Conus
caboblanquensis (Weisbord, 1962)
Description (1)
The Cabo Blanco
group, summarizing from the account of Weisbord (1957),
consists, from the bottom upward, of
the following formations: Las Pailas,
Playa Grande, Mare,
and Abisinia. The youngest
rock unit in the
Cabo Blanco area is the sub-Recent
conglomerate or beachrock on
the coast proper.
The lowest
formation is the
Las Pailas. This is an
unfossiliferous sequence
of interbedded light gray mudstones, siltstones, sandstones, and conglomerates, with
a maximum thickness of at
least 375 meters (1230 feet). An angular
unconformity separates the Las Pailas formation from the overlying Playa Grande formation.
The Playa
Grande formation consists
of a diversified
assemblage of rocks
starting with a basal conglomerate of variable thickness not
exceeding 20 meters (65 feet), and
thinning out to as little as
a foot or two. Because the normal
succession of strata
within the Playa Grande formation from
north to south
is interrupted by faulting or
otherwise obscured, the formation is
divided into two members, the Catia and the Maiquetia.
The Catia member, which is much
the thicker of the two, is
exposed north of
the Bruscas fault, and consists of light-colored siltstones, sandstones and conglomerates interbedded with which are
limestones (often with a yellowish cast), a few
coquinas, and an
occasional mudstone. Macroscopic and microscopic fossils are generally
present in greater or less abundance. The
maximum measured thickness is 235
meters (770 feet), but
the total thickness is probably
greater.
The Maiquetia
member, which is exposed on the
south side of the
Las Bruscas—Mare Abajo fault, is made
up of shales, siltstones, sandstones, and conglomerates
in a series
lying unconformably below
the Mare formation. The rocks
are generally drab
gray and dull tan in appearance, but they are associated here and there with yellowish brown
knobby limestones similar to those of
the Catia member. Fossils are relatively
abundant, and there
are a number of bioherms
of calcareous algae. The maximum thickness exposed is
26 meters (85 feet).
Since the basal conglomerate of the
Catia member immediately overlies the Las
Pailas formation, it may well be that the Catia member
occupies the lower part of
the Playa Grande formation, whereas the Maiquetia
beds, which unconformably underlie the
Mare formation, occupy the upper
part of the Playa Grande formation.
However, nowhere is
there a continuous
section across the
grain of the Playa Grande formation, and inasmuch as there
is some interfingering of rock
types, this relationship of
the two members
is suggestive rather than definitive.
The type
locality of the Mare formation is the area adjacent to Quebrada Mare
Abajo where it constitutes
part of the
hills overlooking this small istream.
The Mare formation is about 12
meters (40 feet) thick at the
type locality but attains
a maximum thickness of perhaps
18 meters (60 feet) elsewhere. The lower three
or four meters are made up of
incoherent grits and sands containing many
well-preseved fossils.
The upper nine meters or
so of the formation consist of tan homogeneous
slightly compacted silts which conformably overlie the
lower grits and sands but
are rather sharply defined from them. The silts
are also highly fossiliferous, albeit more so
below than above, and, at the top of
the Mare formation the silts
may be barren
of fossils. At the type locality where the
Mare formation is in contact
with the Maiquetia
member of the
Playa Grande formation, the unconformity is markedly angular.
At its upper
boundary, the Mare formation is overlain
disconformably by
nearly horizontal deposits of the
Abisinia formation.
The Abisinia
formation
comprises several of
the terraces in the
Cabo Blanco area. The deposits
are probably not over 12
meters (40 feet) thick in any
one terrace, and, depending on locality,
they consist
of clays or silts, or of
sands, or of
pebble to boulder
gravels. The formation
is accordant or slightly disconformable
with the underlying Mare formation
where that is present, and
slightly unconformable with the Playa Grande
formation where the Mare is absent.
