A new species of pliosaur fossil, a predatory marine reptile from the dinosaur age, was unearthed in Russia. The large marine reptile is too big and was described by experts to be the size of a bus.

The new discovery may change how the pliosaur species group evolved. Plesiosaur marine reptiles, which dates back to the "age of dinosaurs," are considered the longest-lived radiations of aquatic tetrapods and are the most diverse as well.

When it comes to appearance, they are believed to have four large flippers, stiff trunk and varying neck length (a feature uncommon with other marine vertebrates). The newly discovered bus-sized marine reptile fossil found in Russia, or the pliosaur, is believed to be another kind of plesiosaurs.

It has a two-meter long skull with humongous teeth and powerful jaw. Because of these features, it's considered as the top predators of the oceans during the age of dinosaursThe details of the new study pertaining to the new species of marine reptile will be published in the journal Current Biology.

The marine reptile fossil was unearthed in Russia in 2002 near the Volga River. It's also believed to be about 130 million years old and is exceptionally well-preserved. Its distinctive skull is also called "Luskhan itilensis," and finding a skull like this size means the owner is relatively a large species.

"This is the most striking feature, as it suggests that pliosaurs colonized a much wider range of ecological niches than previously assumed" Valentin Fischer, lecturer at the Université de Liège and lead author of the study said in a statement.

The team analyzed the different data sets collected from the fossil. They discovered an evolutionary convergences or the phenomenon where species evolve and mimic one another due to their similar roles and feeding strategies. There could have been evolutionary convergences during the time of plesiosaurs.

The data also explains the final extinction of pliosaurs. Based on the data, the species were able to bounce back after the Jurassic extinction but then nothing survived the succeeding extinction phenomenon.