Nerita (Amphinerita) gouetensis, 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 : 58-59

Nerita (Amphinerita) gouetensis sp. nov.

( Fig. 2 a–c)

Type material. Holotype MNHN A31489 (Pacaud leg., Fig. 2 a–c).

Stratum typicum. Late Eocene, Bartonian, “Sands of Bois-Gouët”.

Locus typicus. Bois-Gouët, Saffré, Loire-Atlantique, France. 47˚29ˏ9.25˝ N 1˚36ˏ45.55˝ E.

Derivatio nominis. Named after Bois-Gouët, the type locality and the only locality at which this species has, as yet, been found.

Diagnosis. A small Nerita with prominent, rounded, spiral ribs and a smooth, edentate septum.

Description. Protoconch badly worn in only known specimen. Teleoconch of just over two whorls increasing rapidly in size, earlier rather worn in holotype. Last whorl bears nine prominent, smooth, rounded, spiral ribs, mostly evenly spaced; 6th and 7th below suture closer together. Apart from spiral ribs, surface of teleoconch smooth, lacking any collabral ornamentation other than some fine, rather faint growth lines. No colour pattern discernable but brown colour remains between ribs where shell relatively unworn. Slightly worn septum smooth, edge slightly concave, edentate. Outer lip thickened within, smooth apart from small protuberance about 1 mm from adapical end of septum. Gutter at junction of adapical end of septum and outer lip. Apertural tooth prominent, below abapical end of septum, in form of apostrophe with thicker end inward, higher, sloping to tail of apostrophe.

Size. The holotype is approximately 4 mm high, and 4 mm wide.

Remarks. Nerita (Amphinerita) gouetensis does not fit precisely within any of the generally accepted subgenera of Nerita . Those that share diagnostic characteristics with Na. (A.) gouetensis are:

Lisanerita Krinjen, 2002 (Type species by original designation: Nerita lirellata Rehder, 1980 );

Heminerita Martens, 1887 (type species by monotypy: Nerita pica Gould, 1859 = Nerita japonica Dunker, 1861 );

Amphinerita Martens, 1887 (type species by subsequent designation Crosse, 1892: 98: Nerita umlaasiana Krauss, 1848 );

Cymostyla Martens, 1887 (type species by subsequent designation Crosse, 1892: 98: Nerita undata Linné, 1758 );

Theliostyla Mörch, 1852 (type species by subsequent designation Kobelt, 1879: 147: Nerita albicilla Linné, 1758 );

Subgenus Septum Septum edge Teleoconch Lisanerita Smooth Edentate or with very small teeth Smooth or with finely incised lines Heminerita Smooth Edentate or with 1 or 2 obscure Smooth or with low spiral lirae

low broad projections

Amphinerita Smooth Edentate or with small, obscure Smooth or with spiral ribs or well defined teeth

In his subgenus Amphinerita, Martens (1887) included Na. umlaasiana and Na. georgina Récluz, 1841 . The former has an almost smooth shell but the latter has numerous well developed spiral ribs. Amphinerita is recorded in Europe from as early as the Thanetian [ Na. (A.) semilugubris Deshayes, 1864 , Le Renard & Pacaud 1995]. Although Na. (A.) gouetensis has fewer and broader ribs than Na. (A.) georgina , we consider that it can nevertheless be placed within Amphinerita .

Nerita (A.) gouetensis is superficially similar to some juvenile specimens of Nerita (?) plutonis Basterot, 1825 from the Miocene of the south of France but its septum is normally neither smooth nor edentate but has granules on the surface and several well defined teeth on the edge.

Range and distribution. Only known from type locality.

Figures

FIGURES 1 – 4. 1. Tomostoma angusta sp. nov., holotype, a. apertural, b. abapertural, c-d. side views. Length 5.2 mm, width 2.8 mm. Bartonian, Le Quoniam, Haravilliers, Val d’Oise, France. MNHN A 31487 (J-M Pacaud leg.). 2. Nerita gouetensis sp. nov., holotype, a. apertural, b. abapertural, c. apical views. Height 4 mm, width 4 mm. Bartonian, Bois- Gouët, Saffré, Loire-Atlantique, France. MNHN A 31489 (J-M Pacaud leg.). 3. Clithon barbei sp. nov., holotype, a. apertural, b. abapertural, c. apical views. Height 3.2 mm, width 3.2 mm. Ypresian, Pourcy, Marne, France. NHM PI TG 26448 (M. F. Symonds coll.). 4. Neritodryas guillioui sp. nov., holotype, a. apertural, b. abapertural, c. apical views. Height 15 mm, width 16 mm. Ypresian, Pourcy, Marne, France. MNHN A 31490 (Faullummel coll.).