Conus molis (Brown & Pilsbry, 1911)

Conus aff. molis (Brown & Pilsbry, 1911)

Conus molis bravoi (Spieker, 1922)

Conus concavitectum (Brown & Pilsbry, 1911)

Descrizione e caratteristiche:

Conus molis bravoi

Moderately large, broad-shouldered. Edge of shoulder marked by angulation, generally pronounced, but of varying strength. Spire low, profile smoothly conical, except part formed by strongly emerging early whorls. Protoconch missing. Early post-protoconch whorls worn, but showing suggestion of tuberculate shoulder. Succeeding whorls overlapping to edge of shoulder, or not quite to edge. Anal fasciole flat or somewhat concave, smooth (except for growth lines), or bearing faint to weak spiral threads. Spiral sculpture on lower part of body whorl faint or absent on mature shells, weak on immature shells. Height (incomplete) 64 mm, diameter 44 mm (larger figured specimen). Height 59.4 mm, diameter 36.6 mm (smaller figured specimen).

Type : Peabody Museum, Yale University.

Type locality: Zorritos district, Peru, Zorritos formation.

This Peruvian and Ecuadorian species is fairly abundant in the lower part of the Gatun formation and is represented in the middle part by two specimens. Fourteen, ranging in height from 23.5 to 57 mm, were collected at locality 138e and 23 others at four other lower Gatun localities. Conus bravoi may be recognized by its stubby lowspired outline, and flat or somewhat concave anal fasciole, which lacks spiral sculpture or is faintly to weakly sculptured. Three immature shells from locality 138c have a more distinctly concave anal fasciole than others. A few of the earliest post-protoconch whorls evidently have a tuberculate shoulder, but this feature is not clearly shown. The angulation at the shoulder is weak on the large specimen illustrated on plate 56, figure 11, as it is on C. riosantiagensis. It is also weak on the single specimen from the middle part of the Gatun. In the middle Miocene Tubara formation of Columbia C. bravoi reaches a height of 112 mm. Many of the specimens from that region have a faintly angulated, or even rounded shoulder. A relatively elongate, moderately high-spired shell (locality 136a) is doubtfully referred to C. bravoi. The shoulder angulation is exposed on late spire whorls, but the overlap of the succeeding whorl is not uniform. This shell may be abnormal. Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, localities 136, 136a, 137a, 138c, 138e, 138f. Middle part, eastern area, localities 155, 159d. Tubara formation (middle Miocene), Colombia. Progreso and Angostura formations

(middle Miocene), Ecuador. Zorritos, Cardalitos, and Montera formations (middle Miocene), Peru. ⁽³⁾

Conus molis

Exceptionally large, elongate, moderately wide at shoulder. Edge of shoulder generally abruptly angulated. Spire of moderate height, its profile concave. Protoconch consisting of 2Vss slightly bulging whorls. Early half of first post-protoconch whorl bearing axial riblets, angulated shoulder appearing on later half. Angulated shoulder of first five or six post-protoconch whorls exposed; first three or four slightly tuberculate. Anal fasciole generally concave, bearing spiral threads. Growth lines of fasciole generally exaggerated on some whorls. Lower part of body whorl, or entire whorl, bearing faint spiral sculpture, of decreasing distinctness upward. Spiral threads on lower part of very young shells faintly pustulose. Color pattern faintly showing on some immature shells, consisting of spiral rows of brownish crude rectangles, much like the pattern of Conus spurius. Height (practically complete) 160 mm, diameter 90 mm (larger figured specimen).

Type: Princeton University.

Type locality : Gatun Locks excavation, Canal Zone, middle part of Gatun formation.

Conus molis, based on a mature shell, is given precedence over C. concavitectum, the type of which is immature.

This large species—the largest American fossil species—is found throughout the Gatun formation. A total of 67 specimens, ranging in height from 23.5 to about 180 mm, is available. The largest occur in the upper part of the formation. That shown on plate 55, figure 8, was collected in the western area. A still larger crushed shell from the eastern area would have a height of about 180 mm, if it were complete. With the exception of two specimens, the basic features of these fossils are essentially uniform. The two exceptions are in a collection from the lower part of the Gatun (locality 136a). The shoulder of those specimens is less sharply angulated than that of the others and their anal fasciole is flat or almost flat. Though the shoulder and fasciole suggest C. aemulator (the next species described) , these two fossils are larger than that species and have the elongate outline of C. molis. The distribution of C. molis is clustered around the southeastern border of the Miocene Caribbean Sea : in Costa Rica, Panama, and Columbia. It has a close Miocene ally in Ecuador and Pent : C. acuminatus Spieker (1922, p. 40, pi. 1, fig. 5), which has more strongly tuberculate early whorls, a more deeply concave anal fasciole, and is not known to be of comparable size. C. haytensis Sowerby (Pflug, 1961), p. 60, pi. 16, figs. 1-5; Cercado and Gurabo formations, Dominican Republic) —the most similar fossil species in the West Indies— is wider at the shoulder, and has a less concave anal fasciole and more strongly tuberculate early whorls. It is likely that Maury's C. molis is an immature C. haytensis. On the contrary, Brown and Pilsbry's C. haytensis and C. domingensis, both from the Gatun formation, are likely to be immature C. molis. The stubby outline and flat anal fasciole of the small middle Miocene Venezuelan cone identified as C. aff. C. molis (Jung, 1965, p. 575, pi. 78, figs. 1, 2) indicate that it is more similar to C. aemulator than to C. molis. No similar species is living in the Caribbean Sea, but C. fergusoni Sowerby (Hanna, 1963, p. 42, pi. 4, fig. 2), living in the eastern Pacific Ocean, is closely allied, as pointed out by Hanna and Strong (1949, p. 295) and Hanna (1963, p. 44). Though the two species are similar in size and outline, the anal fasciole of C. molis is generally more concave and more strongly sculptured, and its early whorls are less distinctly tuberculate.

Occurrence: Lower, middle, and upper parts of Gatun formation (middle Miocene) . Lower part, localities 136a, 137a, 138c, 138d. Middle part, eastern area, localities 139e, 139f, 146, 147b (identification doubtful), 147f, 147h (identification doubtful), 151, 153, 155, 155a, 155b, 155c, 157, 158 (identification doubtful), 159, 159b. Upper part, eastern area, localities 171 (identification doubtful), 172, 175, 176a, 177, 177a, 177b, 177c; western area, locality 185. Middle Miocene, deposits, Costa Rica. Tubara formation (middle Mio cene), Colombia. Limon formation (late Miocene), Bocas del Toro area, Panama. ⁽³⁾

Distribuzione temporale: Oligocene Superiore – Miocene Medio

Distribuzione geografica: Colombia, Venezuela, Ecuador, Panama, Lesser Antilles, Grenadine Island


Conus concavitectum

**Conus molis⁽¹⁾ mm. 124,0 x 71,2**	*Conus molis* ⁽³⁾ mm. 54,5 x 27,7	*Conus haitensis*

*Conus molis* ⁽³⁾ 8 : mm. 160 x 90 9/10 : mm. 54,5 x 27,7		*Conus molis*

Conus aff. molis ⁽¹⁾

*Conus molis bravoi* ⁽³⁾ 10: mm. 59,4 x 36,6 - 11: mm. 64 x 44		*Conus molis bravoi* ⁽⁴⁾

*Conus molis bravoi* ⁽⁵⁾ Messico		*Conus virgatus* Creative Commons Attribution-Share Alike 3.0 Unported license