Abstract
ABSTRACT A new rhynchonellide brachiopod genus and species, Skadarirhynchia semicostata gen. et sp. nov., is described from the late Pliensbachian of Livari, Rumija Mountain, southeastern Montenegro. It occurs in shallow-water brachiopod-crinoid packstone beds (bioclastic limestones) of the periplatform facies of the Dinaric Carbonate Platform. Stratigraphy is constrained by means of 87Sr/86Sr dating indicating a late Pliensbachian age, and by the fact that the brachiopod beds lie immediately below the Toarcian marly limestones, which is consistent with the regional stratigraphical position. The new species has a circular to roundly pentagonal outline and semicostate shells with 10‒12 strong angular ribs. Internally, it shows reduced dental plates, narrow and thin hinge plates inclined dorsally with small crural bases, crescent-like and laterally convex, and hamiform crura. The shell microstructure of the new taxon is characterised by a homogeneous secondary layer (a single layer with no sublayers) built of rhombic fibres that are typically of coarse-fibrous type (eurinoid pattern) 35‒50 μm wide and 20‒30 μm thick. Other co-occurring rhynchonellide species such as Prionorhynchia fraasi and Cuneirhynchia dalmasi are also described. Shell microstructures for the genus Cuneirhynchia are presented.
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