Araeoscelis gracilis (Williston 1910; Reisz, Berman and Scott 1984) ~275 mya, Early Permian, 60 cm long, was an early diapsid with closure of the lateral temporal fenestra. Derived from a sister to Petrolacosaurus Araeoscelis left no known descendants. The trend toward closure of the temporal fenestrae in early diapsids is also seen in Mesosaurus and Stereosternum.
Distinct from Petrolacosaurus, the skull of Araeoscelis had a slightly longer rostrum and more robust teeth. An advancing squamosal filled in the lateral temporal fenestra.
The cervicals were slightly more elongated. The torso was deeper and the tail was more gracile.
The robust pectoral girdle was much larger than the pelvis. Metatarsals II-IV aligned with p1.1.
The family tree of the Enaliosauria is here. The complete reptile family tree is here.