapsids:
Cladogram after Bickelmann et al., 2009
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
Lopingian:
Orovenator from the Early Permian of Oklahoma.
Bibliography
