Plagiodontes dealdaleus (Deshayes, 1851) is a variable species occurring in Argentina. Up till now, several subspecies have been recognized. A new study by Piz?? and Cazzaniga (2010) now shows that the nominate subspecies and P. d. strobeli (D??ring, 1877) are in fact two allopatric species.
Like in a previous study [see Snailblog 24-08-2009], the authors have made detailed anatomical research and morphometric studies to investigate the differences found in western and eastern populations of Plagiodontes dealdaleus along the Pampean Sierras in Provs. C??rdoba and San Luis. Their study shows that the distinction between the two taxa mainly lies in subtle differences in shell morphology (but surely recognizable for the trained eye), and a different shape of penis and vagine (with their internal structures).
It would be interesting to see how the morphological differences between the nine species now recognized in Plagiodontes are reflected in molecular studies.
Piz??, J. & Cazzaniga, N.J., 2010. Allopatry and anatomical distinctiveness of two puzzling land snails in genus Plagiodontes, from Argentina (Gastropoda, Orthalicidae). – Malacologia 53: 1-24.