Conus musaensis              (Olsson, 1922)



Description (1):


Shell small and solid; spire short, conic, composed of about 2 pellucid, globular and projecting whorls and 6 post-nuclear whorls; the spire-whorls are flat or slightly concave and project slightly over the anterior sutures; body-whorl with the upper  half smooth, but with 12 deep grooves on the anterior canal which produce wide, spiral bands: these grooves are delicately incised by raised longitudinal lines; color markings are sometimes preserved, which appear as 8 narrow, gray bands on the upper half of the whorl.

 

Length 19, breadth 9 mm.

 

This small species, the Gatun analogue of the recent West Indian Conus agassizi (Dall), is abundant along the Banana River and elsewhere in Costa Rica.

 

Description (2)

 

Small, moderately wide at shoulder, shoulder rounded or subrounded at maturity. Spire of moderate height, its profile slightly concave. Protoconch conspicuous, slender, cylindrical, 1 ˝  whorled. Early postprotoconch whorls sharply carinate at shoulder. Carina gradually suppressed with further growth. Anal fasciole flat. Lower half to two-thirds, or all (especially on immature shells), of body whorl sculptured with flat spiral bands, separated by generally narrower channels. Spiral bands of immature shells nonpustulose or weakly pustulose.

Height 20.6 mm, diameter 10 mm (figured specimen).

Type material: Lectotype (herewith designated), specimen represented by Olsson's fig. 24), Paleontological Research Inst. 20887.

Type locality: Rio Banana, Limon Prov., Costa Rica, middle Miocene.

 

This small species occurs in the middle part of the Gatun formation west of Gatun Lake, where 19 specimens were collected. It is the first occurrence to be recorded outside the type area in southeastern Costa Rica. Immature shells are notably different from mature shells, owing to the carinate shoulder at an early stage.

The small size and general appearance suggest C. jaspideus Gmelin, of the present Caribbean fauna, especially the round-shouldered form, for which Reeve's name C. pygmaeus is used, either as a subspecies of C. jaspideus (Clench, 1942, p. 12, pi. 7, figs. 1, 2), or as an infrasubspecific form of that species (Abbott, 1958, p. 89, pi. 3, fig. j). That the resemblance is superficial is indicated by the noncylindrical, more inflated protoconch and somewhat concave anal fasciole of C. jaspideus

 

Occurrence: Middle part of Gatun formation, western area (middle Miocene), localities 161c, 161d, 170. Middle Miocene deposits, southeastern Costa Rica.

 

 

 

 

Conus musaensis (2)

USNM 645737

mm. 20,6 x 10,0

 

Conus musaensis (1)

 

Conus musaensis

PRI 20887

Costa Rica

(5) PRI 20887, lectotype, Conus musaensis (Olsson, 1922)

Banana River, Costa Rica, SL 17.7 mm

 

(6) USNM 645737, specimen of Conus musaensis (Olsson, 1922)

figured by Woodring (1970, pl. 57, fig. 2), Panama Canal Zone, Woodring locality 170

middle Gatun Formation, SL 20,6 mm.

 

 

 

 





 

 

 


Bibliografia Consultata

 

·         (1) - Olsson, A. A., 1922. The Miocene of Northern Costa Rica with Notes on its General Stratigraphic Relations. Bulletins of American Paleontology, 6 (39 )

·         (2) - Woodring (1970) “Geology and Paleontology of the Canal Zone and adjoining part of Panama - Description of Tertiary Mollusks (Gastropods: Eulimidae, Marginellidae to Helminthoglyptidae)”

·         (3) - Hendricks (2018) “Diversity and preserved shell coloration patterns of Miocene Conidae (Neogastropoda) from an exposure of the Gatun Formation, Colón Province, Panama” May 2018, Journal of Paleontology 92(5):1-34