Nodifaunus Olsson, 1944

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 : 1564-1565

Genus Nodifaunus Olsson, 1944

Type species: Nodifaunus nodosus, 1944 , by original designation. Late Cretaceous, northern Peru.

Remarks

Nodifaunus was created by Olsson (1944) to include high-spired cerithiform gastropods with smooth early teleoconch whorls and tuberculate or coarsely ribbed later whorls, an aperture having a broadly callused inner lip, an outer lip extended posteriorly at the suture, a short anterior canal, and a smooth base. Olsson (1944) noted morphological gradations between N. nodosus and N. costatus Olsson, 1944 ; both from the Upper Cretaceous Tortuga Formation of northern Peru. According to Olsson (1944), some specimens of N. nodosus have weak spiral cords on the base, while others have the smooth base that characterises N. costatus . N. costatus is herein considered a junior synonym of N. nodosus .

Melanatria medialis Olsson, 1944 , also from the Tortuga Formation of northern Peru, is figured by Olsson (1944, pl. 12, figs. 8, 11) alongside Nodifaunus nodosus and N. costatus ( Olsson 1944, pl. 12). Both in illustration and description, the specimens of M. medialis differ little from specimens of Nodifaunus , except that the M. medialis specimens have two spiral rows of tubercles. Olsson (1944) also noted that some specimens of M. medialis have fine spiral lines on the early teleoconch whorls. Melanatria medialis is herein transferred to Nodifaunus , with the diagnosis of Nodifaunus amended to include species that have spiral cords or threads on early teleoconch whorls or on the base, but that nonetheless are largely smooth on later teleoconch whorls.

Olsson (1944) compared Melanatria medialis with M. dimorphica Woods, 1922 , a highspired species with two spiral rows of tubercles found in lower Eocene strata near Negritos, northern Peru. Melanatria dimorphica has fine spiral threads on early teleoconch whorls and spiral cords on the base ( Woods 1922, pl. 9, fig. 11a, 11b). Melanatria dimorphica is herein transferred to Nodifaunus , as are four other early Eocene cerithioids from northern Peru: Melanatria acanthica Woods, 1922 , a large form of M. dimorphica ; M. propinqua Woods, 1922 , a species with a single row of medially situated tubercles and thought by Woods (1922) to be a variety of M. dimorphica ; and M. venusta Woods, 1922 , a species with tuberculate axial ribs resembling those of Nodifaunus costatus .

Emended diagnosis

Whorls flat sided, sutures adpressed or canaliculate. Early whorls smooth or with spiral threads, later whorls smooth, with tubercles or tuberculate axial ribs. Aperture with broad parietal and columellar thickening; anterior canal short, wide; outer lip flaring adjacent to suture of penultimate whorl; posterior canal shallow.