Abstract
Helicina variabilis Wagner, 1827 (Neritimorpha, Helicinidae) is redescribed based on a sample collected in Nanuque, northern Minas Gerais, Brazil. The species description, previously based only on the shell, is expanded to the phenotypic features. The study revealed absorption of the internal shell whorls; a diaphragm muscle connected to the floor of the pallial cavity; a monoaulic pallial oviduct, with the female genital aperture inside the anal aperture, and the lack of a seminal receptacle and provaginal sac; and the pleural ganglia of the nerve ring connected with each other. The significance of these findings is discussed in the light of current taxonomic and phylogenetic knowledge.
Highlights
With the main goal of filling a gap in knowledge of neritimorph phenotypic features, a more complete anatomical description of Helicina vari‐ abilis Wagner, 1827 is provided. Specimens of this species were collected during an expedition by the naturalist and conchologist José Coltro Jr. and his team to the region of Nanuque in northern Minas Gerais state, which recovered many land snails, most of them reported by Simone & Salvador (2016)
Anatomical features in particular have been very useful in comparative analyses, such as taxonomy and phylogeny, at all levels, from closely related species (e.g., Richling, 2009; Richling & Bouchet, 2013) to wider systematic studies, in helicinids (Richling, 2004) and in gastropods in general (Simone, 2011)
As part of a larger project on phenotypic features and phylogeny of the Neritimorpha (= Neritopsina), Helicina variabilis was selected as one of the terrestrial representatives of the group, as it appears to be a typical member of the family
Summary
With the main goal of filling a gap in knowledge of neritimorph phenotypic features, a more complete anatomical description of Helicina vari‐ abilis Wagner, 1827 is provided Specimens of this species were collected during an expedition by the naturalist and conchologist José Coltro Jr. and his team to the region of Nanuque in northern Minas Gerais state, which recovered many land snails, most of them reported by Simone & Salvador (2016). The helicinids are distinguished from the more common Pulmonata snails in having a well-developed, normally calcareous operculum, and the eyes placed at the base of a single pair of cephalic tentacles Their shells are discoid to globose, with a suture plane, sometimes carinate at the periphery, and an umbilicus absent. On the other hand, using the study of Helicina variabilis as an example, together with literature data, it is possible to suggest some features that distinguish the helicinids at least from the marine Neritidae, as discussed below
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