Unio elongatulus, C. Pfeiffer, 1825

Marrone, Federico, Nardi, Gianbattista, Cianfanelli, Simone, Govedič, Marijan, Barra, Salvatore Alessandro, Arculeo, Marco & Bodon, Marco, 2019, Diversity and taxonomy of the genus Unio Philipsson in Italy, with the designation of a neotype for Unio elongatulus C. Pfeiffer (Mollusca, Bivalvia, Unionidae), Zootaxa 4545 (3), pp. 339-374 : 356

Unio elongatulus — Neotype

Description: Shell elongate, more than twice the height, with anterior portion less than 1/4 of posterior one, rather thickened and moderately compressed. Dorsal and ventral margins almost parallel, anterior dorsal margin curved, dorsal margin straight, a little angled at the junction with posterior margin; posterior end tapered. Umbos swollen, with irregular and tubercular rugae. Ligament narrow in dorsal view. External surface dark brown in colour, with well visible growth lines. Hinge plate straight; cardinal teeth thick and flat; posterior-lateral teeth straight and very long (1/3 of shell length). Anterior adductor scar near shell margin, posterior adductor scar at the end of posteriorlateral tooth. Internal surface white and shiny, nacreous, brown along the margin. Shell length: 97.6 mm; shell height: 43.1 mm; breadth of both valves closed: 28.4 mm ( Fig. 6A ). The population from the Vipava River is a little variable in shape and colour, with some shorter specimens, ventral margin also slightly sinuous and brownyellowish colour ( Fig. 6 B–E).

Genetics: The specimen is genetically determined by its sequence of a fragment of the mtDNA gene cytochrome c oxidase subunit I (COI) (GenBank Accession Number: MG967432 ). This way the criteria of Article number 75.3 of the ICZN Code are satisfied and the neotype of Unio elongatulus is hereby formally established.

Ecology and distribution: This species, as other congenerics, lives mostly in rivers, channels and lakes. Its distribution, according to our genetic data, covers all main tributaries of the Adriatic, from the Ofanto River in Southern Italy to the Po River and other North Adriatic basins in Italy, to Croatian and Albanian hydrographical basins flowing into the Adriatic Sea.

Collection: The neotype is stored in the malacological collection of the Natural History Museum of the University of Florence, “La Specola” Zoology section (MZUF BC/53148)

Figures

FIGURE 6. Neotype of U. elongatulus Pfeiffer from Vipava (=Vipacco) River near Gabria Inferiore (A) (Savogna d’Isonzo, Gorizia, Friuli-Venezia Giulia, Italy), G. Nardi & W. De Mattia leg. 30/12/2006, MZUF BC/53148, and other specimens collected in the same locality (B-D), MZUF BC/53149; other specimen collected in the same river, downstream the railway viaduct near Castel Rubbia (E) (Savogna d’Isonzo, Gorizia, Friuli-Venezia Giulia, Italy), S. Cianfanelli & M. Calcagno leg. 29/ 06/2010, MZUF BC/52837.