Contraconus tryoni

Conus (Contraconus) tryoni (Heilprin, 1887)

Conus (Contraconus) tryoni brantleyi (Petuch & Mardie Drolshagen, 2011)

Shell sub-conical, sinistral, rather thin in substance; spire more elevated than in the typical cones, of about eight or nine volutions, terminating in a prominent pointed apex; whorls of the spire subangulated, or carinated above the suture, the carination sharply but minutely crenulated on the first five or six whorls; suture bordered inferiorly by a prominent raised convex line, which is followed by from four to five less prominent (and occasionally quite obscure) revolving lines on the shoulders of the whorls ⁽¹⁾.

Body-whorl about four-fifths the length of the shell, gently convex, crossed for the greater part of its extent by numerous obscure lines or composite bands, which become conspicuous toward the base, and exhibit there a distinct, although irregular, alternation of coarser and finer lines. Aperture somewhat arcuate, broadest near the base; columellar surface slightly folded basally ; outer lip thin ; sinual inflection a half-inch in depth ⁽¹⁾.

Length, five inches; greatest width, 2.3 inches.

Caloosahatchee, in the banks below Fort Thompson.

This beautiful cone, by far the largest reversed species of the genus with which I am acquainted, can readily be distinguished from the only other sinistral form that has thus far been described from the Tertiary deposits of the Eastern United States, Conus adversaries, by its more ponderous proportions, the greater relative elevation of the spire, and the revolving lines on the shoulders of the whorls. These last are obscured through erosion in some specimens, which then more nearly approach the Miocene fossil. There appears to be a narrower form of this type, which possibly represents a distinct species. It differs in the more pronounced angulation of the body-whorl, the lesser relative width of the crown, and a more pronounced straight-sidedness in the bounding lines of the shell. The number of such specimens in our collection is not very great, and scarcely sufficient to warrant a specific separation of the form from the species just described ⁽¹⁾.

Named after Geo. W. Tryon, Jr., the distinguished conchologist of the Academy of Natural Sciences of Philadelphia, from whom the author has received much valuable assistance in the preparation of this and other paleontological papers ⁽¹⁾.

Following Conrad’s (1840) description of Conus adversarius, Heilprin (1887) described a second fossil species of sinistral Conus, C. tryoni, from the banks of theCaloosahatchee River, Florida. He differentiated this species from C. adversarius on the basis of “its more ponderous proportions, the greater relative elevation of the spire, and the revolving lines on the shoulders of the whorls” (Heilprin, 1886: 82) ⁽²⁾.

Dall (1890: 26) designated C. tryoni as a synonym of C. adversarius, noting that “C. Tryoni is merely the fullgrown and most perfect form of C. adversarius.” ⁽²⁾

Olsson & Harbison (1953: 171) recognized C. tryoni as a subspecies of C. adversarius, and assigned it to that rank on the basis of its higher stratigraphic position and “sufficiently well-marked” characters ⁽²⁾.

In her unpublished master’s thesis, Kamp (1967) regarded C. adversarius tryoni as an unnecessary subspecies, and placed it in synonymy with C. adversarius ⁽²⁾.

Dall’s (1890) placement of Heilprin’s (1886) C. tryoni within C. adversarius is accepted here for the reasons stated by Dall, and because the distinguishing features noted by Heilprin (the variable characters of size, height of the spire, and spiral threads on the shoulder whorls) are not considered here to be taxonomically significant for sinistral cones, including at the subspecific level ⁽²⁾.

Contraconus tryoni ⁽¹⁾

Fig. 10

Contraconus tryoni

Museo Cortesi - Castell’Arquato

---------------

Edward Petuch:

a classic Contraconus tryoni from the Gelasian Age of the Early Pleistocene (an index fossil for the Fort Denaud Member of the Caloosahatchee Formation). They often can get very large, like this one.

C. adversarius is an older species from the Piacenzian Age of the Pliocene, found in the Pinecrest Member of the Tamiami Formation and also the Yorktown and Duplin Formations. It is smaller than tryoni and has a flatter spire and sharply-angled shoulder with a distinct sharp edge.

C. mitchellorum is one of the last 2 Contraconus species (the other is C. heilprini) and is confined to the Ayers Landing Member of the Caloosahatchee Formation. It is a much more slender than tryoni, has a higher and more protracted spire, and the spire whorls are heavily ornamented with large beads and coronations; very different from tryoni.

So, the museum can change the label to

"Contraconus tryoni (Heilprin, 1886)

Caloosahatchee Formation, Florida, USA"