Therizinosaur
Therizinosaurs [1] (or segnosaurs) are a clade of theropod dinosaurs which appear to be herbivorous.
| Therizinosaurs Temporal range: Cretaceous, 130–65.5 mya, possible Lower Jurassic record
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Therizinosaur fossils have been found in Cretaceous deposits in Mongolia, the People's Republic of China and Western North America. Various features of the forelimbs, skull and pelvis show they are theropods and maniraptorans, close relatives to birds.
History
Early finds were incomplete, and showed strange anatomy with features typical of theropods, prosauropods and ornithischians. This led some scientists to think that segnosaurs were a late-surviving suborder of primitive dinosaurs.[2]
It was not until the mid-1990s, that their true identity as herbivorous descendants of the carnivorous theropods became generally accepted. Alxasaurus was discovered, and had more typical theropod features; and Therizinosaurus was recognized as a member of the segnosaur group.[3]
The connection between the therizinosaurids and other theropods was made clear when primitive members of the group, such as Beipiaosaurus (1999) and Falcarius (2005) were discovered.[4] The scientists who described Falcarius noted that it seemed to represent an intermediate stage between carnivorous and herbivorous theropods, a sort of "missing link" between predatory maniraptorans and plant-eating therizinosaurs.[5]
Although they are now classified as theropods, therizinosaurs had skulls similar to those of sauropods and the shape of their teeth and jaws do make it likely that they were herbivores.
Therizinosaur Media
Forelimbs of Therizinosaurus, specimen IGM 100/15 displayed at Nagoya City Science Museum
Outdated restoration of a prosauropod-like, quadrupedal Erlikosaurus. Therizinosaurs were often depicted this way until they were definitively identified as theropods
Reconstructed skeleton of Alxasaurus from China, the completeness of which confirmed therizinosaurs as theropods in 1993
Partial forelimb of the basal therizinosaur Beipiaosaurus with impressions of feather structures, Paleozoological Museum of China
Holotype lower jaw of Eshanosaurus
Size comparison of several therizinosaurids
Hips from different genera
Skeletons of various genera (not to scale)
Life restoration of the primitive therizinosaur Falcarius, Early Cretaceous.
References
- ↑ The name therizinosaur is derived from the Greek therizo meaning 'to reap' or 'to cut off' and sauros meaning 'lizard'. The older name segnosaur is derived from Latin segnis meaning 'slow' or 'sluggish' and Greek sauros meaning 'lizard'.
- ↑ Paul G.S. 1988. Predatory dinosaurs of the world: a complete illustrated guide. New York: Simon and Schuster. p464
- ↑ Russell, D.A.; Dong, Z. (1993). "The affinities of a new theropod from the Alxa Desert, Inner Mongolia, People's Republic of China. In Currie P.J. ed". Results from the Sino-Canadian Dinosaur Project. Canadian Journal of Earth Sciences. 30: 2107–2127.
- ↑ Xu, X.; et al. (1999). "A therizinosauroid dinosaur with integumentary structures from China". Nature. 399 (6734): 350–354. Bibcode:1999Natur.399..350X. doi:10.1038/20670. S2CID 204993327.
- ↑ Kirkland, J.I.; et al. (2005). "A primitive therizinosauroid dinosaur from the early Cretaceous of Utah" (PDF). Nature. 435 (7038): 84–87. Bibcode:2005Natur.435...84K. doi:10.1038/nature03468. PMID 15875020. S2CID 4428196.