"Trackways" on an ancient seabed provide insight into how ancient marine reptiles called nothosaurs propelled themselves through the water.

These animals were the top predators during the Mesozoic, which took place between 66 and 252 million years ago, a Bristol University news release reported.

The nothosaurs were "voracious semi-aquatic hunters with elongate bodies and paddle-like limbs," the news release reported.

Researchers have long-wondered if the animals rowed back and forth with their limbs or "flew" under water like a penguin.

The team looked at an ancient seabed from China that contained 10 to 50 swooping lines that came in pairs believed to have been left behind by the ancient animal.

The finding suggests the nothasaur moved by rowing its forelimbs in unison.

The Nothosaurus and the diminutive Lariosaurus species most likely left the tracks.

"We interpret the tracks as foraging trails. The nothosaur was a predator, and this was a smart way to feed.  As its paddles  scooped out the soft mud, they probably disturbed fishes and shrimps, which it snapped up with needle-sharp teeth," Professor Qiyue Zhang from Chengdu Center of China Geological Survey said in the news release.

"The site also holds many fossils of ancient sea creatures.

When I first saw the site, I couldn't believe the amazing quality of the fossils.  It's quite unusual to find skeletons of marine reptiles such as the nothosaurs so close to evidence of their tracks," Professor Michael Benton from the University of Bristol, one of the co-authors of the research said in the news release.

These findings could help researchers gain insight into the Permo-Triassic mass extinction that wiped out about 90 percent of Earth's species.

"Here we see a detailed snapshot of how life was within 8 million years of the mass extinction.  It took all that time for the Earth to settle down from the cataclysm, and the arrival of these large, complex marine predators shows us the ecosystems had finally rebuilt themselves, and life could be said to have recovered from the crisis," co-author Professor Shixue Hu, also from Chengdu Center of China Geological Survey, said in the news release.