Ornithosuchians

Ornithosuchians were a group of archosaur reptiles that lived during the Triassic period. They are classified within the order Ornithosuchia and are notable for their unusual combination of features. Ornithosuchians possessed a semi-erect stance, meaning they could walk on either two or four legs. Their hind limbs were generally more robust than their forelimbs. A distinctive characteristic was their pelvic structure, which had a reversed pubis, a feature also found in birds, although this is considered a case of convergent evolution rather than direct ancestry.

The skull of ornithosuchians was also somewhat unusual. They had large supratemporal fenestrae, openings in the back of the skull, and a relatively short snout. Their teeth were serrated and generally leaf-shaped, indicating a carnivorous diet. While some ornithosuchians, like Ornithosuchus itself, were relatively small predators, others could reach larger sizes. They are considered to be within the broader crurotarsan radiation of archosaurs, meaning they are more closely related to crocodiles than to dinosaurs. The group is extinct and its precise evolutionary relationships within Archosauria are still a subject of scientific investigation.