150-million-year oldie but a goodie

Sauropod skin far older than typical fossil finds

The skin of giant plant-eaters who trod the earth 150 million years ago was bumpy, with little hexagon-shaped knobs of skin protruding slightly from the surface.

One of those lumbering creatures, most likely an apatosaurus, left the imprint of his skin to be discovered last summer at the Mygatt-Moore dinosaur quarry in Rabbit Valley.

Skin imprints from the Age of the Dinosaurs aren’t so rare as to be shocking, but most tend to come from the creatures of the Cretaceous period, which ended about 65 million years ago.

The western Colorado find, however, comes from the late Jurassic period, and skin imprints from those creatures are more rare, said Dr. John Foster, curator of paleontology at Dinosaur Journey in Fruita.

“These guys had bumps and not overlapping scales,” Foster said. “You can certainly see that” in the imprint.

The imprint was found above an apatosaurus pelvis, suggesting the skin belonged originally to the same sauropod, although that’s not a certainty, Foster said.

The find, however, provides some evidence for the theory that the Mygatt-Moore area was a place of relatively fresh kills, or at least recent deaths, and that meat-eaters such as allosaurus were feeding there.

“This proves that there were not entirely rotted carcasses that were out there,” Foster said. “There were carcasses that had skin.”

The area now known as Mygatt-Moore once was a flood plain whose inundation covered up the bones now being discovered after millions of years.

Bits of plant debris and tiny pieces of what appear to be bone are scattered around the rock on which the imprint was found.

Allosaurus bones have been found in the quarry, suggesting the apatosaur was the main meal of the top predator of the late Jurassic not long before the plant-eaters bone, and a bit of skin, were covered up by mud.

Putting the skin imprint on display will require an appropriate display case that can preserve it by limiting the humidity, temperature changes and light that might affect it, Foster said.

The imprint itself is only the impression left behind by a carbonized film of the skin, which itself disappeared over the process of fossilization, Foster said.

How delicate the imprint might be is unclear.

“I haven’t touched it,”  he said, for fear that even a slight disturbance will destroy it.


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