Conomitra glabra ( Ravn, 1902 )

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 143-144

Conomitra glabra ( Ravn, 1902)

Figs 31 K–N

1902 Fasciolaria glabra n. sp. Ravn: 231–232, pl. 2, figs 19–20.

1903 Fasciolaria glabra Ravn—Ravn : 381, 394–395.

Diagnosis. Whorls flat and smooth with narrow adapical shoulder accentuated by spiral rib; whorl height corresponding to 40 % of width. Outer lip smooth or with weak, beaded lirae. Canal moderately long and narrow.

Material. Syntype MGUH 116 , MGUH 33267 , MGUH 33268 , ØSM.10042-80, ØSM.10042-81, 30 specimens with informal sample numbers SH.178, SH.202, SH.325.C, SH.393, SH.407.A–B, SH.510, SS.179.A–B, SS.189. A–B, SS.203.A–B, SR.304.A–B, SR.313, SR.373, SR.397, SR.403.A (2 specimens), SR.465, SR.481, SR.569, SR.621.A–B, SR.644, SO.93, SO.111, DN.3, DN.31.A–B, DN.32.A–B, DN.50 and DN.51.A–B, and an additional 78 external and internal moulds in the uncatalogued old collections of the Natural History Museum of Denmark .

Type stratum and type locality. Cerithium Limestone Member at Stevns Klint.

Occurrence. Conomitra glabra ( Ravn, 1902) ranges from the base of the Cerithium Limestone Member of the Rødvig Formation and up into the base of the succeeding Korsnaeb Member of the Stevns Klint Formation at Stevns. Additionally it is found in the upper part of the ‘dead layer’ at Vokslev and Dania in Northern Jutland.

Description. Shell fusiform, width corresponding to between 40 and 45 % of height. Spire taking up one third of shell height. Protoconch rounded conical, 0.7 mm wide and 0.55 mm high, consisting of 2 ¼ smooth whorls. Transition to teleoconch indistinct.

Teleoconch with up to around six weakly convex whorls with narrow but distinct shoulder accentuating adapical suture; whorls low, height corresponding to approximately 40 % of width. Aperture high and narrow, the height taking up 55 % of shell height, while the width corresponds to just over one quarter the aperture height. Outer lip smooth or with around 10 weakly developed lirae or rows of teeth. Columella with four strong and sharp columellar folds, the adapical one located on transition to parietal region. Canal well developed. Teleoconch smooth but for a weakly developed spiral rib on shoulder and fine, slightly prosocyrt growth lines.

Measurements. Largest specimen at least 12.4 mm high.

Remarks. Conomitra glabra resembles the approximately contemporaneous C. montense Glibert, 1973 from Belgium, but differs in the more pronounced shoulder, the less compact shell and less developed lirae on outer lip. It differs from the Danian Conomitra sp. 2 sensu Kollmann & Peel (1983) from Greenland through the higher whorls and seemingly more slender canal and from the middle Danian Conomitra sp. sensu Ravn (1933) from Denmark in the pronounced suture and less convex whorls.

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.