The ground began to shake with intense vibrations as the water in the nearby sea moved in response. The sky was filled with burning embers, which descended and set fire to the lush primordial forest.
Thescelosaurus panicked and tried to run away, but it was too late. Everything changed in the blink of an eye when a 30-foot-high wave of mud and debris surged 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 waves.
That moment, 66 million years ago at the end of the Cretaceous period, when an earth-shaking asteroid ended the reign of the dinosaurs, is frozen in time today through a stunning fossil found last year at the site of Tanis dig in North Dakota. This perfectly preserved leg clearly shows the skin, muscles, and bones of the three-toed Thescelosaurus.
While the details of the death scenario described above are embellished, they are based on new finds and remarkable accounts from Robert DePalma, Tanis’s lead paleontologist.
“We are never going to say with 100 percent certainty that this leg came from an animal that died that day,” the scientist said. “What we can do is determine the probability that he died on the day the meteorite hit. When we look at the preservation of the leg and the skin around the articulating bones, we are talking about the day of impact or just before. There was no advanced deterioration.
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DePalma and the dinosaur paw will appear 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 Sir David Attenborough will host the programmes, which were produced in conjunction with the BBC.
The leg and several other relics discovered at the North Dakota site are the first real fossils found showing the death and destruction that took place when a 10-mile-long space rock hit the Yucatan Peninsula in the Gulf of Mexico. This impact event 66 million years ago doomed the dinosaurs and led to the mass extinction of 75 percent of plant and animal life on Earth.
At that time, the world was a much warmer place. There were no polar ice caps and the water levels were higher. The North American continent was bisected by the Western Interior Seaway. Tanis stands on what was once the edge of that huge river, which became a chute of carnage after the asteroid hit. Shock waves from nearly 3,000 miles away caused the seaway to erupt with a tsunami of epic proportions.
As DePalma pointed out, Thescelosaurus never really stood a chance.
“You wouldn’t want to be there that day,” he said. “There was a turbulent wall of death heading upriver. Also, all these glowing spheres are falling from the sky. They are like superheated glass beads re-entering the Earth’s atmosphere after being ejected from the crater site in the Yucatan. Then there was all this seismic shaking. It was truly hell on earth.”
However, the loss of a dinosaur is a gain for a paleontologist. After Tanis was discovered in 2008, scientists began to realize that the fossils were likely created during that time of great impact. A number of key discoveries were made, including a dinosaur leg, a pterosaur embryo still in its shell, a turtle impaled on a piece of wood, and the well-preserved skin of a triceratops. Many of these fossils are being introduced to the public for the first time in PBS documentaries.
Perhaps most telling were the fossilized fish unearthed at the site in 2019, which shocked many scientists. In those petrified remains, the researchers found the embedded evidence they needed to substantiate the claim that the animals died when the asteroid hit: the glass spheres, known as ejecta, that rained down from the sky that fateful day.
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“These were fish that died that day,” DePalma said. “We know because they had impact ejecta in their gills.”
Researchers have unearthed countless samples of these glass spheres, all with the characteristic chemical components typical of a large impact event. Composed of sand and other terrestrial materials, the molten glass was expelled into the atmosphere by the explosion caused by the impact of the asteroid against the planet, which is estimated to be equivalent to 10,000 million atomic bombs. Inside one of those circular fossils is a small speck of rock that may be from the killer asteroid itself.
DePalma, a graduate research fellow at the University of Manchester in England and an adjunct professor of geosciences at Florida Atlantic University, has spearheaded efforts at Tanis since 2012. He and other team scientists have published several major papers describing the discoveries and outlining the scientific methodology. used to date fossils and other evidence.
DePalma claims 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,’” she said. “It’s not just for paleo nerds. This applies directly to today. We are seeing mass deaths of animals and biomes that are going through very stressful situations all over the world. By looking through this window into the past, we can apply these lessons to the present.”
To produce the “Nova” episodes, DePalma worked directly with one of his heroes, Attenborough, 96, to review the discoveries and discuss their significance.
“Sir David and I interacted and consulted on everything,” DePalma said. “It was a tremendous experience. He can’t quell his enthusiasm. When we were looking at the fossils and talking about what they meant, you couldn’t separate the two of us. We keep talking and talking about them. We would have been there all day if no one had stopped us.”
“Dinosaur Apocalypse” airs Wednesday at 9 pm ET on PBS.