Pila sp.

Neubert, Eike & Damme, Dirk van, 2012, Palaeogene continental molluscs of Oman, Contributions to Natural History 20, pp. 1-28 : 5-6

Pila sp. ( Fig. 4 )

Stratum typicum: Paludal biomicritic limestones of the Zalumah Formation.

Age: Late Priabonian.

Material: This species probably occurs in most exposures of the Zalumah Formation. The material here described was collected in 2012 by both authors in the Wadi Darbat area and is stored under the catalogue number NMBE 5018961 – 5018962 .

Diagnosis: A palaeogene species of Pila with a very globose shell and a slightly exserted spire.

Description: Medium sized Pila species with dextral very globose shell with a short spire consisting of five evenly rounded, strongly convex whorls, not flattened but slightly depressed at the deep suture; aperture very large, occupying 4/5 of the total height; umbilical margin strongly reflected; umbilicus relatively narrow; shell surface smooth with regular fine growth lines only.

Measurements: Specimen figured: H = 59 mm, W = 52 mm, h = 46 mm; w = ca. 30 mm; a second relatively well preserved specimen but with the lower part of the mouth missing measures as follows: H = 67 mm, W = 55.4 mm; h = 45 mm; w = 32.3 mm.

Remarks: Referred to by Roger & al. (1994) as Pila cf. Sudan form, by which these authors mean P. wernei (PHILIPPI, 1851) (terra typica: Sudan). This Modern African species indeed superficially resembles the Eocene Omani species as to the general form and small spire but distinguishing features such as the strongly malleate surface and spiral lines ( Brown 1994) are absent in the fossils. In addition, P. wernei reaches a size of 115 × 103 mm, hence it is about twice the size of the Omani specimens. At the moment it can be concluded that the fossils cannot be placed in P. wernei or any other known Modern or fossil African Pila . They actually quite closely resemble the Asian Pila ampullacea (LINNAEUS, 1758) . Better material is necessary before it can be decided if the fossils do belong to a still extant (Asiatic) species or that it is a distinct one. In the lower part of the Zalumah Formation large gastropods occur (ca. 90 × 80 mm), resembling a Pila species with a relatively high spire, but these shells probably belong to the marine family Ampullinidae COSSMANN, 1919 (Naticoidea) .

Figures

Fig. 4: Pila sp. Wadi Darbat NMBE 5018961, frontal and apical view. The remains of the operculum can still be seen in the frontal view, lower part of the aperture.