In a search for the evolutionary link between the sea-based ichthyosaurs and its land-roaming reptile ancestors, a group of researchers may have a massive breakthrough.

According to the Washington Post, authors of a study published in the journal Nature have detailed a fossil of an amphibious creature known as Cartorhynchus lenticarpus. The multi-institutional team believe C. lenticarpus is the evolutionary link between the land- and sea-dwellers.

"But now we have this fossil showing the transition," study lead author Ryosuke Motani, a professor of earth and planetary sciences at the University of California Davis, said in a press release. "There's nothing that prevents it from coming onto land."

Resembling a dolphin somewhat, C. lenticarpus lived about 256 million years ago, about four million years after the planet's largest-scale mass extinction. Given the nature of the mass extinction, scientists are also looking for clues as to how life recovered on Earth.

"This was analogous to what might happen if the world gets warmer and warmer," Motani said. "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 ichthyosaurs have also been a central piece in the creationism-versus-evolution argument, because they seemed to contradict the latter. However, the new study may flip creationists' argument on itself.

"Many creationists have tried to portray ichthyosaurs as being contrary to evolution," Motani told the Post. "We knew based on their bone structure that they were reptiles, and that their ancestors lived on land at some time, but they were fully adapted to life in the water. So creationists would say, well, they couldn't have evolved from those reptiles, because where's the link?

"Initially I was really puzzled by this fossil.

"I could tell it was related [to ichthyosaurs], but I didn't know how to place it. It took me about a year before I was sure I had no doubts."