Lanistes thaytinitiensis, Neubert & Damme, 2012

Neubert, Eike & Damme, Dirk van, 2012, Palaeogene continental molluscs of Oman, Contributions to Natural History 20, pp. 1-28 : 9-10

Lanistes thaytinitiensis sp. nov.

( Fig. 7 )

Type specimens: Holotype NMBE 5018966 ; paratypes NMBE 5018967–5018969 , MNHN/2 , SMF 340185 /2.

Type locality: Thaytiniti , Dhofar, Oman .

Stratum typicum: Paludal biomicritic limestones of the Zalumah Formation.

Age: Late Priabonian.

Material: This species was only recovered from the Zalumah exposures at Thaytiniti. Collected by M. Pickford during one of the palaeontological missions led by H. Thomas in 1988–1990.

Etymology: named after the type locality.

Diagnosis: A palaeogene species of Lanistes characterized by the discoid shape and flattened upper side.

Description: Medium sized Lanistes ; discoid shell consisting of 4 ½ whorls with virtually no exserted spire, apex pointed; upper part of the gradually increasing whorls completely flattened, lower part convex, forming a peripheral angle accentuated by a ridge; at the base the periphery of the whorls form a second angle with the flattened walls of the umbilicus, in which the whorls wind downwards (or upwards being hyperstrophic) in a regular spiral; aperture horizontal at the top, the outer margin convex, the upper part of the inner margin, connected to the shell, concave and the free lower part straight, basal margin pointed; growth lines regular and fine, no spiral sculpture; operculum unknown.

Measurements: Holotype ( Fig. 7 ): H = 12.5 mm; W = 38.2 mm; h = 12.0 mm; w = 11.5 mm. Paratype (NMBE 5018967): H = 11.2 mm; W = 32.2 mm; h = 11.2 mm; w = 10.3 mm.

Remarks: We did not find any fossils of this species in the Salalah region, while in the Zalumah exposures at Thaytiniti is seems to be the most common of the two Lanistes . This indicates either a difference in age or in environmental conditions between these two sites. Lanistes thaytinitiensis sp. nov. is the only flattened discoid Lanistes species known.

Figures

Fig. 7: Lanistes thaytinitiensis sp. nov. Thaytiniti, holotype NMBE 5018966 in frontal, apical and ventral view.