Cuisenerita, Symonds, Malcolm Francis & Pacaud, Jean-Michel, 2010

Symonds, Malcolm Francis & Pacaud, Jean-Michel, 2010, New species of Neritidae (Neritimorpha) from the Ypresian and Bartonian of the Paris and Basse-Loire Basins, France, Zootaxa 2606, pp. 55-68 : 62-63

Genus Cuisenerita gen. nov.

Type species. Cuisenerita tuberosa sp. nov.

Derivatio nominis. The only known species within this genus is from the Cuisian of Trosly-Breuil near Cuise-la-Motte and it has many of the characters of a Nerita and so the name is a free combination of Cuise and Nerita .

Diagnosis. Capuliform, apex not terminal, radially ribbed, septum well developed, tuberculate, margin dentate, outer lip thickened, lirate.

Remarks. Cuisenerita is similar in some respects to Velatella Meek, 1873 from the Upper Cretaceous of North America. In describing Neritina ( Dostia ?) carditoides, Meek (1873: 499) commented: “In several respects it agrees with Velates , and possibly might, without impropriety, be called Velates carditoides . I suspect, however, that when better specimens can be examined, it will be found typical of an undescribed section, including also the little species N. bellatula . If so I would propose for the group the name Velatella .” Article 11.5.1 of the Code provides that a name proposed conditionally for a taxon before 1961 is not to be excluded on that account alone. Article 11.9.3.6 provides that a species-group name first published before 1961 in combination with a previously available generic name, but accompanied by a new nominal genus conditionally proposed to contain the new species, is deemed to have been made available in combination with the previously available generic name. The example of Lowe (1843), given in the Code, covers essentially the same situation as that of Meek and Velatella . Accordingly, although Meek only proposed Velatella conditionally, Velatella Meek, 1873 is valid. Between his descriptions of N. bellatula and N. carditoides Meek (1873) also described Neritina ( Dostia ?) patelliformis . In his description he commented that N. patelliformis is evidently very close to N. bellatula and may possibly be a more robust variety of the same. Presumably, therefore, Meek intended to include N. patelliformis with N. bellatula and N. carditoides in the group for which he proposed the name Velatella . No diagnosis or description is given by Meek for Velatella but the three species within the group are described in detail, although not figured. White (1883) considered N. carditoides to be identical with N. bellatula . Both were figured by him [ N. bellatula: White 1883 : pl. 5, figs 8–9, N. carditoides: White 1883 : pl. 5, fig. 10]. White’s figures of N. bellatula and N. carditoides show a dorsal morphology very similar to Cuisenerita , except that the apex is more strongly involute and curved to one side, and this is supported by Meek’s descriptions. White’s figures do not give an apertural view but Meek (1873: 497–498) described N. bellatula as having an “inner lip very broad, or shelf like and occupying more than half of the underside, convex and more or less thickened, with the inner margin concave in the middle, and provided with a slight projection on each side, but not properly crenate or dentate”. White also figured a third species, Neritina (Velatella) baptista White, 1878 ( White 1883: pl. 23, figs 16–20), and included an apertural view, which shows a smooth, edentate septum. This accords with Meek’s description but is in contrast to Cuisenerita , which is strongly dentate on the septum edge and lirate on the outer lip; Cuisenerita is also characterised by its tuberculate septum, a feature that is lacking in Velatella .

Cuisenerita also resembles Gargania Guiscardi, 1857 from the Upper Cretaceous of Italy, which is also radially ribbed and has an apex that is not strongly involute. However the septum is smooth and edentate ( Keen 1960) while in Cuisenerita it is tuberculate and strongly dentate. Keen treated both Velatella and Gargania as subgenera of Pileolus . As mentioned above, Pileolus has a culumella and has now been placed in the family Pileolidae . In Cuisenerita the internal whorls have been reabsorbed and we have no doubt that Cuisenerita belongs in Neritidae not Pileolidae . The base of Cuisenerita is similar to that of some species of Nerita but it differs from that genus in being capuliform with radial ribs. Tomostoma is also capuliform but the dorsum is smooth, without radial ribs, and the base lacks the tubercles, which are a conspicuous feature of Cuisenerita .