The higher
marine terraces are, of course, a little older
than the lower
ones, but the
time interval between them as reckoned geologically was
relatively short. Marine
fossils are present
locally in the
finer, red-stained gravels, and there
is the suggestion,
from the character of their preservation, that some of the shells
were derived from the Mare and Playa Grande formations
and washed into and incorporated with the
Abisinia fauna during
Abisinia time. The
sub-Recent beachrock occurring
along the present shore of
the Cabo Blanco area is
a tabular, seaward-shelving bench of conglomerate (containing occasional present-day shells) formed through the cementation of
beach debris. This bench is awash
during high tide, and is an important determinant of the type of
littoral marine biota that can
accommodate to this
bottom material. Thus, where the
beachrock is present
off shore, the molluscan fauna is
made up principally
of rock-dwelling gastropods.
This species
is one of
the most diversely ornamented of any of the
gastropods in the Cabo
Blanco group. The shells vary from nearly smooth to nearly completely nodulated. The
base of all
of the specimens
is always spirally banded or
ridged, but above the
base the spiral markings
vary from microscopic lineations
to broad flat ribs separated by
prominent grooves.
Within the
range of variation some examples are
close to C. pygmaeus Reeve (1844,
Conch, Icon., vol. 1, pi. 47,
sp. 260), others resemble the Pliocene to Recent C.
stearnsii Conrad (1869, p.
104, pi. 10,
fig. 1), a few are like the living C.
jaspideus Gmelin
(1791, Syst. Nat., ed. 13, p.
3387), and occasional
ones are near
the Pleistocene to Recent C. verrucosus Hwass (see Clench,
1942c, pp. 13-14, pi.
8, figs. 1-4).
Despite the great variation in the
sculpture of the
body whorl, certain characteristics
- the papilliform nucleus, the shape
of the spire
whorls, the frilling of the outer lip
- are so constant, and
the superficial features so gradational,
there is no doubt that we are dealing with the same species.
In the appendix
to his Geologische Studien, Martin (1888) recorded
the presence of C.
echinulatus
Kiener (=C. Verrucosus Hwass) and
C. pygmaeus Reeve from
what is now
known as the Mare
formation of the
Cabo Blanco group in Venezuela. Since the locality
of Martin's Conidae is the same as that from which my specimens
were collected, I believe
it probable that C. jaspideuscaboblanquensis,
n. subsp. is the same as the two species
listed by Martin,
and that his shells, like
mine, are individual variants of one
and the same
species. Whether any of the variants should be referred to
C. pygmaeus or C. verrucosus is, I think,
debatable, and, therefore,
the new subspecific
name is proposed.
Adult shell
of medium size, moderately solid, the angle
of spire 76-81 degrees. Whorls 9-1/2
including the nucleus. Nucleus
smooth, pupoid or papilliform,
consisting of a little over two volutions, the initial tightly
coiled and more
or less fused with the
succeeding, the last
globose and larger
than the first
post-nuclear whorl. The nucleus as
a whole forms a nipple-.like protruberance
at the tip
of the spire. The first post-nuclear
whorl is narrow
and subangulately convex, the angulation forming the medial
periphery; the second
post-nuclear whorl is carinate around
the middle; this carina occurs nearer and nearer the base and
forms a shoulder on all subsequent whorls. The ramp
above the carina
of the third
post-nuclear whorl is
flattish but succeeding
ramps become more and more concave with growth. Sutures fine, distinct.
Whorls of the
spire covered with prominent, closely spaced
fasciolar striae curved
to conform with the excavation of
the anal outlet which forms a rather deep notch oriented parallel with
the short axis of the shell. Generally
there are no fine
spiral striae on the
spire but under a 10-power lens
the last whorl occasion ally
exhibits the merest
suggestion of spiral
lineation. Ultimate whorl acutely
shouldered at the summit,
the body slightly convex above,
a little concave at the
side above the anterior fasciole. Aperture oblique, a little wider toward
the base. Base of shell shallowly excavated into
an oblique, obtusely angled notch. Outer lip thin at the
edge, the inner margin
faintly frilled or fluted, the
number and character
of the frills
dependent on the coverage and strength of
the external spirals. Invariably, however, the flutings
on the inner
edge of the
outer lip fade upward, and are restricted
to the margin
of the lip.
