Major Find of Early Sauropod in Southern Utah

23 03 2010
This image is licensed under the Creative Commons Attribution License (CCAL), held by the authors of the original journal article (Joseph J. W. Sertich and Mark A. Loewen)

Seitaad ruessi, showing the parts of the skeleton found (light parts)

An important new species of prosauropod has been found in southern Utah.  While numerous and widespread in other parts of the world, this type of dinosaur is a rare find in North America.

Described in an article by Joseph J. W. Sertich and Mark A. Loewen, appearing on March 24, in the online journal PLoS One, the new species, named Seitaad ruessi, was an early ancestor of the sauropod dinosaurs.  It lived approximately 185 million years ago (during the lower Jurassic) and was approximately 10-to-15 feet long and 3-to-4 feet high.  Like most other prosauropods, S. ruessi was likely a herbivore.  It walked on its hind legs, with its front ones used for grasping.

While only the central portion of the skeleton was found, it none-the-less constitutes one of the most complete prosauropods found North America.

Prosauropods lived in the late Triassic and early Jurassic periods, eventually giving rise to the large sauropods that are so well known from the later Jurassic and Cretaceous periods.  They were widespread globally, specimens having been found throughout much of the world, though finds in North America have been scarce.  According to the journal article, prior to this find, only one taxon from eastern North America and several “fragmentary specimens” from the western part of the continent were known.

The scientists concluded that S. ruessi was “closely related to plateosaurid or massospondylid” and that “its presence in western North America is not unexpected for a member of this highly cosmopolitan clade.”

The find came to light in 2004, when an artist stumbled across it while studying rock paintings.  Scientists investigated the find immediately, and excavated the site the following year.  The bones were found protruding from the base of a sandstone cliff, directly beneath an ancient Anasazi cliff dwelling.  In honor of this, and the fact that the dinosaur’s body had been covered by a collapsing sand dune shortly after it died, the scientists derived the genus name Seitaad from the Navajo name “Seit’aad”, which was a sand monster in tribal legend, that buried its victims in dunes.

The species name, “ruessi”,  comes from the poet and naturalist Everett Ruess who disappeared in southern Utah in 1934.

The specimen comes from the Navajo Sandstone, which is not known for its dinosaur fossils.  While dinosaur specimens have been found in other Utah formations, they are rare in Navajo Sandstone, which is usually known for preserving other, smaller animals.

For more information, please see the PLoS One article at the following link:



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