BEIJING, May 9 (UPI) -- When scientists first unearthed the fossil remains of Atopodentatus unicus in 2014, they described the ancient creature as possessing a flamingo-like beak.
But in a new study, published this week in Science Advances, researchers argue that the ancient reptile's beak was actually a hammerhead-like jaw -- the first used by an herbivorous marine reptile to filter-feed.
A. unicus was a crocodile-like sea-dwelling reptile that emerged during the Triassic Period in the wake of Earth's most devastating mass extinction event some 252 million years ago. The specimen of interest is 242 million years old and was discovered in southwestern China.
Scientists say the creature's hammerhead-like jaw featured an outer set of larger peg-like teeth and an inner set of needle-like teeth.
"That arrangement wouldn't have been too useful for chewing prey," study co-author Olivier Rieppel, a researcher with the Field Museum, said in a news release. "It's more likely that Atopodentatus used its front teeth to nip algae or other plants from rocky surfaces and then, with its mouth closed, forced mouthfuls of water through its side teeth, which acted as a filter trapping the plants and letting the water back out, like how whales filter-feed with their baleen."
The specimen serves as the earliest evidence of vegetarianism among marine reptiles. Other plant-eating reptilian filter-feeders don't appear in the fossil record for another 8 million years.
Marine habitat during the Triassic Period featured a variety of unusual-looking, hard-to-classify reptiles, including Atopodentatus unicus.
"Overall, the creature is so unusual that it's difficult to tell where it fits on the reptile family tree," explained co-corresponding author Nicholas Fraser, a researcher with the National Museums Scotland.
"Because its fossils are relatively complete, paleontologists will probably need to unearth fossils of yet-to-be-discovered relatives to better figure this out," Fraser added. "In the meantime, Atopodentatus seems to be most closely related to the plesiosaurs, the typically long-necked marine reptiles that often were top predators in dinosaur-era oceans."