Rare Fossil of 183-Million-Year-Old ‘Sea Monster’ Reveals Both Smooth and Scaly Skin
For the first time, scientists have completed an in-depth analysis of fossilized soft tissues from a plesiosaur
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Plesiosaurs were long-necked reptiles that prowled the world’s oceans between 66 million and 215 million years ago. Paleontologists have learned a lot about the bodies of these ancient sea monsters by studying their fossilized skeletons. But from their bones alone, it’s difficult to tell what these now-extinct creatures actually looked like as they roamed the seas in search of food.
Now, a new discovery offers a clearer picture of their external appearance: Scientists re-examined an old plesiosaur fossil, which had been sitting in a museum’s storage for decades, and realized it had both smooth skin and small scales covering its body.
This revelation should not only help scientists create more accurate illustrations and reconstructions of plesiosaurs, but it may also reveal new insights into how the creatures maneuvered through their environment.
Scientists described their findings in a new paper published Thursday in the journal Current Biology.
“These are iconic animals, and the way we reconstruct them hasn’t changed for nearly 200 years, so this is a big update,” says study lead author Miguel Marx, a paleobiologist at Sweden’s Lund University, to the New York Times’ Sara Novak. “It changes our perspective on their evolutionary history and how they adapted to life in the ocean.”
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For the study, scientists analyzed soft tissue samples from a 183-million-year-old plesiosaur. The nearly 15-foot-long specimen, known as MH7, was initially discovered in 1940 in a quarry near Holzmaden, Germany. During World War II, it was briefly buried in a garden to prevent it from becoming damaged. After it was unburied, MH7 was moved into storage at Urwelt-Museum Hauff, where it remained for roughly 75 years. Finally, in 2020, it was taken out of storage and assembled, per New Scientist’s James Woodford.
Because of the unique ocean chemistry of the region where it was found, some of the creature’s soft tissues were preserved—which gave modern researchers a rare opportunity to study 183-million-year-old skin.
The team collected fingernail-sized samples from MH7’s tail and flipper. After processing the samples to strip away any minerals, they looked at them under a microscope—which was an “incredible moment,” Marx says in a statement.
“I was shocked when I saw skin cells that had been preserved for 183 million years,” he adds. “It was almost like looking at modern skin.”
Their analysis revealed an “unusual combination” of smooth skin on MH7’s tail and scaly skin on the rear edge of its flippers, according to the statement. The flippers provided a bit of a surprise, as researchers were not expecting to find scales.
Together, the findings suggest the plesiosaur was “between something like a green sea turtle with scales and the [smooth-skinned] leatherback turtle,” Marx tells New Scientist.
Researchers have been able to examine the soft tissues of other prehistoric marine reptiles. But only around eight plesiosaurs have ever been found with some of their soft tissue still preserved—and many are housed in museums that don’t want to see the flesh destroyed for the sake of research. As such, it’s been a bit more challenging to study this sea monster.
“This is the first time anyone has conducted an in-depth analysis of fossilized soft tissues from a plesiosaur,” Marx adds to New Scientist.
Researchers suspect the plesiosaur’s scaly skin would have helped the reptile propel itself through the water by giving its flippers a stiff trailing edge, similar to how today’s sea turtles move. Or, maybe the scaly skin gave the plesiosaur a better grip as it shuffled along the seafloor in search of fish and squid-like critters to eat. Its smooth skin, meanwhile, may have made the plesiosaur a more sleek and streamlined swimmer as it glided around the ocean.
But these are just hypotheses—it’s difficult to deduce behaviors based solely on physical characteristics. And not everyone is convinced that the presence of scaly skin means plesiosaurs were hanging out on the seafloor.
“You don’t need to go to all the trouble of having a hyper-efficient wing if you’re going to be sitting on the bottom all the time,” says F. Robin O’Keefe, a paleontologist at Marshall University who was not involved with the research, to the New York Times. “This was an active predator that was really cruising around.”
