New species of marine reptile from millions of years ago discovered in Germany

A new species of marine reptile from around 150 million years ago has been described in the journal PeerJ by an international team of scientists. The exceptionally well-preserved specimen from southern Germany belongs to one of the longest plesiosaurs known from the Early Jurassic and provides valuable data on the evolution of marine predators.

A discovery that changes the view on marine reptiles

An international team of paleontologists has reported the identification of a new species of plesiosaur that lived around 183 million years ago, in the early Toarcian, in the waters of what is now Europe. The discovery was made in the Posidonia Shale Formation in Holzmaden – a region famous for exceptionally well-preserved Early Jurassic fossils. This is the first time that an almost complete skeleton of such a large predator has been found in this area.

The new species, named Plesionectes longicollum, is distinguished by its exceptionally long neck compared to other Early Jurassic plesiosaurs. According to the study’s authors, this feature may change existing ideas about the morphological diversity of marine reptiles from that period. The analysis, conducted by a team led by Prof. Sven Sachs from the Naturkunde-Museum Bielefeld in collaboration with Dr. Daniel Madzia from the Polish Academy of Sciences, was published on 4 August 2025 in PeerJ and is based on detailed anatomical and comparative studies with other specimens.

Plesionectes longicollum – a new predator of the Early Jurassic

Plesionectes longicollum belonged to the extinct group of marine reptiles in the clade Plesiosauroidea, which during the Jurassic occupied the position of some of the ocean’s top predators. Its neck contained as many as 43 vertebrae. According to the authors, this feature may have been significant in hunting, increasing the range of attack on fish and other marine organisms.

Skeletal analysis indicates that the specimen measured about 3 meters in length, with the neck making up almost half of that. Limb elements were also well-preserved, allowing further research into the swimming biomechanics of this predator.

Exceptionally well-preserved fossil from Germany

The skeleton of Plesionectes longicollum was discovered in the limestone deposits of the Posidonia Shale Formation in Holzmaden. As described by the authors in PeerJ, the holotype includes an almost complete vertebral column, fragments of the skull and jaw, and limb elements.

Such good preservation is rare for large representatives of Plesiosauroidea, whose remains are usually found as incomplete fossils. According to the researchers, the fine-grained sediment and anoxic conditions at the bottom of the ancient sea inhibited tissue decay, preserving anatomical details, including joint structures and vertebral processes. This material enabled a detailed morphological analysis and comparisons with other Early Jurassic plesiosaurs.

What does the discovery reveal about the evolution of marine reptiles?

The analysis of Plesionectes longicollum remains shows that Early Jurassic plesiosaurs were more morphologically diverse than previously thought. The unusually long neck points to evolutionary experiments in hunting strategies and the exploitation of ecological niches. The research team believes the discovery fills a gap in understanding the transition from typical plesiosaur forms to species with features similar to long-necked elasmosaurids.

The publication, prepared by scientists from Germany, the USA, and the UK, provides detailed anatomical documentation, photographs, and 3D reconstructions that will serve as a reference point for future studies. The authors emphasize that such discoveries are significant not only for paleontology but also for promoting knowledge about the evolution of marine ecosystems from millions of years ago.

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main photo: S. Sachs & D. Madzia/Wikimedia