Anterior fasciole raised, convex, fashioned of three
or four rather widely
spaced spiral cords and covered
completely with closely
spaced sigmoidally
curved growth
striae. Above the anterior
fasciole there are two revolving cords,
and above these four to
six wide revolving bands arranged
in a shingle-like pattern
with the posterior
edge of each
band a little
higher than the anterior edge. The
bands are separated
by wide shallow grooves, the uppermost of which is
near the middle
of the body
whorl. Fine axial growth striae cover
the surface. So much for the
details of sculpture that are constant. The variability
of ornamentation is in the lineation
of the upper half of the body
whorl and in
the amount of beading or
nodulation that is
present.
At one
extreme is the C. pygmaeus variation
with no beads,
and with the upper half
of the body
whorl smooth but with faint rather
widely spaced stripes of color built
into the shell substance itself. Twenty-eight
of the 59
specimens from the type locality
fall within this group.
At the
other extreme is the
C. verrucosus variation, represented by but
one specimen of the
59 from the type locality. On this
specimen there are 14 spiral ridges
from the top of the anterior fasciole to the
shoulder of the whorl
and all of
these are provided
with beads or nodulations, there being about 26
subequally spaced ones on
the summit row but only one or
two on the spiral
ridge just above the anterior
fasciole. The beads
are largest around the middle
of the whorl
and decrease in size above and
below. Between the extremes there
are so many gradations and intergradations
that no basis
is seen for separation. A number
of the specimens
of C. j. caboblanquensis, n. subsp. still exhibit faded
colorations of light
tan, brown, or light peach
on what seems to have
been a whitish or cream-colored
ground. The color pattern is variable
although basically it consists of
narrow, often interrupted spiral lineations
or stripes of peach or
brown, these suffused by irregular, axially disposed,
zigzagged streaks of light brown.
Dimensions—Holotype (J 180a),
length 29,9 mm.; max. width 16,5
mm. Somewhat beaded; paratype (J180b), length 23,7 mm.; max. width 13,0 mm.
Highly beaded; paratype (J180f),
length 21,7 mm.; max. width 13,1
mm. Completely beaded.
Type locality—Lower Mare
formation in small
stream 100 meters
west of Quebrada
Mare Abajo. Fifty-nine specimens.
Other localities.
Lower Mare
formation at W-13,
on hillside above west bank of
Quebrada Mare Abajo. One hundred
twentyseven specimens.
Mare formation
at W-14, on hillside above west bank of Quebrada Mare Abajo. Twenty-four specimens;
Mare formation in stream
250 meters south-southwest of mouth
of Quebrada Las Pailas. Twenty-six specimens;
Mare formation
at W-25, south flank of Punta
Gorda anticline. One poor specimen, the identification
of which is questionable;
Playa Grande
formation (Maiquetia member) at W-23,
north flank of Punta Gorda
anticline. Four specimens;
Playa Grande
formation (Maiquetia member)
at W-4, Quebrada Las Pailas.
Seven specimens;
Playa Grande
formation (Maiquetia
member) at W-26,
in Quebrada Las Bruscas, approximately 120 meters upstream from junction
with Quebrada Las Pailas. Eight
specimens;
Abisinia formation
at W-30, eastern edge of
Playa Grande village. Five specimens, four immature, one a weathered
adult.
Comparisons.—The smooth, nonbeaded variety of
C. jaspideus caboblanquensis is close to C. pygmaeus Reeve but
seems to differ in being more pointed
anteriorly and in
having a more
deeply excavated anterior notch. Furthermore,
large specimens of C. caboblanquensis are relatively narrower, and small specimens
relatively wider
than shells of C. pygmaeus of similar length.
