Araeoscelidia or Araeoscelida is a
clade of extinct
diapsid reptiles superficially resembling
lizards, extending from the Late
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous ...
to the Early
Permian.
The group contains the
genera ''
Araeoscelis
''Araeoscelis'' (from el, αραιά , 'thin' and el, σκελίς , 'ribs of beef') is an extinct genus of reptile, and one of the earliest diapsids. Fossils have been found in the Nocona, Arroyo and Waggoner Ranch Formations in Texas, datin ...
'', ''
Petrolacosaurus
''Petrolacosaurus'' ("rock lake lizard") is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, long reptile, and the earliest known reptile with two temporal fenestrae (holes at the rear part of the skull). T ...
'', the possibly aquatic ''
Spinoaequalis'', and less well-known genera such as ''
Kadaliosaurus'' and ''
Zarcasaurus
''Zarcasaurus tanyderus'' is a species of araeoscelid reptile found in the Cutler Formation (Early Permian) of New Mexico. The only elements of the skeleton known from this animal is a partial jaw bone, vertebra
The spinal column, a defini ...
''.
This clade is 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
sauropsid
Sauropsida ("lizard faces") is a clade of amniotes, broadly equivalent to the class Reptilia. Sauropsida is the sister taxon to Synapsida, the other clade of amniotes which includes mammals as its only modern representatives. Although early syna ...
s 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
''Araeoscelis'' (from el, αραιά , 'thin' and el, σκελίς , 'ribs of beef') is an extinct genus of reptile, and one of the earliest diapsids. Fossils have been found in the Nocona, Arroyo and Waggoner Ranch Formations in Texas, datin ...
'', only the upper temporal opening remains, thus resulting in a derived
euryapsid
__NOTOC__
Euryapsida is a polyphyletic (unnatural, as the various members are not closely related) group of sauropsids that are distinguished by a single temporal fenestra, an opening behind the orbit, under which the post-orbital and squamosal bo ...
condition.
Genera
Araeoscelidia includes well-known genera such as ''
Araeoscelis
''Araeoscelis'' (from el, αραιά , 'thin' and el, σκελίς , 'ribs of beef') is an extinct genus of reptile, and one of the earliest diapsids. Fossils have been found in the Nocona, Arroyo and Waggoner Ranch Formations in Texas, datin ...
''
Williston 1910, ''
Petrolacosaurus
''Petrolacosaurus'' ("rock lake lizard") is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, long reptile, and the earliest known reptile with two temporal fenestrae (holes at the rear part of the skull). T ...
''
Lane 1945 and ''
Spinoaequalis'', known from virtually complete skeletons. ''
Zarcasaurus
''Zarcasaurus tanyderus'' is a species of araeoscelid reptile found in the Cutler Formation (Early Permian) of New Mexico. The only elements of the skeleton known from this animal is a partial jaw bone, vertebra
The spinal column, a defini ...
'', ''
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
mesosaur
Mesosaurs ("middle lizards") were a group of small aquatic reptiles that lived during the early Permian period, roughly 299 to 270 million years ago. Mesosaurs were the first known aquatic reptiles, having apparently returned to an aquatic life ...
s.
New specimens have been discovered in Oklahoma, United States but so far lack a scientific description.
Phylogeny
Phylogenetic relationships:
The majority of phylogenetic studies recover araeoscelidians as
basal diapsids; however, Simões ''et al.'' (2022) recover them as
stem-
amniote
Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are distin ...
s instead, as the sister group to the clade including
Captorhinidae
Captorhinidae (also known as cotylosaurs) is an extinct family of tetrapods, traditionally considered primitive reptiles, known from the late Carboniferous to the Late Permian. They had a cosmopolitan distribution across Pangea.
Description
Cap ...
and ''
Protorothyris
''Protorothyris'' is an extinct genus of Early Permian protorothyridid known from Texas and West Virginia of the United States. It was first named by Llewellyn Ivor Price in 1937 and the type species is ''Protorothyris archeri''. ''P. archeri'' ...
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''). Apart from araeoscelidans, only one other diapsid is known before the
Late Permian
Late may refer to:
* LATE, an acronym which could stand for:
** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia
** Local-authority trading enterprise, a New Zealand business law
** Local average treatment effect, ...
: ''
Orovenator
''Orovenator'' is an extinct genus of diapsid from Lower Permian (Artinskian stage) deposits of Oklahoma, United States. It is known from two partial skulls from the Richards Spur locality in Oklahoma. The holotype OMNH 74606 consists of a ...
'' from the Early Permian of Oklahoma.
References
Further reading
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{{Taxonbar, from=Q136663
Prehistoric diapsids
Pennsylvanian first appearances
Cisuralian extinctions
Taxa named by Samuel Wendell Williston
Fossil taxa described in 1913