Conus cf ngavianus
Material: 1 specimen (silicone moulds)
from Ras Tipuli, Lindi Bay, Tanzania; NHMW 2007zO 181/0045, w.: 16 mm, h.: 38
mm.
Description: A slender shell with a stepped coeloconoid spire consisting
of 8 whorls. The early teleoconch whorls develop a steep sutural ramp which is
terminated by a weak angulation in the lowermost quarter of the whorl. Within the forth teleoconch whorl the ramp
becomes less steep and wider and grades into a slightly concave shelf on
following whorls. The angulation now forms a slightly raised rim, whereas the
adapical part of the whorl forms a narrow collar that reaches close to the
angulation of the preceding whorl. Early whorls are smooth. Starting with the fourth teleoconch whorl, a pattern of up
to six sharp spiral threads appears. These become stronger towards the
upper suture and are most prominent along the adsutural collar, whereas the shoulder is nearly smooth. These spirals are
crossed by densely spaced opisthocyrt axial threads which cause a cancellate sculpture of the adsutural collar.
Below the rounded but very well-defined shoulder, the base starts with subparallel flanks which soon grade into
straight-sided flanks that form a last whorl angle of c. 30°. Aperture of even width and moderately narrow; outer Up
thin. Wrinkled, oblique spiral threads appear on the lower third of the
columellar area, terminated by a narrow but distinct siphonal fascicle. No
sculpture visible on base.
Discussion: This new species apparently belongs
to widespread species-complex in the Miocene and Pliocene of Indonesia: Conus hulshofi martin, 1906, from the Lower Miocene of Java develops a
slightly similar spire sculpture but
is less slender, shows spiral grooves on the base and its spire is shorter.
Subadult shells of Conus odengensis martin, 1895, from the Miocene of
Indonesia are also reminiscent of the Tanzanian species. Especially the structure of the
fasciole, which is delimited by a weak depression, is similar in both
species. The Javanese shells, however, differ distinctly
from the African species in their stout shape, the less coeloconoid spire and the spiral grooves on the lower part of the base.
A near spitting image of Conus n. sp. in respect to shell outline is the Late Miocene to Pliocene
Indonesian Conus
ngavianus martin, 1895. It
differs mainly in the absence of a
fasciole, lacks the adsutural band and develops deep spiral furrows on the
base.
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|
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Conus n. sp. Pl. V
figg. 7-9 mm. 38
x 16 Silicone
mould |
Bibliografia
·
(1)
– Harzhauser (2009) “Aquitanian gastropods of coastal Tanzania and ther bio
geographic implications for the early western Indo-Pacific”