Fossil of the Week

Left to Right: MWC 1.1.6; 5823; 5011; 5464; 6798. Scale bar = 10 cm

Above are examples of Ceratosaurus teeth that have been collected in the Grand Valley over the last few decades. Ceratosaurus was a carnivorous dinosaur that lived during the Jurassic Period, some 150 million years ago. Its bones and teeth are now preserved in the rocks known as the Morrison Formation. This theropod appears to be more rarely preserved.

The Specimens:

• MWC 1.1.6 – This tooth belongs to the type specimen of Ceratosaurus magnicornis, discovered by Lance Eriksen in 1976*.
• MWC 5823 – Dinosaur Journey volunteer Darrel Bay collected this tooth on September 29, 2006 at the museum’s Twin Juniper Quarry.
• MWC 5011 – Pete Mygatt collected this tooth from the Mygatt-Moore Quarry on June 21, 2001.
• MWC 5464 – This tooth was collected from the Mygatt-Moore Quarry on July 22, 1999 by Josh Ray.
• MWC 6798 – Collected in 1998, this tooth also came from the Mygatt-Moore Quarry and was prepared by Lorin King in 2004.

*The Backstory: Lance Eriksen, the first curator of paleontology at the Museum of Western Colorado, and his children collected the type (or first to be discovered) specimen of Ceratosaurus magnicornis from the Fruita Paleontological Area in 1975 and 1976. The fossils collected include a skeleton with skull (MWC 1 – premaxillae, maxillae, nasal, frontal, parietal, prefrontal, lacrimal, postorbital, squamosal, jugal, quatrojugal, quadrate and other skull bones, humerus, femur, tibia, astragalus, calcaneum, metatarsals and numerous vertebrae). This specimen is of a large individual, but not yet fully grown. This specimen was designated as the holotype of the new species by Jim Madsen and Sam Welles in 2000. This specimen is slightly larger than its close relative, Ceratosaurus nasicornis (initially discovered near Cañon City, Colorado), although the nasal horn is a bit longer and lower in Ceratosaurus magnicornis.

Ceratosaurus magnicornis (MWC 1). Image from Madsen and Welles 2000.

The skull of Ceratosaurus magnicornis is currently on exhibit at Dinosaur Journey.

References:

Madsen, James H.  & Samuel P. Welles. 2000. Ceratosaurus (Dinosauria, Theropoda). A revised osteology. Utah Geological Survey, Miscellaneous Publication 00-2: 80pp

Foster, John. 2007. “Gargantuan to Minuscule: The Morrison Menagerie, Part II”. in Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press: 162–242.

Any material in our collections are covered under a permit though the appropriate agency and curated at the Museum of Western Colorado, unless otherwise noted.