A team of paleontologists has described a new species of land snail they discovered in a piece of mid-Cretaceous amber excavated from a mine in Myanmar (formerly known as Burma). It dates from 99 million years ago.
Snails with a hairy shell
The hairy snail specimen in question has been dubbed Archaeocyclotus brevivillosus and is just over 26.5 millimeters long or adorned with short, bristle-like hairs on its shell. Thanks to the resin of the fossilized tree, the snail has been immortalized within, giving scientists a window into the ancient world of the animal.
“The fossil snail is 2.65 cm long, 2.1 cm wide and 0.9 cm high,” explains Adrienne Jochum , a paleontologist at the Senckenberg Research Institute and the Natural History Museum and Natural History Museum of Berna and co-author of the study published in the journal Cretaceous Research . “The outer margin of its shell is lined with short hairs that cluster around the shell opening.”
Using conventional microscopy and 3D X-ray microcomputer tomography, the tiny hairs, measuring between 150 and 200 micrometers in length , were identified by the researchers on the shell of the recently discovered species Archaeocyclotus brevivillosus.
“This is already the sixth species of the hairy-shelled Cyclophoridae , a group of tropical land snails found so far, embedded in Mesozoic amber, about 99 million years old,” says Jochum.
And what was the purpose of these hairs?
Some modern snails also sport hairs, and hairs have appeared in several distantly related species. What is the purpose?
Eight different species of Cyclophoridae have been found in Burmese amber, and six of them had bristling shells. This is not a coincidence, according to scientists. They believe that the hairiness of the snails gave them an evolutionary advantage.
“It is not uncommon for the shells of extant and fossil land snails to be adorned with ridges, hairs, nodules, or folds; however , the development of such ‘decoration’ remains a complex process that generally does not occur without purpose,” he says. Jochum.
Perhaps these little hairs would have helped the snails to cling better to the plants or perhaps they allowed them to regulate their temperature by collecting water droplets adhering to the shell and acting as an air conditioner. Other possible uses could have been as camouflage or protection against predators.
“For example, the hairs could enhance the animals’ ability to better adhere to plant stems or leaves, something that has already been observed in extant snails. They may also have played a role in the snail’s thermal regulation by allowing tiny water droplets cling to the shell, thus serving as an ‘air conditioner.’ Or they may have protected the snail’s shell from corrosion by the highly acidic soil and leaf litter of the ancient tropical forest floor,” says Jochum, summarizing the possible benefits of hairs for snails. “And finally, it cannot be ruled out that the hairs provided an advantage in sexual selection, ” the expert concludes.
Referencia: Jean-Michel Bichain et al, Archaeocyclotus brevivillosus sp. nov., a new cyclophorid land snail (Gastropoda: Cyclophoroidea) from mid-Cretaceous Burmese amber, Cretaceous Research (2022). DOI: 10.1016/j.cretres.2022.105359