Leptoconus sennottorum

Conus (Leptoconus) sennottorum (Rehder & Abbott, 1951)

Diagnosis ⁽¹⁾.

Outline of last whorl typically sigmoidal; protoconch paucispiral; early postnuclear whorls with large tubercles; sutural ramp lacking spiral ornamentation; subsutural flexure asymmetrically curved; anterior third of last whorl with incised spiral grooves.

Description ⁽¹⁾.

Shell dextral, moderately small to mediumsized. Last whorl conical to ventricosely conical; outline sigmoidal to nearly straight. Shoulder angulate to subangulate. Spire moderate to high; outline slightly concave. Protoconch of approximately two whorls, maximum diameter ca. 0.8 mm. Early postnuclear whorls with large tubercles. Teleoconch sutural ramps fl at to slightly concave. Subsutural flexure asymmetrically curved and of moderate depth. Last whorl with incised spiral grooves on anterior third. Color pattern in modern specimens consisting of approximately six rows of spiral dots or small blotches on posterior half of last whorl (color pattern not observed in fossil specimens).

Morphometrics and shell shape as a function of shell size ⁽¹⁾.

Morphometric data collected from the shells of seven fossil and four modern specimens of Conus sennottorum are summarized in Table 15. For the fossil specimens, MD = 0.49(SL) + 0.64 (R2 = 0.90) and MD = 0.71(AH) - 0.27 (R2 = 0.97).

Material examined ⁽¹⁾.

Eight lots (28 specimens) of fossil and three lots (four specimens) of modern Conus sennottorum from the collections of the FLMNH and PRI. As noted above (p. 30), an additional 42 fossil lots (249 specimens) that could not be differentiated from the similar taxon C. cf. largillierti Kiener, 1845 were also examined. Observed fossil specimen lots are listed in the Appendix. Pl. 17 demonstrates the morphological characters of modern (Figs 1-2) and fossil (Figs 3-8) C. sennottorum, in addition to some of the variations that were observed among the studied specimens.

Occurrence ⁽¹⁾.

The type locality of modern Conus sennottorum is “50 miles [80.47 km] S.W. of Campeche, Yucatan, Mexico. 15 to 16 fathoms [27.4-29.3 m]” (Rehder & Abbott, 1951: 64).

Fossil specimens are known from the Plio-Pleistocene of Florida, including the Tamiami (Pinecrest Beds) and Bermont formations; the taxon might also occur in the Caloosahatchee Formation, although unambiguous locality data are lacking.

Remarks ⁽¹⁾.

As noted above, the taxon Conus parkeri (Pl. 17,Figs 9-10) appears to be very similar to C. sennottorum and could be a senior synonym. However, the poor preservation of the type and only specimens of that taxon prevent this designation from being further explored. Among other cooccurring fossil taxa, C. sennottorum is most similar in form to C. cf. largillierti; differences separating these two taxa were discussed above (p. 31).

E’ molto simile al Conus cf. largillierti e talvolta è abbastanza difficile distinguerli ⁽¹⁾: la curvatura subsuturale è simmetrica nel Conus cf. largillierti ed asimmetrica nel Conus sennottorum, nonché per il profilo dell’ultimo giro, rettilineo o leggermente convesso nel Conus sennottorum, nel quale è tipicamente sinusoidale. Inoltre, i tubercoli sui primi giri postnucleari sono di dimensioni maggiori nel Conus sennottorum. La rampa suturale è priva di ornamentazione ⁽¹⁾.

Conus sennottorum Holotype USNM 597519 35 x 20 mm. – Yucatan (Messico)

Conus sennottorum ⁽¹⁾

Comparison of specimens of two similar species ⁽²⁾:

Colombian Gradiconus gibsonsmithorum (Petuch, 1986)

and

Venezuelan Gradiconus tristensis (Petuch, 1987)

A. JKT 4017 Gradiconus gibsonsmithorum (Petuch, 1986), 23.0 mm, trawled by shrimpers in 30-40 fathoms of Guajira Peninsula, muddy sand bottom, 1988

B. JKT 4017 Gradiconus gibsonsmithorum (Petuch, 1986), 20.7 mm, trawled by shrimpers in 30-40 fathoms of Guajira Peninsula, muddy sand bottom, 1988

C. JKT 4017 Gradiconus gibsonsmithorum (Petuch, 1986), 22.2 mm, trawled by shrimpers in 30-40 fathoms of Guajira Peninsula, muddy sand bottom, 1988

D. USNM 784470 Gradiconus tristensis (Petuch, 1987), 35.2 mm, holotype, 35 m, of Tucacas, Carabobo State, Golfo de Triste, Venezuela. Photo by Alan J. Kohn

E and F. JKT 4193 Gradiconus tristensis (Petuch, 1987), 23.6 mm, dredged 27-40 m, in sand, of Punta Fijo, Venezuela, ex Al Fox, 1984

G. JKT 4193 Gradiconus tristensis (Petuch, 1987), 23.1 mm, dredged 27-40 m, in sand, of Punta Fijo, Venezuela, ex Al Fox, 1984