Dr. Michael J. Ryan, a professor of Earth Sciences at Carleton University, has uncovered a new ancient crocodile relative that illustrates a species of the family of crocodiles that persued its prey while breathing underwater. The research was published in the Royal Society Open Science journal on Dec. 8.
The 155-million-year-old relative, Amphicotylus milesi, was discovered in Wyoming, USA. It is a new species and the best-preserved fossil known of a goniopholidid, a close relative of modern crocodilians. With an estimated length of 2.3 m (7.6 ft) and weighing up to 227 kg (500 Ib), the freshwater species inhabited the margins of rivers and shallow lakes where it fed on fish or waited to ambush small dinosaurs.
According to the Crocodile Specialist Group (CSG), a global network of professionals interested in crocodilian conservation, modern crocodilians—crocodiles, alligators, caimans, and gharials—can breathe through their mouths and nostrils on top of their snouts. The nostrils have protective valves at the openings, and air travels through canals and down the back of the throat, where it passes through another valve.
When a crocodilian basks on land, it typically breathes through its open mouth, and the palatal valve in the throat (also known as a gular flap) is open.
However, when it is holding prey in the water, the crocodilian breathes through its nostrils, and the flap is closed, which prevents the animal from inhaling water through its open mouth. When this flap isn’t in use, it rests in the underside of the throat, and a network of muscles lifts the flap into place to block the flow of water.
When the researchers looked at the size, shape, and curvature of A. milesi’s skull structures, they noticed some similarities to modern crocodiles with the gular flap, such as an extension in the roof of the mouth toward the back of the throat and a shortened bone called the ceratobranchial that lies in the throat and supports the tongue, according to Live Science.
According to the study authors, the combination of anatomical traits in A. milesi shows that this ancient croc relative possessed a flap that would have kept it from inhaling water while drowning its prey as long as its nose was above the water.
According to Ryan, adaptations for underwater feeding may explain why the ancestors of contemporary crocodiles survived the catastrophic extinction at the end of the Cretaceous period while their nonavian dinosaur contemporaries perished.