Paleontologists in Madagascar recently discovered an exceptionally well-preserved fossil of a new and extinct species of turtle, dating back to the late Cretaceous Period, which began around 100 million years ago. The newly discovered species would have had a frog-like face and eaten by sucking in mouthfuls of prey-filled water.
The ancient turtle was a freshwater species endemic to Madagascar, with a shell length of around 10 inches (25 centimeters). It had a flattened skull, rounded mouth and large tongue bones, all of which would have made it a great suction feeder and given it an amphibian-like appearance. In a new study describing the species, the researchers named it Sahonachelys mailakavava, which means « quick-mouthed frog turtle » in Malagasy, the language spoken by Indiginous people of Madagascar.
Researchers unearthed the turtle’s fossil in 2015 while searching for the remains of dinosaurs and crocodiles at a site on the island with a history of such finds. While removing the overburden — the typically bare layers of sediment above fossil-rich layers — the team was surprised to find bone fragments from a turtle’s shell and eventually recovered an almost intact skeleton.
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« The specimen is absolutely beautiful and certainly one of the best-preserved late Cretaceous turtles known from all southern continents, » lead author Walter Joyce, a paleontologist at the University of Fribourg in Switzerland, told Live Science. « In all regards, this is an exceptionally rare find. »
The researchers are unsure how far back the quick-mouthed frog turtle may have emerged or when and why it went extinct; but the new species « likely survived the big extinction event that killed the dinosaurs » and brought the Cretaceous Period to an end around 66 million years ago, Joyce said.
Quick-mouthed frog turtles were most likely suction feeders, the researchers said.
« This is a specialized mode of underwater feeding, during which the animal quickly opens its mouth and expands its throat to quasi-inhale a large volume of water, including the desired prey item, » which would have included plankton, tadpoles and fish larvae, Joyce said.
Its flattened skull, mouth shape and delicate jaws are all telltale signs that this turtle used suction for feeding. « Suction feeders need to quickly create a large circular opening through which they suck water, » Joyce said. « As the prey items are transported directly into the esophagus, suction feeders do not have strong jaws, as they do not bite. »
The turtle also had enlarged tongue bones for its size, which suggests it had strong muscles to allow the quick expansion of its throat, Joyce said.
The quick-mouthed frog turtles belonged to the Pelomedusoidea family, which includes living species such as South American and Madagascan river turtles. « Although the group is not particularly diverse today, its fossil record shows that the group nearly conquered all landmasses in the past and was much more diverse, » Joyce said.
The quick-mouthed frog turtle was « likely the first Pelomedusoid » to have evolved as a suction feeder « to such an extreme, » Joyce said. There are several modern-day turtle species that suction feed, most of which belong to the family Chelidae and evolved separately from the quick-mouthed frog turtle.
When Joyce first saw the skull, he thought it belonged to a Chelid, he said. « The shell, however, clearly showed that it is a Pelomedusoid. » This is evidence of convergent evolution and means Chelids and Pelomedusoids, which are distantly related, have each evolved this ability independently of one another, Joyce said.
« It highlights that distantly related animals will converge upon the same shape when adapting to similar lifestyles, » Joyce said.
The study was published online May 5 in the journal Royal Society Open Science.
Originally published on Live Science.