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. 

 


Conus (Dendroconus) planitectum

Holotype PRI 2908

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 ).