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.

Keywords:

• Stylommatophora
• shell morphometry
• anatomy
• pallial complex
• reproductive system
• taxonomy
• Argentina

Acknowledgements

We are very grateful to Alejandro Tablado (MACN, Buenos Aires), María Cristina Damborenea (MLP, La Plata), Gabriela Cuezzo (FML, Tucumán) and Ronald Janssen (SMF, Frankfurt am Main) for loaning part of the material of the collections under their care. We would like to thank Viviana Sorrivas (Centro Científico Tecnológico-CONICET-Bahía Blanca) for her help in obtaining the micrographs; Martín Carrizo for helping with field work and photographs; Natalia Bulnes for photographing the type material from SMF; Pablo Martín, Silvana Burela and Nicolás Pelegrín for providing some material; Sergio Miquel for providing useful literature and Valdemar K. Delhey for his help with reading German bibliography. N.J.C. is a staff researcher in CIC (Comisión de Investigaciones Científicas de la Provincia de Buenos Aires). This work was supported by the Universidad Nacional del Sur (Bahía Blanca, Argentina) and CIC.