By EMILY SCHABACKER/Montana State News
Seventy-five million years ago in northern Montana a lipless creature with scaly facial armor and cornified skin wreaked havoc on duckbilled hadrosaurs and other small carnivores. Newly discovered dinosaur D. horneri, unearthed in Choteau in the early 1990s, has finally been classified as a species closely related to Tyrannosaurus rex and was never before seen by paleontologists.
Twenty-five years since the dinosaur was excavated, the species has finally been named Daspletosaurus horneri or “Horner’s Frightful Lizard,” named after Jack Horner, the renowned former Montana State University paleontologist and Museum of the Rockies curator.
Paleontology professor David Varricchio of Montana State University suggested naming the dinosaur after Horner in honor of the mentorship he provided for paleontology students at MSU as well the contributions he has made to the field, according to Bozeman Daily Chronicle.
Varricchio, the head excavator on the site, unearthed about two thirds of the remains in the early 1990’s and said, “there were so many bones, you couldn’t really choose a big section … to pull out without going through other bones. It was very challenging and exciting!”
According to Varricchio, bones are very soft compared to the encasing rock which may account for why the research has spanned over 25 years.
“One specimen was really hard to prepare. It’s just time consuming. We had one volunteer who worked for several years and had made good progress but she may have done 25 percent of the specimen,” said Varricchio
All together, field researchers found a mostly complete skeleton of an adult D. horneri, which is fairly unusual, according to Varricchio. Researchers also uncovered a partial skeleton and skull of a subadult D. horneri, which uncovered many mysteries about modern day animals.
The rough texture on the surface of the skull lead researchers to believe this tyrannosaur had a scaly, armored face except for a patch of extra sensitive scales located just above its teeth. This pressure sensitive snout allowed the reptile to locate, hunt, and kill its food despite its short arms.
What other creature can you think of that is covered in armor and can deal a lethal blow despite its miniscule arms?
You guessed it: Crocodiles.
“They look a lot like crocodiles with a couple differences,” said lead researcher Thomas Carr of Carthage College in Wisconsin, “they would have had big flat scales on their face and patches of armor like skin and a couple patches of horn.”
These similarities suggest that that D. horneri and modern crocs shared a common ancestor, according to Carr who is certain more research will be done on the topic in the future.
Carr’s own research extends beyond the recently published article. Carr is working on a 1,000 page book on D. horneri’s place in history. Its closest living relative, D. torosus, supports Carr’s hypothesis of anagenesis, a rather uncommon mode of evolution.
Torosus lived about 3 million years before D. horneri, allowing for evolutionary changes to take place. However, both species lived in the same geographic location, indicating that one population changed over time, said Carr. Anagenesis would mean that these tyrannosaurs morphed from one species into another through natural selection.
Typically, these adaptations occur because a geographic barrier splits the species. However, a detailed fossil record supports Carr’s hypothesis of anagenesis in tyrannosaur.
– edited by Michelle Burger