Cristispira caballasensis, 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 : 1570

Cristispira caballasensis sp. nov.

( Figure 5 (i))

Diagnosis

Hypercampanulate; three strong keeled spiral cords on anterior two-thirds of spire whorls; finely spirally threaded interspaces.

Description

Shell small; pleural angle about 12°. Whorls hypercampanulate, sutural area deeply concave. Protoconch unknown, number of whorls in spire cannot be estimated. Spiral cords keeled; spiral formula dCBAr; primary cords about equally strong. Spacing formula C14B45A67; n = 1). Interspaces with microscopic spiral threads. Lateral growth line orthocline; posterior inflexion absent, anterior inflexion barely discernible. Lateral sinus moderately deep, apex close to spiral cord B. Base and aperture not preserved. Allmon formula?-1-M-B-OR.

Remarks

The elements of the spiral sculpture of Cristispira caballasensis sp. nov., evident even from the partial single specimen available, are nearly identical with those of two Peruvian species, the Late Cretaceous C. prechira (Olsson, 1944) and the middle Eocene C. paracasensis (Rivera, 1957) : three keeled primary spiral cords, a deeply con- cave sutural area, wide concave interspaces with microscopic spiral threads, and in some specimens a secondary spiral cord or thread near the posterior suture. The spacing formula for C. caballasensis (C14B45A67; n = 1) does differ from that of the younger C. paracasensis (C35B58A72; n = 8; DeVries 2007) but is the same as that for the older C. prechira (C14B40A69; n = 1). The strength of the anteriormost primary spiral cord of C. caballasensis , however, is like that of C. paracasensis , i.e. much stronger than the anteriormost primary spiral cord of C. prechira .

Material

UWBM 107605 , holotype, B8769 (type locality), L (5.1), W (4.4).

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.