Randall Irmis, curator of paleontology at the Natural History Museum of Utah and an assistant professor at the University of Utah, is investigating the rise of dinosaurs in southeastern Utah.
Tuesday, Aug. 21
Taking in the awe-inspiring arid vistas of canyons, mountains and deserts in the American Southwest, it?s difficult to imagine that this was once an area that teemed with giant reptiles and amphibians.
In these places, traveling back in time some 200 million years (give or take a couple of million), some of the earliest dinosaurs could be found. But this wasn?t yet the time of their dominance, with giant dinosaurian behemoths roaming the landscape. Instead, it was the age of crocodilians.
Over the next three weeks, I?ll be part of a team investigating this ancient alien world as it is preserved in some of the red rocks of southeastern Utah that are 200 million to 215 million years old. We?re hoping to discover new fossils that will tell us about the different creatures (both crocodilian and dinosaurian, as well as fishes and amphibians) that lived during this time, and what kind of environment and climate they lived in.
During the Triassic Period, between 252 million and 201 million years ago, the reptiles on land were dominated by early relatives of modern crocodiles and alligators. But these animals were not your typical sprawling aquatic predators that haunt today?s B-movie horror flicks. Instead, they were a disparate bunch of beasts, including sail-backed predators called ctenosauriscids, armadillolike herbivores named aetosaurs, and weird beaked forms that walked on two legs, like Effigia.
These crocodile ancestors ruled the land for 50 million years in the wake of the greatest mass extinction of all time at the end of the Permian Period, 252 million years ago.
The earliest dinosaurs appeared 230 million years ago, yet for the first 30 million years of their evolutionary history, most were small, scrawny creatures that would have made easy lunch for their larger crocodilian brethren. In some places, like South America, Europe and Africa, larger dinosaurs became more numerous by 215 million to 210 million years ago, but here in North America, dinosaurs didn?t take over until 200 million years ago, after another mass event called the end-Triassic extinction .
Our team is interested in why dinosaurs became so successful for the next 100 million years, and specifically why they took so long to rise to dominance in North America compared with other parts of the Triassic world. The rocks we?re searching in Utah preserve the time just before this transition, and will help us understand how these ancient ecosystems evolved through time.
This research is supported by a grant from the National Geographic Society?s Committee for Research and Exploration, and is conducted with research permits from the Bureau of Land Management.
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