Clanculus tonnerrei
A trochid snail often misidentified as Euchelus bicinctus.
Clanculus tonnerrei is a marine gastropod mollusk in the family Trochidae, commonly known as top snails. According to Herbert (1996), many specimens of this species were mistakenly labeled as Euchelus bicinctus due to an earlier error by Issel (1869).
The shell reaches 14 mm in height and 14.5 mm in diameter. It is umbilicate and conoidal in shape, with granulate spiral ridges that are unevenly raised. Between the suture and the periphery, there are five to six smaller ridges interspersed among the larger ones, and seven to eight on the base of the body whorl, which is obtusely angled. The granules are rosy-red with white alternating patches. The suture is moderate. The aperture is very oblique and subquadrangular, with a grooved interior that mirrors the external ridges. The outer margin is blunt and slightly crenulated, while the basal margin is finely plicate. The columella is detached, prominently toothed above, and oblique, with one or two tubercles where it meets the basal margin. The narrow umbilicus is white, with a smooth margin and an elevated fold inside the periphery.
A description of the misidentified *Euchelus bicinctus* (not Philippi, 1849) by Philippi notes a small, conical, perforate shell with transverse striae, white with rose rays. It is angular below the suture, with a nodose angle. The body whorl has a keel in the middle, and the base is rounded. The aperture is as high as it is wide, with a striated throat. The columella is curved, ending in a bipartite tooth at the base. G.W. Tryon further describes five whorls, with two shallow spiral furrows above the shoulder angle, four between that and the peripheral keel (with interspaces of equal width), and about twelve on the base.
This species is found in the Red Sea and the Indian Ocean, including waters off Djibouti, the Mascarene basin, Kenya, Mozambique, and Tanzania.
Quick Facts
- Taxon
- Clanculus tonnerrei
Facts from the source article.
Lore & Background
The shell of Clanculus tonnerrei is umbilicate, conoidal, and granulate-cingulate with unequally elevated cinguli. The smaller cinguli are interpolated, numbering 5 to 6 between the suture and the periphery, and 7 to 8 on the base of the body whorl, which is obtusely angulated. The granules are rosy-red with white subalternating. The suture is moderate, and the aperture is very oblique and subquadrangular, with a sulcate fauces corresponding to the exterior ridges. The outer margin is obtuse and subcrenulated, the basal margin plicatulate. The columella is disjoined and prominently denticulate above, oblique, with 1 or 2 tubercles where it joins the basal margin. The umbilicus is narrow and white, its margin not crenate, with an elevated fold within the periphery.
A description of Euchelus bicinctus (auct. non Philippi, 1849) by Philippi describes a small, conical, perforate shell, transversely striate, white radiated with rose, angular below the suture with the angle nodose, the body whorl carinated in the middle, base rounded, aperture as high as wide, throat striated, and columella arcuate terminating in a bipartite tooth at the base. A further description by G.W. Tryon notes 5 whorls, with two shallow spiral furrows above the shoulder angle, four between that and the peripheral carina, and about 12 on the base.
Reader's Guide
The significance of Clanculus tonnerrei lies in its history of misidentification, as many specimens were incorrectly assigned to Euchelus bicinctus following Issel's 1869 error. This confusion was clarified by Herbert in 1996, who provided observations that distinguished the species. The detailed shell morphology—including the granulate-cingulate sculpture, rosy-red and white granules, and the distinctive columellar denticles—helps separate it from similar trochids. Its distribution across the Red Sea and Indian Ocean, from Djibouti to Kenya, Mozambique, Tanzania, and the Mascarene basin, indicates a broad but specific range. The species is documented in works such as Drivas & Jay (1988) on shells of Réunion and Mauritius, and Herbert's 1996 study in Tropical Zoology. The entry underscores the importance of careful taxonomic revision in marine gastropods, as misidentifications can persist for over a century.
Did You Know?
- Many specimens of Clanculus tonnerrei were misidentified as Euchelus bicinctus due to an error by Issel in 1869.
- The shell height of Clanculus tonnerrei attains 14 mm, with a diameter of 14.5 mm.
- The granules on the shell are rosy-red with white subalternating.
- This species occurs in the Red Sea and Indian Ocean off Djibouti, Kenya, Mozambique, Tanzania, and the Mascarene basin.
More in Marine Snails, Part 3 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced