A previously unknown Jurassic sea reptile has been uncovered from Germany’s renowned Posidonia Shale fossil beds. The discovery sheds new light on the oceans around about 183 million years ago.
Scientists at the Naturkunde‑Museum Bielefeld, working with colleagues from the Polish Academy of Sciences, examined a nearly complete skeleton that has preserved traces of soft tissue.
Sea creature with distinctive features
While unearthed back in 1978 from Holzmaden quarry, the distinctive aspects of the fossil have been overlooked.
“This specimen has been in collections for decades, but previous studies never fully explored its distinctive anatomy,” said Sven Sachs, lead author of the study.
“Our detailed examination revealed an unusual combination of skeletal features that clearly distinguish it from all previously known plesiosaurs.”
The species has been named Plesionectes longicollum, which translates to long‑necked near‑swimmer.” The creature represents a new species within the plesiosauroid group – a lineage of long‑necked marine reptiles that sailed Earth’s seas during the age of dinosaurs.
Despite representing an immature individual, the fossils’ anatomical traits were pronounced enough to confirm a new genus and species.
What are plesiosaurs?
Plesiosaurs were marine reptiles that lived during the time of the dinosaurs. They first appeared in the Late Triassic and became especially common in the Jurassic period. These animals lived in oceans all over the world and could grow to impressive sizes.
There are two major body types among plesiosaurs. Some had small heads, long necks, and wide bodies with four flippers – like the newly identified Plesionectes longicollum.
Others had shorter necks, larger heads, and strong jaws built for powerful bites. Both types were excellent swimmers, using their flippers to glide through water in a motion similar to underwater flying.
They likely fed on fish, squid, and other small marine creatures. Their fossils have been found on every continent, which shows how widespread they were.
Despite their success, plesiosaurs eventually went extinct at the end of the Cretaceous period – around the same time as the dinosaurs.
This makes every new discovery, like Plesionectes longicollum, important for understanding how these animals lived, evolved, and fit into ancient ocean ecosystems.
Insights from the Jurassic reptile
This reptile is now the oldest known plesiosaur from the Holzmaden region. The study shows that the Posidonia Shale holds even more diversity than scientists realized.
Although other plesiosaurs have been found in the same formation – five in total from all three major plesiosaur lineages – this new specimen reveals yet another branch on the family tree of Jurassic marine life.
“This discovery adds another piece to the puzzle of marine ecosystem evolution during a critical time in Earth’s history,” explained Dr. Daniel Madzia of the Polish Academy of Sciences.
“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.”
Why fossils like this still matter
Uncovering a new species is always exciting – but what makes the Plesionectes longicollum fossil even more remarkable is how it reminds us that science is always evolving.
Museum collections everywhere contain thousands of specimens that were tagged, shelved, and perhaps forgotten for years. As instrumentation improves and new questions are asked, these old discoveries can gain new significance.
Re-examining fossils with modern techniques allows scientists to spot differences that might have been missed before.
In this case, those differences were enough to rewrite part of the plesiosaur family tree. The research shows how much we still have to learn – not just from new digs, but from existing collections.
Fossils like this one offer more than a glimpse into extinct species – they provide insight into how life adapted to past climate shifts, ocean changes, and extinction events. Ultimately, they help scientists better anticipate how modern ecosystems might respond to the environmental challenges we face today.
The Plesionectes longicollum fossil – catalogued as specimen SMNS 51945 – is on permanent display at the Staatliches Museum für Naturkunde Stuttgart (Stuttgart State Museum of Natural History).
The full study was published in the journal PeerJ.
Image Credit: Peter Nickolaus
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