Calliomphalus (Calliomphalus)

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 77

Calliomphalus (Calliomphalus) sp.

Fig. 22Q

Material. MGUH 33118 and a very fragmentary external mould of the last whorl stored in the old collections at the Natural History Museum of Denmark.

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

Description. Shell moderately bulbous. Last whorl convex with evenly rounded periphery and weakly convex base; umbilicus deep. Growth lines prosocyrt and prosocline. Sculpture consisting of approximately 25 fine and closely spaced, somewhat flattened spiral ribs, changing from relatively high and rounded, widely spaced adapical ones over closely spaced peripheral ribs to wider and lower abapical ones. Base with unevenly distributed, coarse growth ridges.

Measurements. Whorl diameter of MGUH 33118 is 2.8 mm.

Remarks. The specimens resemble the Danian C. firketi ( Briart & Cornet, 1887) from Belgium as illustrated by Glibert (1973: pl. 1: 22), but has a more rounded periphery; relatively wider spacing of the adapical spiral ribs and prosocyrt abapical growth lines. It differs from the Maastrichtian C. (C.) granulatus ( Kaunhowen, 1898) from Belgium by the smooth adapical spiral ribs. It differs from the Late Cretaceous C. (C.) americanus Wade, 1926, C. (C.) nudus Sohl, 1960 and C. (C.) paucispirilus Sohl, 1964b from the USA by the higher number of spiral ribs, which lack beading adapically, and by the narrower umbilicus.

Figures

FIGURE 22. A. Phorcus sp., Silicone cast of MGUH 33109. Exposed width 2.2 mm. B–C. Stomatella sp., External mould of MGUH 33110. Figure B has been colour inverted and mirrored to show it in positive. Width 1.5 mm. D–F. Solariella sp. D–E. Silicone cast of MGUH 33111. Width 6.2 mm. F. Silicone cast of aperture of MGUH 33112. Width 5.95 mm. G–I. Skenea sp. G–H. Inner mould of MGUH 33113. Width 5.2 mm. I. Inner mould of MGUH 33114. Width 10.2 mm. J–K. Leucorhynchia sp., Silicone cast of MGUH 33115. Width 2.4 mm. L–N. Tectus? indecorus n. sp., L. Umbilical view of inner mould of paratype ØSM.10042-327-b. Width 19.7 mm. M–N. Silicone cast of holotype MGUH 33116. Width 1.7 mm. O–P. Homalopoma sp., Silicone cast and inner mould of MGUH 33117. Width 9.6, 6.9 mm respectively. Q. Calliomphalus (Calliomphalus) sp., Silicone cast of MGUH 33118. Width 3.1 mm. R–U. Arene jakobseni n. sp. R–T. Silicone cast of holotype MGUH 33119. Width 8.6 mm. U. Silicone cast of paratype MGUH 33120. Width of aperture 4.8 mm.