Everybody knows Moab is home to one of the greatest dinosaur fossil records on the planet, but what was the area like before then? Say, 300 to 330 million years ago?
That’s the question Randy Irmis answered at the latest lecture sponsored by the Canyonlands Natural History Association and the Moab Museum at the Moab Information Center July 11.
Irmis, the chief curator, curator of Paleontology and an associate professor of Geology and Geophysics at the University of Utah, portrayed a Grand County that was tropical, on the edge of desert dunes, where the climate was going through a big change.
There were no continents 300 million years ago. Instead, there was one primary landmass, the supercontinent Pangaea. North America was much closer to the Equator and Moab was on the west coast of an inland ocean.
Earth had transitioned from an icehouse to a hothouse after the polar ice caps melted completely away, carbon dioxide levels were relatively high before they returned to pre-Industrial Revolution levels. Mammals and amphibians shared the land while reptiles were not yet in play – according to the fossils uncovered in Indian Creek in San Juan County near the confluence of the Green and Colorado rivers.
It was there they found in the rock fish teeth, skulls and partial skeletons – ancient amphibians that are distant relatives to modern amphibians, seeds, leaves and petrified wood. Irmis said he and his team are attempting to reconstruct the complete environment.
The work requires tremendous patience, he said, because the fossils contained in rocks are difficult to remove because the rock is much harder than are the bones, making preservation a difficult task. He said rock saws are often used. Bones are easier to get out of softer rock, but those fossils are generally more fragmented.
Once they are removed, however, Irmis and his team have reconstructed a world that was a bit more frightening than today. They recovered an eyrops, a meat-eating amphibian that was between eight and 10 feet long, including the tail. “You wouldn’t want to go swimming in Permian ponds,” he said. Eyrops spent its life in water and on land and was an apparent wanderer as an eyrops nearly identical to what was found in Indian Creek was recently found in Texas, as well as closer to home in southern Utah’s Valley of the Gods.
They also found fossils belonging to a sphenacodon, an early mammal relative before dinosaurs. He said recovering fossils from the earth is a time-consuming process, but removing the fossils from the bones in which they are trapped is a true labor of love, with as many as 1,000 hours dedicated to the task.
Irmis’ crew also worked closer to Moab, where the land turned more from desert dunes to tropic rivers and streams, where they found a seymouria morph, an ancestor to both mammals and reptiles.
All of this, said Irmis, illustrates the importance of southeastern Utah in helping him and other paleontologists understand what was occurring in North America’s portion of the supercontinent all those eons ago. The area of modern Moab, as a matter of fact, was the furthest western point of Pangaea.