Alberta fossil find gives researchers a glimpse into how dinosaurs interacted

There have only been a handful of bone finds like a recent one from Dinosaur Provincial Park with a tooth mark in it.

Alberta researchers, along with other paleontologists from around the world, are presenting their findings on dinosaur behaviour after analyzing fossils found in Dinosaur Provincial Park.

In a study published in January in the Journal of Paleontology, researchers at the Royal Tyrrell Museum of Palaeontology, the University of Reading (UK) and the University of New England (Australia) shared their findings of a fossilized neck bone of a pterosaur that shows signs of being bitten by a crocodile-like creature 76 million years ago.

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“Somebody was chomping on it,” said Caleb Brown, lead author and Royal Tyrrell Museum curator.

“So first off, we can’t really easily differentiate between active predation and scavenging in the fossil record; the traces they leave in the bone look identical but we know that something ate this.”

Brown says pterosaurs are flying reptiles that lived at the same time as dinosaurs and the largest pterosaurs ever to evolve got to be the size of a giraffe with a 12-metre wingspan.

He says they had big heads, really long, toothless beaks; long necks, big wings and a very short tail.

“They’re kind of mysterious,” he said. “We don’t know what they were eating, we don’t know what their lifestyle was, we know they were carnivores, but we don’t know if they were scavengers, if they were kind of heron-like stalkers; we don’t really know what they were eating, but ironically we know a lot more of what was eating them.”

Brown says the majority of bite marks found on fossils are from large dinosaurs, like a tyrannosaur feeding on horned or duckbill dinosaurs.

“Pterosaur bones are actually quite rare,” he said. “Finding pterosaur bone with bite marks on it is even more rare, and although they’re big animals, the bones are very light because they fly. The bone is literally like credit card thin on the outside, so it’s basically like a fossilized toilet paper tube.”

Brown says the tooth mark measures about eight millimetres wide and left a circular pattern in the vertebra, so the animal that made it could be a variety of species with similar bites.

“We can’t fully eliminate (other) crocodile-like animals,” he said.

“And also mammals, something like a marsupial with a big canine could have also made a similar mark like that, so we’re not entirely sure what it was. Our best guess is a crocodilian, but we have to kind of hedge our bets a bit because we only have the one mark and there’s only so much you can do with one mark.”

Dinosaur Provincial Park is a hotbed for fossil discoveries and that’s why Brian Pickles from the University of Reading established a paleontology field research course.

For the last four years he’s been bringing 10 students to Alberta to collect fossils. It was his latest class that unearthed the rare pterosaur bone.

“We’d been excavating this bone bed for most of the two weeks of the trip,” he said. “It was the last day that we were collecting up the last few things on the surface and sat back in the research trailers trying to identify everything and I noticed that this fossil was different.”

It was the first pterosaur bone that he and the students have ever found and says it creates a sense of what was happening in these ecosystems so long ago when they were thriving with life.

“When you get something like a tooth mark, it gives you an example of species interactions,” he said.

“So finding a bone that retained species interactions from 76 million years ago is pretty special, so you can imagine there’s a crocodile, finds a dead pterosaur and has its dinner or maybe it grabbed the pterosaur and pulled it into the river; you can’t really tell the difference between those, but it’s amazing when you find something like that, it’s just such a rare event.”

Pickles' students contributed to the writing of the published paper.

“It’s amazing to be able to give students that opportunity,” he said. “And that they’re so excited, it’s one of those sort of lifetime achievements to get to go to Dinosaur Provincial Park and find just amazing things from 76 million years ago; it’s always mind-blowing, whatever you find.”

Brown says even though the specimen is relatively small and from a juvenile pterosaur it still packs quite the story.

“We don’t have the full skeleton yet,” he said. “But partial fragmentary specimens can actually reveal unique data, unique evidence about what happened in the ancient past, which is really exciting.”

The specimen is currently on display in the Fossils in Focus exhibit at the Royal Tyrrell Museum of Palaeontology.