Colus sekiuensis Kiel and Goedert, 2007

Kiel, Steffen, Hybertsen, Frida, Hyžný, Matúš & Klompmaker, Adiël A., 2020, Mollusks and a crustacean from early Oligocene methane-seep deposits in the Talara Basin, northern Peru, Acta Palaeontologica Polonica 65 (1), pp. 109-138 : 128

Colus sekiuensis Kiel and Goedert, 2007

Fig. 17A, B .

2007 Colus sekiuensis sp. nov.; Kiel and Goedert 2007: 43, figs. 3D, E.

Material.— One specimen ( NRM Mo187062; H = 21 mm) from Cerro La Salina block 2 , one specimen ( NRM Mo187063; H = 7 mm) from Cerro La Salina block 4. Both upper Oligocene, Talara Basin, Peru .

Remarks.—The specimens are rather imperfectly preserved; with their evenly convex whorl profile and spiral sculpture consisting of 11 low, nearly flat-topped, beaded spiral cords, the specimens are identical to those of Colus sekiuensis known from whale and wood falls from early Oligocene strata in Washington state, USA ( Kiel and Goedert 2007). Cyrtochetus ? chiraensis Olsson, 1931 from the Chira Formation in the Talara Basin, northern Peru, which is stratigraphically well below the Heath shale and now considered to be late Eocene in age ( Higley 2004), is remarkably similar. That species differs from Colus sekiuensis by having finer and more numerous spiral cords with a more convex profile compared to the nearly flat-topped spiral of Colus sekiuensis . In general, the buccinid genus Cyrtochetus differs from Colus by having a varix at the aperture and denticles on the inner lip ( Garvie 2013); however, those features cannot be recognized in the available material.

Olsson (1931) reported two species of Siphonalia ? from Belén and Pajarabobo, S.? belenensis and S.? tessaria . Both differ from Colus sekiuensis by their more angular whorl profile. At least judging from the published drawing, Siphonalia noachina ( Sowerby, 1846) as illustrated by Ortmann (1902: pl. 34: 5) from the late Oligocene to early Miocene of Patagonia, Argentina, has a similar overall sculpture, but a more convex whorl profile and fewer spirals per whorl.

In his faunal list for the limestone rocks near Belén and Pajarabobo, Olsson (1931: 22) lists “ Austrofusus? belenensis n. sp. ”, but a species of this name is neither described nor figured in his report. He also did not figure any neogastropods other than S.? belenensis and S.? tessaria from the Heath shale. Hence, Austrofusus? belenensis is a nomen dubium.

Stratigraphic and geographic range.—Oligocene to early Miocene of western Washington state, USA; early Oligocene of the Talara Basin, northern Peru.

Figures

Fig. 17. Neogastropod and opisthobranch gastropods from early Oligocene seep deposits at Cerro La Salina (block 2, A; block 4, B; block 6, E; block 7, D) and Belén seep site (C), Talara Basin, northern Peru. A, B. The buccinid Colus sekiuensis Kiel and Goedert, 2007. A. Large specimen (NRM Mo187062), showing shape of last whorl. B. NRM Mo187063, fragment of an early whorl. C. Buccinidae indet. (NRM Mo187064), fragmentary specimen. D. NRM Mo187065, the opisthobranch “Acteon” sp. in apertural (D1) and lateral (D2) views. E. The opisthobranch Cylichna sp. (NRM Mo187066).