Anodontia sp.

Kiel, Steffen & Taviani, Marco, 2018, Chemosymbiotic bivalves from the late Pliocene Stirone River hydrocarbon seep complex in northern Italy, Acta Palaeontologica Polonica 63 (3), pp. 557-568 : 564

Anodontia sp.

Fig. 9 .

Material.― Two specimens: MGGC.22018 is an articulated shell reaching 25 mm in length, MGGC.22017 is a 23 mm long left valve; from the late Pliocene of Italy, Stirone seep complex .

Description.—Small to medium-sized Anodontia (sensu lato), strongly inflated (T/L ca. 0.35), umbones elevated, somewhat prosogyrate; posterodorsal area poorly defined; no lunule; external surface with irregular, commarginal growth lines. Hinge plate very narrow and edentulous, ligament long and external, sunken in narrow groove, ligament plate thin.

Remarks.—The Anodontia group is known to host a remarkable cryptic diversity ( Taylor and Glover 2005). Sacco (1901) and Chirli (2015) assigned specimens of Anodontia (sensu lato) from the Pliocene of Italy to the extant shallow-water species Anodontia fragilis ( Philippi, 1836) . But most likely the Stirone representative is a new taxon; unfortunately, features of the pallial line and muscle scars are unknown, hence we keep these specimens in open nomenclature. Anodontia has been also reported from a Miocene seep deposit in northern Italy ( Kiel et al. 2018). However, it is apparently excluded from modern deep-water cold seep situations in the eastern Atlantic Ocean and Mediterranean.

Figures

Fig. 9. The lucinid bivalve Anodontia sp. from the late Pliocene of Italy, Stirone River seep deposit. A. MGGC.22017, smaller specimen, close-up of edentulous hinge area of left valve (A1), dorsal view (A2), and view of outer side of left valve (A3). B. MGGC.22018, larger specimen, left valve, exterior view.