Some tyrannosaurus species were opportunistic scavengers, even feasting on the remains of their much larger T rex relatives, according to a surprising fossil discovery.
The name “Tyrannosaurus”, meaning tyrant lizard, was coined in 1905 by the American palaeontologist Henry Fairfield Osborn for the dinosaur’s large size and role as an apex predator.
There were three to five species of tyrannosaurs, including the iconic T rex, depicted in films such as Jurassic Park as powerful, relentless predators.
The new discovery reveals that tyrannosaurs also took advantage of opportunities to scavenge, and sometimes the carcasses of their larger relatives.
Researchers at Aarhus University in Denmark identified precise bite marks on a massive foot bone, showing a smaller tyrannosaur had fed on the corpse of a larger relative about 75 million years ago.
They identified 16 distinct bite marks on the fossil bone, indicating the scavenger fed on the corpse down to the last scraps.
“I have analysed the depth, angle, and placement of the marks in a virtual 3D environment and can document that these bite marks did not occur by chance,” Josephine Nielsen, the author of a study published in the journal Evolving Earth, said.
“They are precise impressions from the teeth of a smaller tyrannosaur that fed on a larger relative.”
There were no signs of healing on the bone, indicating the bite marks were from late-stage carcass consumption. “The small size and spacing of the marks indicate that they were produced by a small tyrannosaurid, most likely scavenging on the carcass of a significantly larger conspecific or closely related taxon,” the study noted.
The findings were evidence that tyrannosaurs didn’t let resources go to waste, consuming even tough bones with little decaying meat, Ms Nielsen, a Master’s student in geoscience from Aarhus University, noted.
“Since the marks are located on the foot, where there’s very little meat, it suggests that the dinosaur was ‘cleaning up’ and eating the last remains of an old carcass,” she explained.
The original fossil bone measured 10cm long and came from a tyrannosaur that likely reached 10-12m in height and weighed several tonnes.
It was discovered by an amateur collector in the Judith River Formation in Montana, US, an area known for preserving a rich record of a 75-million-year-old ecosystem.
Ms Nielsen constructed a digital model of the fossil bone and analysed a 3D-printed version at Aarhus University.
“By creating a digital version, I’ve been able to zoom in on very small details,” she said, adding it was “far too risky” to send the real bone by mail to Denmark.
“It has been like solving an ancient murder mystery.”
The study shows that modern techniques can help reveal crucial information about dinosaur behaviour from even small traces preserved in fossils.