“It’s amazing paperAnd this discovery is just over the top,” said David Burnham, a paleontologist at the University of Kansas who was not involved in the study.
Gorgosaurus, a tyrannosaurid, is a slightly smaller cousin of the most famous tyrannosaurid. tyrannosaurus rex. The boy was probably between 5 and 7 years old, weighed approximately 740 pounds, and was 13 percent the size of an adult. His length from nose to tail was approximately 15 feet, suggesting that he was approximately the same height as an average human adult.
Darren Tanke, a technician at the Royal Tyrrell Museum of Paleontology, collected the fossil in 2009 from a wasteland in Alberta’s Dinosaur Park, Canada. He was buried with his left side facing down. As he worked to prepare the fossil, he noticed something strange poking through his ribcage: some little toe bones.
Upon careful examination, they turned out to be part of the hind limbs of two one-year-old bird-like dinosaurs called Sitipes, each of which would have been about the size of a turkey.
Outside paleontologists said the discovery was unusual. There’s a long list of reasons. The bones were found fully articulated and in place, rather than being assembled in pieces by scientists. The animal is a juvenile, providing important clues to the era before Gorgosaurus grew into a giant, bone-crushing apex predator. But most dazzlingly, its stomach contents were intact, allowing scientists to confirm that it had recently eaten two separate meals before its death.
“This is a once-in-a-lifetime fossil,” said Darla Zelenitsky, a paleontologist at the University of Calgary and one of the authors of the study published Friday in Science Advances.The adolescent dinosaur “was probably a very precise eater. It had a very narrow skull and blade-like teeth.” [and] Perhaps you can easily tear off the hind legs of these animals. ”
Dinosaur drumstick and “killer banana”
Scientists have pondered the development of Tyrannosaurus rex for years. The adult is a celebrity in the dinosaur world. Most known species are stout, sturdy animals that are thought to have hunted giant duck-billed dinosaurs and horned dinosaurs.
But until they reached maturity (11 years old for a Gorgosaurus), they were almost like a separate species, lighter and faster than their elders, and without the bone-crushing chomping sounds. Their teeth were not round, like the “killer bananas” of adult tyrannosaurs, but were more like sharp blades, said François Therrien, curator of dinosaur paleoecology at the Royal Tyrrell Museum.
Changes in physiology suggest that, like modern-day Komodo dragons, tyrannosaurs may have experienced changes in diet throughout their lives, eating small prey as young and occupying a different ecological niche than adults. This led to a theory.
“It had been suggested for some time, but there was no evidence that it was the case. It was all based on modeling and assumptions,” Therian said.
Well, at least when it comes to Gorgosaurus, there’s no need to guess.
“It’s kind of like Thanksgiving because it mainly ate legs,” says University of Maryland paleontologist Thomas Holtz. He is one of the scientists who previously theorized that tyrannosaurs experienced major changes in their diet as they matured.
“This is a great example of how small tyrannosaurs fed on small dinosaurs that were much smaller than themselves,” he said. Adults. ”
A glimpse into the life of Gorgosaurus
Evidence about what Tyrannosaurus ate comes primarily from connecting the dots in the fossil record.Analysis of bite marks on prey bones fossilized tyrannosaurus Feces have helped paleontologists reconstruct diets.
But the new fossil is the first example of a Tyrannosaurus rex with preserved stomach contents, the authors say. Animal carcasses are rarely buried directly after death, so dinosaurs with stomach contents remaining are rare. Scavengers can come and eat the bones, including the contents of the intestines, and environmental conditions can cause the bones to become mushy before being preserved.
In this case, the feathered dinosaur, whose hind limbs were preserved, is also the most complete fossil ever discovered at Sitipes. Ironically, because they were protected by the stomachs of the dinosaurs that ate them. One bone appeared to be slightly more digested than the other, suggesting the two meals were hours or days apart, Zelenitsky said.
With only one sample, it is difficult to determine how generalizable this finding is. Did the young Gorgosaurus prefer to eat citipes? Did it selectively butcher the citipes to eat only the drumsticks? Did you hunt these two animals? Could another juvenile Gorgosaurus have swallowed the other half?
Joseph Peterson, a paleontologist at the University of Wisconsin-Oshkosh who was not involved in the study, said it is difficult to explain why only the legs were in the stomach. “Maybe they encountered a few carcasses and this was the only one left and they ate them,” he says. “That’s where you have to be a little bit careful. It’s very tempting to want to move on to the next stage.”
Despite the limitations, some scientists have speculated that the dietary changes may be common to other tyrannosaurids, rather than unique to this individual or the species. He said there was.
“Tyrannosauruses weren’t just bone-crushing beasts that ate what they wanted, when they wanted. They were actually very sophisticated feeders, and their diet changed as they grew.” wrote Stephen Brusatte, a paleontologist at the University of Edinburgh, in an email. “They had to develop into bone-crushing personalities.”