Distorsio shells, were formerly classified with members of the present Ranellidae. Alan J. Beu, 1988, states that they belong to a distinctly separate family, the Personidae, for the following reasons:
1) Paleontologically, the shells have evolved along a parallel lineage distinct from most Ranellidae, at least 15-30 million years earlier, and with no discernable common ancestor in the fossil record.
2) The mollusc shows anatomic details of the upper pharyngeal and gastric tract that are similar to those of the Ficidae.
3) The radula has teeth like spiny crescents rather than the ribboned teeth of most Ranellidae.
4) The small black operculum is similar to that of certain Ficidae, despite the strikingly different appearance of the overall shell.
Distorsio shells are distinctive in a showing a rather distorted coiling of the knobbed whorls, which are found even around the aperture. Soft tissue features are common to all three genera of the Personidae family. The Indo-Pacific species are found at moderate depths in warm waters.
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