Fossilised tooth challenges Late Triassic assumptions

A 220 million years old tooth lodged in the thigh bone of the largest predator of the time has revealed two predators at the top of their respective food chains interacted
– with the smaller potentially having eaten the larger animal.

The tooth belongs to a smaller semi-aquatic phytosaur and it was lodged in the thigh bone of a terrestrial rauisuchid – a creature about 25 feet long and four feet tall.

The tooth lay broken off and buried about two inches deep in the thigh bone and then healed over, indicating that the rauisuchid survived the initial attack.

“These rauisuchids were the largest predators in their environments. You might expect them to be the top predators as well, but here we have evidence of phytosaurs, who were smaller, semi-aquatic animals, potentially targeting and eating these big carnivores,” explained Stephanie Drumheller, lecturer of earth and planetary sciences at the Vigninia Institute of Technology (Virginia Tech).

To study the tooth without destroying the bone, the team partnered computed tomographic (CT) data with a 3D printer.

This, along with an examination of the bite marks, revealed a story of multiple struggles.

The team found tissue surrounding bite marks illustrating that the rauisuchid was attacked twice and yet survived.

Evidence of crushing, impact and flesh-stripping but no healing showed the team that the animal died later in another attack.

The findings also suggest previous distinctions between water- and land-based food chains of the time, the Late Triassic period, might be built upon mistaken assumptions made from fossil remains.

“This research will call for us to go back and look at some of the assumptions we’ve had in regard to the Late Triassic ecosystems,” concluded study co-author Michelle Stocker from Virginia Tech.

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