Terebralia Swainsonı 1840

DeVries, Thomas J., 2019, Early Paleogene brackish-water molluscs from the Caballas Formation of the East Pisco Basin (Southern Peru), Journal of Natural History 53 (25), pp. 1533-1584 : 1562-1563

Genus Terebralia Swainsonı 1840

Type species: strombus palustris Linnaeus, 1767, by subsequent designation ( Sacco 1895).

Remarks

Two small specimens from the Caballas Formation strongly resemble the early teleoconch whorls of species of Terebralia Swainson, 1840 , except that both specimens from the East Pisco Basin lack varices and a columellar fold. The absence of varices alone is insufficient to rule out Terebralia as a correct generic placement, inasmuch as some individuals of Terebralia lack varices on early teleoconch whorls. Also, the absence alone of a columellar fold (or columellar callus, an extension of the anteriormost of two internal columellar plaits; see Houbrick (1991)) may be insufficient to exclude Terebralia ; the Miocene Cerithideops Pilsbry and Harbison, 1933 , which lacks a columellar fold, is included among fossil Terebralia by Reid et al. (2008). Assignment to other potamidid genera, however, seems unwarranted; other genera do not have flat-sided whorls that exhibit the pattern of sculpture seen on the whorls of Caballas Formation specimens and early teleoconch whorls of specimens of Terebralia : few and equally strong spiral cords that are equal in strength to the axial ribs and do not produce nodes or spines at their intersections.

Reid et al. (2008) propose that the oldest examples of Terebralia lived during the middle Eocene in Europe and made their appearance in the Americas during the Miocene. The presence of Terebralia in southern Peru well before the Miocene, therefore, constitutes a biogeographical puzzle that can only be resolved by finding larger specimens of the two species from the Caballas Formation.