The infraorder Segnosauria was named in 1980 for some strange new dinosaurs
that had just been found in Mongolia. These were lightly built meat-eaters with
curious skulls. The most unusual feature was the hip, which was not at all like
a typical saurischian lizard hip: the two bones at the bottom both ran backward
and side-by-side, instead of pointing in opposite directions.
Segnosaurus is known from a skull and partial skeleton. The skull has
sharp teeth at the back for eating meat, but no teeth at the front of the jaw,
which is very strange. Each foot had four toes, and the hip was quite unusual
in shape. In Segnosaurus, the hip looks rather like that of an ornithischian
dinosaur, rather than a saurischian. The primitive three-pointed lizard hip
has become a two-pointed bird hip. However, in detail it is clear that Segnosaurus
is still a saurischian dinosaur. The scientists who named Segnosaurus
in 1979 suggested that it might have been a swimmer and that it fed on fish.