Gobius ukrainicus, Schwarzhans & Klots & Ryabokon & Kovalchuk, 2022

Schwarzhans, Werner, Klots, Oleksandr, Ryabokon, Tamara & Kovalchuk, Oleksandr, 2022, A rare window into a back-reef fish community from the middle Miocene (late Badenian) Medobory Hills barrier reef in western Ukraine, reconstructed mostly by means of otoliths, Swiss Journal of Palaeontology (18) 141 (1), pp. 1-35 : 10-11

publication ID	https://doi.org/ 10.1186/s13358-022-00261-3
persistent identifier	https://treatment.plazi.org/id/039D7D5B-FE40-FFA8-F872-FDD0FE8EFBF2
treatment provided by	Felipe
scientific name	Gobius ukrainicus
status	sp. nov.

Treatment

Gobius ukrainicus n. sp.

Figure 4g –k View Fig

Holotype NMNHU-P PI 2558 , Shydlivshchyna , western Ukraine, late Badenian, Fig. 4j View Fig .

Paratypes 30 otoliths: 8 specimens same data as holotype, NMNHU-P PI 2560 ; 11 specimens, Mlyntsi, NMNHU-P PI 2559 ; 11 specimens, Kozatskyi Yar, NMB P1212 View Materials .

Etymology Named after Ukraine.

Diagnosis OL:OH = 1.2–1.3. Anterior rim inclined at 80–85° with short preventral projection; posterior rim with moderately developed postdorsal projection. Dorsal rim regularly curved. Sulcus narrow, relatively short (OL:SuL = 1.95–2.1), inclined at 15–20°. Ostial lobe moderate; subcaudal iugum small, below anterior part of cauda. Inner face flat; outer face markedly convex.

Description Moderately slender, massive otoliths reaching about 2.2 mm in length (holotype 1.8 mm). OH:OT = 2.4–2.7. Anterior rim slightly inclined, with very feeble concavity at about tip of ostium and distinct but relatively short preventral angle. Predorsal angle distinct, positioned high on anterior rim. Ventral rim nearly straight, smooth. Dorsal rim regularly curved usually without prominent angles or concavities, sometimes slightly undulating or crenulated, slightly ascending toward posterior, with distinct moderately strong postdorsal projection with rounded tip and not bent outward. Posterior rim below postdorsal projection slightly incised, thereafter nearly vertical, with orthogonal postventral angle.

Inner face slightly convex, nearly flat, with narrow, somewhat deepened, centrally positioned, distinctly inclined sulcus. SuL:SuH = 2.4–2.8. Sulcus with moderate to low ostial lobe, sole-shaped, and somewhat pointed anterior tip and more rounded posterior tip, inclined at 15–20°. Subcaudal iugum small, knob-like, sometimes poorly discernible ( Fig. 4g, h View Fig ), positioned below sulcus indentation marking ostial–caudal joint. Ventral furrow broad, deep, distinct, reaching from anterior to posterior tips of sulcus, more regularly curved than ventral rim of otolith. Ventral field between ventral furrow and sulcus slightly bulged. Dorsal field with long, distinct and relatively broad dorsal depression, ventrally marked by distinct crista superior toward sulcus and dorsally closed to dorsal rim of otolith. Outer face convex, distinctly more convex than inner face, and very regularly shaped, smooth.

Discussion Gobius ukrainicus is the most common species at Horodok in the Medobory back-reef environment. It belongs to the Gobius mustus complex and differs from the coeval G. bratishkoi in the regularly curved dorsal rim (vs. anteriorly with broad concavity), the slightly inclined anterior rim (vs. vertical), and the moderately developed ostial lobe (vs. very low ostial lobe), which results in the sole-shaped sulcus. It also resembles G. mustus , which occurs in non-reef-related environments during the same time, and differs in a number of subtle but nevertheless stable characters. Gobius ukrainicus differs from G. mustus in the regularly curved dorsal rim, the not outward bent postdorsal projection (vs. slightly outward bent), the shorter sulcus (OL:SuL = 1.95–2.1 vs. 1.65–1.9), and the ventral furrow clipping the pre- and postventral angles (vs. more strictly following the shape of the ventral rim of the otolith).