Spirancilla milthersii ( Ravn, 1902 )

Hansen, Thomas, 2019, Gastropods from the Cretaceous-Palaeogene boundary in Denmark, Zootaxa 4654 (1), pp. 1-196 : 144-145

publication ID

https://doi.org/ 10.11646/zootaxa.4654.1.1

publication LSID

lsid:zoobank.org:pub:CFD82CC0-3110-472E-972B-7ADC0C523A04

persistent identifier

https://treatment.plazi.org/id/BF18F633-A98F-FF75-2B9C-C667FE83FAEC

treatment provided by

Plazi

scientific name

Spirancilla milthersii ( Ravn, 1902 )
status

 

Spirancilla milthersii ( Ravn, 1902)

Figs 31 View FIGURE 31 Q–R

1902 Ancilla Milthersii n. sp. Ravn: 234–235, pl. II, fig. 18.

Diagnosis. Protoconch conical with just over two convex whorls. Teleoconch shell elongated with weakly ex- pressed sutures and no spire furrows. Columella almost vertical, bearing four to six narrow, oblique plaits. Parietal callus very thin except in front of adapical part of aperture, forming weak tongue adapically of aperture. Aperture taking up slightly over half the shell height; its outer lip lacking a labral denticle.

Material. Holotype MGUH 33270 View Materials (cast), MGUH 33271 View Materials , a mould with the informal sample number SH.192. A–B, and two uncatalogued specimens deposited in the collections of the Natural History Museum, Copenhagen.

Type stratum and type locality. The single specimen of Ravn (1902), MGUH 33270, and therefore the holotype, is from the Cerithium Limestone Member at Stevns Klint. The last known location for the specimen was in the collections of DGU [= Danmarks Geologiske Undersøgelse], which is now part of the semi-private institution GEUS in Denmark. In spite of several attempts at contacting GEUS for more information on its whereabouts, no information has come to hand, and the specimen may very well have become lost.

Occurrence. Rare in the Cerithium Limestone Member at Stevns Klint.

Description. Shell small, narrowly ovate with bluntly pointed apex. Protoconch low conical with just over two convex whorls, about 0.45 mm high and 0.65 mm wide. Teleoconch spire weakly convex with flat whorls covered by thin callus obscuring sutures. Last whorl contributing around 78 % of shell height, moderately convex, evenly contracted anteriorly, with broad uncallused zone between abapical edge of spire callus and posterior fasciole.Aperture elongate-ovate, strongly notched anteriorly, taking up about 54 % of shell height. Outer lip with evenly curved anterior margin lacking labral denticle. Columella thickened, gently concave, with four to six narrow plaits continuing into the aperture. Columellar callus bordered adapically by shallow anterior fasciole furrow, furrow terminating at aperture. Middle fasciole slightly wider, terminating just adapical to columella, and divided from the former by more or less distinct groove. Posterior fasciole widest, often indistinct due to effacement of adapical groove, groove terminating at adapical aperture angle. Spire grooves, including ancillid groove and band absent. Parietal callus very thin but for weak, rather narrow and nearly straight-sided tongue reaching up from aperture to spire callus, widening just before reaching the latter.

Measurements. Holotype MGUH 33270 is 3.3 mm wide and 7.8 mm high, composed of protoconch and about four teleoconch whorls.

Remarks. Ravn (1902) did not explain the reason for the taxon name, but it was clearly in honour of the geologist and collector of the specimen, Poul Christian Vilhelm Madsen Milthers, who found it in the year 1900.

In spite of what was indicated by Vermeij (2001: p. 508) Spirancilla milthersii does not posses a labral denticle, but has an evenly curved anterior outer lip margin.

Spirancilla milthersii ( Ravn, 1902) resembles the Selandien Spirancilla flexuosa ( von Koenen, 1885) from Denmark, but it appears smaller with a more blunt spire, a deeper anterior fasciole furrow and with stronger columellar plaits.

MGUH

Museum Geologicum Universitatis Hafniensis

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Neogastropoda

Family

Olividae

Genus

Spirancilla

Loc

Spirancilla milthersii ( Ravn, 1902 )

Hansen, Thomas 2019
2019
Loc

Spirancilla milthersii ( Ravn, 1902 )

D. D. D. D. 1902
1902
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