Mataxa, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 158

Mataxa s.l. sp.

Fig. 34G

Material. Specimen MGUH 33300 is an external mould.

Occurrence. Lithified top of the Maastrichtian Højerup Member at Holtug.

Description. Protoconch not preserved. Teleoconch bucciniform with weakly convex whorls separated by distinct, but fairly shallow suture. Whorls 2 ½ times as wide as high. Last whorl relatively large with evenly rounded sides and poorly developed canal. Aperture moderately wide and high, the height corresponding to at least 60 % of shell height. Siphonal canal short, wide, turned slightly to the left abapically. Columella moderately long, slightly curved, with weak columellar fold centrally. Outer lip slightly thickened but otherwise simple, without teeth.

Teleoconch sculpture consisting of fine, slightly irregular, flattened spiral ribs. A single stronger spiral rib borders the adapical suture. Growth lines prosocline and weakly sigmoid.

Measurements. MGUH 33300 is 3.8 mm wide and 5.7 mm high, but lacks the apex.

Remarks. The taxon differs from typical Mataxa species by the shorter siphonal canal and the presence of only one weak columellar fold. It seems thus not to be a Mataxa in the strict sense, but nonetheless appear closely related. It is here regarded as a Mataxa sensu lato.

This taxon differs from the Late Cretaceous Mataxa elegans Wade, 1916 of North America by the more convex whorls, the lack of teeth and by the presence of only one weak columellar fold. It differs from the Maastrichtian Mataxa arida Squires & Saul, 2003a from California by the much less sigmoid growth lines; the much finer sculpture and by the distinctly shorter siphonal canal.

Figures

FIGURE 34. A–E. Admetula sp. A–D. Silicone cast and internal mould of MGUH 33297. Widths 6.6, 7.2, 7.0 and 6.1 mm respectively. E. Internal mould of MGUH 33298. Width 5.6 mm. F. Kroisbachia sp., Silicone cast of MGUH 33299. Width 2.4 mm. G. Mataxa s.l. sp., Silicone cast of MGUH 33300. Width 3.9 mm. H–I. Neogastropoda genus et sp. indet., Silicone cast of MGUH 33301. Width 0.7 mm. J–N. Ravniella danica (Ravn, 1902). J–K. Silicone cast of MGUH 33202. Widths 4.7 and 4.3 respectively. L. Silicone cast of lectotype MGUH 126. Width 4.3 mm. Photograph by S.L. Jakobsen. M–N. Silicone cast of MGUH 33303. Width 4.1 and 3.8 mm. O–S. Disculus selandicum (Ravn, 1902). O. Silicone cast of MGUH 33304. Width 8.7 mm. P–Q. Silicone cast of paralectotype MGUH 80 figured by J.P.J. Ravn (1902, Pl. I: 6). Width 7.1, 6.9 mm respectively. R. Silicone cast of lectotype MGUH 79. Width 6.0 mm. Photograph by S.L. Jakobsen. S. Silicone cast of MGUH 33305. Width 5.9 mm.