Araeoscelidia

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 historical phylogenetic studies recovered araeoscelidians as the most basal group of diapsids, however this has recently been challenged, and it has been suggested that the araeoscelidians convergently evolved their diapsid condition separately from those of other diapsids (Neodiapsida). and Reisz et al., 2011, showing classical position of Araeoscelidia at the base of Diapsida sister to Neodiapsida:However, Simões et al. (2022) recover them as stem-amniotes instead, as the sister group to the clade including Captorhinidae and Protorothyris archeri. }}}}}}}}}}}}}}}}|label1=Reptiliomorpha}} Cladogram of Reptilia after Jenkins et al 2025, which found Araeoscelidia as the most basal group of sauropsids: |3= }} }} }} }} }} }} }} }} }}|style=|label1=Reptilia/Sauropsida}} ==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 ==