Striatoconulus sp.

Ferrari, S. Mariel, 2009, Cosmopolitan Early Jurassic marine gastropods from west-central Patagonia, Argentina, Acta Palaeontologica Polonica 54 (3), pp. 449-461 : 451

Striatoconulus sp.

Fig. 2C .

Material.—MPEF−PI 1867a and b (part and counterpart); poorly preserved teleoconch.

Description.—Medium−sized, oval and low−spired shell. Protoconch unknown. Dextral teleoconch with four convex whorls; last whorl is incomplete. The spire represents about 1/3 of teleoconch height and is characterized by the presence of a high expansion rate. Sutures are incised.

On first whorls of the teleoconch ornament is poorly developed. In the later whorls of the teleoconch ornament consists of regularly spaced spiral furrows. No axial ornament is present. Apertural and umbilical features are not preserved.

Dimensions.—MPEF−PI 1867b: maximum height 25.6 mm; spire height 12.7 mm.

Remarks.—The convex teleoconch whorls, low spired shape, incised sutures, and the spiral ornament suggest an assignment to Striatoconulus (compare Gründel 2000; Kaim 2004).

Striatoconulus sp. is the first ataphrid recorded in the Early Jurassic of South America. The type species, Striatoconulus latus Gründel, 2000 is very similar to the Argentinean species. S. latus has a base weakly convex, with rounded edge to the flanks of the whorls, aperture broadly oval, inner lip with a broad callus and a halfmoon−shaped cavity on the columella ( Gründel 2000: 228, pl. 6: 11–15; Kaim 2004: 29, fig. 15). Basal, apertural and umbilical features are regrettably not preserved in Striatoconulus sp. and that is why the species is left in open nomenclature.

Figures

Fig. 2. Early Jurassic gastropods from the “El Córdoba” fossiliferous locality, Chubut Province, Argentina. A. Amberleya? espinosa sp. nov. MPEF−PI 1882, holotype, latex cast of external mold in lateral view (A1, A2), juvenile teleoconch in lateral view (A3), last whorl in lateral view (A4), basal and apertural view (A5), ornament pattern and sutural detail (A6). B. Colpomphalus? sp. MPEF−PI 1863, latex cast of external mold of incomplete teleoconch in apical and lateral view (B1–B3), last whorl ornament detail showing the spiral furrow (B4). C. Striatoconulus sp. MPEF−PI 1867b, latex cast of external mold in apical view (C1), apical detail (C2), first teleconch whorls lateral view (C3). Scale bars 2 mm unless otherwise indicated.