Medoborichthys podolicus, 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 : 15-16

Medoborichthys podolicus n. sp.

Figure 6a–d

Holotype NMNHU-P PI 2563 , Kozatskyi Yar , western Ukraine, late Badenian, Fig. 6b .

Paratypes 30 otoliths: 12 specimens same data as holotype, NMB P1215 ; 9 specimens, Mlyntsi, NMNHU-P PI 2564 ; 9 specimens, Shydlivshchyna, NMNHU-P PI 2565 .

Etymology Named after the region Podolia of western Ukraine.

Diagnosis OL:OH = 1.2–1.25. Anterior rim inclined at 75–80° with short preventral projection; posterior rim with moderately developed postdorsal projection. Dorsal rim relatively shallow. Sulcus wide, inclined at 10–15°. Ostial lobe moderate; no subcaudal iugum. Ventral furrow deep, distant and divergent from ventral otolith rim and connected around sulcus to dorsal depression; area around sulcus distinctly bulged.

Description Moderately slender, rectangular, massive otoliths reaching about 1.6 mm in length (holotype). OH:OT = 2.2–2.5. Anterior rim slightly inclined, with 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 shallow, with variably developed mostly blunt postdorsal angle, slightly ascending toward posterior, with moderately strong postdorsal projection not bent outward. Posterior rim with distinct concavity below postdorsal projection and orthogonal postventral angle.

Inner face moderately convex, with area around sulcus and interior of ventral furrow and dorsal depression distinctly bulged. Sulcus wide, relatively deep, centrally positioned, moderately inclined at 10–15°. OL:SuL = 2.0– 2.5; SuL:SuH = 1.8–2.1. Sulcus with moderate ostial lobe, smoothened sole-shaped, with rounded anterior and posterior tips. No subcaudal iugum. Ventral furrow broad, deep, distinct, regularly curved, distant and divergent from ventral rim of otolith, connected around sulcus to moderately wide and deep dorsal depression. Outer face convex, more convex than inner face and very regularly shaped and smooth.

Discussion Medoborichthys podolicus differs from M. renesulcis n. sp. described below in the less reduced and larger sulcus and the anteriorly not depressed predorsal angle (vs. depressed). Te dorsal depression is wider in M. podolicus than in M. renesulcis n. sp. Medoborichthys podolicus is as common as Gobius ukrainicus in the assemblage, and both can be confused in atypical or eroded specimens. Consistent differences between the two include the wider sulcus (SuL:SuH = 1.8–2.1 vs. 2.4–2.8), the missing subcaudal iugum (vs. present), the shape of the ventral furrow, and the strongly bulged area around the sulcus in M. podolicus .

Figures

Fig. 6 Otoliths of Medoborichthys and Vanderhorstia: a–d Medoborichthys podolicus n. gen. et n. sp., b holotype, NMNHU-P PI 2563, Mlyntsi, a, c, d paratypes,a Mlyntsi, NMNHU-P PI 2564,c Shydlivshchyna,NMNHU-P PI 2565, d (reversed) Kozatskyi Yar, NMB P1215. e–g Medoborichthys renesulcis n. gen. et n. sp., e holotype, NMNHU-P PI 2566, Mlyntsi,f, g paratypes,f Kozatskyi Yar, NMB P1216, g (reversed) Mlyntsi, NMNHU-P PI 2567. h–j Vanderhorstia prochazkai Schwarzhans et al., 2020a, 2020b, h (reversed), j (reversed) Mlyntsi, NMB P1223, h (reversed) Shydlivshchyna, NMNHU-P PI 2582. k Vanderhorstia sp., Shydlivshchyna, NMB P1224