Nodifaunus gainesi, DeVries, 2019

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 : 1565-1566

Nodifaunus gainesi sp. nov.

( Figure 4 (dd – ii))

Diagnosis

Early teleoconch whorls smooth; later whorls with tubercles or tuberculate axial ribs situated near posterior suture. Base smooth, separated from side of whorl by single spiral cord. Anterior canal short.

Description

Shell length to about 45 mm, high-spired, cerithiform, spire angle about 35° for early whorls, 15° for later whorls. Protoconch unknown. Teleoconch of nine or 10 slightly convex whorls; sutures impressed; sutures of early teleoconch whorls weakly canaliculate to turriculate. Spiral sculpture on earliest five or six whorls smooth; later whorls with spiral row of tubercles along posterior margin, present as blunt spines or developed as coarse prosocline, orthocline, or opisthocline axial ribs (variable orientation between and within individual shells) with blunt erect spines rising above posterior suture and extending partly or entirely to anterior suture; as many as 12 tubercles/axial ribs per whorl at first appearance, as few as eight on last whorl. No varices or ventrolateral varix. Faint spiral lines may be diagenetic artefacts. Growth lines orthocline to opisthocyrt. Base poorly preserved; steeply rounded, smooth, separated from side of whorl by spiral cord. Aperture rhombohedral; parietal area with broad callus, raised above body whorl; columella straight, thickened, without folds; anterior canal very short, slightly recurved abaxially. Outer lip mostly missing, posterior portion adjacent to suture extended abaxially with extension aligned with last subsutural tubercle; shallow posterior canal present.

Remarks

Nodifaunus gainesi sp. nov., with one spiral row of tubercles, differs from the early Eocene species, N. dimorphica , from the Talara Basin of northern Peru, which has a second row of nodes at the angled boundary of the base. Nodifaunus gainesi differs from N. propinqua and N. venusta , both also from the Talara Basin, which have one row of tubercles, but medially located. All three northern Peruvian species also have spiral cords or threads on the base and on the early whorls. The posterior suture-hugging single row of tubercles on specimens of N. gainesi most resembles the sculpture of specimens of Late Cretaceous N. nodosus , which also lack spiral cords, but the number of tubercles on the earliest nodose teleoconch whorls of N. gainesi (about 12) is double the number on the Late Cretaceous species.

Juvenile specimens of Nodifaunus gainesi have a widely flaring aperture with a thickened outer lip. Both a twisted anterior canal and posterior canal are present.

Etymology

‘ Gainesi ’, in recognition of Arthur G. Gaines, Oceanographer Emeritus, of the Woods Hole Oceanographic Institution, Woods Hole, MA, USA, and ocean sciences mentor to the author in the early 1970s.

Material

UWBM 107609 , holotype, B8769 (type locality), L (42.4), W (19.1) ; remainder are paratypes: UWBM 107591 , B8769, L (31.8), W (19.9) ; UWBM 107610 , B8769, L (25.9), W (17.0) ; UWBM 107611 , B8770, L (36.9), W (18.2) ; UWBM 107612 , B8770, L 14.2, W 7.4 ; UWBM 107613 , B8769, L 18.0, W 8.0 ; UWBM 107614 , B8772, L (11.9), W 7.4 ; UWBM 107615 , B8769, L (22.0), W (13.7) ; UWBM 107616 , B8769, L (11.9), W (6.0) ; MUSM INV 263 , B8769, L (33.0), W (15.8) ; MUSM INV 264 , B8772, L (31.0), W (16.5) ; MUSM INV 265 , B8769, L 15.9, W 8.1.

Occurrence

Lower Paleogene, Cuenca Member, Caballas Formation, East Pisco Basin, southern Peru.

Figures

Figure 4. Gastropods from the Caballas Formation. (a–e) Nerita squatina sp. nov., B8771. (a) UWBM 107577, holotype, W 5.7 mm, spire. (b) UWBM 107648, paratype, W 8.5 mm, shoulder of last whorl. (c) UWBM 107649,paratype, W 10.1 mm, anterior of outer lip.(d) UWBM 107647,paratype,W 7.8 mm,inner surface of outer lip. (e) UWBM 107646, paratype, W 6.2 mm, columnar teeth. (f) Calyptraea cf. C. aperta Solander, 1766, UWBM 107578, B8772,W (diameter) 9.9 mm, external mould. (g) Ampullina ortoni Gabb, 1870, UWBM 107,627, B8772, L 36.8 mm, abapertural view, last whorl mostly missing; left margin annotated. (h–l) Melanella indicaformis sp. nov. (h) UWBM 107620, paratype, B8772, L 8.2 mm, apertural view. (i) UWBM 107619, paratype, B8769, L 9.4 mm, apertural/lateral view. (j) UWBM 107623, paratype, B8769,L 8.2 mm, apertural view. (k) UWBM 107618, paratype, B8772, L 10.6, abapertural view. (l) UWBM 107617, holotype, B8769, L 11.1 mm, abapertural view. (m–q) Potamides henryi sp. nov. (m) UWBM 107582, holotype, B8772, L 17.8 mm, lateral view. (n) UWBM 107582, W 6.9 mm, basal view. (o) UWBM 107586, paratype, B8771, L 11.2 mm, lateral view. (p) UWBM 107587, paratype, B8769, L 9.5 mm, abapertural view. (q) UWBM 107650, paratype, B8770, L 15.4 mm, lateral view, shell compressed. (r–t) Potamides janeae sp. nov., B8771.(r) UWBM 107579, holotype, L 9.0 mm, lateral view. (s) MUSM INV 249, L 8.8 mm, lateral and columellar view. (t) UWBM 107580, L 9.5 mm, layeral and columellar view. (u, v, x) Papposilenus utriculus gen.nov., sp. nov. (u) UWBM 107592,paratype, B8772, L 18.7 mm, oblique view of base. (v) UWBM 107589, holotype, B8772, L 25.5 mm, lateral view. (x) UWBM 107590, B8770, L 17.6 mm, lateral view.(w, y,z,jj) Rhinotamides everriculum sp.nov. (w) UWBM 107598,paratype, B8772,L 23.5 mm, abapertural view, juvenile. (y) UWBM 107593, holotype, B8769, L 21.1 mm, abapertural view. (z) UWBM 107594, paratype, B8772, L 19.4 mm, apertural view, posterior and anterior missing. (jj) UWBM 107593, apertural view.(aa,bb) Terebralia pauli gen. nov.sp.nov., UWBM 107599,holotype,B8771, L 9.2 mm.(aa) Abapertural view. (bb) Apertural view, outer lip missing. (cc) Terebralia marki gen. nov. sp. nov., UWBM 107600, holotype, B8771, L 9.8, lateral view. (dd–ii). Nodifaunus gainesi sp. nov. (dd) UWBM 107609, holotype, B8769, L 42.4 mm, apertural view. (ee) MUSM INV 264, paratype, B8772, L 31.0 mm, apertural view, anterior missing. (ff) UWBM 107609, abapertural view. (gg) UWBM 107612, paratype, B8770, L 14.2 mm, abapertural view, juvenile. (hh) UWBM 107612, apertural view. (ii) UWBM 107610, paratype, B8769, L 25.9 mm, apertural view, anterior missing.