Bourdieria, Lozouet, 2004

Lozouet, Pierre, 2004, The European Tertiary Neritiliidae (Mollusca, Gastropoda, Neritopsina): indicators of tropical submarine cave environments and freshwater faunas, Zoological Journal of the Linnean Society 140 (4), pp. 447-467 : 451-454

BOURDIERIA GEN. NOV.

Type species: Bourdieria faviai sp. nov.

Etymology: Dedicated to the late Franck Bourdier, one of the most original French Quaternary geologists of the last century.

Description: The shell is small, typically about 3.2- 4.4 mm maximum adult width, very solid, with a flat spire. The protoconch is multispiral, tilted relative to the teleoconch coiling axis and ornamented with spiral ridges. The teleoconch is ornamented with strong spiral cords. The inner lip bears five to six teeth and the outer lip bears four strong teeth. The semicircular aperture is highly prosocline.

Remarks: Superficially, B. faviai is more similar to members of Neritidae than to any genus of Neritiliidae . In fact, Bourdieria is unique among the Neritiliidae because of the presence of strong spiral cords on the teleoconch. Compared to other Neritiliidae , the spire is also especially flat. The protoconch is tilted relative to the teleoconch ( Fig. 4I ) with spiral ridges ( Fig. 4G ) clearly indicating its position in Neritiliidae .

BOURDIERIA FAVIAI SP. NOV.

( FIG. 4 )

1917 Nerita (Pila) basteroti Recluz, 1850 – Cossmann & Peyrot, n∞144, pl. 10, figs 38, 39 [not Recluz, 1850].

1974 Nerita subcaronis d’Orbigny, 1852 – Magne & Vergneau-Saubade: 5 (pars) [not d’Orbigny, 1852].

Etymology: Dedicated to Raymond Favia for his assistance in field collection.

Type specimens: Holotype ( MNHN-PL1634 A), 4 paratypes ( MNHN-PL1634 B-E).

Type locality and horizon: France, Landes , Peyrehorade (Peyrère), Upper Oligocene, marls with Eulepidina .

Other material examined: Upper Oligocene , France, Landes, Peyrehorade (Peyrère), 50 ex. (MNHN- PL1634 F) .

Measurements (holotype): Height 3.0 mm; max. width 4.0 mm.

Description: The shell is small, very solid, obliquely ovate in shape, with a very flat spire. The teleoconch consists of more than 2.5 rounded whorls, increasing very rapidly, with a depressed suture line that is difficult to observe due to the development of spiral cords. The globular protoconch (poor state of preservation in available material) is partially covered by the first teleoconch whorl; the boundary between protoconch and teleoconch is very clearly differentiated. Three or four spiral ridges are present close to the apertural line; the suture separating embryonic and larval shells is not clearly visible on the available specimens. The teleoconch is sculptured with 14–15 spiral cords and axial growth lines. The semicircular aperture is highly prosocline (about 49∞ relative to the shell axis) with a thick septum (inner lip callus) and a very blunt outer line; the arcuate septum is slightly convex and smooth. The columellar area bears 5–6 blunt teeth deeply situated inside the aperture, the adapical three being smaller. The blunt outer lip is thickened by a well-developed inductura, bearing four regularly spaced strong teeth. Inside the aperture there is a relatively long ridge near the base probably representing the innermost limit of the opercular retraction.

Remarks: Bourdieria faviai has been variously interpreted. Cossmann & Peyrot (1917) incorrectly identified it as a young specimen of one of the most common neritids ( Nerita basteroti ) of the Lower Miocene. Magne & Vergneau-Saubade (1974) identified young specimens of N. basteroti sensu Cossmann & Peyrot with N. subcaronis d’Orbigny, 1852 , a problematic Lower Miocene species initially described by Grateloup (1847) under the name N. caronis . Despite several visits to the collections of the University of Bordeaux-Talence, where the Grateloup collection is housed, I have been unable to locate the figured and only known specimen of N. subcaronis . According to the figures of Grateloup (1847: pl. 5, fig. 45) and Magne & Vergneau-Saubade (1974), the septal lip of Nerita subcaronis bears many small denticles which B. faviai lacks. B. faviai is therefore easily differentiated from the Neritidae by its small size, the heavy, smooth, convex callus, the large regular teeth on the outer lip and the tilted protoconch typical of the Neritiliidae . B. faviai occurs only in the Saubrigues palaeocanyon and is only common in one site.

Figures

Figure 4. Bourdieria faviai sp. nov. from Peyrère (Upper Oligocene). A, broken specimen (apical whorls removed) showing (arrowed) the ridge inside the aperture (MNHN-PL1634E). B & C, juvenile specimen of 0.8 adult whorl (MNHN- PL1634C). B, apical view of the protoconch showing the position of three weak ridges (arrowed). D-F, views of the holotype (MNHN-PL1634A); D, apertural view, E, right lateral view, F, dorsal view. G, view of the apical part showing the ridges of the protoconch (arrow). H, broken specimen showing internal view of the columellar area. I & J, apical view of the protoconch; arrow indicates the embryonic shell. I, detail of the embryonic shell.