ScienceDaily (May 31, 2010) — More than 100 years ago paleontologist E. D. Cope of "Dinosaur Wars" fame found a few fragmentary bones of a reptile in the deserts of New Mexico. He named the reptile Typothorax. A century later Typothorax, which belongs to a group of reptiles called aetosaurs, remained something of a mystery, known mainly from pieces of armor, a few limb bones, and some sections of tail.
Paleontologists are finally revealing what Typothorax really looked like, how large it was, how it walked, and myriad other questions. Typothorax is also one of the last large herbivores to evolve in the Late Triassic, before dinosaurs would come to dominate the planet.
(Credit: Image courtesy of Society of Vertebrate Paleontology)
Reminiscent of giant armadillos, aetosaurs were widespread during Late Triassic times (230 -- 200 million years ago). The largest species of aetosaur grew up to 5 meters long, although the two new specimens, representing a species called Typothoraxcoccinarum, were smaller growing up to 2.5 meters long. All were covered by a protective armor of overlapping bony plates, but some species sported massive spikes protecting the neck region -- an additional deterrent to any hungry predator. Fragments of the characteristic bony armor are well known to paleontologists, but complete specimens of any aetosaur are very rare and none were known for Typothorax prior to the discovery of these specimens. The ornamentation on the plates varies from species to species and paleontologists have long recognized them as a diverse and important group of plant eaters living alongside some of the earliest dinosaurs. However, because of the rarity of more complete material they remain something of an enigma. Now we can say a lot more about these strange creatures which Dr. Andy Heckert, the lead author of the study and a geology professor at Appalachian State University, regards as an "animal designed by a committee combining a crocodile with a cow and armadillo."
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Authors: Andrew B. Heckert a; Spencer G. Lucas b; Larry F. Rinehart b; Matthew D. Celeskey b; Justin A. Spielmann b;Adrian P. Hunt b
Affiliations: a Department of Geology, Appalachian State University, Boone, North Carolina, U.S.A.
b New Mexico Museum of Natural History and Science, Albuquerque, New Mexico, U.S.A.
DOI: 10.1080/02724631003763524
Published in: Journal of Vertebrate Paleontology, Volume 30, Issue 3 May 2010 , pages 619 - 642
Abstract
We report two nearly complete, articulated skeletons of the crurotarsan archosaur Typothorax coccinarum from the Upper Triassic Bull Canyon Formation of east-central New Mexico. These are the most complete, articulated aetosaurs from North America and provide a wealth of new anatomical and paleobiological data, including articulated presacral armor that confirms the distinctiveness of T. coccinarum from the closely related T. antiquum and from Redondasuchus. Cervical vertebrae are small, but the corresponding reduction in armor is accomplished by a reduced number of cervical osteoderms. The third row of osteoderms includes a thin, elongate, lateral spike. The ventral armor consists of 10 thoracic columns and four caudal columns of osteoderms. Spiked osteoderms near the cloacal vent are the first spikes reported in aetosaurian ventral osteoderms. The forelimb of T. coccinarum was very short, only ∼0.65 the length of the hind limb, possesses some adaptations found in digging taxa, and was held in a sprawling or 'semi-erect' position. In contrast the hind limb is much more robust, 'pillar erect,' and functionally mesotarsal. The articulated pes, including unguals, has, minimally, the phalangeal formula 2-3-3?-4?-3? with relative digit lengths III > II > IV > I > V, digits I-IV equally as wide as long and other characteristics of the footprint ichnogenus Brachychirotherium, often attributed to an aetosaurian trackmaker. Both specimens are ∼2.5 m long and the preserved armor and limb bones are as large or larger than known Typothorax fossils, suggesting that this approximates the upper size limit of T. coccinarum, and we calculate body mass estimates of ∼100-104 kg for both specimens.
