A new species of Plagiodontes from Argentina, and new data on the anatomy of four other species in the genus (Gastropoda: Orthalicidae, Odontostominae)

Abstract

Plagiodontes weyrauchi sp. nov. is among the smallest species in the genus Plagiodontes (Doering, 1877). Statistical multivariate analyses confirmed its distinctiveness from other species, mostly because of its high number of whorls (8–9.75), relatively small width, and low proportions of last whorl and aperture length to shell length; multivariate discriminant analysis applied to this species and its most similar relative, P. multiplicatus parvus, correctly identified 100% of specimens. Pallial and genital anatomy supports P. weyrauchi as a different species, mainly because of the position of the ureteric pore, the small general size of the genital system, the presence of an accessory lobe alongside the verge, and the vaginal internal structure. Internal anatomy of four other small-sized taxa in the genus was studied. Two of them have a verge with no accessory lobe [P. dentatus (Wood, 1828) and P. patagonicus (d'Orbigny, 1835)], while the remaining two have an accessory lobe with different characteristics [P. rocae Doering, 1881 and P. multiplicatus parvus (Hylton-Scott, 1952)]. Internal structure of the vagina also shows specific differences among Plagiodontes species; their phylogenetic significance will be further investigated.

Keywords:

• land snails
• Stylommatophora
• shell variability
• morphometry
• pallial anatomy
• genital anatomy
• taxonomy

Acknowledgements

We are very grateful to Gabriela Cuezzo (FML, Tucumán), Alejandro Tablado (MACN, Buenos Aires) and María C. Damborenea (MLP, La Plata) for loaning part of the material of the collections under their care; to Viviana Sorrivas (Centro Científico-Tecnológico CONICET Bahía Blanca) for her help in obtaining the micrographs; to Martín Carrizo for helping with field work and photographs; and to Lea Cazzaniga, for English language editing. J.P. is a fellow of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas); N.J.C. is a staff researcher of the CIC (Comisión de Investigaciones Científicas de la Provincia de Buenos Aires). This work was supported by grants from Universidad Nacional del Sur (Bahía Blanca, Argentina) and CIC.