Therizinosauridae

Therizinosaurids Temporal range: Late Cretaceous, 94–66 Ma Possible Early Jurassic record PreЄ Є O S D C P T J K Pg N
Reconstructed skeleton of Nothronychus mckinleyi
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Superfamily:	†Therizinosauroidea
Family:	†Therizinosauridae Maleev, 1954
Type species
Therizinosaurus cheloniformis Maleev, 1954
Genera
See text.
Synonyms
Segnosauridae Perle, 1979 Enigmosauridae Barsbold & Perle, 1983 Nanshiungosauridae Dong & Yu, 1997

Therizinosauridae ("reaper lizards") is a family of advanced herbivorous or omnivorous theropod dinosaurs. Therizinosaurid fossil remains have been recovered from mid-late Cretaceous Period deposits from Mongolia, China, and the United States.

Classification

The family Therizinosauridae was coined by Evgeny Maleev in 1954 to contain the enigmatic Therizinosaurus cheloniformis, which Maleev originally thought to be a species of giant "turtle-like lizard."^[1] It was long considered a strange, probably carnivorous, species. Relatives of Therizinosaurus were later found but not recognized as such for some time. These more complete specimens were herbivores, and had a bizarre mixture of what looked to early researchers like a mix between ornithischian and "prosauropod" dinosaurs. Collectively, these were included in the family Segnosauridae, or "slow lizards", due to their heavy bodies, short legs, and presumably slow, ground sloth-like lifestyle.^[2] Subsequent studies found that segnosaurids were neither prosauropods nor ornithischians, but actually bizarre theropods, and that the previously enigmatic Therizinosaurus was also a member of this group. Since the family Therizinosauridae was named earlier than Segnosauridae, the later name became a junior synonym of the former, despite the fact that Therizinosaurus was a new addition to the segnosaurid group.^[3]

Therizinosauridae was first given a phylogenetic definition by Paul Sereno in 1998, who defined it as all dinosaurs closer to Erlikosaurus than to Ornithomimus. As the relationship of therizinosaurids to other theropods clarified and more members of the larger therizinosaur group were found, a more restrictive definition has come to be preferred for the family-level name Therizinosauridae. Sereno himself, for example, re-defined the name in 2005 as the clade containing Therizinosaurus cheloniformis, Nothronychus mckinleyi, and Neimongosaurus yangi.^[4]

Taxonomy

• Family Therizinosauridae
  • Enigmosaurus
  • Erliansaurus
  • Erlikosaurus
  • Nanshiungosaurus
  • Neimongosaurus
  • Nothronychus
  • Segnosaurus
  • Suzhousaurus
  • Therizinosaurus (type)

Phylogeny

The cladogram presented here follows a 2007 phylogenetic analysis by Phil Senter.^[5]

Therizinosauridae	Erliansaurus Nothronychus unnamed Neimongosaurus unnamed Segnosaurus unnamed Erlikosaurus Therizinosaurus

See also

• Timeline of therizinosaur research

References

1. Maleev, E. (1954). "New turtle-like reptile in Mongolia." Priroda, 1954: 106-108.
2. Perle, A. (1979). "Segnosauridae—a new family of theropods from the Late Cretaceous of Mongolia." Trans. Joint Soviet–Mongolian Palaeontological Expedition, 8: 45–55.
3. Clark, J. M., Perle, A. & Norell, M. A. (1994). "The skull of Erlicosaurus andrewsi, a Late Cretaceous ‘‘Segnosaur’’ (Theropod: Therizinosauridae) from Mongolia." American Museum Novitates, 3115: 1–39.
4. Sereno, P. C. 2005. Stem Archosauria—TaxonSearch [version 1.0, 2005 November 7]
5. Senter, P. (2007). "A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)." Journal of Systematic Palaeontology, (doi:10.1017/S1477201907002143).