''Shuvosaurus'' (meaning "Shuvo's lizard") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of beaked

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

of western

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

. Despite looking superficially similar to a

theropod dinosaur Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

, it is actually more closely related to

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

ns.

Discovery and classification

''Shuvosaurus'' was described by

Sankar Chatterjee Sankar Chatterjee (born May 28, 1943) is a paleontologist, and is the Paul W. Horn Professor of Geosciences at Texas Tech University and Curator of Paleontology at the Museum of Texas Tech University. He earned his Ph. D. from the University of ...

in 1993 after it was discovered by his son Shuvo in the early 1990s.Chatterjee, S. (1991) An unusual toothless archosaur from the Triassic of Texas: the world's oldest ostrich dinosaur? Abstract, Journal of Vertebrate Paleontology, 8(3): 11A. It was initially interpreted as a Triassic member of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

dinosaur family

Ornithomimidae Ornithomimidae (meaning "bird-mimics") is a family of theropod dinosaurs which bore a superficial resemblance to modern ostriches. Ornithomimids were fast, omnivorous or herbivorous dinosaurs known mainly from the Late Cretaceous Period of Lauras ...

because it had toothless jaws. Like the avian placement of ''

Protoavis ''Protoavis'' (meaning "first bird") is a problematic taxon known from fragmentary remains from Late Triassic Norian stage deposits near Post, Texas. Much controversy remains over the animal, and there are many different interpretations of what ...

'', the ornithomimosaur placement of ''Shuvosaurus'' was greeted with scepticism by others, and in their 1995 monograph on Late Triassic tetrapods from the American Southwest, Robert Long and Philip Murry considered ''Shuvosaurus'' to be possibly the same species as their new taxon ''Chatterjeea'', which was based on 10 postcranial skeletons that had been previously referred to the rauisuchid ''Postosuchus'' by Chatterjee (1985), noting that the ''Shuvosaurus'' and the ''Chatterjeea'' material didn't overlap in terms of available material. For his part, Rauhut (1997, 2000, 2003) agreed with Long and Murry (1995) in questioning the ornithomimosaur placement of ''Shuvosaurus'' but classified it as a basal theropod.Rauhut, O. W. M. (1997). "On the cranial anatomy of ''Shuvosaurus inexpectatus'' (Dinosauria: Theropoda)." In: Sachs, S., Rauhut, O. W. M. & Weigert, A. (eds) 1. ''Treffen der deutschsprachigen Palaeoherpetologen'', Düsseldorf, 21.-23.02.1997; Extended Abstracts. Terra Nostra 7/97, pp. 17-21. In the early 2000s, Sterling Nesbitt and Mark Norell prepared previously unopened jackets of an archosaur from the Whitaker Quarry at Ghost Ranch, which they named ''

Effigia ''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 ornithomim ...

'' in 2006. This discovery showed that ''Shuvosaurus'' is more closely related to crocodilians, and that similarities between this animal and ornithomimids result from

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

, while demonstrated that the taxon ''Chatterjeea'' was synonymous with ''Shuvosaurus''.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.

References

Poposauroids Late Triassic archosaurs of North America Chinle fauna Fossil taxa described in 1993 Prehistoric pseudosuchian genera {{triassic-reptile-stub