Alvania, Risso, 1826

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 98

Alvania sp. B

Fig. 26C

Material. MGUH 33165 and an external mould in the uncatalogued collections of the Natural History Museum of Denmark.

Occurrence. The lower Danian ‘dead layer’ in Vokslev Quarry, Northern Jutland.

Description. Protoconch obtusely conical with 2 ¼ to 2 ½ convex whorls. Whorls seemingly smooth, but could have been weakly postulate. Protoconch height between 0.3 and 0.35 mm, while the width reaches 0.55 mm.

Shell high trochiform with weakly convex whorls separated by fairly distinct suture. Transition to base at periphery moderately sharp. Aperture not preserved.

Teleoconch sculpture dominated by about 22 to 25 opisthocyrt transverse ribs per whorl. Ribs reaching down to periphery before fading out. Transverse ribs crossed by generally weaker spiral ribs; adapical one much stronger than succeeding ones, carrying small beads representing adapical part of transverse ribs. Spiral ribs increasing in strength at and just abapically of periphery with up to five moderately distinct spirals on adapical part of base.

Measurements. MGUH 33165 is 0.8 mm wide, consisting of the last protoconch whorl and the succeeding teleoconch whorl.

Remarks. Alvania sp. B resembles the late Maastrichtian A. sp. A described above, but differs by the stronger spiral sculpture and the more opisthocline nature of the transverse ribs.

Figures

FIGURE 26. A–B. Alvania sp. A. Silicone cast of MGUH 33164. Width 1.5 mm. C. Alvania sp. B. Silicone cast of MGUH 33165. Width 0.8 mm. D. Zebina sp., Wax cast of MGUH 33166. Width 0.9 mm. E–H. Ceratia rodvigensis n. sp. E–F. Silicone cast of holotype MGUH 33167. Width 0.8 mm. G–H. Silicone cast of paratype MGUH 33168. Width 0.9 mm. I–J. Ceratia? sp. I. Mould of MGUH 33169. Width 0.9 mm. J. Silicone cast of MGUH 33170. Height 1.1 mm. K. Anchura sp., Silicone cast of MGUH 33171. Width 8.6 mm. L–M. Columbellaria tuberculosa (Binkhorst, 1861). Silicone cast of ØSM.10042-202-a–c. Width 5.2 mm, height 5.9 mm. N. Tylostoma? sp., inner mould MGUH 33172. Width 19.9 mm. O–P. Cassidae genus et sp. indet. Silicone cast and internal mould of ØSM.10042-315-a–b and c, respectively. Width 9.2 and 8.6 respectively. Q–U. Sassia faxense Ravn, 1933. Q. Detail of apex of MGUH 33173. Width of protoconch 1.4 mm. R. Silicone cast of MGUH 33174. Width 6.0 mm. S. Silicone cast of MGUH 33175. Width 6.5 mm. T. Silicone cast of MGUH 33176. Width 7.8 mm. U. Silicone cast of MGUH 33177. Width 5.2 mm. V–X. Hipponix sp. V–W. Internal mould MGUH 33178. Length 23.8 mm, width 19.5 mm. X. Inner mould MGUH 33179. Width 19.1 mm. Y–Z. Eulima? danica Ravn, 1933. Y. Silicone cast of MGUH 33180. Width 2.5 mm. Z. Silicone cast of MGUH 33181. Width 2.0 mm. AE. Eulima? sp., Mould MGUH 33182. Width 1.3 mm.