The xenophorids of the Pliocene Basin of Siena (Gastropoda, Caenogastropoda, Xenophoridae)

The systematics of fossil Eura-Mediterranean xenophorids is still relatively unknown, due to the many problems involved in studying them (very conservative shell structure, few available shell characters, the fact that the attached objects modify whorl shape and vary in amount, the rarity of certain species and the difficulty of finding well preserved specimens). Most of the relevant literature dates back to the classic monographs on Tertiary molluscs by M. Hörnes, F. Sacco and M. Cossmann. Seven species have been reported from the Euro-Mediterranean Pliocene: Xenophora crispa (König, 1825), X. deshayesi (Michelotti, 1847), X. infundibulum (Brocchi, 1814), X. plioitalica Sacco, 1896, X. scaldensis Glibert, 1958, Stellaria plioextensa (Sacco, 1896), and S. testigera (Bronn, 1831). However, all but three (X. crispa, X. infundibulum, and S. testigera) are practically unknown. This paper is devoted to six species found in the Siena Pliocene Basin, a classic Italian Pliocene area. Five of them (X. crispa, X. infundibulum, X. plioitalica, S. plioextensa, and S. testigera) are redescribed and current knowledge about them summarized; the sixth species, known from a dozen specimens, is described as new: X. davolii n. sp. In the remarks to the new species, the status and the relationships of some classical Euro-Mediterranean Tertiary xenophorid species, i.e. X. deshayesi (Michelotti, 1847), X. burdigalensis (Grateloup, 1847) and X. grateloupi (D'Orbigny, 1852), are discussed. A neotype is designated for two species (X. crispa and S. testigera) and a proposal of neotype designation is made for some Miocene species: X. deshayesi, X. burdigalensis, and X. grateloupi.