Fossil found near Colorado Springs identified as new species of mammal

Courtesy Denver Museum of Nature and Science
A reconstruction of Militocodon lydae, a new genus and species of mammal uncovered from the Corral Bluffs fossil site. Militocodon lydae lived 65.5 million years ago, was about the size of a modern-day chinchilla or large rat, and likely had an omnivorous diet.

A fossil of a newly identified animal found east of Colorado Springs has revealed new information about life on Earth after the mass extinction of dinosaurs. 

Skull and jaw fragments from what's now known as the Militocodon lydae were unearthed in 2019 and 2021 in Corral Bluffs Open Space.

A new study published in the Journal of Mammalian Evolution says the small, chinchilla-sized omnivore belonged to a group of mammals that eventually gave rise to all hoofed mammals, known as ungulates.

Journal of Mammalian Evolution
A screenshot of the fossilized lower jaw bone and teeth of the Militocodon Lydae found at Corral Bluffs in 2021 from the study recently published in the Journal of Mammalian Evolution.

"Rocks from this interval of time have a notoriously poor fossil record and the discovery and description of a fossil mammal skull is an important step forward in documenting the earliest diversification of mammals after Earth’s last mass extinction,” said Tyler Lyson, Curator of Vertebrate Paleontology at the Denver Museum of Nature and Science (DMNS).  

Lyson co-authored the study and is on the team that found the fossils. He said the 2021 discovery happened while hiking in Corral Bluffs with his family. He found a small concretion, a type of rock that forms around fossils. 

"And the way we figure out if there's any fossils inside is we break 'em open. So I picked up this small peanut-sized one," he said. "I broke it open and I could see a couple of really teeny tiny teeth poking out at me and I knew it was a remarkable find because I could see that it was both the skull as well as both lower jaws. From a small mammal, that's really, really rare."

Courtesy Denver Museum of Nature and Science
Researchers examine preliminary Computed Tomography results of a Corral Bluffs fossil at the Northglenn Veterinary Hospital.

Adding to the rarity of the find is the fact that Corral Bluffs has been home to paleontological endeavors for at least 100 years. Lyson said it came down to pure luck. He said the team found fossils of at least two kinds of crocodilians at the site, as well as more than 20 different varieties of turtles, and a dozen or so distinct mammals – all of which are new species.

"We're just now starting to publish lots of papers on them because science takes time," Lyson said. "We're going to be doing a lot of work down here in the future, and there's going to be a lot more exciting announcements in the coming years." 

Courtesy Denver Museum of Nature and Science
From left to right: Sharon Milito, Tyler Lyson, and Ian Miller at Corral Bluffs. Lyson and Miller are paleontologists with the Denver Museum of Nature and Science and lead the research at the Corral Bluffs site. The Militocodon lydae, a new mammal found at Corral Bluffs, is named, in part, for Milito. She's a volunteer who uncovered the first small mammal fossil in 2019.

Lyson and his team used detailed X-rays from CT scans to examine and digitally reconstruct the fossil species they found and "bring these animals back to life."

"We're able to use those to peer inside the skulls or skeletons of these animals. From that data we can look at the size of the brain, the size of the olfactory ball, which is the organ of the sense of smell, and look at the inner ears, which is the organ of balance," he said. 

Lyson also named the mammal. Its genus – Militocodon – honors Sharon Milito, a volunteer from Colorado Springs who found the first fossil of the new mammal. Its species – lydae – refers to local philanthropist and DMNS donor Lyda Hill.

Courtesy Denver Museum of Nature and Science
Lyda Hill and Tyler Lyson at an event in Colorado Springs. Lyson chose to name the Militocodon Lydae, in part, after Hill in honor of her contributions to the Denver Museum of Nature and Science and the Colorado Springs region.

Paleontological work in the area will continue with the help of a recently awarded collaborative research grant from the National Science Foundation's Frontier Research in Earth Sciences. It includes 12 scientists from various institutions including Colorado College, Smithsonian National Museum of History, and the University of Colorado Boulder. Lyson said the nearly $3 million award is the largest research grant ever received by the Denver Museum of Nature & Science.

Editor's note: This story has been updated. A previous version described the activities at Corral Bluff as archaeology as opposed to paleontology.