Barrels and pagodas: clarifying the identity and variability of two nominal taxa of carinated land snails in the genus Plagiodontes (Gastropoda: Orthalicidae: Odontostominae)

Abstract

Plagiodontes weyenberghii (Doering, 1877) has a shell with a strong suprasutural keel; the species inhabits a restricted area in Central Argentina. Plagiodontes weyenberghii minor (Parodiz, 1939) was described as a subspecies with obese shells and broader geographic distribution; some populations were sympatric with Plagiodontes daedaleus (Deshayes, 1851). A discriminant analysis on 244 adult shells combined with original information on the internal anatomy confirmed the distinctiveness of P. weyenberghii weyenberghii, whereas P. weyenberghii minor showed a broad overlap with P. daedaleus and no evidence of anatomical differences. As a consequence, P. weyenberghii minor is considered a junior subjective synonym of P. daedaleus daedaleus (Deshayes, 1851). Plagiodontes weyenberghii (Doering, 1877) has unique characteristics such as the weak vascularization of the pallial system, the relative size of the penial papilla and its accessory lobe, the markedly swollen distal portion of the bursa copulatrix duct, the spermoviduct with two whorls, and the vagina with a medial depression.