Tag Archive for: cedar mountain formation

Poison Strip area, east of Arches National Park, Grand County, Utah
Photographer: Don DeBlieux

A geologist examines a sequence of Early Cretaceous-aged paleosols (ancient soils) in the Yellow Cat Member of the Cedar Mountain Formation. Many dinosaur fossils are found in these rocks, and the study of paleosols can provide valuable
information about the environments in which these dinosaurs lived.

Utah State Paleontologist, Jim Kirkland, is happily reunited with this unique (the first fully intact) shark coprolite from the Cedar Mountain Formation.

In August, the UGS received an important piece of Utah history in the form of an Early Cretaceous coprolite.  A coprolite is a fossil feces; and in this example a fully intact feces from an Early Cretaceous fresh water spiny (hybodont) shark. Although discovered in the early 1990s, the fossil had been missing for about 20 years.

The discovery goes back to when Utahraptor had first been discovered; I was exploring the outcrops of the upper Yellow Cat Member of the Cedar Mountain Formation with geologist Dan Howe (Howe Resources, Buena Vista, CO) who picked up an unusual blob of rock that included fish scales within it. Fragments of such things were not uncommonly found in this interval throughout the area and were an important line of evidence that these rocks had been deposited in a lake. A spiral, layered structure indicated these lumps were coprolites from a fish with a spiral intestine (spiral valve). Of the fish known from these beds only lungfish and hybodont sharks had spiral intestines and only hybodont shark coprolites were apt to consistently include fish scales within them. However, this was, and still is, the only complete example of this kind of fossil known from these rocks. Later, I called Dan and asked him where the fossil was and he assured me he had given it to me. After an intensive search through all my sample bags, it did not turn up. So, I assumed I had stupidly put it down and walked off without it.

A couple of weeks ago, I got a call from Dan who had stumbled across it going through some boxes (he had moved his life a few times across three states).  Dan quickly sent it back over to Utah.

While, future scientific studies of these coprolites can be carried out on the many fragmentary specimens, this remains the sole specimen for which the complete external morphology can be appraised. This specimen will be added to the Natural History Museum of Utah’s collections, where it may be examined by students and researchers in perpetuity.

Yellow Cat Road Section with Hybodont Shark level indicated.


Utah’s Cedar Mountain Formation has yielded two new species of iguanodont, cousins of the famous iguanodon, the plant-eating, beaked-mouthed dinosaur known for its ability to walk on its hind legs.

Working on federal land in two eastern Utah sites, teams led by the Utah Geological Survey discovered the two specimens in 2004. It took years of careful fieldwork to extract the bones, which include a nearly complete skull, and prepare them for study.

The most carefully dated of the two was discovered near Arches National Park by Andrew Milner, of the St. George Dinosaur Discovery Site. It was estimated to be 124 million years old and dubbed Hippodraco.

The survey’s Don DeBlieux discovered the other specimen near Green River. This one was dubbed Iguanacolossus.




Hellmut H. Doelling and Paul Kuehne

The Sagers Flat quadrangle is located northeast of Arches National Park in eastern Utah. Exposed strata range from Early Cretaceous Cedar Mountain Formation to Late Cretaceous Mancos Shale. The area overlies the ancestral Paradox basin and is influenced by salt-related folds, including the Salt Valley anticline to the west and Cisco Dome to the east.

CD (2 pl., 1:24,000)