Effigia okeeffeae

''Effigia'' was an extinct genus of shuvosaurid known from the Late Triassic of New Mexico, south-western USA. With a bipedal stance, long neck, and a toothless beaked skull, ''Effigia'' and other shuvosaurids bore a resemblance to the ornithomimid dinosaurs of the Cretaceous Period. However, shuvosaurids were not dinosaurs, but were instead a specialized family of poposauroid pseudosuchians, meaning that their closest living relatives are crocodilians.

Discovery

The 2-meter (6 ft 7 in) holotype fossil was collected by Edwin H. Colbert in 1947. At this time Colbert led an excavation to collect blocks of rock from the Whitaker Quarry of Ghost Ranch, near Abiquiu, New Mexico. Colbert's expedition intended to recover abundant fossils of the basal theropod dinosaur ''Coelophysis'', and he believed that no other large vertebrates were present in the quarry. As a result, his crew did not even open the plaster jackets of most of the blocks that were shipped to the American Museum of Natural History. The plaster jacket containing the holotype of ''Effigia'' started to be prepared in 2004, and the specimen was uncovered by graduate student Sterling Nesbitt at the AMNH. Nesbitt was opening jackets of blocks in order to find new specimens of ''Coelophysis''. Upon finding the remains of ''Effigia'', he instantly recognized this was not a dinosaur and proceeded to track down the rest of the blocks from that area of the quarry. Nesbitt and Mark Norell, curator at the museum, named it ''Effigia okeeffeae'' in January 2006 after Georgia O'Keeffe, who spent many years at Ghost Ranch.

Convergence

''Effigia'' is noted for its remarkable similarity to ornithomimid dinosaurs. In 2007, Nesbitt's description demonstrated that ''Effigia'' was very similar to ''Shuvosaurus'', and is definitely a member of the archosaur subgroup Pseudosuchia (the line leading towards modern crocodilians). Its similarity to ornithomimids represents a case of "extreme" convergent evolution. Nesbitt also demonstrated that ''Shuvosaurus'' was the same animal as ''Chatterjeea'', and that it belonged to an exclusive clade containing closely related suchians such as ''Shuvosaurus'' and ''Poposaurus'' (Poposauroidea). Within this group, ''Effigia'' forms an even more exclusive clade with ''Shuvosaurus'' and the South American ''Sillosuchus'' (Shuvosauridae).Nesbitt, S. (2007). "The anatomy of ''Effigia okeeffeae'' (Archosauria, Suchia), theropod-like convergence, and the distribution of related taxa." ''Bulletin of the American Museum of Natural History'', 302: 84 pp. http://digitallibrary.amnh.org/dspace/handle/2246/5840 In 2007, Lucas and others suggested that "''Effigia''" was synonymous with "''Shuvosaurus''" and used the new combination "''Shuvosaurus okeeffeae''" for the animal. This proposal has not been accepted by other archosaur workers.

Paleobiology

Examination of ''Effigia's'' jaws suggest it nipped and sheared off vegetation when feeding, due to its weak jaws and sharp beak. It was previously suggested that it pecked for food like ostriches or other ratites, but biomechanical studies have estimated that its skull could not withstand such forces.

References

External links

''Effigia'' at the website for the 2007 IMAX documentary, "Dinosaurs Alive!

Toothless Crocodile Relative, 210 Million Years Old, Walked On Two Feet (2006) - American Museum of Natural History press release


* ttps://www.nytimes.com/2006/01/26/science/26croc.html?_r=2 Fossil Yields Surprise Kin of Crocodiles (2006) – New York Times press release

{{Taxonbar, from=Q2324943

Poposauroids
Late Triassic archosaurs of North America
Prehistoric pseudosuchian genera