Tawa

Name: Tawa ‭(‬Named after the Puebloan sun god‭)‬.
Phonetic: Tah-wah.
Named By: Sterling J.‭ ‬Nesbitt et al‭ ‬-‭ ‬2009.
Classification: Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Saurischia,‭ ‬Eusaurischia,‭ ‬Theropoda.
Species: T.‭ ‬hallae‭ (‬type‭)‬.
Diet: Carnivore.
Size: Estimated about‭ ‬2‭ ‬meters long.
Known locations: USA,‭ ‬New Mexico‭ ‬-‭ ‬Chinle Formation,‭ ‬Ghost Ranch.
Time period: Norian of the Triassic.
Fossil representation: At least eight individuals represented by partial skeletons.

       Tawa is yet another dinosaur genus from the late Triassic of the Ghost Ranch North America,‭ ‬and as you might expect,‭ ‬one quite primitive in form.‭ ‬Tawa were bipedal dinosaurs of the theropod line,‭ ‬noted for having femurs that were proportionately quite long when compared to the lower leg bones.‭ ‬Tawa also had a kink between the maxilla and premaxillae,‭ ‬the tooth bearing bones of the upper jaw.‭ ‬This means that in life Tawa may have had a notch in the upper jaw similar to Dilophosaurus of the early Jurassic,‭ ‬though perhaps not quite as pronounced.‭ ‬Tawa are also noted as having a more slender build compared to other‭ ‬early dinosaurs,‭ ‬a trait that would continue to some later descendants.
       One area of interest about Tawa which has wider implications for other dinosaurs,‭ ‬is that the neck vertebrae are known to have air sacs,‭ ‬almost identical to the air sacs of birds.‭ ‬This reveals that Tawa had an avian like‭ (‬bird-like‭) ‬respiratory system,‭ ‬something which has been seen in other dinosaur genera such as the sauropodomorph Plateosaurus and the late Cretaceous theropod Aerosteon.‭ ‬The presence of an avian-like respiratory system in Tawa however is an indication that this system first evolved in the early dinosaurs of the Triassic.‭ ‬This is also yet further support for the theory that birds are directly evolved from dinosaurs,‭ ‬and is an indicator the avian respiratory system is at least as old as the late Triassic.‭ ‬This kind of respiratory system also suggests that Tawa had an endothermic metabolism,‭ ‬meaning that it lived more as a‭ ‘‬warm-blooded‭’ ‬creature than a‭ ‘‬cold-blooded‭’ ‬one.
       In terms of evolutionary placement,‭ ‬Tawa seems to have been more advanced than forms such as Eoraptor and Herreasaurus,‭ ‬but not as advanced as other dinosaur genera like Coelophysis.‭ ‬Also,‭ ‬because Coelophysis is known to have lived in the same time and locations as Tawa,‭ ‬then it raises the notion that Tawa may have been a late surviving form.
       The point of origin of the Dinosaurs is still thought to have been South America since this is where the oldest true dinosaur genera are known from.‭ ‬However the discovery of Tawa has helped to establish that by the late Triassic there were at least several genera of early dinosaurs living in North America.‭ ‬Dinosauromorph reptiles‭ (‬similar to dinosaurs but not quite dinosaurs‭) ‬are also starting to be discovered in higher numbers,‭ ‬and in the future Africa may‭ ‬also‭ ‬become a key area of study in our wider understanding of early dinosaur evolution.

Further reading
-‭ ‬A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs,‭ ‬S.‭ ‬J.‭ ‬Nesbitt,‭ ‬N.‭ ‬D.‭ ‬Smith,‭ ‬R.‭ ‬B.‭ ‬Irmis,‭ ‬A.‭ ‬H.‭ ‬Turner,‭ ‬A.‭ ‬Downs‭ & ‬M.‭ ‬A.‭ ‬Norell‭ ‬-‭ ‬2009.



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