Segnosaurus is a genus of therizinosaurid theropod dinosaur that lived in what is now Mongolia and China during the Late Cretaceous period, approximately 102–86 million years ago.
Segnosaurus was a large-bodied therizinosaur, estimated at approximately 6–7 metres in length and 1.3 tonnes in body mass. It was bipedal, with an upward-sloping torso, a small head with a beak at the front of the jaws, and a long, slender neck. Its lower jaw curved downwards at the front. Its teeth had additional denticles, and some rear teeth had a third cutting edge. The robust forelimbs bore three fingers with very large claws. Its feet had four weight-bearing toes, unlike the three-toed feet typical of other theropods.
Segnosaurus and its relatives such as Therizinosaurus were slow-moving animals that, as their unusual characteristics indicate, were primarily herbivorous, occasionally omnivorous, while most other theropod groups were carnivorous. Segnosaurs probably used their long forelimbs, long necks, and beaks to feed on the vegetation in the trees.
Dinosaur eggs containing embryos, assigned to the egg type Dendroolithus from the Nanchao Formation in China were identified as belonging to therizinosaurs and described by Martin Kundrát and his colleagues in 2007. The development of the embryos and the fact that no adults were found associated with the nests indicate that the therizinosaur hatchlings were precocial (capable of locomotion at birth) and could leave their nests to feed themselves independently of their parents.
