The Southern Newsroom
| April 12, 2022
It is assumed that the rising waters buried the animals at Tanis. (Picture: BBC)
Scientists have revealed the discovery of an incredibly well-preserved dinosaur leg.
The limb, complete with skin, is just one of a series of remarkable finds recovered from the Tanis archaeological site in North Dakota.
But it’s not just the condition of the pieces there that catch the eye – what these ancient specimens represent for science is also quite remarkable.
The scientists’ main hypothesis is that the creatures found on Tanis were killed and buried the day a giant asteroid hit Earth.
It was on this day, 66 million years ago, that the reign of the dinosaurs ended and the rise of mammals began.
Very few dinosaur remains have been found in the rocks that tell the story of the last thousands of years before the impact. And to have a specimen from the Cataclysm era itself would be amazing.
The BBC spent three years filming in Tanis for a program which will air on April 15 on British television, narrated by environmentalist Sir David Attenborough.
Sir David will present the finds, many of which will have their first public display.
In addition to the dinosaur leg, there are fish that breathed in debris from the impact as it rained down from the sky.
There is also a fossil of a turtle that was impaled by a wooden stake; the remains of small mammals and the burrows they dug; skin of a horned triceratops; the embryo of a flying pterosaur inside its egg; and what appears to be a fragment of the asteroid itself.
“We find a lot of detail on this site that tells us what happened at every moment, it’s almost like it happened in the movies. You look at the rock column, you look at the fossils and it takes you back to that day,” says Robert DePalma, a graduate student from the University of Manchester in the UK who is leading the excavations at Tanis.
Currently, the idea that a space rock about 12 km wide hit our planet to cause the last mass extinction is widely accepted.
The impact site has been identified in the Gulf of Mexico, off the Yucatan Peninsula. The place is about 3,000 km from Tanis, but the energy transmitted by the event was such that its devastation was felt everywhere.
Animal and plant remains appear to have been carried into a sediment deposit by waves of river water triggered by unimaginable earthquakes. Aquatic organisms are mixed with terrestrial creatures.
Amidst the tangle of pieces, fossils of sturgeons and oars are fundamental. They have tiny particles stuck in their gills. They are spherules of molten rock expelled by the impact which then fall back on the planet. The fish would have inhaled the particles upon entering the river.
The spherules were chemically and radiometrically bound to the Mexican impact site. And in two of the resin particles recovered from preserved trees, there are also small inclusions that imply an extraterrestrial origin.
“When we realized that there were inclusions inside these tiny glass spherules, we chemically analyzed them in the Diamond X-ray synchrotron near Oxford,” explains Professor Phil Manning, thesis director from DePalma to Manchester.
“We were able to separate the chemistry and identify the composition of this material. All of the evidence, all of the chemical data in this study strongly suggests that we’re looking at a piece of the asteroid that ended the dinosaurs.
The existence of the Tanis site and the discoveries made at the site were first announced in The New Yorker Magazine in 2019. It caused a stir at the time.
Science often demands that the initial presentation of new discoveries be made in the pages of an academic journal. A few peer-reviewed papers have already been published, and the dig team promises much more as they work through the painstaking process of extracting, preparing and describing the fossils.
To make its TV show, the BBC brought in outside experts to review several of the findings.
Professor Paul Barrett of the Natural History Museum in London examined the leg. He is an expert on ornithischian (mainly herbivorous) dinosaurs.
“It’s a Thescelosaurus. This is a group of which we had no previous record of the appearance of their skin, and it shows very conclusively that these animals were very scaly like lizards. They were not feathered like their carnivorous contemporaries.
“It looks like an animal whose leg has just been torn off very quickly. There is no evidence of disease on the leg, there are no obvious pathologies, there are no signs of tearing of the leg, like bite marks or bits that have disappeared,” he tells me. “So the best idea we have is that this is an animal that died more or less instantly. “
To return to