The nearly complete specimen of a known plesiosaur species is opening scientists’ eyes to the diversification of these ancient marine reptiles during the Early Jurassic period.

Found in southern Germany, Plesiopterys wildi, a relatively small species measuring 10 feet long, is the only member of its genus, and a study published in the journal PeerJ Life and Environment details the discovery and analysis of the “exceptionally well-preserved” fossil.

It offers new clues about the evolution and geographic distribution of plesiosaurs in Europe nearly 180 million years ago, particularly about how isolated each was from all others, and how this isolation affected the animals’ development.

Unearthed from the Lower Jurassic Posidonienschiefer Formation near the German town of Holzmaden, the fossil, referred to as MH 7, is one of the most complete articulated plesiosaur skeletons found in the region.

Unlike ichthyosaurs and marine crocodile relatives which dominate the fossil record of the formation, plesiosaurs are comparatively rare.

The researchers say MH 7 represents a “subadult” individual, refining the known characteristics of the species and confirming its validity as a distinct taxon.

The team’s analysis positions Plesiopterys wildi as an early-diverging plesiosauroid, closely related to Franconiasaurus brevispinus, suggesting a gradual evolutionary transition towards more derived Cryptoclidids, another family of plesiosaurs from the Late Jurassic.

The researchers say the discovery supports the idea that plesiosaur species may have been “regionally distinct” within the epicontinental seas of Early Jurassic Europe.

“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 study lead author Miguel Marx, of Lund University, Sweden.

“It also suggests that distinct plesiosaur communities may have evolved in different regions of the European seas during the Early Jurassic.”

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He said 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 researchers say that 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.

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“Our research reinforces that plesiosaurs were already evolving specialised adaptations and distinct regional lineages much earlier than we used to believe,” said study co-author palaeoherpetologist Sven Sachs.

“This has important implications for understanding how marine reptiles responded to environmental changes in the Jurassic seas.”