Naricopsina, Chelot, 1886

Ferrari, S. Mariel, 2013, New Early Jurassic gastropods from west-central Patagonia, Argentina, Acta Palaeontologica Polonica 58 (3), pp. 579-593 : 588-590

Naricopsina ? sp.

Fig. 4E .

Material.—MPEF−PI 3560; teleoconch fragment preserved as external mould. BET 32 site from Lomas de Betancourt locality, Chubut province, Argentina, Mulanguiñeu Formation, Upper Pliensbachian–Lower Toarcian, Lower Jurassic.

Dimensions.—MPEF−PI 3560: height 9 mm; width 10.7 mm.

Description.—Conical, turbiniform to naticiform and low spired shell with strongly gradate outline. The protoconch is not preserved. The fragmentary teleoconch comprises four strongly convex whorls. The suture is deeply incised in a concave spiral furrow. The shell surface is smooth, and neither axial elements nor growth lines are observed. On the upper portion of last whorl a weak spiral keel appears. The aperture and base are not preserved.

Remarks.—The naticiform shell with strongly convex whorls, the deeply incised sutures and the poorly developed ornament suggest an assignment to Naricopsina . However, apertural,

http://dx.doi.org/10.4202/app.2011.0090

basal and umbilical characters are not preserved in the single specimen available, so it is left in the open nomenclature.

Naricopsina ? sp. is the first, though uncertain, report of the genus in the Early Jurassic of South America.

Naricopsina guerangeri (Davoust, 1885) ( Gründel 2001: 62, pl. 5: 7−3) from the Middle Jurassic of Europe is comparable to the Chubutean species; however, N. guerangeri has orthocline to slightly sinuous and distinctly prosocline growth lines, with their apical part prosocyrt; growth lines are absent in the Patagonian species. Naricopsina montreuilensis (Hébert and Eudes−Deslongchamps, 1860) ( Gründel 2001: 64, pl. 6: 1–5) from the Callovian (Middle Jurassic) of Europe differs from Naricopsina ? sp. in having stronger collabral elements. Naricopsina? sinuosa Gründel, 2001 from the Callovian (Middle Jurassic) of Europe ( Gründel 2001: 65, pl. 6: 1–6) resembles the species here described although the European species has fine and slightly opisthocyrt growth lines near the adapical suture and on the base; these characters are absent in Naricopsina ? sp. Naricopsina laevis (Stoliczka,1861) ( Szabó 2008: 98, fig. 91) from the Sinemurian (Early Jurassic) of Europe differs from Naricopsina ? sp. in having strongly prosocline and fine growth lines. The material described by Szabó and Jaitly (2004: 19, pl. 2: 37–39) as Naricopsina cornelia (Laube, 1868) from the Callovian (Middle Jurassic) of India is comparable to the Patagonian species; the Indian specimen, however, has irregularly spaced and strongly prosocline growth lines.

Figures

Fig. 4. Early Jurassic gastropods from Lomas Occidentales and Cerro La Trampa fossiliferous localities.A–C. Globularia cf. catanlilensis (Weaver, 1931). A. MPEF−PI 4112; teleoconch in lateral (A1, A2) and apertural (A3) views. B. MPEF−PI 4114; teleoconch in lateral (B1, B2) and latero−apical (B3) views. C. MPEF−PI 4116, teleoconch in lateral views (C1, C2). D. Globularia sp. MPEF−PI 4119; teleoconch in lateral (D1) and apertural (D2) views. E. Naricopsina? sp.; MPEF−PI 3560, teleoconch in latero−apical views (E1, E2). F. Nerinea? sp. 1. MPEF−PI 4123, fragmentary teleoconch in lateral views (F1, F2). G–I. Nerinea? sp. 2. G. MPEF−PI 4124, fragmentary teleoconch in lateral view. H. MPEF−PI 4125, fragmentary teleoconch in lateral view. I. MPEF−PI 4126, fragment of last teleoconch whorl in lateral view. Scale bars: A–D 10 mm, E–I 3 mm.