Amaurellina ravni, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 91

Amaurellina ravni n. sp.

Figs 24 M–Q

Diagnosis. The shell is high-spired with distinctly concave base, a deeply grooved suture, a whorl periphery located well above abapical suture, a very narrow umbilical opening and with pitted spiral grooves.

Derivation of name. In honour of J.P.J. Ravn, who greatly contributed to our knowledge of the gastropod faunas from the Cretaceous and especially Palaeocene deposits of Denmark.

Type material. The holotype MGUH 33147 is a nearly complete external mould . Paratype MGUH 33150 is an external mould of the protoconch from Stevns Klint . Paratype MGUH 33149 is a mould with replaced shell from Holtug . Paratype MGUH 33148 is an internal mould from Holtug . All paratypes come from the Cerithium Limestone Member.

Additional material. Three specimens are found in the informally catalogued samples SH.278, SH.325.A and C, and SR.525. Another seven external and internal moulds have been studied from the uncatalogued old collections at the Natural History Museum of Denmark.

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

Occurrence. The lower Danian Cerithium Limestone Member at Stevns Klint.

Description. Protoconch conical, with seemingly around 2 ½ moderately convex and smooth whorls. Height and width approximately 0.6 mm.

Teleoconch coeloconoid with a moderately high spire and a globose last whorl. Spire whorls moderately convex with periphery located just below 1/3 the whorl height from the abapical suture. Suture initially shallow, on later whorls becoming deeply grooved with nearly axially oriented sides and bordered by a sharp abaxial shoulder. Base evenly rounded. Umbilical opening narrow. Aperture semicircular with width corresponding to about 70 % of height; aperture height approximating 60 % of shell height. Callus on inner lip thin, not reaching outside aperture opening.

Growth lines fine, prosocline, crossed by weak, but more or less unevenly distributed pitted spiral grooves.

Measurements. Holotype MGUH 33147 is 14.0 mm high and 9.9 mm wide, consisting of at least seven whorls. Largest specimen paratype MGUH 33148 is 13.2 mm wide and in excess of 15.4 mm in height.

Remarks. Amaurellina ravni n. sp. differs from the Danian Amaurellina sp. and “aff. Amaurellina ” sp. sensu Kollmann & Peel (1983) from Greenland by the distinctly higher spire and more deeply incised suture. It is distinguished from the Danian Amaurellina julei ( Briart & Cornet, 1873) by the relatively larger last whorl, a concavesided spire and a narrower umbilical opening. It has some resemblance to Amaurellina guerrera Perrilliat, Vega & Corona, 2000 from the Maastrichtian of Mexico, but differs by the more convex spire whorls and the presence of faint spiral grooves.

Figures

FIGURE 24. A. Tenagodus sp., Silicone cast of MGUH 33139. Tube diameter 5.6 mm. B–D. Campanile selandicum (Lundgren, 1867). B–C. Silicone cast of MGUH 33140. Width 11.4 mm. D. Silicone cast of MGUH 33141. Width 4.5 mm. E–F. Campanile sp. A. Silicone cast of MGUH 33142. Whorl height 2.1 mm. G. Campanile sp. B. Silicone cast of MGUH 33143. Height 4.2 mm. H–K. Metacerithium balticum (Ravn, 1902). H. Silicone cast of protoconch MGUH 33144. Width 0.45 mm. I. Silicone cast of MGUH 33145. Height 26.0 mm. J. Silicone cast of lectotype MGUH 91 figured by Ravn (1902, pl. I: 17). Width 11.7 mm. K. Silicone cast of MGUH 93, figured type for Cerithium sartorii Ravn, 1902. Height 7.1 mm. L. Dzikella? sp., Silicone cast of MGUH 33146. Width 6.0 mm. M–Q. Amaurellina ravni n. sp. M–N. Silicone cast of holotype MGUH 33147. Width 10.3 mm. O. The internal mould of paratype MGUH 33148. Width 13.2 mm. P. Paratype MGUH 33149, a mould with replaced shell. Height 12.8 mm. Q. Silicone cast of paratype MGUH 33150. Width of picture 3.0 mm. R. Trochocerithium sp., Silicone cast of MGUH 33151. Width 9.0 mm. S–W. Galericulus sp. S–T. Internal mould ØSM.10042-311. Length 5.8 mm. U. Internal mould MGUH 33152. Width 8.5 mm. V–W. Internal mould and external cast of MGUH 33153. Length 10.3 mm. Width of figure W 7.7 mm. X. Natica sp. A. Silicone cast of MGUH 33154. Width 7.9 mm.