Prehistoric sea monster the size of a bus discovered in Russia

Scientists have identified a "highly unusual" new species of extinct sea-dwelling reptile in Russia.

Similar in appearance to a river dolphin or gharial crocodile, the fish-eating sea beast would have had a long beak-like snout.

Related to the top predators who ruled the ocean during the dinosaur age, its lengthy "rostrum" set it apart from its relatives who had large and powerful toothed jaws.

The "pilosaur Luskhan itilensis" is estimated to have measured about 6.5m (21.3ft) - the size of a small bus - according to research published in the journal Current Biology .

It would have had four large flippers which evolved from feet over a long period of time, and an oar-like tail.

It is thought to have lived 130 million years ago at the same time as stegosaurus and diplodocus. Tyrannosaurus rex lived 66 million years ago.

The marine reptile's skull fossil was unearthed from the bank of the Volga River near the Russian city of Ulyanovsk 15 years ago.

The skull alone, with its long and slender snout, measured 1.5m (5ft) - the average height of a 13-year-old boy.

Scientists believe that the animal's unusual beak suggests that this family of marine reptiles - called plesiosaurs - colonised a much wider range of ecological niches than previously believed.