Palaeolebias winogradskyi, Schwarzhans & Klots & Kovalchuk & Dubikovska & Ryabokon & Kovalenko, 2024

Palaeolebias winogradskyi n. sp.

Figure 6 View FIGURE 6 Y-AC zoobank.org/ 8FC7AD5B-5620-45FD-8747-8E17D76800F6

Holotype. NMNHU-P PI 2715 ( Figure 6 View FIGURE 6 Y-AA), Lisohirka , western Ukraine, late Badenian.

Paratypes. 2 otoliths, SMF PO 101.353 , same data as holotype .

Etymology. Named in honour of Serhii Winogradsky, a famous Ukrainian microbiologist, discoverer of the process of chemosynthesis, the founder of soil microbiology and ecology, an employee of the Pasteur Institute ( France), a foreign member of the Royal Society of London and the last owner of Horodok (Thorton, 1953; Gumeniuk and Kryvyi, 2016; Kryvyi et al., 2022).

Diagnosis. OL:OH = 0.95–1.05; OH:OT = 2.7–2.8. Inner face relatively flat and outer face distinctly convex. Dorsal field wide; dorsal rim rounded. Rostrum short, blunt. Sulcus slightly supramedian; cauda widened with rounded tip.

Description. Small, compact, and high bodied otoliths reaching about 0.6 mm in length (holotype); OL:OH = 0.95–1.05; OH:OT = 2.7–2.8. The dorsal rim is broadly rounded, wide, and slightly crenulated. The ventral rim is moderately deep, regularly curved. The rostrum is short, blunt, and rounded, 7–10% OL; antirostrum and excisura are minute. The posterior tip forming an obtuse inferior angle at the junction of inclined posterior rim and the ventral rim. The inner face is almost flat to slightly convex, with a slightly supramedian sulcus. The latter is moderately deep, relatively short (OL:SuL = 1.3– 1.4), divided by a broad and indistinct ventral collum in nearly equally long ostium and cauda. The cauda is slightly widened, with a rounded tip. The dorsal field is wide, with a wide depression. The dorsal depression is well marked toward the sulcus by a distinct crista superior. There is no ventral furrow. The outer face is convex and smooth.

Discussion. Cyprinodontid otoliths are common in the Oligocene and Miocene freshwater sediments of Europe (e.g., Reichenbacher, 1996; Reichenbacher and Weidmann, 1992; Reichenbacher and Prieto, 2006; Reichenbacher et al., 2007, 2019; Reichenbacher and Kowalke, 2009), and extant cyprinodontid otoliths from Europe and the Middle East have also been extensively studied (e.g., Reichenbacher et al., 2007, 2009). A few fossil otoliths have been placed in the extant genus Aphanius Nardo, 1827 , and several extinct genera ( Prolebias Sauvage, 1874 ; Palaeolebias Reichenbacher and Weidmann, 1992 ; Aphanolebias Reichenbacher and Gaudant, 2003 ). The otoliths from the Medobory backreef resemble most those of the fossil genus Palaeolebias because of its high body, the relatively regularly ventral rim, the short rostrum and posterior tip, and the shape of the sulcus. In fact, Palaeolebias winogradskyi represents the latest record of this genus, which otherwise is primarily known from the Late Oligocene and Early Miocene (Reichenbacher, 1996). Although reatively small it is nevertheless within the range of sizes reported from fossil Prolebias and Palaeolebias species (Reichenbacher and Weidmann, 1992; Reichenbacher, 1993) and show well-developed diagnostic features. Palaeolebias winogradskyi is distinguished from its congeners by the wide dorsal field, regularly rounded dorsal rim, and the rounded caudal tip. The species furthermore represents one of the rare indicators of fresh or brackish water faunal influx.