Ancient Bizarre Sea Monster the Size of a Bus Discovered in Russia

A bus-sized sea monster that lived alongside the dinosaurs 130 million years ago has been discovered in Russia. The well-preserved 5 foot-long skull of an extinct reptile was first discovered on the bank of the Volga River in 2002, but until now had not been identified as a new species.

The fossil belongs to a group of marine reptiles called plesiosaur. These predatory creatures lived in the Triassic and Jurassic Period, eventually being wiped out in the same mass extinction event that killed all the dinosaurs 66 million years ago.

The new species was a pliosaur, a type of short-necked plesiosaur that could swim faster than their long-necked relatives, and had huge teeth and powerful jaws—making them one of the top ocean predators at the time.

In a study published in the journal Current Biology on Thursday, an international team of scientists set about identifying the fossil from the Volga River deposits. In it, they show that the fossil is not only a new species, but its unusual features means we may have to rethink the evolution of this group of ancient reptiles altogether.

Researchers estimate the species, which they have called Luskhan itilensis, was around 21 feet long—making it about average-sized. (Pliosaurs range from 5 to 49 feet.)

What was remarkable about the fossil, however, was its mishmash of characteristics from several distinct species. Previously, short-necked plesiosaurs were thought to have been constrained to very specific ecological niches and were generally considered to have been apex predators. The distantly related clade Polycotylidae, on the other hand, was a fast-swimming piscivore.

Luskhan itilensis, the researchers report, has features of both. This indicates evolutionary convergence, where species not closely related develop similar features because they live in similar environments.

The most notable feature was its long, slim rostrum (a beak-like snout), which would have meant it resembled fish-eating creatures like river dolphins far more than other pliosaurs. "This is the most striking feature, as it suggests that pliosaurs colonized a much wider range of ecological niches than previously assumed," lead author Valentin Fischer, lecturer at the Université de Liège, Belgium, said in a statement.

Luskhan itilensis
Artist impression of Luskhan itilensis. The new species of pliosaur has raised questions about the evolution of these marine reptiles. Andrey Atuchin, 2017

In an interview with Newsweek, he says the team had been looking for unique features, such as distinctive morphology in the cranium and fins. "On this pliosaurs, we found I believe 20 to 22 unique features. It's definitely an oddball. Contrary to its cousins it has a very elongated rostrum the two teeth at the front are like two small tusks and they are pointing forward, which is very strange."

"Pliosaurs were the top predators of the Middle Jurassic-early Late Cretaceous times. So these animals probably ate turtles, birds, large fishes, other plesiosaurs, etc," he continues. "But Luskhan itilensis has peculiar features such as a long and slender snout and small teeth which indicate a diet composed of smaller and softer prey items, such as small fishes and cephalopods. So we think Luskhan wasn't the apex predator at the time."

Luskhan itilensis would have lived alongside other pliosaurs—fossils have been found in the same deposits of the Volga River. As a result, the researchers say the new fossil shows pliosaurs were far more ecologically diverse than once thought.

"Our analysis suggest that the emergence of the diverse and long-lived clades of short-necked plesiosaurs was not driven by precocious [early development] colonization of the particular ecological niches proposed for the later branching of members of the clades," they wrote. "The evolution of plesiosaurs as a whole appears to be characterized by frequent and profound convergence ranging from anatomical details to entire body plans."

Commenting on the study, paleontologist Dean Lomax, tells Newsweek : "The new specimen is a member of the Pliosauridae, a group that includes some of the largest marine reptiles to have ever lived. However, this new species has a body plan that is more similar—i.e., convergent—to a totally unrelated group of pliosaurs, called the Polycotylidae.

"The new discovery helps to further our understanding of the complex evolutionary relationships among pliosaurs.