A study has identified a new species of plesiosaur named Plesionectes longicollum that is thought to have swam the oceans during the Toarcian period, nearly 183 million years ago.
Excavated from a quarry in Germany in 1978, the specimen has been stored in collections at the Stuttgart State Museum of Natural History for almost 50 years. The new research investigates the anatomy of the skeleton in great detail, revealing a number of unusual characteristics – not least the animal's extraordinarily long neck.
The work, conducted by vertebrate palaeontologist Sven Sachs and co-author Dr. Daniel Madiza from the Polish Academy of Sciences, has been published in the journal PeerJ Life & Environment.
What makes the new reptile unique?
The specimen was excavated from a quarry in Holzmaden, part of the Posidonia Shale fossil beds in south-west Germany. The area is famous for its exceptionally preserved and complete fossils, but Sachs says that whilst fossils of other species, such as ichthyosaurs, have been unearthed in high numbers within the shale, plesiosaurs are “much rarer”, making the discovery significant.
The name of the newly classified species – Plesionectes longicollum – means 'long-necked near-swimmer’ and reflects the distinctive long-necked characteristic that defines the group of early Jurassic marine reptiles referred to as plesiosaurs.
The prehistoric predator has 21 dorsal vertebrae and an extremely lengthy neck composed of 43 vertebrae, that’s more than double the number of vertebrae belonging to the land-roaming Diplodocus.
Despite not being fully mature, the skeleton – measuring 2.95 metres long (around 9.5 feet) – was already larger than many of the other plesiosaurs from the Posidonia Shale.
Sachs says P. longicollum "represents the oldest known plesiosaur from the Posidonia Shale. All other finds are younger.”
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Dr. Madzia says, "This discovery adds another piece to the puzzle of marine ecosystem evolution during a critical time in Earth's history. The early Toarcian period when this animal lived was marked by significant environmental changes, including a major oceanic anoxic event that affected marine life worldwide."
The authors say the find suggests the regional biodiversity of the prehistoric ecosystem in which P. longicollum lived was higher than previously thought. The research also shows the importance of studying historically collected specimens, as many hold significant information about Earth's past environments.
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Top image Plesionectes longicollum. Credit: Staatliches Museum für Naturkunde Stuttgart
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