Wednesday, January 4, 2012


Allosaurus has been the Utah state fossil for well neigh forty years. Utah is a remarkable state when it comes to dinosaur fossils, in part because it has so much in the way of Mesozoic terrestrial rocks and in part because it is so arid. The extensive desert ecosystems of Utah means that there is little in the way of forests, grasslands, cities, roads, etc. to cover up the rocks. And the more rock exposed the better the chance of finding fossils. If Utah, as it has sometimes been referred to, is “The Dinosaur State” then how did Allosaurus end up being selected as the state fossil? Well there’s damn good reason for that.

The Cleveland-Lloyd Dinosaur Quarry in Emery County, near the city of Price in southeastern Utah, is the motherload for Allosaurus fossils. Discovered in the 1930s, it was worked for a time by Princeton University and then on a more sustained basis by first Lee Stokes and later James H. Madsen of the University of Utah. The CLDG had produced thousands upon thousands of dinosaur bones, most belonging to Allosaurus fragilis. The remains of over 40 Allosaurus have been collected, ranging in size from very small to very large individuals. The skeletons were in water for some period of time and are completely disarticulated --- with even skulls falling apart into their individual bones --- but the abundance, size range, and quality of preservation make this one of the world’s great carnivorous dinosaur sites. With most of the quarry unexcavated much work remains to be done. The existing collections from the CLDQ have been studied by many paleontologists, including myself, and have contributed to many scientific publications. The quarry is managed by the Bureau of Land Management and there is a small visitor center with exhibits at the site.

The CLDG is world renowned in scientific circles and every dinosaur paleontologist knows of it. It is, without a doubt, one of the best understood (scientifically) meat-eating dinosaurs in the fossil record. So it’s not surprising that when Utah selected a state fossil they chose Allosaurus. That brings us to the title of this post.

Along U.S. Highway 40, at the Utah-Colorado border, there is a billboard welcoming those traveling westwards as they enter Utah. The big image on the billboard is a flesh restoration of a carnivorous dinosaur. You might reasonably think that this would be famous Allosaurus, since that is the state fossil, but you would be WRONG!

The dinosaur shown has a prominent horn over the nose and is clearly the carnivorous Ceratosaurus (whose name, not surprisingly, means “horn lizard”). The nasal horn core is a diagnostic feature of Ceratosaurus and easily separates it from Allosaurus. This is not some obscure morphological feature, such as whether branches II and II of the trigeminal nerve exit the braincase through a common foramen or via separate canals. Really, the nasal is horn is big and obvious to anyone willing to taking a few moments to look.
Skull of Ceratosaurus nasicornis (from Gilmore 1920)
Skull of Allosaurus fragilis (from Madsen 1976)

Unlike Allosaurus, Ceratosaurus is a pretty rare dinosaur, although one fairly good specimen is known from the CLDQ. To further the confusion, the dinosaur on the sign has three fingers on its hand (like Allosaurus) and not four fingers (like Ceratosaurus). How this chimaera came to be is unknown but I am sure they though it was Allosaurus. Whoever selected the graphic knew nothing about dinosaurs and certainly no careful checking was done. I guess a dinosaur is a dinosaur, so who would know or care? Come on even an elementary school dinosaur enthusiast can tell the difference. Maybe this seems a small point to the reader, but imagine if New Jersey had a welcome sign with its nickname “The Garden State” and below that there was a silhouette of chemical plants and storage tanks. Ooops -- never mind.

Thinking about visiting the CLDQ? Visitor information can be read at

Gilmore, C.W. 1920. Osteology of the Carnivorous Dinosauria in the United States National Museum, with Special Reference to the Genera Antrodemus (Allosaurus) and Ceratosaurus. Smithsonian Institution, U.S. National Museum Bulletin 110: 159 pp + 36 plates.

Madsen, J.H. 1976. Allosaurus fragilis: a Revised Osteology. Utah Geological and Mineral Survey Bulletin 109: 163pp.

GLDQ photos: BLM website given above.

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