Cylichnidae Adams and Adams, 1854

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 : 129

Family Cylichnidae Adams and Adams, 1854 Genus Cylichna Lovén, 1846

Type species: Bulla cylindracea Pennant, 1777 , by subsequent designation; Recent , North Atlantic Ocean .

Cylichna sp.

Fig. 17E .

Material.— One specimen ( NRM Mo187066, H = 5 mm) from Cerro La Salina block 1, one unnumbered specimen from Cerro La Salina block 6. Both upper Oligocene, Talara Basin, Peru .

Remarks.—The two available specimens are 5 mm high, have an evenly convex whorl profile, and show numerous fine spiral incisions. Olsson (1931) rarely reported specimens smaller than a centimeter and, hence, such small opisthobranchs are virtually unknown from the Peruvian fossil record. A similar species is Cylichna atahualpa ( Dall, 1908) from the Pacific coast of Costa Rica ( Valdés and Camacho-García 2004). Cylichna -like shells have occasionally been reported from fossil seep deposits, including an Early Cretaceous site in California ( Kaim et al. 2014), a Paleocene site in Spitsbergen ( Hryniewicz et al. 2019), and an Oligocene site in Washington, USA (Kiel 2006).

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).