It turns out the Thornton triceratops, which was discovered on a construction site in August and nicknamed “Tiny” by school children, isn’t actually a triceratops after all, but rather the dinosaur’s rare close cousin: A torosaurus.

The two are practically indistinguishable, according to a statement from the Denver Museum of Nature & Science. Both have a large horn over each eye and a smaller nose horn, hence the assumption that Tiny was the more common triceratops.

Joe Amon, The Denver Post Mike Getty, chief preparator at the Denver Museum of Nature & Science gives Saunders Construction, inc. founder and chair Dick Saunders a close look after exposing the post orbital horn of the dinosaur fossil that was found in Thornton.

Joe Amon, The Denver Post Mike Getty, chief preparator at the Denver Museum of Nature & Science gives Saunders Construction, inc. founder and chair Dick Saunders a close look after exposing the post orbital horn of the dinosaur fossil that was found in Thornton.

Provided by Denver Museum of Nature and Science Joe Sertich, curator of dinosaurs at the Denver Museum of Nature and Science, talks to students at Brantner Elementary School in Thornton about the discovery of triceratops fossils at a construction site across the field from their school. Kids from the school came up with the name "Tiny" for the most complete Cretaceous Period fossil discovered in Colorado.



Joe Amon, The Denver Post Denver Museum of Nature & Science uncased the post orbital horn of the dinosaur fossil that was found in Thornton.

Joe Amon, The Denver Post Mike Getty, chief preparator at the Denver Museum of Nature & Science talks to the crowd and reporters on Sept. 8, 2017 after exposing the post orbital horn of the Triceratops fossil that was found in Thornton.

Joe Amon, The Denver Post Mike Getty, chief preparator at the Denver Museum of Nature & Science exposing the post orbital horn of the dinosaur fossil that was found in Thornton. The protective jacket was sawed into to expose a piece of one of the fossils in Denver Sept. 8, 2017.



Daniel Brenner, Special to the Denver Post Fossil Preparator Natalie Toth, left, points out which fossils were recently found Saturday, Sept. 2, 2017 at the Denver Museum of Nature and Science. A total of twelve bones were discovered at a Thornton construction site earlier in the week. The bones are 66 million years old and were transported in plaster jackets.

Daniel Brenner, Special to the Denver Post Helen Moore, 3, looks at recently found dinosaur fossils Saturday, Sept. 2, 2017 at the Denver Museum of Nature and Science. A total of twelve bones were discovered at a Thornton construction site earlier in the week. The bones are 66 million years old and were transported in plaster jackets.

City of Thornton Scientists from the Denver Museum of Nature & Science (DMNS) are working at the site of a fossil discovery in Thornton.



City of Thornton ​Rare dinosaur fossil is uncovered in Thornton.

But torosaurus were longer, thinner and had a more delicate frill with two very large holes. Museum workers discovered those features while cleaning the bones. This is the first recorded torosaurus find in Colorado, the museum said.

“Not only is the fossil more complete and better preserved than I imagined, but it has also revealed itself to be something extremely rare,” museum curator of dinosaurs Joe Sertich said in a statement. “The Thornton beast is by far the most complete, and best preserved, ever found.”

Provided by the Denver Museum of Nature & Science An illustration of a Torosaurus by artist Sergey Krasovsky.

Provided by the Denver Museum of Nature & Science A skeleton map of the Torosaurus. The yellow bones have been found by the museum. (Provided by the Denver Museum of Nature & Science)



He said there are likely more than 2,000 quality triceratops specimens in the American West but only about seven partial torosaurus skulls prior to this find.

Tiny is still the most complete Cretaceous Period fossil discovered in Colorado. About 95 percent of the skull and at least 20 percent of the skeleton have been identified, according to the museum.

The fossils were found by construction workers building an upcoming Fire and Police Substation at East 132 Avenue and Quebec Street. An operator scooping dirt was told to stop suddenly when an on-site geotechnical engineer — someone who reviews soil conditions — noticed something inconsistent with the surrounding claystone and sand.

Excavators found several bones, including two brow bones, a lower jaw beak, shoulder bones and a stray tooth from a scavenging T. rex. Cleaning has also revealed more skull bones and a complete tibia. People can watch the torosaurus being cleaned at the museum’s fossil prep lab.