Leptomaria meyeri Pacaud, 2004

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 66-67

Leptomaria meyeri Pacaud, 2004

Figs 20Q , 21 A–B

2004 Leptomaria meyeri n. sp. Pacaud: 620–623, figs 22, 23B.

Diagnosis. Cyrtoconoid; umbilicus narrow or closed; whorls moderately to strongly sigmoid with relatively sharply rounded keel; rather indistinct selenizone located on most convex part of whorl nearly one third of distance between sutures from adapical suture; teleoconch sculpture of well-developed spiral ribs cancellated by weaker collabral threads.

Material. MGUH 33097 and two internal and external moulds without numbers are found in the collections of the Natural History Museum of Denmark.

Type stratum and type locality. The holotype MNHN R63509 stored at Muséum national d’Histoire naturelle, Paris, collections du domaine Sciences de la Terre, was found in Danian deposits at Montainville, France.

Occurrence. Leptomaria meyeri Pacaud occurs in the lower Danian Cerithium Limestone Member of the Rødvig Fm. at Stevns Klint, where the shells are found in the limestone and in Thalassinoides burrows containing material from the succeeding Stevns Klint Formation. The specimen from a burrow, however, belongs to a now eroded upper layer of the Cerithium Limestone Member as evidenced by its internal mould consisting of Cerithium Limestone (pers. comm. Claus Heinberg Clausen, Roskilde University, Denmark). Additionally it is known from the middle Danian Faxe Formation, Denmark, and from Danian deposits at Montainville and Bray-et-Lü in France ( Pacaud 2004).

Description of Cerithium Limestone material. Shell cyrtoconoid with a spire angle of approximately 80˚; whorls sigmoid in outline with convex adapical part, changing to distinctly concave on central to abapical part outside selenizone; abaxial part of whorl fairly weakly convex. Last whorl with moderately pronounced, sharply rounded keel. Selenizone narrow, generally very indistinct, located on most convex part of whorl between 1/4 and 1/3 the distance between sutures from adapical suture. Selenizone replaced by open slit on last whorl. Umbilicus on internal moulds taking up between 1/5 and ¼ of whorl diameter. Teleoconch sculpture above keel consisting of moderately coarse spiral threads of varying strength, cancellated by fine collabral threads, giving the surface a slightly granular appearance. Number of spiral threads increases rapidly on first whorls, but keep around 3 spirals adapically of selenizone.Abapical part of whorl has up to at least 13 spirals between selenizone and abapical suture. Sculpture below keel consisting of weak spiral threads.

Measurements. MGUH 33097 is approximately 14.5 mm wide and 12.5 mm high.

Remarks. Leptomaria meyeri Pacaud is distinguished from the Danian L. penultima ( d’Orbigny, 1850a) from northern Europe, which was redescribed by Pacaud (2004), in the generally more step-like outline of the spire and in the generally more pronounced teleoconch sculpture. It differs furthermore from the large L. niloticiformis ( Schlotheim, 1820) treated above in the smaller size and the more adapical location of the selenizone. In contrast to what was postulated by Pacaud (2004) no difference may be found between the two species in the relative width of the umbilicus, at least on internal moulds found in Denmark.

Figures

FIGURE 20. A–B. Palaeoloxotoma sp., inner mould of MGUH 33087. Length 17.2 mm. C–I. Anatoma sp. A. C–E. Silicone casts of MGUH 33088. Width 1.3 mm. F–G. Silicone cast of MGUH 33089. Width 1.9 mm. H. Silicone cast of MGUH 33090. Preserved width 1.35 mm. I. Silicone cast of MGUH 33091. Preserved width 1.35 mm. J. Anatoma? sp. B, Silicone cast of MGUH 33092. Preserved width 1.05 mm. K–M. Temnotropis stevniensis n. sp. K–L. Silicone cast of holotype MGUH 33093. Width 3.5 mm. M. Umbilical view of paratype MGUH 33094. Width 2.1 mm. N–P. Leptomaria niloticiformis Schlotheim, 1820. N–O. Inner mould of MGUH 33095. Width 44 mm. P. Silicone cast of MGUH 33096. Middle Danian Coral Limestone from Faxe, Denmark. Height nearly 11 cm. Q. Leptomaria meyeri Pacaud, 2004. Silicone cast of MGUH 33097. Cast 14.5 mm wide, 12.5 mm high.

FIGURE 21. A–B. Leptomaria meyeri Pacaud, 2004. Silicone cast and inner mould of MGUH 33097. Width of cast 14.5. Width of inner mould 11.4 mm. C–H. Bathrotomaria jakobseni n. sp. C–F. Silicone cast and inner mould of holotype MGUH 33098. Width of exposed shell 21.3, 21.3, 15.6, 17.3 mm respectively. G. Outer mould of paratype MGUH 33099. Preserved radius 4.4 mm. H. Silicone cast of last whorl of paratype MGUH 33100. Width 16.2 mm. I. Bathybembix? sp., Silicone cast of MGUH 33101. Width 3.65 mm. J–K. Danilia sp., Silicone cast of MGUH 33102. Width 1.25 mm. L–Q. Chilodonta rudis (Binkhorst, 1861). L–M. Silicone cast of MGUH 33103. Width 6.0 mm for complete specimen, 0.25 mm for protoconch. N–O. Silicone cast of MGUH 33104. Width 7.35 mm. P. Silicone cast of aperture MGUH 33105. Height 4.8 mm. Q. Silicone cast of MGUH 33106. Width 4.65 mm. R–T. Eucycloscala gracilicostatus n. sp. R. Silicone cast of paratype MGUH 33107. Width of fragment 1.3 mm. S–T. Silicone cast of holotype MGUH 33108. Width 2.3 mm. U. Phorcus sp., Silicone cast of MGUH 33109. Height 3.2 mm, exposed width 2.2 mm.