Nerita squatina, 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 : 1552-1553

publication ID

https://doi.org/ 10.1080/00222933.2018.1524032

DOI

https://doi.org/10.5281/zenodo.3671230

persistent identifier

https://treatment.plazi.org/id/03BB2338-E35C-E22E-FE5E-A2265E88FC59

treatment provided by

Valdenar

scientific name

Nerita squatina
status

sp. nov.

Nerita squatina sp. nov.

( Figure 4 View Figure 4 (a – e))

Diagnosis

Spire flattened. Whorls with strong spiral cords. Columella with strong teeth, without papillae. Outer lip deeply fluted.

Description

(Based on fragments of multiple specimens): shell thick; length and width less than 20 mm. Spire flat to slightly sunken. Four whorls, angulate posteriorly and medially. Sculpture of about 15 steeply rounded primary spiral cords, subequal and evenly spaced anteriorly and posteriorly, alternatingly larger medially; rarely with secondary spiral cords. Interspaces flat. Axial sculpture absent except growth lines. Colour maculated black and cream. Apertural margin of columellar callus with strong anterior tooth, weaker medial tooth, and strong posterior bifid tooth; other teeth possibly present posteriorward. Abapertural portion of columellar callus with six well-spaced transversely elongate teeth, not aligned with apertural teeth; no papillae present. Outer lip with posterior inner edge bevelled and fluted; inflexions of bevel with small, spirally elongate spirally denticles along entire length. Base of columella separated from basal portion of bevelled outer lip by shallow sulcus.

Remarks

Nerita squatina does not resemble the smooth-shelled Nerita jayanca Olsson, 1944 from the upper Campanian Tortuga Formation in the Sechura Basin of northern Peru. Rather, the flattened shell form and arrangement of spiral cords of N. squatina resemble specimens of the late Eocene Nerita listrota Woodring, 1973 from Panama and the Paleocene to middle Eocene Nerita triangulata Gabb, 1869 from western North America, but some spiral cords on the latter two species are beaded and the columellar callus of those species is papillate ( Woodring 1973; Squires and Saul 2002).

The coarse adapertural and abapertural teeth on the columellar callus and the prominence of the spiral cords on N. squatina appear on modern species of the subgenera Nerita s. s., N. ( Ritena ) Gray, 1858, and N. ( Cymostyla ) Martens, 1887, closely related clades with a common ancestor inferred to have lived during the Oligocene or earlier ( Frey and Vermeij 2008; Frey 2010). Absent from the Caballas Formation species of Nerita , however, is the high spire characteristic of the Nerita s.s. - Ritena-Cymostyla clade ( Frey and Vermeij 2008).

Etymology

‘ Squatina ’, Latin noun meaning ‘ shark ’, referring to the row of adapertural teeth and row of parallel abapertural ridges on the columellar callus.

Material

All localities B8771 (type locality); all material fragmentary. UWBM 107577 About UWBM , holotype, spire, W (5.7) ; UWBM 107646 About UWBM , paratype, columellar callus teeth, W (6.2) ; UWBM 107647 About UWBM , paratype, outer lip, W (7.8) ; UWBM 107648 About UWBM , paratype, shoulder, W (8.5) ; UWBM 107649 About UWBM , paratype, anterior of outer lip, W (10.1)

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Occurrence

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

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Cycloneritimorpha

Family

Neritidae

Genus

Nerita

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