Missing Link Between Land and Sea Discovered in New Ancient Ichthyosaur Fossil

Scientists have just filled in an evolutionary gap. They've discovered the first fossil of an amphibious ichthyosaur in China, which is the first ever link to the dolphin-like ichthyosaur to its terrestrial ancestors.

The fossil itself actually represents a missing stage in the evolution of ichthyosaurs, which are marine reptiles that lived during the time of the dinosaurs about 250 million years ago. Until now, though, there have been no fossils that have marked their transition from land to sea. This latest fossil, though, remedies that gap. It reveals a creature that actually represents that transition.

The fossil itself is about 248 years old, and the creature itself probably lived during the Triassic period. Stretching about 1.5 feet long, it wasn't completely adapted to life at sea-like most ichthyosaurs. Instead, it had flexible wrists, which are essential for crawling on the ground.  And instead of a long, beak-like snout like most ichthyosaurs, the fossil had a short nose, such as what is found in land reptiles.

The creature also had thicker bones. This keeps with the idea that most marine reptiles that transitioned from land first became heavier in order to swim through rough coastal waters before entering the deep sea.

Yet the fossil doesn't just represent a transition in evolution; it also shows what happened during the worst mass extinction in Earth's history about 252 million years ago. Scientists have long wondered how long it took animals and plants to recover after this destruction.

"This was analogous to what might happen if the world gets warmer and warmer," said Ryosuke Motani, one of the researchers, in a news release. "How long did it take before the globe was good enough for predators like this to reappear? In that world, many things became extinct, but it started something new. These reptiles came out during this recovery."

The findings are published in the journal Nature.