North Dakota. — A group of scientists has presented a leg of dinosaur amazingly well preserved. The limb, complete with skin, is just one of a series of remarkable finds emerging from the Tanis fossil site in the US state of North Dakota.
But it’s not just their exquisite condition that is striking, it’s what these ancient specimens purport to represent. The claim is that the Tanis creatures were killed and buried on the same day a giant asteroid hit the Earth.
It happened 66 million years ago, when the reign of the dinosaurs ended and the rise of mammals began. Very few dinosaur remains have been found in the rocks that record even the last few thousand years before the impact. Having a specimen of the cataclysm itself would be extraordinary.
As we have mentioned on AmericanPost.News, the BBC has been filming the Tanis site for three years for a program that will broadcast on April 15, narrated by Sir David Attenborough.
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Sir David will review the discoveries, many of which will have their first public viewing. Along with the dinosaur leg are fish that breathed-in debris from the impact as it rained down from the sky.
We see a fossil turtle that was skewered with a wooden stake; the remains of small mammals and the burrows they made; skin of a horned triceratops; the embryo of a flying pterosaur inside its egg; and what appears to be a fragment of the asteroid impactor itself.
“We have so much detail with this site that tells us what happened moment by moment, it’s almost like seeing it in the movies. You look at the column of rock, you look at the dinosaur fossils there, and it brings you back to that day,” says Robert DePalma, a graduate student at the University of Manchester, UK, who is leading the Tanis dig.
It is now widely accepted that a space rock about 12 km wide hit our planet to cause the last mass extinction.
The impact site has been identified in the Gulf of Mexico, off the Yucatan Peninsula. That is some 3,000 km from Tanis, but the energy releasted by the event sent waves of devastation far and wide.
The North Dakota fossil site is a chaotic jumble. The remains of animals and plants seem to have been washed over a sediment dump by waves of river water caused by unimaginable earth tremors. Aquatic organisms mix with land creatures.
The sturgeon and paddlefish in this tangle of fossils are key. They have small particles trapped in their gills. These are the spheres of molten rock ejected by the impact that then fell all over the planet. The fish would have breathed in the particles when they entered the river.
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The spherules have been linked chemically and by radiometric dating to the impact site in Mexico, and in two of the recovered particles of preserved tree resin there are also small inclusions that imply an extraterrestrial origin.
“When we noticed there were inclusions inside these little glass spheres, we chemically analyzed them at the Diamond X-ray Synchrotron near Oxford,” explains Professor Phil Manning, DePalma PhD supervisor in Manchester.
“We were able to separate the chemistry and identify the composition of that material. All the evidence, all the chemical data from that study strongly suggests that we’re looking at a part of the impactor; of the asteroid that finished it off for the dinosaurs.”
The existence of Tanis and the claims being made about him first emerged in the public sphere in the New Yorker magazine in 2019. This was all the rage at the time.
Science often requires that the initial presentation of new discoveries be made in the pages of an academic journal. A few peer-reviewed articles have been published, and the excavation team promises many more as they go through the meticulous process of extracting, preparing, and describing the fossils.
To make its television show, the BBC called in outside consultants to examine several of the findings. Professor Paul Barrett of the Natural History Museum in London looked at the leg. He is an expert on ornithischian (mainly herbivorous) dinosaurs.
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“It’s a Thescelosaurus. It’s from a group for which we had no prior record of what their skin looked like, and it shows very conclusively that these animals were very scaly, like lizards. They didn’t have feathers like their carnivorous contemporaries. It looks like an animal that just had its leg ripped off very quickly. There is no evidence of disease on the leg, no obvious pathology, no trace of the leg having been picked, such as bite marks or fragments of it that are missing.”, professor Barrett says.
“So the best idea we have is that this is an animal that died more or less instantly,” he added.
The big question is whether this dinosaur actually died the day the asteroid hit, as a direct result of the cataclysm that followed. Tanis’s team thinks it most likely is, given the position of the branch in the sediments from the excavation.
If that’s the case, that would be quite a find. But Professor Steve Busatte of the University of Edinburgh says he’s still a bit skeptical at the moment.
He has acted as another of the BBC’s external consultants. He wants to see the arguments made in more peer-reviewed articles, and to have some paleoscientists with very specific specialties come onto the site to give their independent assessment.
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Professor Busatte says that it is possible, for example, that animals that had died before the impact were exhumed by the violence of the day and then reburied in such a way that their deaths appeared to be simultaneous.
“Those fish with spherules on their gills are an absolute calling card for the asteroid. But for some of the other claims, I’d say they have a lot of circumstantial evidence that hasn’t been presented to the jury yet,” he says.
“However, for some of these discoveries, does it matter if they died the day before or years before? The pterosaur egg with a baby pterosaur inside is super rare; there’s nothing like it in North America. It doesn’t all have to be about the asteroid.” professor Busatte added.
There is no doubt that the pterosaur egg is special. With modern X-ray technology it is possible to determine the chemistry and properties of the eggshell. It was probably leathery rather than hard, which may indicate that the mother pterosaur buried the egg in sand or sediment like a turtle.
It’s also possible with X-ray tomography to virtually extract the bones of the pterosaur chick inside, print them out, and reconstruct what the animal would have looked like. Mr. DePalma has done this.
The baby pterosaur was likely a type of azhdarchid, a group of flying reptiles whose adult wings could reach more than 10m from tip to tip.
Mr DePalma gave a special lecture on the discoveries from the Tanis fossil site to an audience at the US space agency NASA’s Goddard Space Flight Center on Wednesday. He and Professor Manning will also present their latest data to the General Assembly of the European Geosciences Union in May.