Paleontologists discover 'unusual' long-necked plesiosaur in Germany

In 1978, paleontologists discovered the remarkable, nearly complete skeleton with even some fossilized tissue surviving, at a quarry in the famous Posidonia Shale fossil bed roughly 18 miles southeast of Stuttgart. Initial analysis clearly indicated the specimen was a plesiosauroid—a family of long-necked marine reptiles that swam Earth’s ancient oceans. Researchers soon transferred it to the Stuttgart State Museum of Natural History, but the creature never received a thorough examination. Instead, it remained within the institution’s archives for years.

After nearly 50 years of storage, paleontologists were finally able to carve out time for a thorough evaluation of the mystery. And according to their analysis published August 4 in the journal Peerj Life & Environment, the bones belong to a previously unknown species: Plesionectes longicollum, or the “long-necked near-swimmer.” The Loch Ness monster-esque reptile lived around 184 to 175 million years ago during the Lower Jurassic period.

The full Plesionectes skeleton is largely complete, although the skull is heavily damaged. Credit: Stuttgart State Museum of Natural History

“This specimen has been in collections for decades, but previous studies never fully explored its distinctive anatomy,” study lead author and paleontologist Sven Sachs said in a statement. “Our detailed examination revealed an unusual combination of skeletal features that clearly distinguish it from all previously known plesiosaurs.”

Although experts determined the specimen had yet to reach adulthood by the time it died, its details are so significantly different from other plesiosauroids that it required a new genus and species, including an impressive backbone.  The remarkable skeleton measures nearly 10.5 feet long with a 4.1 feet neck composed of at least 43 vertebrae.

“This number is considerably higher than in most other Early Jurassic plesiosauroids,” they wrote in their analysis.

While largely well-preserved, the researchers noted the same can’t be said for its “heavily damaged” skull.

P. longicollum lived during a “critical time in Earth’s history” known as the early Toarcian period—an era kicked off by a mass extinction known as the Toarcian Oceanic Anoxic Event. At that time, the planet hosted vast, thin ice sheets that stretched into lower latitudes. A major volcanic event is believed to have kickstarted the anoxic event, resulting in global warming from rising atmospheric carbon dioxide levels. This in turn raised ocean temperatures anywhere between 1.8 to 10.8 degrees Fahrenheit, depending on latitude. At its height, Toarcian surface ocean temperatures averaged 69.8 degrees Fahrenheit.

“This discovery adds another piece to the puzzle of marine ecosystem evolution during a critical time in Earth’s history,” study co-author Daniel Madzia explained.

P. longicollum is now the sixth plesiosaur species discovered at the Posidonia Shale in Holzmaden—including representatives from all three major plesiosaur lineages.