Mesalia, Gray, 1847

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 85

Mesalia sp.

Fig. 23Z

Material. MGUH 33137 and the two informally catalogued and fragmentary moulds SR.918.A and SR.1041 stored at the Natural History Museum of Denmark.

Occurrence. Lithified top of the Maastrichtian Højerup Member of the Tor Formation at Rødvig, Stevns Klint.

Description. Shell high turriform, slender. Protoconch only poorly preserved, conical, consisting of up to two or three whorls. Transition to teleoconch not discerned.

Teleoconch whorls strongly convex, more than twice as wide as high with impressed suture. Transition to narrow and flattened, slightly thickened base marked by spiral cord or rib. Narrow umbilical opening present. Aperture seemingly rounded ovoid.

Teleoconch sculpture on early whorls consisting of three strong spiral ribs, adapical two strongest, situated around whorl periphery. Last whorl carrying an additional spiral rib between adapical three and the spiral rib delimiting the base; distance between ribs decreasing abapically on whorl. Spiral ribs increasing in number on later whorls.

Measurements. Specimen MGUH 33137 is 1.0 mm high and 0.6 mm wide, consisting of the initial four or five whorls.

Remarks. The taxon resembles Mesalia danica n. sp. described above from the same stratigraphic level, but differs by its smaller size, slender spire, convex and relatively higher whorls and narrower base. It is distinguished from the Danian Mesalia marthae ( Briart & Cornet, 1873) from Belgium by the slightly less densely spaced spiral ribs; a narrow, but smooth base and possibly by a relatively higher whorl. It does not seem to have the siphonal canal seen on the Danish middle Danian Mesalia ? sp. 1 sensu Lauridsen & Schnetler (2014: p. 50), which in any case appears more similar to the cerithiid genus Fastigiella Reeve, 1848 than to any members of the family Turritellidae .

Figures

FIGURE 23. A. Arene jakobseni n. sp., Silicone cast of paratype MGUH 33120. Preserved width 8.9 mm. B–E. Ataphrus (Ataphrus) knoesensis n. sp. B–C. Silicone cast of holotype MGUH 33121. Width 4.0 mm. D. Silicone cast of paratype MGUH 33122. Width 4.2 mm. E. Silicone cast of paratype MGUH 33123. Width 3.9 mm. F–H. Cerithium sp. F. Silicone cast of MGUH 33124. Width 10.7 mm. G. Silicone cast of MGUH 33125. Width 9.9 mm. H. Silicone cast of MGUH 33126. Width 10.7 mm. I. Pseudovertagus? sp., Silicone cast of MGUH 33127. Width 1.6 mm. J–K. Striovertagus? sp., Silicone cast of MGUH 33128. Width 2.5 mm. L–O. Cerithidea? sp. L–M. Silicone cast of MGUH 33129. Cast height on figure L 7.4 mm. Cast width on figure M 3.3 mm. N–O. Silicone casts of MGUH 33130. Width 3.7 mm. P–S. Cirsocerithium crassilabris (von Koenen, 1885). P–Q. Silicone casts of MGUH 33131. Width 5.0 mm. R. Lectotype MGUH 865. Upper Palaeocene Lellinge Greensand, Denmark. Height 12.7 mm. Photograph by S. L. Jakobsen. S. Lateral view of MGUH 33132. Upper Palaeocene Lellinge Greensand, Denmark. Width 4.4 mm. T–U. Turritellid genus et sp. indet, Silicone cast of MGUH 33133. Width 1.0 mm. V–W. Turritella cf. plana Binkhorst, 1861. Silicone cast of MGUH 33134. Whorl width at least 17.2 mm. Height of last whorl 17.8 mm. X–Y. Mesalia danica n. sp. X. Silicone cast of holotype MGUH 33135. Width 2.2 mm. Y. Silicone cast of paratype protoconch MGUH 33136. Width 0.7 mm. Z. Mesalia sp., Silicone cast of MGUH 33137. Width 0.6 mm. AE. Tenagodus sp., Silicone cast of MGUH 33138. Width 4.3 mm.