Caballasea segmentata, 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 : 1567-1568

Caballasea segmentata sp. nov.

( Figure 5 (a – e))

Diagnosis

As for genus.

Description

Shell length about 20 mm, cerithiform, spire angle about 12°. Protoconch unknown. Teleoconch of six or seven weakly convex whorls. Sutures impressed. Shoulder canaliculate. Spiral sculpture on spire whorls of six evenly spaced, rounded, primary spiral cords; interspaces quadrate, at least half as wide as spiral cords. Base of last whorl with additional four primary spiral cords, equally spaced and equally strong. Axial sculpture of about nine primary ribs on each whorl, variably rounded to flange-like, orthocline to slightly opisthocline, often extending to anterior end, weakly sinuate posteriorly, sometimes aligned across sutures. Thin growth lines between primary axial ribs. Varices and ventrolateral varix absent. Aperture axially elongate. Outer lip thin. Columella smooth, thickened, without folds; anterior portion of lip produced with very shallow anterior canal.

Etymology

‘ Segmentata ’, Latin adjective for ‘ frilled ’, referencing the frilled axial ribs of this species.

Material

UWBM 107606 , holotype, B8769 (type locality), L 12.6, W 5.6 ; remainder are paratypes, B8769: UWBM 107607 , L 12.4, W 5.7 ; UWBM 107608 , L (15.3), W (5.7) ; MUSM INV 261 , L (11.5), W (5.3) ; MUSM INV 262 , L (8.3), W (5.2).

Occurrence

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

Figures

Figure 5. Gastropods from the Caballas Formation. (a–e) Caballasea segmentata gen. nov., sp. nov. B8769. (a) UWBM 107607, paratype, L 12.4 mm, apertural view. (b) UWBM 107607, abapertural view. (c) UWBM 107606, holotype, L 12.6 mm, abapertural view. (d) MUSM INV 262, paratype, L 8.3 mm, oblique view of parietal callus and columella. (e) UWBM 107608, paratype, L 15.3 mm, abapertural view. (f, g) Turritella capistrata sp. nov. (f) MUSM INV 259, paratype, B8772, L 16.3 mm, lateral view. (g) UWBM 107601, holotype, B8770, L 14.4 mm, apertural view. (h) Turritella saposa Olsson, 1944, UWBM 107602, B8770, L 15.5 mm. (i) Cristispira caballasensis sp. nov., UWBM 107605, holotype, B8769, L 5.1 mm, fragment. (j, k, m, n) Rhombopsis longinquus sp. nov. (j) UWBM 107630, holotype, B8772, L 18.3 mm, apertural view, outer lip missing. (k) MUSM INV 269, paratype, B8769, L 19.9 mm, abapertural view. (m) UWBM 107631, paratype, B8772, L 22.5 mm, abapertural view. (n) UWBM 107632, paratype, B8769, L 16.4 mm, lateral view of spire and columella. (l, o–q) Tristeirostoma saxaquadrata sp. nov. B8771. (l) UWBM 107636, paratype, L 10.0 mm, spire. (o) UWBM 107,635, holotype, L 7.6 mm, abapertural view. (p) UWBM 107635, lateral view of columella. (q) UWBM 107635, apertural/lateral view.