Just east of Colorado Springs, near Corral Bluffs, sits a unique paleontological site. It has been investigated off and on for over a century, but it wasn’t until the last decade that its greatest secrets began to be unearthed.
Tyler Lyson, Curator of Vertebrate Paleontology at the Denver Museum of Nature & Science (DMNS), is the lead paleontologist for the site and he explained just what it is that makes it so special.
Why Corral Bluffs?
The area known as Corral Bluffs sits just to the east of Colorado Springs. It is marked by high desert plants and animals, expansive prairie views, and rugged bluffs rising out of the plains. These bluffs house a slice of geological time that covers the extinction of the dinosaurs 66 million years ago through the first million years following the extinction. There are few comparable sites in the world, making the Corral Bluffs site special.
Another feature of this site that makes it stand out is how complete the fossil finds are. Lyson explains, “It is remarkable … a mostly complete crocodile skeleton was found, as well as new mammals, turtles, and crocodiles,” some of which will be described in new papers coming out this year.
Most paleontologists are lucky to find bits of bone, usually scattered by the forces of time and nature. However, at Corral Bluffs, they often need to just pick up a certain type of rock and break it open. These rocks have preserved many nearly complete skulls and skeletons. Thanks to the completeness of these skeletons, paleontologists have been able to thoroughly document mammal size during this period when mammals began to rise after dinosaurs fell. The finds also keep coming, with more fossils found at new locations within the site and four new scientific papers related to the site published in 2022.
Ancient History
So just what were Corral Bluffs and the surrounding region like during the post-mass extinction recovery, 66-65 million years ago? Lyson explained that the asteroid impact that wiped out the non-avian dinosaurs also took out 75% of all species of life, including plants. The world would have appeared rather barren and sparse. Lyson referred to it as how things look after a wildfire.
The mammals that had survived were small – about the size of a rat – and omnivorous. Ferns began to grow as the area started to slowly recover. About 300,000 years after the extinction event, palm trees moved in and the mammal species began to grow larger, now about the size of a small pig and mostly herbivorous, thanks to the growing diversity of plant life.
After about 700,000 years, forests began to move in and mammals the size of small wolves appeared, once again omnivorous, but now with more of a preference for meat than plants.
The environment these animals developed in was much different than Colorado we know today. These new forests were subtropical, and Lyson says the average temperature would have been between 65-75 degrees (as opposed to today’s average temperature of 44 degrees). There was much more rain than there is today, creating a lush, warm environment where many species could thrive.
The evidence for these species can be found in the many fossils found at the site, which include not only the new mammals but also reptiles such as turtles and crocodiles, diverse plants (including the earliest legumes), and indicators of a wide variety of insects.
A Brief (Modern) History of the Site
In more recent times, Corral Bluffs has drawn the interest of a variety of scientific institutions. Lyson says the Smithsonian had researchers checking the area as far back as the late 1800s and early 1900s when it was discovered that there were dinosaurs at the base of the bluffs and mammals higher up. “This was the first place where they recognized a mass extinction” he reports. However, the fossils were “not abundant”, and the researchers went on to other sites with more known fossil records.
Lyson says that in the 1980s and 1990s, UC Boulder had teams also doing work in the area, and the DMNS also started sending people out in the ‘90s off and on. Lyson joined DMNS in 2014 and knew of the site, but after seeing the plant fossils that had been found he decided to investigate further.
Lyson had little luck at first until he realized something that had been overlooked. Tapping into his experience working in South Africa with similar rocks, Lyson realized that the area was full of a certain type of rock known as a “concretion”, and he hypothesized that if he broke them open, there may be fossils inside. However, what he found went beyond any expectations. He and his team discovered five well-preserved mammal skulls in one afternoon, something nearly unheard of in paleontology.
Ever since, the DMNS team, along with teams from other institutions (even international ones) have returned to the site, sifting through the sands for more clues about life after the mass extinction. They work in teams of 8-15 people, a mix of paleontologists, interns, and volunteers.
Finds Heard Around the World from Corral Bluffs
A site like Corral Bluffs is rare, and as such, it has generated quite a bit of press. The site has been featured in a NOVA special, “Rise of the Mammals.” It has also been the subject of several French documentaries and has been featured in Japan as well.
According to Lyson, America, France, and Japan house the three largest science television news audiences in the world and the finds from Corral Bluffs have been aired in all three countries. In addition, the site has been covered by such institutions as National Geographic, The Washington Post, PBS, and the Smithsonian Magazine, and specific finds have been published in a variety of scientific journals.
Closer to home, the site is currently the feature of a special exhibit in Denver titled “After the Asteroid: Earth’s Comeback Story.” The exhibit is scheduled to remain up at least through the rest of 2023, according to Lyson. It uses murals and multimedia displays to share many of the most interesting and impactful finds of the area and offers hands-on activities, such as a fossil sorting station and an art station.
What does the future hold for Corral Bluffs? It is such a unique site with such an abundance of fossils that Lyson expects “scientists will be looking at the area forever, basically.”
