Dinosaurs never stood a chance
Documentary series looks back at the end of the Cretaceous period
The Thescelosaurus moved stealthily along the seashore.
Featuring prominent bony eyebrows and a pointy beak, Thescelosaurus plodded along on two feet with the bulk of its body leaning forward while a long tail stretched backward for balance. Suddenly, the dinosaur lifted its head and looked around, alarmed as the calm was broken by a series of unnerving natural forces.
The ground started shaking while water in the nearby sea sloshed about in response.
Everything changed in a heartbeat as a 30-foot-high wave of mud and debris came racing up the seaway from the south, sweeping away life and limb in the process. The dinosaur was caught in the destructive deluge, its leg ripped off at the hip by the devastating surge.
That moment — 66 million years ago at the end of the Cretaceous period, when an Earth-shattering asteroid ended the reign of the dinosaurs — is frozen in time today through a stunning fossil found last year at the Tanis dig site in North Dakota. This perfectly preserved leg clearly shows the skin, muscle and bones of the three-toed Thescelosaurus.
While the details of the death scenario described above are embellished, they're based on remarkable new findings and accounts by Robert DePalma, lead paleontologist at Tanis.
“We're never going to say with 100 per cent certainty that this leg came from an animal that died on that day,” the scientist said. “The thing we can do is determine the likelihood that it died the day the meteor struck. When we look at the preservation of the leg and the skin around the articulated bones, we're talking on the day of impact or right before. There was no advanced decay.”
DePalma and the dinosaur leg will be featured in two episodes of Nova on PBS airing back-to-back on Wednesday: Dinosaur Apocalypse: The New Evidence and Dinosaur Apocalypse: The Last Day. Biologist and natural historian David Attenborough will host the programs, which were produced in conjunction with the BBC.
The leg and several other relics discovered at the North Dakota site are the first actual fossils found showing the death and destruction that took place when a 10-milelong space rock struck the Yucatán Peninsula in the Gulf of Mexico. This impact event 66 million years ago doomed the dinosaurs and led to the extinction of 75 per cent of animal and plant life on Earth.
At the time, the world was a much warmer place. There were no ice caps, and water levels were higher. The North American continent was split in two by the Western Interior Seaway. Tanis is located on what was the edge of that massive river.
After Tanis was discovered in 2008, scientists began to realize the fossils there were probably created during that big-impact moment. A series of key discoveries were made, including the dinosaur leg, the embryo of a pterosaur still in its shell, a turtle pierced by a chunk of wood and the well-preserved skin of a triceratops. Many of these fossils are being presented to the public for the first time in the PBS documentaries.
Perhaps most telling were the fossilized fish unearthed at the site in 2019, which caught many scientists by surprise. In those petrified remains, researchers found the embedded evidence they needed to substantiate the claim that the animals died when the asteroid struck: the glass spheres, known as ejecta, that came raining down from the sky that fateful day.
DePalma asserts that what happened then is directly relevant to the world today.
“I've been asked, `Why should we care about this? Dinosaurs have been dead for so long,'” he said. “It's not just for paleo nerds. This directly applies to today.
“We're seeing mass die-offs of animals and biomes that are being put through very stressful situations worldwide. By looking through this window into the past, we can apply these lessons to today.”