Massive pliosaur gave rise to a dynasty of mega-predators

Fossils dating back to 170 million years have been identified as belonging to the oldest-known mega-predatory pliosaur from the Age of Dinosaurs. 

This discovery not only improves our understanding of these ancient marine reptiles, but also provides significant insights into the evolution of plesiosaurs.

The remains of this ancient sea monster were originally discovered 40 years ago in northeastern France. Now, these fossils have been meticulously analyzed by an international team of paleontologists.

New pliosaur genus 

The combined efforts have led to the classification of these remains under a new pliosaur genus named Lorrainosaurus.

Pliosaurs, a type of plesiosaur known for their short necks and massive skulls, have been around for over 200 million years. Yet, they became dominant apex marine predators only after a global decline of other marine reptiles over 170 million years ago. 

Huge pliosaurs 

“Lorrainosaurus was one of the first truly huge pliosaurs. It gave rise to a dynasty of marine reptile mega-predators that ruled the oceans for around 80 million years,” explained Sven Sachs, a researcher at the Naturkunde-Museum Bielefeld who led the study.

Lorrainosaurus, which is the oldest large-bodied pliosaur represented by an associated skeleton, boasted of jaws extending over 1.3 meters with large conical teeth. The creature’s body resembled a bulky torpedo propelled by four flipper-like limbs. 

It is estimated that this massive reptile spanned over 6 meters from snout to tail and roamed the oceans during the early Middle Jurassic period. Interestingly, this is a period from which very little is known about plesiosaurs.

Mega-predatory pliosaurs 

“Our identification of Lorrainosaurus as one of the earliest mega-predatory pliosaurs demonstrates that these creatures emerged immediately after a landmark restructuring of marine predator ecosystems across the Early-to-Middle Jurassic boundary, some 175 to 171 million years ago,” explained Daniel Madzia from the Institute of Paleobiology of the Polish Academy of Sciences.

“This event profoundly affected many marine reptile groups and brought mega-predatory pliosaurids to dominance over ‘fish-like’ ichthyosaurs, ancient marine crocodile relatives, and other large-bodied predatory plesiosaurs.”

Successful marine predators 

Benjamin Kear from The Museum of Evolution at Uppsala University provided context on the dominance of pliosaurs, which were some of the most successful marine predators of their time.

“Famous examples, such as Pliosaurus and Kronosaurus – some of the world’s largest pliosaurs – were absolutely enormous with body-lengths exceeding 10 m,” said Kear.

“They were ecological equivalents of today’s Killer whales and would have eaten a range of prey including squid-like cephalopods, large fish and other marine reptiles. These have all been found as preserved gut contents.”

Study implications 

After their discovery near Metz in Lorraine by paleontology enthusiasts, the fossils examined for the study were donated to the Natural History Museum in Luxembourg. 

A brief report on Lorrainosaurus was published in 1994. Otherwise, the fossils remained largely unexplored until this study.

According to the researchers, Lorrainosaurus indicates that the reign of gigantic mega-predatory pliosaurs must have commenced earlier than previously thought, and was locally responsive to major ecological changes.

“Lorrainosaurus is thus a critical addition to our knowledge of ancient marine reptiles from a time in the Age of Dinosaurs that has as yet been incompletely understood,” said Kear.

The study is published in the journal Scientific Reports.

Image Credit: Joschua Knüppe

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