A group of scientists presented a remarkably preserved dinosaur foot. The limb, complete with skin, is just one of a series of notable finds that have emerged from the site of 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 can represent.
Scientists believe the Tanis creatures died and were buried on the same day that a giant asteroid hit the Earth.
Era the day 66 million years ago ended the reign of the dinosaurs and the rise of mammals began.
Very few dinosaur remains have been found in the rocks that even record the last thousands of years before the impact. Having a specimen of the cataclysm itself would be extraordinary.
The BBC spent three years filming a program in Tanis to air April 15, narrated by David Attenborough.
Attenborough will review the findings, many of which will be seen in public for the first time.
Next to the leg, here fish breathing impact debris as it rained from the sky.
Also seen is a fossil turtle stuck 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 many details on this site that tell us what happened moment by moment, it’s almost like seeing it in movies. You look at the rock column, you look at the fossils there and it takes you back to that day, ”said Robert DePalma, a graduate student at the University of Manchester who is leading the Tanis excavation.
It is now widely accepted that a space rock about 12 kilometers wide hit our planet and caused the latest mass extinction.
The impact site was identified in Gulf of Mexico, off Chicxulub (Yucatan Peninsula). It is 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 camp is chaotic chaos.
The remains of animals and plants appear to have been washed on a sediment dump by river water waves caused by unimaginable earthquakes.
Aquatic organisms mix with the creatures of the earth
The sturgeon and paddlefish in this tangle of fossils are key. They have small particles trapped in their gills. These are the molten rock spheres ejected by the impact that then fell all over the planet.
Scientists believe it the fish breathed the particles when they entered the river.
The spherules have been 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 that there were inclusions within these small glass spheres, we chemically analyzed them at the Diamond X-ray Synchrotron near Oxford,’ explained Professor Phil Manning, supervisor of the DePalma PhD 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 piece of the asteroid that killed the dinosaurs“, He added.
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 during the meticulous process of extracting, preparing and describing the fossils.
To make its TV show, the BBC called in outside experts to review many of the results.
Professor Paul Barrett of the Natural History Museum in London and an expert on ornithischian dinosaurs (mainly herbivores) studied the leg.
“You are a Thescelosaurus. It comes from a group for which we had no precedent on the appearance of their skin and very conclusively shows that these animals were very scaly, like lizards. They didn’t have feathers like their carnivorous contemporaries, “she said.
“It looks like an animal that has just been ripped off a paw very quickly. There is no evidence of leg disease, there is no obvious pathology, there is no evidence that the leg has been pulled, such as bite marks or parts of it that have disappeared, “she said.
“So the strongest idea we have is that this it is an animal that died more or less instantly“, He added.
The big question is whether this dinosaur actually died the day the asteroid struck as a direct result of the cataclysm that followed.
Tanis’ team thinks it most likely is, given the location of the limb in the excavation’s sediments.
If so, it would be a nice find.
This was stated by Professor Steve Busatte of the University of Edinburgh I’m a bit skeptical right now.
Busatte, who was another of the BBC’s external consultants, wants to see the arguments made in more peer-reviewed articles and that some paleoscientists with very specific specialties log on to the site to give their independent assessment.
The expert said it is possible, for example, that animals that died before the impact were brought to light by the violence of the day and then returned to the ground, so that their deaths appear simultaneous.
“Those fish with the spherules on their gills are a real calling card for the asteroid. But for some of the other claims I would say that they have a lot of circumstantial evidence that has not yet been presented to the jury”, He assured.
“However, for some of these discoveries, does it matter whether they died the day before or the years before? The pterosaur egg with a baby pterosaur inside is super rare; there is nothing like it in north america. Not everything has to be about the asteroid.
With modern X-ray technology it is possible to determine the chemistry and properties of the egg shell. It was likely leathery rather than tough, which could indicate that the pterosaur mother 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 and reconstruct what the animal would have been like. De Palma did it.
The baby pterosaur was likely a type of azhdarchid, a group of flying reptiles whose adult wings could reach more than 10 meters from tip to tip.
On Wednesday, DePalma gave a special lecture on Tanis’ findings to an audience at the US space agency NASA’s Goddard Space Flight Center. He and Manning will also present their latest data to the European Union’s Geosciences General Assembly in May.
For Jonathan Amos
BBC News World