Prowling Predators of Poison Creek, Utah.

By Zach Sepulveda and Steven Wade Veatch

Around 190 million years ago dinosaurs crossed the dune fields in the Moab area, leaving tracks in the damp sands.  These tracks were rapidly covered by other dune sands and preserved them when the sand layers hardened to sedimentary rook over time.

Three therapods: Allosaurus, Eubrontes, and Grallator are thought to have made some of the tracks.  These theropods were three-toed predators that walked on two legs and used arms for holding and grasping.  The animals are estimated to be travelling three mph. There are tracks of at least ten different meat-eating dinosaurs preserved in blocks of the Jurassic Navajo Sandstone Formation.  The sandstone has eroded from the cliffs above and split along bedding planes that preserved them.  Both original tracks and the layer that filled them are present.

 

Some of the dinosaur tracks are noted by red rectangles.
Photo date 10/27/2012
 © by S. W. Veatch

 

Grallator is an ichnogenus (taxa based on footprints) of small, bipedal dinosaurs from the late Triassic and early Cretaceous period. They are found all over the world, but mostly on the east coast of the US.

Eubrontes is another ichnogenus of bipedal dilophosaurs from the east coast of the US from the early Jurassic. It would have been about one metre tall and 5-6 meters long. It is also the Connecticut state fossil. It is a junior synonym of Grallator.

Allosaurus is well known theropod dinosaur mostly from the US Morrison Formation, but has also been found in Portugal, and unconfirmed remains have been reported in Tanzania. It had an average length of 8.5 meters and would have weighed anywhere between 1,400 and 2,000 kilograms. The presence of extremely large upper neck muscles, and extremely wide gape, and small, blade-like teeth indicate that it may have hunted by "hatchetting" its prey to death by using its neck muscles to forcefully drive its upper jaw into prey, causing trauma and blood loss. The small size and relative simplicity of its teeth indicate they would have been easily replaced. It lived during the Jurassic alongside animals like Diplodocus, Stegosaurus, and Torvosaurus.

Author bios:

Zach Sepulveda has been a member of the Pikes Peak Pebble Pups and is an Earth Science Scholar in that program.  He is a published author and poet who has many interests.  He has taught several of the Pebble Pup classes and recently assisted with the Cool Science event at the University of Colorado, Colorado Springs.



Steven Wade Veatch has been a member of the Colorado Springs Mineralogical Society since 5th grade.  Because of his membership in the CSMS and their field trips he had a life-long passion for Earth science and eventually pursued an MS in Earth science. He has been the leader of the Pikes Peak Pebble Pups for over 20 years.