Vexillum tenestolidum Hansen 2019, n. sp.
Creators: name: Hansen, Thomas
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neogastropoda
Costellariidae
Vexillum
Vexillum tenestolidum

description: Vexillum tenestolidum n. sp.
Figs 30X, 31 A–C
Diagnosis. Protoconch obtusely conical with around two and a half moderately inflated whorls. Teleoconch small, slender with around 12 to 14 distinct transverse ribs per whorl on adapical five whorls, changing to fine but unevenly cancellate sculpture on later whorls.
Derivation of name. Compound word for obtuse (stolidus) and young (tener), referring to the obtusely conical protoconch.
Type material. Holotype MGUH 33259 is a nearly complete mould with protoconch collected by A. Rosenkrantz in 1943. Paratype MGUH 33260 is an external mould collected by K.I. Ingemann in 1986 from Dania Quarry, Northern Jutland.
Additional material. Two moulds with informal sample numbers SH.278 and SR.376, and 33 uncatalogued and more or less fragmentary moulds are found in the collections of the Natural History Museum of Denmark.
Type stratum and type locality. The lower Danian Cerithium Limestone Member at Skeldervig, Stevns Klint.
Occurrence. Relatively common in the Cerithium Limestone Member at Stevns Klint and the corresponding ‘dead layer’ at Dania, Northern Jutland.
Description. Protoconch obtusely conical with around 2 ½ low, inflated whorls, possible smooth. Transition to teleoconch sharp, marked by distinct change in spire angle and the appearance of transverse ribs.
Teleoconch slender, fusiform with high, flattened whorls, which are only around 1.5 times as wide as high. Whorls separated by marked suture. Whorls widest centrally or slightly adapically from here and characterized by distinct constriction slightly abapically of adapical suture. Last whorl takes up approximately 2/3 the total shell height, while aperture corresponds to around 40 %. Aperture narrow with weakly convex outer margin and sigmoid inner margin; columella carrying four strong folds, their distance and strength decreasing abapically from parietal region to wide siphonal canal.
Teleoconch sculpture on first five whorls dominated by around 12 to 14 moderately sharp and strong transverse ribs per whorl, which due to adapical constriction appear strongest just over 1/3 the whorl height from adapical suture, forming a slight shoulder on the whorl. Transverse ribs cancellated by relatively weak and densely spaced spiral threads. Transverse ribs becoming finer and closely spaced on later whorls; in some specimens even replaced by distinct growth lines of a like strength with the spiral threads.
Measurements. Holotype MGUH 33259 is 14 mm high and 4.8 mm wide, consisting of six teleoconch whorls. Protoconch measuring 0.7 mm in width and 0.5 mm down to teleoconch suture.
Remarks. The Danish taxon corresponds well to the subgenus Vexillum Röding, 1798 except in the multispiral protoconch, which differs from the typical form by its obtusely conical shape.
According to Stilwell (2003) the oldest members of the subgenus Vexillum appears around the Cretaceous-Palaeogene boundary, and the Danish taxon could therefore perhaps represent an early form or merely a close relative.
description: Published as part of Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, pp. 1-196 in Zootaxa 4654 (1) on page 139, DOI: 10.11646/zootaxa.4654.1.1, http://zenodo.org/record/3365803