In such bipedal creatures the legs and pelvis became transformed to a condition similar to that of Dinosaurian reptiles.
Certain footprints in the coal measures of Kansas have been supposed to belong to lacertilian or dinosaurian forms.
The separation of the Ratitae from the other birds, and their seemingly fundamental differences, notably the absence of the keel and of the power of flight, induced certain authors to go so far as to derive the Ratitae from the Dinosaurian reptiles, whilst Archaeopteryx (q.v.) and the Carinatae were supposed to have sprung from some Pterosaurian or similar reptilian stock.
The imprints in the enormously older new red sandstone or Lower Trias of Connecticut, and originally named Ornithichnites, belong to Dinosaurian Reptiles.