Biomphalodonta, Herbert, 2020

Herbert, David G., 2020, Revision of the aperturally dentate Charopidae (Gastropoda: Stylommatophora) of southern Africa - genus Afrodonta s. lat., with description of five new genera, twelve new species and one new subspecies, European Journal of Taxonomy 629, pp. 1-55 : 25

Genus Biomphalodonta gen. nov.

urn:lsid:zoobank.org:act:CE2A2B8F-D281-4E81-BF8D-5A705868D71A

Type species

Biomphalodonta forticostata gen. et sp. nov.

Diagnosis

Shell relatively large (max. diameter 2.7 mm), biconcave with deeply sunken spire; umbilicus wide; whorls deep and tightly coiled, strongly rounded apically and basally, less so at periphery; last adult whorl not descendant. Protoconch with fine, close-set, regularly spaced axial riblets; riblets crisp and simple. Teleoconch with relatively coarse, widely spaced, lamellate axial riblets; intervals between riblets with numerous, fine, intermediary axial threads and even finer spiral threads. Aperture narrowly lunate; parietal dentition absent; palatal region with 1–2 axially aligned rows of denticles set back up to ½ whorl behind outer lip.

Etymology

From the Latin bi-: two, twice and the Greek omphalos (Ομφαλός): navel, and donta: a contraction of Afrodonta ; with reference to the biconcave shell morphology. Gender feminine.

Remarks

Biomphalodonta gen. nov. is proposed for a single highly characteristic, range-restricted species. The axially costate protoconch is similar to that found in Costulodonta gen. nov., but the deep, relatively large, biconcave shell and coarse teleoconch sculpture set it apart from members of that genus. The shape of the shell and the iterodont palatal dentition resemble those of Amatholedonta gen. nov., but in that genus the protoconch is smooth and globose, and the teleoconch sculpture much finer.

A number of small, edentate charopid species currently referred to Trachycystis Pilsbry, 1893 are conchologically similar to B. forticostata gen. et sp. nov., except for their lack of apertural dentition. These include, inter alia, Trachycystis bathycoele (Melvill & Ponsonby, 1892) and T. bifoveata Connolly, 1932 . Further study is needed in order to establish whether these also belong to Biomphalodonta gen. nov. It may be that the presence/absence of apertural dentition is of limited phylogenetic significance and that the genus contains both dentate and edentate species.