Typothorax: Prehistoric Animal of the Week

Greetings from New Mexico!  This week we shall be checking out an animal that Gary and I actually work with and dig up in the field.  Introducing Typothorax coccinarum!  Typothorax was not a dinosaur, but a relative of modern crocodilians, called an aetosaur.  It was closely related to its fellow aetosaur, Desmatosuchus, and more distantly to Postosuchus and Shuvosaurus.  Typothorax lived 200 million years ago during the late Triassic period in what is now the Southwestern United States.  It would have been mostly a plant-eater and measured about eight feet long from snout to tail.  When alive it would have coexisted with other Triassic reptiles like Redondasaurus, a still unnamed species of Shuvosaurus, and the dinosaur, Coelophysis. 

Typothorax coccinarum life reconstruction by Christopher DiPiazza.

Typothorax, like all known aetosaurs, possessed a body that was covered in broad plates of bony armor, called scutes.  These scutes were similar to what we see on modern crocodilians, but they were much broader and covered more surface area of the aetosaur's body.  Typothorax had two rows of wide, rectangular plates running down the surface of its back, small, shallow spike-shaped scutes lining the sides, smaller scutes covering its belly, jagged scutes on the tail, and tiny, almost square-shaped armor bits on its legs.  It wouldn't have been able to move very quickly because of all this but hey, when an animal is that well protected, it had little need to.  It even had a series of small armor plates surrounding its cloaca!  (reptilian equivalent of a butt hole)

Typothorax armor and limb bones on display at the Mesalands Dinosaur Museum in New Mexico.

Typothorax had a narrow snout that was upturned at the tip, somewhat like a modern pig's nose.  This suggests that it may have plowed around in the earth with its snout for roots and possibly insects for food.  The proportions of its arms, which possessed shorter forearms and were angled to the sides, also suggests that it was a powerful digger.

Back armor plat from a juvenile Typothorax about to be collected from the field.

In the field, remains from Typothorax are some of the more common fossils that we find in the Redonda Formation.  Of these, we most commonly get pieces of armor plating.  Last year our team found a scute from a Typothorax's back that was about a foot wide!  Hopefully this year we will find more fossils from this amazing reptile!

 That is all for this week!  For more on Typothorax and its environment check out my article about our trip to New Mexico last year.  As always feel free to comment below or on our facebook page.  Farewell until next time!

References

Heckert, A. B.; Lucas, S. G. (1999). "A new aetosaur (Reptilia: Archosauria) from the Upper Triassic of Texas and the phylogeny of aetosaurs". Journal of Vertebrate Paleontology 19 (1): 50–68. doi:10.1080/02724634.1999.10011122.

Heckert, A.B.; Lucas, S.G.; Rinehart, L.F.; Celesky, M.D.; Spielmann, J.A.; and Hunt, A.P. (2010). "Articulated skeletons of the aetosaur Typothorax coccinarum Cope (Archosauria: Stagonolepididae) from the Upper Triassic Bull Canyon Formation (Revueltian: early-mid Norian), eastern New Mexico, USA". Journal of Vertebrate Paleontology 30 (3): 619–642. doi:10.1080/02724631003763524.

Martz, J.W. 2002. The morphology and ontogeny of Typothorax coccinarum (Archosauria, Stagonolepididae) from the Upper Triassic of the American southwest. M.S. thesis, Geosciences, Texas Tech University, Lubbock, 279 pp.