Petrolacosaurus kansensis

Petrolacosaurus is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, 40-centimetre long reptile, and the earliest known reptile with two temporal fenestrae. This means that it was at the base of Diapsida, the largest and most successful radiation of reptiles that would eventually include all modern reptile groups, as well as dinosaurs and other famous extinct reptiles such as plesiosaurs, ichthyosaurs, and pterosaurs. However, Petrolacosaurus itself was part of Araeoscelida, a short-lived early branch of the diapsid family tree which went extinct in the mid-Permian.

The first Petrolacosaurus fossil was found in 1932 in Garnett, Kansas by a field expedition from the University of Kansas Natural History Museum. The party consisted of Henry H. Lane, Claude Hibbard, David Dunkle, Wallace Lane, Louis Coghill, and Curtis Hesse. Unfortunately, no field notes or documentation of their discovery are available. Petrolacosaurus fossils were found preserved within a layer of laminated shale that was also plant bearing.
 * Skull Specimens reveal that Petrolacosaurus had a slightly elongated skull with two temporal fenestrae. The upper temporal fenestra is located posteriorly to an enlarged orbit. This is a distinctly diapsid character. The largest teeth in the jaw were at the front of the snout, erupting.
 * Axial skeleton There are seven elongated cervical vertebrae, 2 sacrals, and 60 caudal vertebrae. The number and placement of the vertebrae show that Petrolacosaurus was a rather long-necked reptile with a shorter torso. The number and spool-like shape of the vertebrae, in addition to the poses.
 * Pectoral girdle The pectoral girdle in Petrolacosaurus is light in comparison to the massive girdles found in taxa such as pelycosaurs. Petrolacosaurus specimens had a clavicle with an expanded ventral blade, yet shorter than that of Captorhinus or pelycosaurs.
 * Petrolacosaurus is a member of the basal diapsid order Araeoscelidia, along with the aquatic, late Pennsylvanian Spinoaequalis. The specific taxonomic placement of Petrolacosaurus is a highly debated topic. Because of the unusual osteological characters and how old the reptile is, scientists go back and forth between what position makes the most sense.


 * Diet Petrolacosaurus teeth were of moderate length, slightly recurved, and possessed no lateral compression. Located on the premaxilla of the upper jaw are two teeth, reminiscent of fangs. On the dentary were around 25 smaller teeth, all of different lengths. Placement in the jaw.
 * Environment The mud that the reptile was fossilized in is known to create well preserved insect and plant prints, allowing extrapolation about the surrounding environment. Because of fossil evidence of winged insects, the fruits of conifers, and other pteridosperms, Petrolacosaurus is though.