Jurassic Sea Monster Resurfaces: Rare Fossil Unveils Secrets of Plesiosaur Evolution

A remarkably complete plesiosaur fossil found in southern Germany is shedding light on the early evolution of these iconic marine reptiles.

This Plesiopterys wildi specimen, unearthed from Holzmaden’s Posidonienschiefer Formation, reveals new insights into how plesiosaurs diversified and spread during the Early Jurassic.

Rare Glimpse into Early Jurassic Marine Reptiles

A newly identified plesiosaur fossil from southern Germany is offering valuable insights into how these ancient marine reptiles diversified during the Early Jurassic period. Published today (March 31) in PeerJ Life and Environment, the study describes a remarkably well-preserved specimen of Plesiopterys wildi, shedding light on the early evolution and geographic distribution of plesiosaurs in Europe around 180 million years ago.

Discovered in the Lower Jurassic Posidonienschiefer Formation near Holzmaden, the fossil, designated MH 7, is one of the most complete articulated plesiosaur skeletons ever found in the area. While ichthyosaurs and marine crocodile relatives are more commonly uncovered in this formation, plesiosaurs are much rarer. This find offers a unique window into the biodiversity of these long-necked marine reptiles during a key moment in their evolutionary history.

Key Findings:

• Well-Preserved Subadult Specimen: The MH 7 fossil represents a subadult Plesiopterys wildi, helping researchers refine the known features of the species and confirm its status as a distinct taxon.
• Clues to Evolutionary Transition: Phylogenetic analysis places Plesiopterys wildi as an early-diverging plesiosauroid, closely related to Franconiasaurus brevispinus. This suggests a gradual evolutionary shift toward more advanced cryptoclidid plesiosaurs of the Late Jurassic.
• Evidence of Regional Endemism: The find supports the idea that plesiosaurs may have evolved into regionally distinct species within the shallow seas of Early Jurassic Europe, pointing to early patterns of geographic isolation and specialization.

“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,” said lead author Miguel Marx from Lund University. “It also suggests that distinct plesiosaur communities may have evolved in different regions of the European seas during the Early Jurassic.”

A Turning Point in Plesiosaur History

The findings highlight the Early Jurassic as a crucial period for plesiosaur evolution, as early forms diversified and set the stage for later groups that would dominate marine ecosystems. The presence of unique plesiosaur species in different parts of Europe reinforces the hypothesis that early members of this group may have been geographically restricted.

“Our research reinforces that plesiosaurs were already evolving specialized adaptations and distinct regional lineages much earlier than we used to believe,” added co-author Sven Sachs. “This has important implications for understanding how marine reptiles responded to environmental changes in the Jurassic seas.”

Reference: “A new specimen of Plesiopterys wildi reveals the diversification of cryptoclidian precursors and possible endemism within European Early Jurassic plesiosaur assemblages” by Miguel Marx, Sven Sachs, Benjamin P. Kear, Mats E. Eriksson, Klaus Nilkens and Johan Lindgren, 31 March 2025, PeerJ.
DOI: 10.7717/peerj.18960

The study was conducted by an international team of researchers from Lund University, Naturkunde-Museum Bielefeld, Uppsala University, and Urwelt-Museum Hauff.

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