Conus
planitectum (Weisbord, 1962)
Descrizione e caratteristiche (1):
Shell corroded, large, thick,
pyriform, the spire low and obtuse, with a divergence of about 146 degrees.
Post-nuclear whorls at least eight, the
nucleus decollate causing the apex to appear blunt and truncated. Spire whorls hardly
convex to flat, the sutures narrow. Body whorl broadly and evenly rounded at
the shoulder, the sides tapering
rather rapidly toward the base, the profile nearly straight save for a slight contraction
near the base above the anterior fasciole. Aperture moderately wide, oblique,
the sides nearly parallel. Base
shallowly notched, the notch reinforced with incremental layering of shell
material. Outer lip thick, the margin rolled toward
the aperture from about the middle to near the anterior
end, the lip broken back posteriorly. Surface with
axial growth striae but
seemingly devoid of spiral markings anywhere.
Dimensions. — Holotype (nucleus decollate), length
59 mm.; max. width 36.5
mm.
Type locality. — Playa Grande formation (Maiquetia
member) at W-4, Quebrada
Las Pailas. One specimen, the holotype.
Comparisons.
Among living Western Atlantic
Conidae, the nearest species
is C. ranunculus Hwass (see Clench, 1942, pp. 32-34, pi. 15, figs, 6, 7). In Venezuelan
waters C. ranunculus (syn. Conus achatinus) has been found along the Paria Peninsula, at Porlamar
on the Island of Margarita, and
on Aves Island. It differs from C. planitectum, n, sp. in the somewhat
lesser divergence of the spire (117 degrees), in being less pyriform, and in
being sculptured at the base with spiral threads.
Among fossil species, the
following ones resemble C. planitectum but differ as noted.
Conus bramkampi Hanna and Strong (1949, p.
314, pi. 8, fig. 14) from the Pliocene on the south side of Carrizo Mountain,
Imperial County, California. The spire is gently concave whereas on C.
planitectum it is gently convex.
Conus apicum Woodring (1928, pp. 202-203, pi.
9, fig. 3) from the Bowden Miocene of Jamaica. The spire is also slightly
concave, and there are obscure wavy threads on the anterior half of the shell.
Conus veatchi Olsson (1922, p. 216, pi. 2,
figs. 5, 8) from the Miocene of Costa Rica. This has fine irregular spirals on
the base,it is proportionally wider across the shoulder than C. planitectum,
and the arc from shoulder to
spire is sharper than on the Venezuelan shell.
Conus bravoi Spieker (1922,
p. 41, pi. 1, fig. 6) from the Miocene of Peru has a somewhat higher spire and
is less pyriform than C.
planitectum.
Conus williamgahbi
Maury (1917, p. 200, pi. 5, fig. 2) from the Miocene of the Dominican Republic
is subangulately rounded at the shoulder of the body whorl, whereas the
shoulder of the Venezuelan species
is smoothly and evenly rounded.
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Conus
(Dendroconus) planitectum
PRI 26319 |
Conus
(Dendroconus) planitectum
Plate 40, fig. 1, 2 Holotype Q185a – PRI 26319 mm. 59 x 36,5 Playa Grande Formation – Maiquetia Member - Venezuela |
Bibliografia Consultata
·
(1) - Weisbord, N. E., 1962. Late
Cenozoic Gastropods from Northern Venezuela. Bulletins of American
Paleontology, 42 (193 ).