Araeoscelis gracilis (Williston 1910; Reisz, Berman and Scott 1984) ~275 mya, Early Permian, 60 cm long, was an early diapsid described with closure of the lateral temporal fenestra--but that may not be true on closer examination. 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. The quadrate articulation was far below the jaw line.
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.