- Jonathan Amos
- BBC Science Correspondent
David Attenborough sought the help of experts to understand the significance of the fossilized dinosaur leg.
A group of scientists presented an amazingly preserved dinosaur leg.
The limb, complete with skin, is just one of a series of remarkable finds emerging from the site of get to know, in the state of North Dakota (United States).
But it is not only their exquisite condition that is striking, but also what these ancient specimens may represent.
Scientists believe that the Tanis creatures died and were buried on the same day that a giant asteroid hit the Earth.
Was el day 66 million years ago in what the reign of the dinosaurs ended and the rise of mammals began.
Very few dinosaur remains have been found in rocks that record even the last few thousand years before the impact. Having a specimen of the cataclysm itself would be extraordinary.
The BBC spent three years filming in Tanis for a program to be broadcast on April 15, narrated by David Attenborough.
Attenborough will review the discoveries, many of which will be seen in public for the first time.
David Attenborough presents the program.
evidence in fish
Next to the leg, there fish that breathed in impact debris as it rained from the sky.
Also seen is a fossil turtle driven in with a wooden stake, the remains of small mammals and the burrows they made, the skin of a horned triceratops, the embryo of a flying pterosaur inside its egg, and what appears to be a fragment of the pterosaur itself. asteroid.
“We have so much detail at 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 fossils there, and it brings you back to that day,” Robert DePalma said. , a graduate student at the University of Manchester (UK) leading the Tanis dig.
It is now widely accepted that a space rock about 12 kilometers wide hit our planet and caused the last mass extinction.
The impact site was identified in the Gulf of Mexico, off Chicxulub (yucatan peninsula). That’s about 3,000 kilometers from Tanis, but such was the energy of the event that its devastation was felt far and wide.
The North Dakota field 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.
Scientists believe that the fish breatheron the particles when they entered the river.
The spherules were linked chemically and by radiometric dating to the impact site in Mexico, and in two of the recovered preserved tree resin particles there are also small inclusions that have a 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,” explained Professor Phil Manning, DePalma’s Manchester PhD supervisor.
“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 are looking at a piece of the asteroid that ended with the dinosaurs“, he added.
Exploration in Tanis
The existence of Tanis, and the claims made about this place, were first made public by the magazine The New Yorker in 2019, which 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.
The excavation site is full of rounded particles; debris ejected from the impact site 3,000 kilometers away.
To make its television show, the BBC called in outside experts to examine several of the findings.
Professor Paul Barrett, of the Natural History Museum in London and an expert on ornithischian (mainly herbivorous) dinosaurs, studied the leg.
“You are an 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,” he said.
“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 being pulled, such as bite marks or parts of it missing.” “, he claimed.
“So the strongest idea we have is that this it is an animal that died more or less instantly“, he added.
It is believed that a rising tide buried all the creatures in Tanis (digital recreation).
The big question is whether this dinosaur actually died on 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 limb in the sediments from the excavation.
If that’s the case, it would be quite a discovery.
Skepticism
Professor Steve Busatte of the University of Edinburgh argued that is a so much skeptical at the moment.
Busatte, who was another of the BBC’s external consultants, 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.
The expert said that it is possible, for example, that animals that had died before the impact were unearthed by the violence of the day and then returned to the ground, so that their deaths appear 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 is yet to be presentó to the jury“, he assured.
“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 is nothing like it northmeter. Not everything has to be about the asteroid.”
Reconstruction of the pterosaur
A pterosaur embryo is a rare find, especially for North America.
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 egg shell. It was probably leathery rather than hard, which may indicate that the mother pterosaur buried the egg in sand or sediment, as turtles do.
It is 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. DePalma did.
The baby pterosaur was probably a type of azhdarchid, a group of flying reptiles whose adult wings could reach more than 10 meters from tip to tip.
It is virtually possible to extract fossil bones and print them to make a model.
DePalma gave a special lecture on the Tanis discoveries to an audience at the US space agency NASA’s Goddard Space Flight Center on Wednesday. He and Manning will also present their latest data to the European Geosciences Union General Assembly in May.
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