Dolicholatirus lorenzi, Hansen, 2019

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 138

Dolicholatirus lorenzi n. sp.

Figs 30 U–W

Diagnosis. Species of Dolicholatirus with a relatively short shell only three times as high as wide, and with a very fine spiral sculpture, sparse transverse ribbing and a smooth outer lip.

Derivation of name. In honour of Mr. Lorenz, who found the holotype.

Type material. Holotype MGUH 33257 is a nearly complete external and fragmentary internal mould collected by a Cand. [Candidate of Science?] Lorenz in 1881 . Paratype MGUH 33258 is an external mould with preserved protoconch from the Cerithium Limestone Member at Skeldervig, Stevns Klint .

Additional material. 38 external and internal moulds without numbers are found in the collections of the Natural History Museum of Denmark.

Type stratum and type locality. The Cerithium Limestone Member of the Rødvig Formation at Stevns Klint.

Occurrence. The Cerithium Limestone Member from the southern to central part of Stevns Klint (Skeldervig and up to Barmhjertigheden).

Description. Protoconch obtusely conical, consisting of 2 ½ smooth whorls; exposed height approximating 0.8 mm and width measuring 0.7 mm. Teleoconch high-spired fusiform; whorls twice as wide as high, convex with slight adapical constriction. Sinuous suture relatively deep, emphasized by weak subsutural inflation on succeeding whorl. Last whorl taking up nearly 2/3 of shell height. Aperture and siphonal canal high and narrow, corresponding to half the shell. Outer lip smooth on inner side. Inner lip with two strong and sharp columellar folds.

Teleoconch sculpture starting with 9–10 broad and strong, slightly prosocline transverse ribs, later decreasing in number to two or three per whorl; ribs largely organized into axial rows. Adapical end of transverse ribs nearly effaced, increasing in strength abapically to centrally between sutures, where a weak shoulder is formed. Ribs fading out on base, completely disappearing at transition to canal. Transverse ribs crossed by fine and numerous spiral cords, which may be completely effaced on older specimens, but usually increases in strength on base. Growth lines slightly sigmoid to nearly orthocline.

Measurements. The holotype MGUH 33257 is 30.0 mm high and 9.6 mm wide with 8 or 9 teleoconch whorls. The largest shell fragment in the museum collections measures 12.6 mm in width.

Remarks. Dolicholatirus lorenzi n. sp. differs from the late Cretaceous D. torquatus Sohl, 1964a from the U.S. by the decreasing number of transverse ribs on later whorls and the much finer and weaker spiral sculpture. It is distinguished from the Danian D. striatulus ( Briart & Cornet, 1871) from Belgium by the stronger columellar folds, lack of pseudoumbilicus and by the adapical effacement of the transverse ribs. It differs from the Danish middle Danian Dolicholatirus sp. 1 sensu Lauridsen & Schnetler (2014: p. 94) by fewer transverse ribs per whorl and finer spiral ribs.

The external part of the shell may resemble that of Fusinus schnetleri n. sp. but for a stronger spire, the very slightly sigmoid growth lines and the generally finer and often nearly effaced spiral cords on the whorls.

Figures

FIGURE 30. A–B. Amaea sp.A. Details of protoconch on external mould of MGUH 33242 shown in natural view and mirrored with inverted colours. Width of protoconch 0.6 mm. C–D. Amaea sp. B. C. Silicone cast of protoconch MGUH 33243. Width 0.6 mm. D. Silicone cast of protoconch MGUH 33244. Width 0.4 mm. E. Amaea? sp. C, Silicone cast of ØSM.10042-373. Width 5.5 mm. F–G. Acirsa torensis n. sp. F. Silicone cast of holotype MGUH 33245. Width 0.8 mm. G. Silicone cast of paratype MGUH 33246. Width 1.1 mm. H. Acirsa sp., Silicone cast of MGUH 33247. Height 6.2 mm. I–K. Opaliopsis carlsbergi n. sp. I. Silicone cast of holotype MGUH 33248. Height 2.2 mm. J. Silicone cast of paratype MGUH 33249. Height 1.7 mm. K. Silicone cast of paratype MGUH 33250. Height 3.0 mm. L–M. Fusinus schnetleri n. sp. L. Silicone cast of holotype MGUH 33251. Height 23.9 mm. M. Silicone cast of paratype MGUH 33252. Height 13.4 mm. N–O. Streptochetus sp. A. Silicone cast of MGUH 33253. Width of figure N 2.7 mm. Width of teleoconch 3.5 mm. P–Q. Streptochetus? sp. B. Silicone cast of MGUH 33254. Teleoconch width 2.6 mm.Width of protoconch 0.6 mm. R–T. Latirulus? sp. R–S. Silicone cast of MGUH 33255. Width of protoconch 0.7 mm. Height of teleoconch 10.5 mm. T. Silicone cast of MGUH 33256. Width 3.7 mm. U–W. Dolicholatirus lorenzi n. sp. U. Silicone cast of holotype MGUH 33257. Height 30.8 mm. V–W. Silicone cast of paratype MGUH 33258. Width of teleoconch 5.5 mm. Width of protoconch 0.7 mm. X. Vexillum tenestolidum n. sp., Silicone cast of holotype MGUH 33259. Width of teleoconch 4.3 mm.