After a month of careful cleaning and examination by volunteers and staff at the Denver Museum of Nature & Science
, a nearly complete dinosaur skull and partial skeleton discovered in Thornton, Colo., and originally determined to be a Triceratops has been reidentified. The frill, or the shield of bone projecting backward from the head, shows that the specimen is instead a rare Torosaurus, a close cousin of Triceratops.
The two animals are nearly indistinguishable because both had a large horn over each eye and a smaller nose horn. During excavation, it was assumed the fossils belonged to the more common Triceratops. However, unlike Triceratops, Torosaurus had a longer, thinner, and more delicate frill, with two very large holes. These frill features were revealed as the skull was cleaned and compared to Triceratops specimens already in the Museum collections.
Not only is the fossil more complete and better preserved than I imagined, but it has also revealed itself to be something extremely rare, said Joe Sertich, curator of dinosaurs at the Museum. While the number of good Triceratops specimens collected from the American West likely exceeds 2,000 individuals, there are only about seven partial skulls of Torosaurus known. The Thornton beast is by far the most complete, and best preserved, ever found.
On Aug. 28, the City of Thornton and the Museum confirmed that a dinosaur fossil, now nicknamed Tiny, had been unearthed at a Saunders Construction site for a new Public Safety Facility. Cleaning efforts have also revealed several more skull bones and a complete tibia. An estimated 95 percent of the skull and at least 20 percent of the skeleton have now been identified, making this the most complete Cretaceous Period fossil discovered in Colorado. The sand and rock encasing the Torosaurus are being cleaned in the publicly visible Fossil Prep Lab at the Museum, a process that is expected to take several more months.