In a stunning paleontological find, a fossil of an ancient aquatic reptile with preserved skin has been found in Switzerland.
The virtually complete fossil specimen belongs to Lariosaurus valceresii, which lived 240 million years ago (Middle Triassic).
It was unearthed from the UNESCO World Heritage area of Monte San Giorgio in Switzerland.
Interestingly, it is the first known Lariosaurus specimen with preserved skin and scales.
“The skin is preserved as a carbon film, revealing the shape of the scales. It outlines the body and limbs, showing that the hands and feet were webbed,” the researchers from the University of Insubria, Italy, wrote in the study paper.
Well-preservation of the skin
Lariosaurus is the name of an extinct nothosauroid genus — a type of marine reptile — that existed during the Middle Triassic period (roughly 247–235 million years ago).
These reptiles resembled the lineage that evolved into the plesiosaurs, the Mesozoic Era’s iconic “sea monsters.”
Lariosaurus valceresii was a small aquatic reptile that appeared shortly after the devastating Permian mass extinction 252 million years ago.
Following this mass extinction, the oceans were largely empty of competitors but rich in food. This environment allowed small reptiles to easily move into the marine habitats and rapidly evolve into new species.
The new specimen is highly significant because its near-perfect state preserved the soft tissues, which usually decay over time.
Once a tropical lagoon with poor water circulation, the Monte San Giorgio area developed a unique environment that encouraged fossil preservation.
The environment, rich in chemicals and low in oxygen due to bacterial mats, was unsuitable for scavengers.
As a result, when animals died and sank, their soft tissues were occasionally preserved instead of being consumed or decaying.
This rare preservation has made the task of paleontologists much easier, providing clear evidence to determine the creature’s anatomy and behavior.
The fossil remains were studied using high-resolution photographs and a scanning electron microscope.
It shows that the body was largely covered in scales compared to plesiosaurs with only scaled limbs.
Swimming style like seals
The skin allowed researchers to make several key determinations.
It clearly outlines the limbs, confirming that L. valceresii had webbed hands and feet, which would have aided in pushing through the water.
Moreover, the patches of skin behind the upper arms and on the trunk reveal that the reptile had powerful muscles for retracting its forelimbs.
Together, these features paint a vivid picture of Lariosaurus‘s aquatic lifestyle.
The researchers suggest the creature likely used its front limbs to swim in a “rowing-flying” motion, similar to how modern seals use flippers for bursts of rapid acceleration.
“The forelimbs indicate that Lariosaurus could have performed a paraxial, otariid-like, ‘flying-rowing’ swimming for rapid acceleration,” the team stated.
This evidence challenges the known fact regarding how nothosaurs swam.
Experts previously believed the tail was the main propulsive organ in nothosaurs.
However, the preserved skin and the muscles suggest that Lariosaurus likely relied on its forelimbs for swimming.
Reportedly, this specialized swimming technique might set Lariosaurus apart from other related marine predators of the time, such as Ceresiosaurus.
The discovery demonstrates that different swimming strategies were essential for survival in the ancient oceans 240 million years ago.
The findings were published in the Swiss Journal of Palaeontology.