A newly described plesiosaur fossil from southern Germany is providing vital new information about the diversification of these iconic marine reptiles during the Early Jurassic. The discovery, which has been published in PeerJ, sheds light on the evolution, geographic distribution, and early developmental stages of plesiosaurs, a group of long-necked, prehistoric reptiles that roamed the seas almost 180 million years ago.
The specimen, a remarkably well-preserved Plesiopterys wildi, was unearthed from the Lower Jurassic Posidonienschiefer Formation near Holzmaden, a region renowned for its wealth of fossilized marine life. This fossil, designated as MH 7, is considered one of the most complete articulated plesiosaur skeletons ever discovered in the area, offering scientists an unparalleled opportunity to study a lesser-known chapter in the story of these ancient creatures.
Plesiosaurs, though they have captured the imagination of paleontologists and the public alike due to their distinct long necks and large, paddle-like limbs, have remained elusive in the fossil record of the Posidonienschiefer Formation. This formation, famous for preserving ancient marine ecosystems, is dominated by the remains of ichthyosaurs—fish-like reptiles—and marine crocodile relatives. By contrast, plesiosaurs are comparatively rare, making the MH 7 fossil a significant addition to our understanding of Early Jurassic marine life.
Unearthing a Unique Specimen
The newly discovered specimen represents a subadult individual of Plesiopterys wildi, providing crucial evidence of its developmental stage. The remarkable preservation of the fossil has allowed the research team to refine their knowledge of this species and confirm its classification as a distinct taxon within the broader plesiosaur family. The fossil provides important clues not only about the morphology and growth patterns of Plesiopterys wildi but also about the early evolution of plesiosaurs.
The MH 7 fossil is part of a broader trend in recent years, where increasingly complete plesiosaur fossils are providing clearer insights into the evolutionary pathways of these fascinating marine reptiles. Through careful analysis, scientists were able to examine the skeletal features of this subadult, offering more details on the species’ life history, anatomical development, and eventual role in the Jurassic marine ecosystem.
“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.”
Phylogenetic Analysis and Evolutionary Insights
One of the most significant aspects of this study is the phylogenetic analysis of Plesiopterys wildi, which positions this species as an early-diverging plesiosauroid. The fossil places it in close relation to Franconiasaurus brevispinus, another early plesiosaur from the region, and suggests a gradual evolutionary transition toward the more derived cryptoclidids that would dominate marine ecosystems during the Late Jurassic.
This finding provides essential context for understanding how plesiosaurs evolved during the Early Jurassic, a period when they were diversifying and filling various ecological niches in the marine environment. The phylogenetic relationship between Plesiopterys wildi and other early-diverging plesiosaurs suggests that the species represents an important evolutionary step in the development of more specialized forms of these long-necked reptiles.
The discovery also has important implications for the geographical distribution of plesiosaurs. It supports the hypothesis that early plesiosaur species may have been regionally distinct, with different groups evolving in separate parts of the European seas. This idea reinforces the concept of paleobiogeographical segregation, where species’ distributions were influenced by both environmental factors and the physical barriers of ancient seas.
A Glimpse into Early Jurassic Marine Life
The research team’s findings suggest that the Early Jurassic period was a crucial time for the diversification of marine reptiles like plesiosaurs. As the seas were undergoing significant ecological shifts, early plesiosaur species were beginning to evolve specialized adaptations. These changes eventually set the stage for the larger, more derived plesiosaur groups that would dominate the oceans during the Late Jurassic.
As paleontologists continue to unearth more fossils from this time period, it is becoming increasingly clear that the diversification of marine reptiles was not as sudden as once thought. Instead, early forms of plesiosaurs were evolving more slowly, with distinct regional lineages forming as they adapted to different marine environments across Europe.
“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. “This has important implications for understanding how marine reptiles responded to environmental changes in the Jurassic seas.”
The Holzmaden region, with its rich fossil deposits, has long been a key site for the study of ancient marine life. The discovery of MH 7 adds to the growing body of evidence supporting the idea that different species of marine reptiles coexisted in distinct regions, each adapting to their own ecological niches. This insight provides a clearer picture of how marine ecosystems were structured during the Early Jurassic, a time when marine reptiles were undergoing significant evolutionary changes.
An International Team Effort
This exciting discovery is the result of a collaborative effort by an international team of researchers from Lund University, Naturkunde-Museum Bielefeld, Uppsala University, and Urwelt-Museum Hauff. The team’s combined expertise in paleontology, evolutionary biology, and fossil preparation was crucial to the success of this study, highlighting the importance of interdisciplinary approaches in modern paleontological research.
The research team utilized cutting-edge imaging techniques to examine the fossil in detail, including CT scanning and 3D reconstruction, which allowed them to study the bones without damaging the specimen. These advanced methods helped reveal previously unknown features of Plesiopterys wildi, contributing to a deeper understanding of its anatomical and evolutionary characteristics.
The discovery of MH 7 is part of a broader trend in recent years, where increasingly complete plesiosaur fossils are being found in Europe, offering scientists an unparalleled opportunity to refine their understanding of plesiosaur evolution. These new fossils provide not only insights into the species’ morphology but also into the broader evolutionary and ecological dynamics of the Early Jurassic.
Conclusion: A New Chapter in Plesiosaur Research
The newly described Plesiopterys wildi fossil from Holzmaden marks an important milestone in our understanding of plesiosaur evolution and their geographic distribution during the Early Jurassic. With its exceptional preservation and the wealth of information it provides, MH 7 opens new avenues for further research into the early development of marine reptiles.
As scientists continue to explore the fossil-rich deposits of the Posidonienschiefer Formation, it is likely that even more discoveries will shed light on the biodiversity of ancient marine ecosystems and the evolutionary history of plesiosaurs. The Holzmaden specimen, with its clear implications for the evolutionary and biogeographical patterns of Early Jurassic marine reptiles, promises to be a key reference point in the ongoing study of these fascinating creatures. The study of Plesiopterys wildi and its peers not only expands our knowledge of plesiosaurs but also helps us understand how marine ecosystems evolved in response to dramatic environmental changes during the Mesozoic Era.
Reference: Miguel Marx et al, A new specimen of Plesiopterys wildi reveals the diversification of cryptoclidian precursors and possible endemism within European Early Jurassic plesiosaur assemblages, PeerJ (2025). DOI: 10.7717/peerj.18960