Pisulinella, KANO & KASE, 2000

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 : 454-455

GENUS PISULINELLA KANO & KASE, 2000

Type species (by original designation): Pisulinella pacifica Kano & Kase, 2000 ; Miocene of Eniwetok Atoll .

Description: The shell is small, about 4 mm maximum adult width, globulous, very solid. The protoconch is multispiral, tilted relative to the teleoconch coiling axis and ornamented with spiral ridges. The shell surface is smooth and ornamented with fine growth lines. The inner lip septum is slightly convex and the adaxial margin bears three or four inconspicuous teeth. A shallow groove on the inner lip callus extends along the inner line. The outer lip is prosocline and bears many weak tubercles.

PISULINELLA ? AUCOINI SP. NOV.

( FIG. 5 )

Etymology: Dedicated to Didier Aucoin, a very active fossil collector in the Paris and Aquitaine Basins.

Type specimens: Holotype ( MNHN-PL15355 A), 1 paratype ( MNHN-PL15356 B).

Type locality and horizon: France, Landes , Meilhan (Vives), Lower Miocene (Aquitanian stage) .

Other material examined: Lower Miocene, Landes, Meilhan (Vives), 1 ex. (coll. Aucoin, private collection)

Measurements (holotype): Height 2.6 mm; max. width 2.9 mm.

Description: The shell is small, very solid, obliquely ovate in shape, with a low spire. The teleoconch, which consists of little more than two rounded whorls, increases rapidly, with an impressed suture. The globular protoconch is poorly preserved in the available material and while partially covered by the first teleoconch whorl, the limit between protoconch and teleoconch is clear; the suture between the embryonic and larval shells is not distinguishable in our specimens. The glossy teleoconch is sculptured with fine axial growth lines only, which are better developed close to the aperture. The semicircular aperture is highly prosocline (38–40∞ relative to the shell axis), with a thick septum (callus) and a blunt outer line. The septum is slightly convex, smooth, the columellar area bearing two main teeth; a third results from the subdivision of the abapical tooth. The outer lip is blunt, thickened by a well-developed inductura, and bears five strong teeth. Inside the aperture there is a relatively long ridge near the base, probably representing the innermost limit of the opercular retraction.

Remarks: P. aucoini differs from B. faviai by a more elongate shell form and the absence of spiral cords. The presence of spiral cords being unique among the Neritiliidae , their absence in P. aucoini excludes a placement in Bourdieria . P. aucoini is very similar in shape to Pisulinella miocenica Kano & Kase, 2000a , but is easily distinguished by the large teeth on the outer lip; it is possible that the absence of a shallow groove on the inner lips callus of P. aucoini could be an apomorphic character of Pisulinella ( Kano & Kase, 2000a) resulting from the poor preservation of the available specimens. In any event, the generic assignment of P. miocenica cannot be clearly indicated.

The three specimens of P. aucoini were collected together with abundant reef coral debris ( Pocillopora ) and many other rare molluscs such as the muricid Galeropsis lavenayanus Hupé, 1860 (see Lozouet & Renard, 1998). Judging from the morphology of coral fragments and the limited thickness of this layer, it is not possible to be sure that a true coral reef was their habitat. Nevertheless, the layer yielded coral patches of Porites exceeding 3 m in length and 1.5 m in height ( Lozouet et al., 2001b). It may be suggested with some confidence that P. aucoini was a cryptic species living in crevices of a coral patch-reef.

Figures

Figure 5. Pisulinella? aucoini sp. nov. from Meilhan (Lower Miocene). A, broken specimen (apical whorls removed) showing (arrowed) the ridge inside the aperture (MNHN-PL15356B). B & C, holotype (MNHN-PL15355A). B, in apertural view; C in right lateral view.