A snail preserved in amber with an intact fringe of tiny fine hairs along its shell is helping biologists better understand why one of the world’s funniest animals can develop such a hairstyle.
This unusual mollusk fossil, found in Myanmar’s Hukawng Valley, has rows of stiff, tiny hairs, each between 150 and 200 micrometers long, following the whorl of its 9-millimeter-long, 3.1-millimeter-high shell.
INor is it the first hairy snail to be discovered, joining an exclusive club of gastropods.
“This is already the sixth species of hairy-shelled Cyclophoridae – a group of tropical land snails – found so far, embedded in Mesozoic amber, which is about 99 million years old,” explains palaeontologist Adrienne Jochum from the University of Bern.
They’re not just some weird extinct creatures, either. Several land snails still living today also have cloudy shells.
A team of researchers led by molluscologist Jean-Michel Bichain from the Museum of Natural History and Ethnography in France named the newly discovered animal Archaeocylotus brevivillosus – its species name combining the Latin words small (brevis) and shaggy (villōsus).
Of the eight species found in Myanmar amber, six have hairy shells, suggesting that this may be the ancestral state of these land snails. In fact, this fuzz may have helped snails transition from an aquatic environment to life on land during the Mesozoic period 252 to 66 million years ago, the researchers suggest.
Hairs are formed from the protein-filled outermost layer of the snail’s shell – the skin of the shell – called the periosteum. Adding hairs to a shell would have cost the tiny animals energy, so it must have given these tiny prehistoric snails some sort of selective advantage in their tropical environment to make it worthwhile.
Bichain and team speculate that these could have included water retention and protection against shell desiccation, allowing these animals to branch out into dry soil niches. And just like our own mammalian hair, it’s possible that shell fuzz helped with thermoregulation.
“The hairs could also have served as camouflage or protected the snail from a direct attack by stalking birds or ground predators,” explains Jochum. “They may also have played a role in thermal regulation for the snail by allowing tiny droplets of water to adhere to the shell, thus serving as an ‘air conditioner.’ And finally, it cannot be ruled out that the hairs provided an advantage in sexual selection.”
In addition to shaggy snails, Myanmar’s amber has preserved over two thousand unique species from delicate flowers to a remarkably preserved feathered dinosaur tail, providing an amazing window into the biodiversity of the Cretaceous period.
Signs of ancient species from the tropics are difficult to find, since the warm, humid conditions are ideal for the decomposition and recycling of organic matter. Thus, animals preserved in amber fill in some of these gaps in our fossil record, providing details of the soft tissues and even the metallic colors of ancient insects that would otherwise be lost to time.
One such specimen preserved what may be the first evidence of live births in land snails (rather than spawning), with newborn snails still attached to their mothers by mucus.
Unfortunately, while amber has many valuable exquisite specimens, the fossil trade is currently funding devastating conflicts in Myanmar. In recognition of this dire problem, the researchers note that the amberjack snail specimen was legally collected in 2017, before the current conflicts resumed.
Their study was published in Cretaceous Research.
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