Leptomaria meyeri Pacaud 2004
Creators: name: Hansen, Thomas
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Vetigastropoda
Pleurotomariidae
Leptomaria
Leptomaria meyeri

description: 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.
description: Published as part of Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, pp. 1-196 in Zootaxa 4654 (1) on pages 66-67, DOI: 10.11646/zootaxa.4654.1.1, http://zenodo.org/record/3365803