Hudlestoniella hammeri, Nakrem, 2017

Nakrem, Hans Arne, 2017, Gastropods from the Late Jurassic - Early Cretaceous seep deposits in Spitsbergen, Svalbard, Zootaxa 4329 (4), pp. 351-374 : 360-361

Hudlestoniella hammeri sp. nov.

( Fig. 5A–G )

2015 Hudlestoniella sp.; Hryniewicz et al. 2015a, table 1.

Diagnosis. Teleoconch high spired. Three earliest teleoconch whorl ornamented with strong opisthocline axial ribs and fine spiral lirae. Ornamentation fading away later in ontogeny.

Holotype: PMO 224.754, H = 3.6 mm.

Type locality and age: Seep # 9 in Sassenfjorden area, Svalbard; late Berriasian, Early Cretaceous.

Paratype: PMO 224.755, H = 8.8 mm, W = 7.0 mm.

Additional material: Seventeen specimens; one from seep #5 (late Berriasian), five specimens from seep #8 (late Tithonian), four specimens (two illustrated PMO 224.756 and PMO 224.757) from seep #9 (late Berriasian), and seven specimens from seep #12 (late Berriasian), Sassenfjorden, Svalbard.

Description. Protoconch low spired, seemingly smooth. Demarcation between protoconch and teleoconch not observed. Early teleoconch ornamented with strong, strongly opisthocyrt axial ribs and fine spiral lirae. After the third teleoconch whorl axial ribs absent and spiral lirae are only weakly expressed in the adapical and abapical portion of the shell. Growth lines opisthocyrt throughout ontogeny. Aperture not preserved.

Remarks. Hudlestoniella hammeri is most similar to H. undulata ( Tullberg, 1881) (see also Kaim et al. 2004) in having strong opisthocyrt axial ribs, but H. undulata has slightly broader shells and differs in having spiral striae instead of lirae, and its axial ribs persist longer during ontogeny. Hudlestoniella pusilla ( Tullberg, 1881) (see also Kaim et al. 2004) is similar in being ornamented by spiral lirae and smooth ontogenetically late whorls, but differs from H. hammeri in being less elongated and in having weaker and only weakly opisthocyrt axial ribs.

Distribution. Late Tithonian–late Berriasian of Sassenfjorden, Svalbard.

Etymology. After Øyvind Hammer, palaeontologist and member of the team that collected the fossils described here.

Figures

FIGURE 5. A – H. Hudlestoniella hammeri sp. nov. Seep deposit # 9, Sassenfjorden, Svalbard; late Berriasian (Early Cretaceous). A, B, F. Holotype (PMO 224.754). C, G, H. Paratype (PMO 224.755). D. PMO 224.756. E. PMO 224.757. I – M. Hokkaidoconcha sp. Seep deposit # 12, Sassenfjorden, Svalbard; late Berriasian (Early Cretaceous). I. PMO 217.509. J, L. PMO 217.511 b. K, M. PMO 217.507.