The partially
beaded variation
of C. caboblanquensis is
near C. stearnsii Conrad,
but that species has a higher spire and the
nucleus is not papilliform.
The highly
beaded variation of C. caboblanquensis is
like C. verrucosus Hwass but may
be differentiated from that by its
shorter spire, by being proportionately a little wider at
the shoulder, and in its somewhat
more delicate shell.
In his
recent monograph on the marine mollusks of Grand
Cayman Island, Abbott (1958,
pp. 88-91, pi. 3a
- j) considered
many of the
species mentioned above
to be synonymous
with, or variants
of, C. jaspideus Gmelin
and showed that C. jaspideus exhibits the same
range of variation as does the fossil
C. caboblanquensis. Adult specimens
of C. caboblanquensis seem consistently to be broader across
the shoulder and to
have a shorter spire than the
various forms of
C. jaspideus but there is no doubt that it is of
the same stock, and if
not the same species perhaps the
progenitor of the Recent
shell. However, as the Venezuelan shell has been
found only as a fossil (in the Playa
Grande, Mare, and
Abisinia formations), and
as the fossils
are generally broader
than the jaspideus
clan, the new
subspecific name caboblanquensis is
proposed.
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Conus jaspideus caboblanquensis mm. 29,9 x
16,5 PRI Station
2896 Zancleano –
Mare Formation Vargas -
Venezuela |
Conus jaspideus caboblanquensis mm. 23,7 x
13,0 PRI Station
2896 Zancleano –
Mare Formation Vargas -
Venezuela |
Conus jaspideus caboblanquensis mm. 21,7 x
13,1 PRI Station
2896 Zancleano –
Mare Formation Vargas -
Venezuela |
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Conus jaspideus caboblanquensis mm. 25 PRI Station
2896 Zancleano –
Mare Formation Vargas -
Venezuela |
Conus jaspideus caboblanquensis mm. 28 PRI Station
2896 Zancleano –
Mare Formation Vargas -
Venezuela |
Conus jaspideus caboblanquensis mm. 12,5 PRI Station
2896 Zancleano –
Mare Formation Vargas -
Venezuela |
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Conus caboblanquensis mm. 25 Venezuela |
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Conus
caboblanquensis
mm. 22,3 x 13,1 Mare Formation - Zancleano Vargas - Venezuela [AZFC 547-01] |
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Conus
selenae
Holotype MNHN-IM-2000-3318 Fortaleza (Brasile) mm. 13,7 |
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Conus jaspideus caboblanquensis Holotype PRI 26313 mm. 29,9 x 16,5 |
Conus jaspideus caboblanquensis Paratype PRI 26317 mm. 28 |
Conus jaspideus caboblanquensis Paratype PRI 26316 mm. 25 |
Conus caboblanquensis mm. 25 Venezuela |
Conus jaspideus caboblanquensis Paratype PRI 26314 mm. 23,7 x 16,5 |
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Conus
caboblanquensis
mm. 22,3 x 13,1 Zancleano Venezuela [AZFC 547-01] |
Conus jaspideus caboblanquensis Paratype PRI 26315 mm. 21,7 x 13,1 |
Conasprelloides sp. (2) NMB H18983 NMB locality 17547 height 15.5 mm |
Conus
selenae
Holotype Fortaleza (Brasile) mm. 13,7 |
Conus jaspideus caboblanquensis Paratype PRI 26318 mm. 12,5 |
Bibliografia Consultata
·
(1) Late Cenozoic Gastropod from Northern
Venezuela – Norman E. Weisbord
(1962) – Bulletins of American Paleontology Vol.
XLII n. 193
·
(2) - Systematics of the Gastropods of the
Lower–Middle Miocene Cantaure Formation,
Paraguaná Formation, Paraguaná Peninsula, Venezuela Bernard M. Landau, Carlos
Marques da Silva, and Antoine Heitz