A Voyage of Discovery on an Ancient Sand Sea

14 January 2013 Written by  Dan Chure

Utah is an undeniably hot and arid place, but in the Early Jurassic, 190,000,000 years ago, things were much worse. At that time a vast sea of desert sand covered some 850,000 square miles of intermountain west. In northeastern Utah, the sediments of that desert are known to geologists as the Nugget Sandstone.

Despite being an extreme and generally inhospitable environment, over time, plants and animals evolved and adapted to live there. To understand more about how this transition took place , a group of paleontologists and students from Dinosaur National Monument, the University of Nebraska, Brigham Young University, and the University of Utah, has been investigating the area for the past several years. Nugget field work is not for the faint of heart. Patience and perseverance is essential and you must be prepared for many hot and frustrating days when no fossils can be found. But hey, if working in the Nugget was easy someone would have already done the research!

Left to right, Drs. George Engelmann (University of Nebraska), Dan Chure (Dinosaur National Monument), and Brooks Britt (Brigham Young University) at the Saints and Sinners Quarry.

Much of what we know comes from trace fossils, the trails, trackways, and burrows made by animals going about their lives in and around the dune fields. We have found the trackways of various kinds of herbivorous and carnivorous dinosaurs. At one site, hundreds of Brasilichnium footprints record the ancient passage of small mammal-like reptiles as they walked up the steep fronts of large dunes. As in modern deserts, arthropods were common, and we have numerous trails of scorpions and spiders, as well as small burrows made by adult and larval arthropods of various types, and burrows of large scorpions. In most cases, trace fossils are the only evidence we have of those organisms.

A small Brasilichnium footprint in the Nugget Sandstone.

Then there are those moments when the miraculous happens. I will never forget the day we found the Saints and Sinners Quarry --- stepping onto a sandstone surface and spying more than fifty dinosaur bones naturally exposed. In that instant we knew we had made the find of a lifetime. We eventually uncovered a phenomenal deposit of thousands of bones preserved in a small desert lake. Most of these fossils belong to a new, small, predatory dinosaur, but bones of several other kinds of small reptiles have also been recovered. While optimism is essential for paleontologists, never, in our wildest dreams, did we imagine finding such a treasure trove of fossils! This one quarry has produced orders of magnitude more bones than all previous work in the rocks of this ancient desert.

A spectacularly complete foot of a small reptile from the Saints and Sinners Quarry.

Uncovering the abundance at Saints and Sinners Quarry was just the beginning. Our diverse group continues to explore, excavate, prepare, map, and analyze the remarkable fossils of this ancient desert, from SSQ and beyond. Work continues in both the field and in the lab, and the first manuscripts about our SSQ findings are in preparation. But more remains to be done and summer field work is approaching. Who knows what that may bring?

Part of a long scorpion trackway (Paleohelcura) from the Nugget Sandstone.
The upper jaw of a carnivorous dinosaur from the Saints and Sinners Quarry.
Footprint of a large predatory dinosaur in the Nugget Sandstone.
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