Umbra euronota, Schwarzhans & Klots & Kovalchuk & Dubikovska & Ryabokon & Kovalenko, 2024

Umbra euronota n. sp.

Figure 2 View FIGURE 2 D-G

zoobank.org/ C90F1413-6370-409D-8B5E-D751B3178EEB

Holotype. NMNHU-P PI 2596 ( Figure 2 View FIGURE 2 D-G), Novyi Pliazh , western Ukraine, late Badenian.

Etymology. From euronotus (Latin) = easterly, referring to the occurrence of the species.

Diagnosis. OL:OH = 1.45. Ventral rim nearly flat and horizontal; dorsal rim domed, broadly crenulated. Rostrum long (17% of OL), inferior, with rounded tip. OL:SuL = 1.35. Cauda short and narrow compared to funnel-shaped ostium; OsL:CaL = 1.8; OsH:CaH = 2.3.

Description. A single, well-preserved and relatively small otolith of 1.65 mm in length. OL:OH = 1.45; OH:OT = 2.5. Its dorsal rim is domed, regularly curved without angles, with a broad, regular crenulation. The ventral rim is flat, horizontal, and slightly undulating. The anterior tip has a massive inferior rostrum (17% of OL, measured from the tip of the rostrum to the deepest notch of the excisura); antirostrum and excisura are minute. The posterior tip is angular, inferior, at about the same level as rostrum but more rounded. The inner face is almost flat with a centrally positioned, deepened sulcus. The sulcus is widely opening anteriorly, terminating distant from the posterior rim (OL:SuL = 1.35). The ostium is funnel-shaped, distinctly longer and wider than small and narrow cauda (OsL:CaL = 1.8; OsH:CaH = 2.3). The dorsal depression is distinct, narrow, and broad triangular; the ventral field lacks the ventral furrow but has a distinct crista inferior below the cauda. The outer face is moderately convex with a broad and smooth postcentral umbo.

Discussion. Nolf (2013) listed 14 otolith-based umbrid species from the European Cenozoic ranging in age from Eocene to Late Miocene and pertaining to three different genera. Nine species are placed in the genera Umbra, Palaeumbra or are generically undefined. Another group of small umbrid otoliths have been placed in the fossil otolith-based genus Mikroumbra Reichenbacher and Weidmann, 1992 , but these species do not resemble U. euronota (see Reichenbacher and Weidmann, 1992; Reichenbacher, 1993). Umbra euronota differs from all of them in the relatively short sulcus and the extremely narrow and short cauda, which we consider adequate for a diagnostic definition. The species is morphologically closest to Umbra praekrameri Weinfurter, 1950 , from the Late Miocene, Pannonian of Austria. Umbra euronota represents one of the rare freshwater fishes found in the Medobory backreef and is probably derived from the presumed nearby river discharge.