Skeleton of the new plesiosaur at the Urwelt-Museum Hauff in Holzmaden, Germany
Klaus Nilkens/Urwelt-Museum Hauff
The soft tissue of a plesiosaur has been studied in detail for the first time, revealing that the marine reptiles, which lived during the age of dinosaurs and went extinct at the same time, had scales similar to those of modern sea turtles.
The 183-million-year-old, 4.5-metre-long plesiosaur fossil, known as MH7, was first excavated from a quarry near Holzmaden, Germany, in 1940 but it was buried in a museum garden to protect it during the second world war. It then spent the next 75 years or so in storage until it was finally assembled and prepared for study in 2020.
Miguel Marx at Lund University in Sweden and his team prepared thin sections of the fossil, which were then treated so the minerals were dissolved away, leaving the organic remains. This allowed them to study the microscopic structure of the fossil tissue.
Illustration of a plesiosaur with scales on the flipper and smooth, scale-less skin along the body
Joschua Knüppe
Although at least eight other plesiosaur fossils are known to have soft tissue preserved, most are historically significant museum specimens and it isn’t possible to study them using destructive sampling methods, says Marx. “This is the first time anyone has conducted an in-depth analysis of fossilised soft tissues from a plesiosaur,” he says.
The team was amazed to discover that the reptile had areas of both smooth and scaly skin. “Taken together, this plesiosaur was an interesting chimera between something like a green sea turtle with scales and the [smooth-skinned] leatherback turtle,” says Marx. “I would have expected this plesiosaur to be scale-less like contemporary ichthyosaurs.”
The scaled skin on the flippers probably helped the plesiosaur swim through the water by providing stiffness or aided it in moving along the seafloor when searching for food, he says. The scale-less skin on the rest of the body would have reduced the effects of drag when swimming.
“The actual external appearance of long-necked plesiosaurs is really anyone’s guess, but now we have a better idea thanks to this new fossil,” says Marx.
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