183-million-year-old fossil gives incredible new insights into plesiosaurs from well-preserved skin

The ocean that covered southern Germany nearly 180 million years ago wasn’t a welcoming place for soft tissue. When a creature died, skin and muscle usually vanished long before minerals replaced bone.

That is why most museum displays of the elegant, long-necked plesiosaurs show nothing but ribs and vertebrae. Yet every rule has an exception, and one extraordinary fossil is now letting scientists peek beneath the armor of time.

Unearthed in 1940 and cataloged as MH 7, the skeleton of Plesiopterys wildi rested in storage for decades. In 2020, technicians finally removed the surrounding rock and noticed shreds of skin clinging to the tail and left flipper.

Those faint traces turned a routine preparation into a landmark study, offering the first detailed look at how a plesiosaur was really put together.

Plesiosaur skin and tissue

Once freed from its limestone cradle, the specimen revealed more than show-floor spectacle. Under scanning electron microscopes, the tail skin proved smooth, layered, and peppered with tiny pigment bodies called melanosomes.

Their pattern hints at subtle tones or mottling along the rear half of the body – an idea that challenges the traditional picture of uniformly pale marine reptiles.

The flipper told a different story. Minute, triangular scales lined its trailing edge, forming a reinforced paddle capable of slicing water with the precision of a modern sea turtle’s forelimb.

Textured skin on limbs but not on the torso is unheard-of in the reptile world today, yet it fits the hydrodynamic demands of a swimmer that needed both thrust and fine steering.

Understanding plesiosaur evolution

“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 lead author Miguel Marx from Lund University.

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

Co-author Sven Sachs added, “Our research reinforces that plesiosaurs were already evolving specialized adaptations and distinct regional lineages much earlier than we used to believe.”

Their research has important implications for understanding how marine reptiles responded to environmental changes in the Jurassic seas.

Skin stories from plesiosaur stone

What makes MH 7 exceptional is the geological stage on which it perished. The Lower Jurassic Posidonia Shale accumulated in sluggish, oxygen-poor water roughly 350 feet deep – conditions that slowed decay and encouraged soft-tissue preservation.

Nature’s low-oxygen embalming has also locked in ink sacs of squids and filaments of ancient algae, but complete reptile skin remains vanishingly scarce. The few square inches on MH 7, therefore, carry outsized scientific weight.

Chemical tests showed remnants of keratin in the scaly flipper sheath, matching the tough beta-keratin that stiffens bird beaks and snake rattles.

Meanwhile, the smoother tail patch held alpha-keratin, the flexible protein common in lizard skin. That distribution hints that Plesiopterys invested in extra rigidity where the limb flexed against water pressure, while keeping the rest of its hide supple for smooth cruising.

Flipper physics and tail tales

The fossil’s broad, fleshy tail fin – rarely preserved in plesiosaurs – suggests the animal used more than its four trademark paddles.

A flexible, skin-lined rudder would have added snap to turns and bursts of speed, similar to the caudal flukes of today’s penguins.

Coupled with a rib cage barely three feet long but a neck stretching farther than many cars are wide, the design paints a picture of surprising agility.

That agility mattered. Early Jurassic seas swarmed with bullet-shaped ichthyosaurs and armored crocodile kin chasing the same fish and cephalopods.

A plesiosaur that could pivot quickly and hold a stable glide would carve its own feeding niche, avoiding direct competition with faster sprinters or lurking ambush predators.

Plesiosaur skin rewrites their evolution

Before MH 7, Plesiopterys wildi was known from juvenile remains that blurred its family tree. The new skeleton confirms it sits near the base of the plesiosauroid branch, close to Franconiasaurus brevispinus.

That placement connects primitive, shorter-necked ancestors with the later cryptoclidids that flourished in the Late Jurassic.

The soft-tissue clues dovetail with the bones: gradual changes in limb reinforcement and tail design now look like stepping-stones toward more specialized swimmers yet to come.

Unlike the open oceans that span the globe today, Early Jurassic Europe was a patchwork of shallow basins separated by islands and sandbars. Those barriers limited migration, so local populations often struck out on their own evolutionary tangents.

The Posidonia Shale community, recorded near what is now Holzmaden, holds species not seen in Britain’s Lias Group or France’s Causses Basin.

The mix implies that each marine pocket brewed its own cast of reptiles, fish, and invertebrates – Plesiopterys among them – shaped by slight differences in temperature, salinity, and prey.

Why soft tissue matters

Every extra scrap of plesiosaur skin shifts our picture of prehistoric life from silhouette to portrait.

By revealing where pigment once lay, MH 7 offers the chance to test camouflage theories against real evidence rather than artistic guesswork.

Its scale patches give engineers hints about natural flow control that might inspire quieter submersibles or more efficient underwater drones.

Most of all, the fossil reminds researchers to recheck drawers labeled “prepared” decades ago; treasures can hide in plain sight until fresh eyes and modern tools unlock their stories.

When a bit of Jurassic skin survives the journey to the twenty-first century, it connects us to a world that thrummed beneath warm, shallow waves while dinosaurs thundered overhead on land.

That connection, fragile though it is, makes every fleck of fossilized hide worth a closer look – even if it measures no more than the width of a thumbnail.

The full study was published in the journal Current Biology.

Image Credit: Joschua Knüppe

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