Archaeocyclotus brevivillosus sp. nov., a new cyclophorid land snail (Gastropoda: Cyclophoroidea) from mid-Cretaceous Burmese amber

Land snails in mid-Cretaceous Burmese amber (ca. 99-98 Ma) have attracted great interest from paleontologists in recent years. Here we describe a new species of the genus Archaeocyclotus belonging to the family Cyclophoridae, from a well-preserved fossil, using classic light microscopy and modern micro-CT scans with computer 3D reconstructions. The shell of Archaeocyclotus brevivillosus sp. nov. is characterized by short, densely implanted periostracal hairs that emerge at growth line margins from the shell periphery. This new species is the eighth cyclophorid species described from Burmese amber, six of which also have hairy shells. It thus, reinforces the hypothesis that the hairiness is an ancestral state in cyclophorids and that it may have played a role through multiple selective advantages in the terrestrialization of the group during the Mesozoic.