Evrim Yazgin
Cosmos science journalist
A 183-million-year-old plesiosaur fossil found in Germany has preserved soft tissue which reveals that the ancient marine reptiles had turtle-like scales.
The new research helps bring these prehistoric creatures to life in a way that hasn’t been possible despite 200 years of research.
Plesiosaurs are often mistaken for dinosaurs. While they lived at the same time, these ancient reptiles were part of a different lineage. Plesiosaurs died out at the end of the Cretaceous period 66 million years ago in the mass extinction event which spelled the end of the “Age of Dinosaurs”.
During the reign of dinosaurs on land, plesiosaurs were among several groups of marine reptiles which dominated Earth’s ancient seas.
Almost all the ancient marine reptiles went extinct 66 million years ago. Today, the only remnants of this once dominant group are sea turtles, marine iguanas, sea snakes and saltwater crocodiles.
Plesiosaurs are distinguished by their long necks, small heads and 4 paddle-like fins. Plesiosaur teeth were long and conical – perfectly adapted for catching slippery prey like fish and squid.
The largest plesiosaurs could grow to at least 12m long and weighed between 3 and 10 tonnes.
In research published in the journal Current Biology, researchers have analysed soft tissue from a plesiosaur fossil for the first time. The ancient marine reptile was found near the southern German town of Holzmaden.
The researchers note that the general shape of plesiosaurs in reconstructions hasn’t changed in 200 years. “However, the actual external appearance of these famous Mesozoic reptiles is largely unknown,” they write.
“Fossilised soft tissue, such as skin and internal organs, is exceptionally rare,” says lead author Miguel Marx, a PhD student at Sweden’s Lund University.
“We used a broad range of techniques to identify smooth skin in the tail region as well as scales along the rear edge of the flippers. This provided us with unparalleled insights into the appearance and biology of these long-extinct reptiles.”
A well-preserved, 4.5m-long plesiosaur specimen, denoted MH 7, was uncovered in a quarry in 1940. But it was not until preparation of the skeleton beginning in 2020 that researchers realised there were soft tissue traces around the tail and the right forelimb of the creature.
What the researchers found was a surprising mix of skin textures which may have performed different functions in life.
The smooth, hydrodynamic skin near the tail – which resembles the skin of modern leatherback turtles – would have helped the marine reptile swim quickly to catch its prey. But its scaly flippers – more akin to the skin of a green sea turtle – would have helped it traverse the rough seafloor.
“Our findings help us create more accurate life reconstructions of plesiosaurs, something that has been extremely difficult since they were first studied over 200 years ago. Also, the well-preserved German fossil really highlights the potential for soft tissue in providing valuable insights into the biology of these long-extinct animals,” Marx explains.
Not only did the palaeontologists uncover the texture of the skin, but the fossil had also preserved the skin cells themselves.
“Apart from the mosaic of smooth skin and scales, it was an incredible moment to visualise the cells in thin sections of the fossilised plesiosaur’s skin. I was shocked when I saw skin cells that had been preserved for 183 million years. It was almost like looking at modern skin,” Marx says.
