Tawa hallae
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Tawa Temporal range: Late Triassic, 215 Ma |
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| Life restoration | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | Saurischia |
| Suborder: | Theropoda |
| Genus: |
†Tawa Nesbitt et al., 2009 |
| Species: | †T. hallae |
| Binomial name | |
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Tawa hallae Nesbitt et al., 2009 |
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Tawa (named after the Hopi word for the Puebloan sun god) is a genus of theropod dinosaur from the Late Triassic period. The fossil remains of Tawa hallae were found in the Hayden Quarry of Ghost Ranch, New Mexico, USA. Its discovery alongside the relatives of Coelophysis and Herrerasaurus supports the hypothesis that the earliest dinosaurs arose in Gondwana during the early Late Triassic period in what is now South America, and radiated from there around the globe. The specific name honours Ruth Hall, founder of the Ghost Ranch Museum of Paleontology.
Tawa was estimated to have been 2 m (6.5 ft) long, almost 75 cm at the hips. Other estimates suggest that Tawa weighed 30 kilograms (66 pounds) at most. The holotype, a juvenile individual, cataloged GR 241, consists of a mostly complete but disarticulated skull, forelimbs, the pectoral girdle, a partial vertebral column, hindlimbs, the pelvic girdle, ribs, and gastralia. The determination was made that this specimen is a juvenile based on the presence of an open braincase and unfused neurocentral sutures. An isolated femur, GR 244, suggests that adults were at least 30% larger than the juvenile holotype. Tawa preserves characters that can be associated with different dinosaur taxa. Its skull morphology resembles that of coelophysoids and the illium approximates that of a herrerasaurid. Like the coelophysoids, Tawa has a kink in its upper jaws, between the maxilla and the premaxilla. With respect to limb proportion, the femur is very long compared to the tibia. A neck vertebrae adaptation in Tawa supports the hypothesis that cervical air sacs predate the origin of the taxon Neotheropoda and may be ancestral for Saurischians, and also links the dinosaurs with the evolution of birds. Compared to earlier dinosaurs like Herrerasaurus and Eoraptor, Tawa had a relatively slender build.
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