Sharks vs Pterosaurs

Who would win in a fight between a shark and a pterosaur? Only kidding, we’re not that kind of blog. However, in September of last year a paper was published that inevitably generated a lot of headlines not too unlike this one. The find in question was a finger bone from a pterosaur and it was recovered from a thick bed of chalk in the USA, dated to the late Cretaceous. That in itself it pretty unusual. The chalk beds of Alabama represent the remains of an ancient ocean and pterosaur remains are relatively rare. What was even more interesting about this particular metacarpal though was that something had taken a bite out of it.

456px-Pteranodon_amnh_martyniuk
Skeletal reconstruction of a Pteranodon. Source: Wikimedia Commons

Pterosaur is actually the name for a whole group of flying reptiles that thrived alongside the dinosaurs from the early Triassic all the way until the meteorite impact that wiped out 65% of all life at the end of the Cretaceous. This finger bone belonged to a specific type of Pterosaur called a Pteranodon (pronounced ‘ter-an-o-don’, the P is silent). They were big, with a wingspan that could reach up to 7m, and lived across a vast swathe of what is now North America. Their remains are found from Alabama to Wyoming, and they probably ranged along the coastlines, hunting fish in the same way as modern seabirds. Fossilised fish bones have been recovered from the stomach contents of some Pteranodon specimens, along with fragments of scales. Early reconstructions had them daintily swooping across the water’s surface before opportunistically scooping up some unlucky fish, but more recent evidence suggests that they were probably capable of diving, at least to a limited extent, and could then take off again straight from the water’s surface.  These were no casual gliders; they were dynamic, active, aerial acrobats, as capable as any modern diving bird.

So what about the bone and its bite mark? The bone actually shows a couple of different bite marks, one set serrated and then a second set of marks caused by unserrated teeth. By looking at the size and layout of the serrated tooth marks the researchers were able to match them to a known predator from the time, a shark species called Squalicorax kaupi. The other marks probably came from a bony fish of some kind, probably a member of a group called the Saurodontidae.

Squalicorax kaupi was a medium-sized shark, averaging around 2m in length. It was likely a coastal scavenger, with teeth similar in shape to a modern day tiger shark. They were obviously widespread, with teeth being recovered from Europe, North Africa and North America, and these teeth have been found embedded in a range of different species from turtles to mosasaurs suggesting a rather catholic diet. The question is though how did these tooth marks come to be on the bones of a fellow coastal hunter? Especially one that could fly.

1024px-Tigershark3
Modern day tiger shark. Source: Wikimedia Commons

We’ve probably all seen footage of tiger sharks hunting fledgling albatrosses, or Great White Sharks throwing themselves athletically out of the water as they attack their prey. It’s all too tempting to imagine some unsuspecting Pteranodon swooping low over an ancient ocean, only to have the waters suddenly erupt around it as a tooth-filled jaw clamps shut around one wing. Sadly the truth is probably far more prosaic. It’s much more likely that the Pteranodon was already dead long before Squalicorax ever laid a tooth on it. Most likely the animal either died on the edge of the sea and was washed out with the next tide, or else it drowned while fishing. Either way it offered an opportunistic meal for coastal living predators. Interestingly tiger sharks actually live in a very similar way. Despite a reputation as a ferocious hunter they probably also get a lot of their food from scavenging. Individuals have been found with a baffling array of different stomach contents including goats, monkeys, dogs and even inland songbirds!

This isn’t even the first time that this particular species of shark has been caught scavenging on large reptiles. In 2006 a Hadrosaur was found that showed evidence of being scavenged by a shark. Researchers in that case also placed the blame firmly on Squalicorax. Obviously like their modern cousins these animals never turned up a free meal.

 

Reference:

DANA J. EHRET and T. LYNN HARRELL “FEEDING TRACES ON A PTERANODON (REPTILIA: PTEROSAURIA) BONE FROM THE LATE CRETACEOUS (CAMPANIAN) MOOREVILLE CHALK IN ALABAMA, USA,” Palaios 33(9), 414-418, (1 September 2018)

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