Foster found the fossil bone in 2005 on Bureau of Land Management property in the Chinle Formation, located just north of Moab. It was more or less an average day for Foster and a volunteer, Ray Bley, when they stumbled upon the unique find.
“It was a blind-luck find in a way,” Foster said. “We knew the rock type to look at and we were specifically looking for reptiles in the Chinle, but most that are found in that unit are non-dinosaurs. I was looking for teeth and bones exposed and visible on loose blocks of rock, and my assistant ... decided to chisel open a similar rock but one that had no indication of bone on or in it. You could do that a thousand times and see only scrap, but Ray split a chunk off and said ‘What’s this?’ I walked over and there they were, the fused vertebrae of a dinosaur.”
The fused vertebrae they found is part of the pelvis of a dinosaur similar to the Coelophysis, a small, flesh-eating dinosaur found previously in New Mexico and Arizona. Scientists have suspected this dinosaur would have been found in Utah, but Foster’s find is the first evidence confirming the suspicion. After Foster and Bley unearthed the fossil, a team of three paleontologists set out to determine its origin. Joining Foster were Arizona State University’s Xavier Jenkins and Colorado Canyons Association’s Robert Gay.
“There are plenty of footprints that suggest these predatory dinosaurs were around during this important time, but footprints can be affected by lots of factors, and many non-dinosaurian reptiles of the time had very similar feet,” Gay said. “The few bones that have been found previously in Utah and called ‘dinosaurs’ were really scrappy, and we can’t actually be sure that they really came from dinosaurs. The Triassic Period in Earth’s history is critical because it spans the rise of dinosaurs from these small creatures to those that dominate pretty much every land ecosystem five million years later.”
The team of paleontologists — Foster, Jenkins and Gay — carried on a comparison study that was published in the Utah Geological Association’s journal Geology of the Intermountain West. The study concluded the fossil did indeed belong to a small, meat-eating dinosaur from the late Triassic Period, which occurred 225 to 200 million years ago.
“The Triassic Period marks the beginning of the age of dinosaurs,” said Julia McHugh, curator of paleontology for the Museums of Western Colorado. “This fossil helps give us a starting point for their evolution and diversity in the Triassic of Utah. This specimen is the oldest known dinosaur bone from Utah, and the first found from the Triassic Period. It helps to fill in some of the gap to show us that for sure some of the oldest dinosaurs were present in ancient Utah.”
Other suspected Triassic dinosaur specimens previously found in Utah have been fragmented, and the ambiguity and lack of evidence for these samples has prevented definitive age classification.
“I think what this helps illustrate very well is that the rise of dinosaurs was rather gradual and that for some time after their first appearance, dinosaurs were in fact very rare,” Foster said. “Evidence of large reptiles is found all over the Moab area in the Chinle Formation, but it took until now to find one that is definitely a dinosaur. And this pattern of actual dinosaurs being rare is true in the Triassic in places like Arizona too.”
The study can be accessed for free at utahgeology.org/openjournal/index.php/GIW/article/view/22.