On a summer day 110 million years ago, an armoured dinosaur likely ambled through the remains of a wildfire in what is now Alberta, Canada, gobbling up delicate green ferns peeking out from the ash. Somehow, shortly after, the dinosaur ended up dead in a river among the Cretaceous landscape and was swept out to sea. The ancient creature remained entombed in marine sediments until 2011, when an oil-sands miner stumbled across the remains: the best-preserved dinosaur of its kind ever discovered.
Already, the fossil has shed new light on how armoured dinosaurs’ hardened exteriors looked and functioned. Now, scientists studying the extraordinary fossil have made a new discovery: a ball of plant matter in the dinosaur’s gut that not only reveals the animal’s diet, but also chronicles the season the dinosaur died.
Hours after Borealopelta enjoyed its last meal, the dinosaur somehow got swept out to sea. The dinosaur’s undersea burial in what's now northern Alberta preserved its armor—and its stomach contents—in exquisite detail.
Borealopelta's gut contents included stones the dinosaur ingested to help break down its food.
By embedding some gut-content fragments in resin, scientists were able to slice them thin enough to study under a microscope, revealing thousands of tiny plant fossils.
“The preservation is just so great, we can actually say something about the stomach contents,” says lead study author Caleb Brown, the a dinosaur curator at Alberta’s Royal Tyrrell Museum of Palaeontology.
The research, announced today in Royal Society Open Scienceand partially funded by the National Geographic Society, provides an unprecedented look at the world this large plant-eating dinosaur inhabited—down to charcoal bits it swallowed.
“It paints a really evocative picture of this environment that this dinosaur would have been passing through,” says Victoria Arbour, the curator of dinosaurs at Canada’s Royal BC Museum. “You can envision the very specific event that happened in this dinosaur’s lifetime, and I thought that was really, really cool.”
In general, finding fossilised gut contents is rare. Fossils that unequivocally preserve herbivores’ final meals are rarer still. The chemical conditions that preserve bone also tend to break down plant matter, and plant material can often get swept into a fossil animal’s body during burial, making it hard to judge what’s a meal and what’s infill. Only one other armoured dinosaur, the Australian Kunbarrasaurus, has been found with digested plant matter in its stomach. But the Albertan dinosaur, Borealopelta markmitchelli, was bigger, roughly 18 feet long and nearly 3,000 pounds in life, and its stomach contents were better preserved.
Borealopelta was a nodosaur, a type of armoured dinosaur that lacked the tail club of its better-known cousin Ankylosaurus. It lived about 110 million years ago in what is now northwestern North America. The dinosaur fossilised under remarkable circumstances: Somehow, the animal ended up dead in a river and was swept more than 100 miles into a seaway that once split North America in two, from the Gulf of Mexico to the Arctic Ocean.
The dinosaur’s improbable burial at sea in what is now northern Alberta preserved its body in impeccable detail. Not only does its bony armour remain intact, but many of the keratin sheaths that covered it also fossilised. These clues are helping scientists understand how the dinosaur’s plates appeared and functioned, as well as providing possible evidence of its skin color. (Take a virtual 3D tour of Borealopelta, including the fossil's stomach contents.)
Borealopelta was freed from its stony tomb in 2011, when an excavator at Suncor’s Millennium Mine, an oil sands operation, in northern Alberta uncovered the fossil as he was digging. A crew from Alberta’s Royal Tyrrell Museum of Palaeontology flew up to the mine to excavate it, and museum preparator Mark Mitchell spent the next six years painstakingly removing excess rock from the fossil with hand tools. The dinosaur’s species name is markmitchelli in his honor.
When Borealopelta was unveiled in 2017, scientists marvelled at the quality of its preservation. Brown and his colleague Don Henderson, a fellow curator of dinosaurs at the Royal Tyrrell Museum, harboured suspicions that the fossil also contained stomach contents. The left side of the dinosaur’s chest cavity featured a curious mass of multicoloured pebbles, right about where the stomach ought to have been. So Brown and Henderson took small pieces of the mass that had fallen off, embedded them in resin, and made paper-thin slides that they could examine under a microscope.
SOURCE: Michael Greshko
VIA: National Geographic UK
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