A remarkable fossil discovery in southern Germany is offering scientists new insights into the plesiosaur, one of the most mysterious marine reptiles of the Jurassic period.
The nearly complete skeleton of Plesiopterys wildi, described in a new study published in PeerJ Life and Environment, provides rare and valuable information about how these long-necked swimmers diversified and spread across ancient European seas nearly 180 million years ago.
“Our research reinforces that plesiosaurs were already evolving specialized adaptations and distinct regional lineages much earlier than we used to believe,” said co-author Sven Sachs in a recent statement. “This has important implications for understanding how marine reptiles responded to environmental changes in the Jurassic seas.”
Plesiosaurs: A Marine Dinosaur
Although often called “marine dinosaurs,” creatures like plesiosaurs, ichthyosaurs, and mosasaurs weren’t technically dinosaurs—they were marine reptiles that lived during the Mesozoic Era (about 252 to 66 million years ago) alongside their land-dwelling counterparts. These animals played important roles in ancient ocean ecosystems, functioning like modern whales, dolphins, sharks, and large fish.
Plesiosaurs were marine reptiles with broad bodies, long necks, and paddle-like limbs. These features made them well-adapted for life in the water, where they fed on fish and other sea creatures. While ichthyosaurs and their marine crocodile relatives are more commonly found in the fossil record, plesiosaur fossils are relatively rare—especially well-preserved ones.
That’s why discovering a nearly complete Plesiopterys wildi skeleton in the famous Posidonienschiefer Formation near Holzmaden, Germany, is such a big deal. This fossil, known as MH 7, is one of the region’s most complete articulated plesiosaur skeletons ever found.
A Window into Early Plesiosaur Evolution
MH 7 represents a subadult individual of Plesiopterys wildi, giving researchers a clearer picture of this early plesiosaur species.
“The Holzmaden specimen gives us an unprecedented look at Plesiopterys wildi in a more mature stage of development, allowing us to refine our understanding of this species and its place in plesiosaur evolution,” lead author Miguel Marx from Lund University explained.
By analyzing the skeleton, the team confirmed Plesiopterys wildi as a distinct species and placed it near the base of the plesiosaur family tree. Specifically, it appears to be an early relative of later, more advanced plesiosaurs known as cryptoclidids—suggesting a step-by-step evolutionary shift from simpler to more specialized forms.
The study also suggests that different species of plesiosaurs may have been regionally distinct, evolving in separate areas of the shallow seas that once covered much of Europe. “It also suggests that distinct plesiosaur communities may have evolved in different regions of the European seas during the Early Jurassic,” Marx added.
Regional Specialization in Marine Ecosystems
This discovery reinforces the idea that the Early Jurassic was a time of rapid diversification for plesiosaurs as they evolved into new shapes and ecological roles. It also supports the concept of regional endemism—where distinct species evolved in different geographic areas, possibly due to environmental barriers or varying ocean conditions.
Ultimately, the MH 7 specimen adds to our knowledge of plesiosaur diversity and helps paleontologists piece together how marine ecosystems changed and adapted over time. As more fossils like this are discovered and studied, they continue to reveal life’s rich and dynamic history beneath the waves in Earth’s distant past.
Kenna Hughes-Castleberry is a freelance science journalist and staff writer at The Debrief. Follow and connect with her on BlueSky or contact her via email at kenna@thedebrief.org