Dimorphodon macronyx hunting an insect
On January 11th, 2018 we learned about

Wear and tear on fossilized teeth used to update assumptions about pterosaur diets

Puffins have a deep, almost domed beak that they use to retrieve fish from the sea. When feeding offspring or a mate, they often carry around 10 fish at a time, clearly demonstrating how well-suited their mouths are for handling seafood. From this reference point, it would seem reasonable to assume that other animals with similarly shaped mouths would also use them to hunt fish, which is how paleontologists once concluded that the pterosaur Dimorphodon macronyx was a piscivore back in the Jurassic period. The catch is that no other anatomy on this ancient creature really aligned with the rest of a puffin’s lifestyle, starting with its teeth.

An absence of corroborating evidence

Unlike birds, pterosaurs had mouths full of teeth, although figuring out what they used them on hasn’t always been easy. Some teeth are highly specialized, with flesh-slicing serrations, or baleen-like density, but pterosaurs like D. macronyx leave more to the imagination. Since pterosaurs have lightweight, hollow bones, few of their skeletons have been well preserved as fossils to say nothing of the handful of stomach contents that survived the test of time. As such, this has left researchers with a limited range of evidence to figure out what pterosaurs once ate, forcing them to rely on things like mouth shapes and the environment where the fossils were found.

Dimorphodons did have a rather puffin-esque mouth, but its body didn’t really live up to a fully pescatarian lifestyle. Most estimates of the small pterosaur’s flying ability haven’t been terribly optimistic, suggesting that D. macronyx wouldn’t have been able to gracefully soar over the water’s surface to snatch fish out of the sea. Even other species that were likely adept at air travel have raised questions about their buoyancy and ability to take off from a watery start. Fortunately, a new line of evidence has finally been opened up in the form of an infinite-focus microscope, which is finding new clues written in the pterosaurs’ teeth.

Dental details in 3D

The images compiled from the infinite-focus microscopes allowed researchers to not only look closely at the small scrapes, scratches and chips in a fossil’s teeth, but also to produce 3d models of them to better display those markings. Once a clear pattern was identified, it was compared to living animals with familiar diets, such as crocodiles, bats and lizards. After scanning the wear and tear on D. macronyx’s teeth, it became clear that they weren’t sushi lovers, but instead lived off of small vertebrates and insects, which seems to be a much better match for a non-marine predator. Other species’ diets have been amended as well, all without the need to excavate new fossils.

This doesn’t mean that no pterosaurs lived off of seafood, or that mouth morphology can’t be used to understand how extinct animals lived. Even if D. macronyx wasn’t carrying fish, it probably couldn’t use its short snout to chew tough plants either. But tooth damage does provide a widely-shared reference point that will hopefully help build richer, and more accurate, pictures of extinct animals’ ecology.

Source: Tooth scratches reveal new clues to pterosaur diets by John Pickrell, Nature News