Scientists have identified a new species of mosasaurs (photo) that once dwelled in freshwater environments, according to a new study.

A team of researchers have been unearthing several specimens of marine species including mosasaurs, lizards, turtles and crocodiles from an open coal mine in the Bakony Hills of western Hungary since 1999.

Several specimens of the mosasaurs, ranging from three feet long small juveniles to 20 feet long adults, were also uncovered in the coal mine.

This site was once part of a group of tropical islands located in the middle of a massive freshwater "seaway" that separated Africa and southern Europe during the Upper Cretaceous period (90 to 65 million years ago). The discovery of several specimens of mosasaurs in one site suggests that the marine mammal was a freshwater dweller, reports National Geographic.

Researchers named the species as Pannoniasaurus inexpectatus. While "Pannonia" refers to the place in Hungary where the specimens were found, "saurus" means lizard. "Inexpectatus" refers to the unexpected presence of the mosasaurs in freshwater, explains LiveScience.

The new species possessed a crocodile-like skull and a tail that does not match with any other member of the mosasaur family. Pannoniasaurus had sharp teeth suggesting that the aquatic species fed on fish, lizards and amphibians. According to the researchers, the limbs of Pannoniasaurus resembled legs, which could mean that the species was an amphibian that used its legs occasionally to climb onto land.

"I suspect they behaved a lot like modern crocodiles do today. They spent a lot of time in the water, but there's nothing wrong with crawling from river to river when things dry up or even using shallow water to bask and moderate their body temperature," study co-author Michael Caldwell, a mosasaur expert at the University of Alberta in Canada, told National Geographic.

Researchers are further planning to study Pannoniasaurus in order to understand their biology, how they moved and what they ate.

The findings of the study are published in the open access journal PLOS ONE.