Segnosaurus is a genus of therizinosaurid dinosaur that lived in what is now southeastern Mongolia during the Late Cretaceous, about 102–86 million years ago. Multiple incomplete but well-preserved specimens were discovered in the Gobi Desert in the 1970s, and in 1979 the genus and species Segnosaurus galbinensis were named. The generic name Segnosaurus means "slow lizard" and the specific name galbinensis refers to the Galbin region. The known material of this dinosaur includes the lower jaw, neck and tail vertebrae, the pelvis, shoulder girdle, and limb bones. Parts of the specimens have gone missing or become damaged since they were collected.
Right half of the holotype mandible in outer and inner view, with component bones marked by different colors; the dentary bone (green) bore the teeth.
Life restoration
Skull and foot bones of Erlikosaurus, which together with Segnosaurus (both from Mongolia) became the basis of the new infraorder Segnosauria; this group is now a junior synonym of Therizinosauria.
Therizinosaurus, the first known therizinosaur, was originally known only from forelimb bones from Mongolia (cast shown here, in Aathal Dinosaur Museum), which created confusion about its affinities with other theropods.
Therizinosauridae is an extinct family of derived (advanced) therizinosauroid dinosaurs whose fossil remains have been found in mostly Late Cretaceous boundary. Even though representative fossils have only been found throughout Asia and North America, the range of Therizinosauridae is believed to have spanned much of the supercontinent of Laurasia based on several footprints and isolated remains in Europe and Africa. Currently, Therizinosauridae comprises eight described and named taxa.
Therizinosauridae
Holotype claw cast of Therizinosaurus (PIN 551–483)
Frontal view of the arms in Therizinosaurus IGM 100/15
Skeletal composite of two specimens of Alxasaurus
