Angelosaurus

Angelosaurus dolani ('Dolan's Angel lizard', Olson & Berrbower 1953) was a pelycosaur (an extinct clade) of reptile. It is known from a partial skull from the Middle San Angelo Formation, Knox County, Texas, USA. It dates from the Kungurian (Early Permian). It was from three to three and a half metres long and weighed about 300 kilograms. It belongs to the family Caseidae. Like its contemporary, another caseid, Cotylorhynchus, it was large, heavily built, and herbivorous. It also shared its environment with the caseids Caseoides and Caseopsis. It may have been preyed upon by the large sphenacodont pelycosaur Dimetrodon.

Like all caseids, Angelosaurus was an evolutionarily conservative reptile which would appear to have been one of the dominant herbivores of the time, occupying a similar ecological role to cows. Caseid skulls are distinguished from other pelycosaurs by large temporal openings, large nasal and pineal openings and an upper jaw that distinctively overhangs the teeth of the lower jaw.The skull is pitted. The teeth are uniform. The body was probably barrel-shaped, like other caseids, with massive limbs and small cervical vertebrae. And unlike the more well-known pelycosaurs such as Dimetrodon and Edaphosaurus, caseids do not have the exaggerated elongation of the vertebrae that form a sail.

Two other species of Angelosaurus have been described so far: Angelosaurus greeni Olson 1962, and Angelosaurus romeri Olson and Barghusen, 1962.