Gastropods from the Cretaceous-Palaeogene boundary in Denmark
Author
Hansen, Thomas
text
Zootaxa
2019
2019-08-12
4654
1
1
196
journal article
26049
10.11646/zootaxa.4654.1.1
9ce1d103-9234-4fbe-9544-f1c294bb8783
1175-5326
3365803
CFD82CC0-3110-472E-972B-7ADC0C523A04
Exilia
sp.
Figs 31
S–T
Material.
A single nearly complete external mould,
MGUH
33272.
Occurrence.
Cerithium Limestone Member
at Skeldervig, Stevns Klint.
Description.
Protoconch high conical with around 3 ¼ to 3 ½ weakly to moderately convex and smooth whorls. Protoconch
0.6 mm
wide and
0.65 mm
high.
Teleoconch slender, high-spired, with moderately convex and thin-shelled whorls having a width corresponding to twice the height. Suture deep. Last whorl with gradual transition to convex base and moderately short canal. Aperture relatively short and narrow, the height taking up 36 % of the shell height, and with a width corresponding to 30 % of the height. Columella long, slightly curved and smooth, lacking columellar folds. Siphonal canal moderately wide and deep, not terminating in a notch.
Teleoconch sculpture reticulate with moderately strong spiral and transverse ribs forming tubercles at nodes. First teleoconch whorl only with opisthocyrt and somewhat opisthocline transverse ribs, the number amounting to about 24 per whorl. Following whorl with three and later five spiral ribs in addition to and nearly as strong as transverse ribs. Spiral ribs numbering 15 on last whorl. Transverse ribs die out on adapical part of base.
Measurements.
MGUH
33272 is
5.5 mm
high and
1.6 mm
wide, consisting of protoconch and 4 ½ teleoconch whorls.
Remarks.
The specimen corresponds well with the diagnostic features of
Exilia
but for the short aperture, which takes up much less than half the shell height. Even so it is clear that it is closely related to species like the slightly younger
Exilia crassistria
(
von Koenen, 1885
)
. Therefore it is assigned to this genus.
Exilia
sp. differs from the Palaeocene
E. crassistria
(
von Koenen, 1885
)
from
Denmark
by the coarser sculpture and slightly shorter aperture. It resembles the Selandian
Parvisipho
(
Andonia
)
crispatus
Ravn, 1939
from
Denmark
, but differs by the relatively higher protoconch and the higher number of transverse ribs.