Conus hyaena kakegawaensis (Nobuhara & Tanaka, 1999)
Descrizione.
Type
specimens:
Holotype
(ESN2887 Pl.1 figs.1a,1b)
A mature
specimen from pebble conglomerate of the Dainichi Formation (upper Pliocene)
exposed in a north-facing roadside cliff at Gomyo, Kakegawa Cit, Shizuoka
Prefecture,Japan (Lat.34°47’25” N, Long. 138°O’26” E )
Paratypes-ESN
2888(figg. 4a, 4b),
2921(figg. 2a, 2b) 2922 (fig.3a,3b) −2940 ;nineteen specimens collected
with the holotype.
Material.
In addition to the type material, twentyfour
fagmented specimens were obtained from the same locality.
Diagnosis.
A
subspecies of Rhizoconus hyaena (Hwass) characterized by an angulate to
subangulate shoulder and a spiral keel just above the suture.
Description.
The
shell is medium-sized. The last whorl is conical to broadly conical, adapically
conyex, and its left side is slightly concave, The shoulder is angulate to
subangulate. The spire is low to moderately high, with its profile is concave
to steps-like, and is characterized by a projecting multispiral protoconch and
early teleoconch. Maximum diameter of the protoconch is 1.01 mm
(Holotype:ESN2887). The early postnuclear whorls are weakly tuberculate. The
teleoconch sutural ramps are flat to concave with a spiral keel just above the
suture. The sutural ramps are sculptured by two to seven distinct spiral
grooves crossed by growth lines. Wrinkled spiral ribs occur on the base, but
the upper two-thirds of the body whorl is smooth, The shell surface is ornamented
with lighter-colored axial streaks that appear under ultraviolet light having a
wave length of 352nm.
Comparison:
Rhizoconus hyaena
kakegawaensis n. subsp. most closely resembles Rhizoconus hyaena
hyaena (Hwass),now livingin India, Indonesia and the South China Sea
north to Hong Kong, but differs from it by having concave sutural ramps, a
spiral keel just above the suture, and a more-angulate shoulder.
This new subspecies also
resembles Rhizoconus hyaena concolor (Sowerby
II, 1841), now living in the Solomon Islands and Papua New Guinea, in having an
angulate to subangulate shoulder, but differs from it by haying a more-convex
body whorl and a spiral keel just above the suture.
Rhizoconus hyaena
kakegawaensis n. subsp. also resembles Rhizoconus lischkeanus (Weinkauff,1875)
in having a concave to step-like spire profile and an angulate shoulder.
However, the new subspecies differs from Rhizoconus lischkeanus in the
following characters:
1)
the left side of the base of R. hyaena kakegawaensis is concave
and the base of R. lischkeanus is straight to slightly convex;
2)
a spiral keel just above the suture is distinct in R. hyaena
kakegaveaensis and obscure in R. lischkeanus;
3)
distinct spiral grooves occur on all sutural ramps in R. hyaena
kakegaveaensis, but become obsolete adaperturally in R. lischkeanus.
Distribution: Upper Pliocene, Dainichi Formation, Shizuoka Prefecture,
central Japan
Etymology: The subspecies name refers to the Kakegawa area, the type
locality of the Kakegawa type fauna, a Pliocene to early Pleistocene warm-water
molluscan fauna that flourished on the Pacific side of Southwest Japan.
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Conus hyaena (1) Holotype
(ESN2887 Pl.1 figs.1a,1b) Paratypes-ESN
2921(figg. 2a, 2b) Paratypes-ESN 2922
(figg. 3a, 3b) Paratypes-ESN
2888 (figg. 4a, 4b) |
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Conus hyaena concolormm. 36,5 Tomini Bay, Indonesia |
Conus hyaenamm. 74,4 Keelakarai, India |
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Bibliografia
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(1) - Nobuhara & Tanaka (1999) “A New
Subspecies of Rhizoconus hyaena （Caenogastropoda： Conidae）from the Upper Pliocene Dainichi
Formation, Shizuoka Prefecture， Central Japan”
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