Exilia, Conrad, 1860

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 145-146

Exilia sp.

Figs 31 S–T

Material. A single nearly complete external mould, MGUH 33272.

Occurrence. Cerithium Limestone Member at Skeldervig, Stevns Klint.

Description. Protoconch high conical with around 3 ¼ to 3 ½ weakly to moderately convex and smooth whorls. Protoconch 0.6 mm wide and 0.65 mm high.

Teleoconch slender, high-spired, with moderately convex and thin-shelled whorls having a width corresponding to twice the height. Suture deep. Last whorl with gradual transition to convex base and moderately short canal. Aperture relatively short and narrow, the height taking up 36 % of the shell height, and with a width corresponding to 30 % of the height. Columella long, slightly curved and smooth, lacking columellar folds. Siphonal canal moderately wide and deep, not terminating in a notch.

Teleoconch sculpture reticulate with moderately strong spiral and transverse ribs forming tubercles at nodes. First teleoconch whorl only with opisthocyrt and somewhat opisthocline transverse ribs, the number amounting to about 24 per whorl. Following whorl with three and later five spiral ribs in addition to and nearly as strong as transverse ribs. Spiral ribs numbering 15 on last whorl. Transverse ribs die out on adapical part of base.

Measurements. MGUH 33272 is 5.5 mm high and 1.6 mm wide, consisting of protoconch and 4 ½ teleoconch whorls.

Remarks. The specimen corresponds well with the diagnostic features of Exilia but for the short aperture, which takes up much less than half the shell height. Even so it is clear that it is closely related to species like the slightly younger Exilia crassistria ( von Koenen, 1885) . Therefore it is assigned to this genus. Exilia sp. differs from the Palaeocene E. crassistria ( von Koenen, 1885) from Denmark by the coarser sculpture and slightly shorter aperture. It resembles the Selandian Parvisipho (Andonia) crispatus Ravn, 1939 from Denmark, but differs by the relatively higher protoconch and the higher number of transverse ribs.

Figures

FIGURE 31. A–C. Vexillum tenestolidum n. sp. A–B. Silicone cast of holotype MGUH 33259. Width of protoconch 0.7 mm. Width of last whorl 3.4 mm. C. Silicone cast of paratype MGUH 33260. Width 5.8 mm. D–G. Vexillum? rosenkrantzi n. sp. D–E. Silicone cast and inner mould of holotype MGUH 33261. Width 1.9 and 1.6 mm respectively. F. Silicone cast of paratype MGUH 33262. Width 3.2 mm. G. Silicone cast of paratype MGUH 33263. Width 2.9 mm. H. Vexillum? sp. Silicone cast of MGUH 33264. Width 3.5 mm. I. Columbarium heberti (Briart & Cornet, 1880). Silicone cast of last whorl MGUH 33265. Width 7.7 mm. Photograph by S.L. Jakobsen. J. Columbarium sp. Silicone cast of MGUH 33266. Width 13.3 mm. K–N. Conomitra glabra (Ravn, 1902). K. Silicone cast of MGUH 33267. Width 3.6 mm. L–M. Silicone cast of MGUH 33268. Width 3.6 and 3.9 mm respectively. N. External cast of syntype MGUH 116. Height 8.2 mm. Photograph by S.L. Jakobsen. O. Volutomitra cf. quinqueplicata Ravn, 1902. Silicone cast of MGUH 33269. Width 11.6 mm. P. Volutomitra quinqueplicata Ravn, 1902. External cast representing last whorl of type specimen MGUH 117. Middle Danien Faxe Formation, Denmark. Height 38.6 mm. Photograph by S.L. Jakobsen. Q–R. Spirancilla milthersii (Ravn, 1902). Q. Silicone cast of holotype MGUH 33270. Width 3.3 mm. R. Silicone cast of MGUH 33271. Width 3.1 mm. S–T. Exilia sp., Silicone cast of MGUH 33272. Width 1.6 mm. U–W. Latiromitra? sp. External cast and inner mould of MGUH 33273. Width 4.6 mm for casts and 4.0 mm for mould.