Small skull imprint of grouse-like bird 45 million years old
By GARY HARMON
Smallish grouse-like birds foraged for shoots and roots, possibly the occasional insect, along the shores of Lake Uinta some 45 million years ago, a find by the Museum of Western Colorado suggests.
The discovery, the imprint of a skull that bears a strong resemblance to a modern sage grouse, is the first of its kind from the Green River Formation as it outcrops in western Colorado.
The imprint, which still contains tiny bits of fossilized bone, fills in some of the picture of what the land area now known as western Colorado looked like during the Eocene Epoch.
The shale beds left behind by Lake Uinta have yielded some fish, mostly warmwater gar, crocodilians, insects, the occasional feather and bits of twigs and leaves, said John Foster, curator of paleontology for Dinosaur Journey in Fruita.
Grand Junction sits on what would have been the south shore of Lake Uinta, which inundated thousands of square miles of what is now northwestern Colorado and eastern Utah.
“The Eocene Epoch was one of the hottest periods in Earth’s history,” Foster said, noting that the presence of a grouse-like bird similar to the modern sage grouse seems to run counter to the tropical climate that dominated the region.
The Eocene, though, was far from a stranger to odd inhabitants.
The duck of the day had a skull and bill similar to that of modern-day ducks, but it’s legs were as long as those of modern-day flamingoes, said Mike Perry, executive director of the Museum of Western Colorado, the umbrella organization for Dinosaur Journey, Museum of the West and Cross Orchards Living History Farm.
The grouse-like specimen adds to the general knowledge about the Eocene and its animals and will serve as a marker for further research.
“In all likelihood, this is a brand new taxa, a new species,” Perry said of the bird.
The find is unusual because only the skull was found. Researchers could say more about the bird had its feet been found, Perry said, but more work is being done.
Foster confirmed its similarity to modern grouse by taking the specimen to the University of Utah to compare it to the bird specimens there.
The skull imprint has been in the museum’s collection for several years now, but only late last year was it rediscovered in trays of material awaiting additional work.
It was found originally on a dig high above the Grand Valley on Douglas Pass and placed in storage.
Jim Kirkland, the Utah state paleontologist, had been urging him to find the imprint, Foster said.
“It’s one of those found-in-the-museum-collection stories,” Foster said. “It just goes to show how hard it is to recognize a specimen in the field.”
The grouse-like head was found on land administered by the Bureau of Land Management on Douglas Pass near a Green River Formation outcrop frequently explored for fossils.
Fossil hunters can keep the fossils and impressions of insects, twigs and leaves.
Fossils of vertebrates, however, cannot be taken from the rock in which they are found and should be reported to the BLM or experts licensed by the federal agency, such as Dinosaur Journey.