Medoborichthys renesulcis, 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 : 16-17

Medoborichthys renesulcis n. sp.

Figure 6e–g

Holotype NMNHU-P PI 2566 , Mlyntsi , western Ukraine, late Badenian, Fig. 6e .

Paratypes 6 otoliths: 4 specimens same data as holotype, NMNHU-P PI 2567 and NMB P1217 ; 2 specimens, Kozatskyi Yar, NMB P1216 .

Etymology From reneformis (Latin) = reniform in combination with sulcus indicating the reniform shape of the sulcus.

Diagnosis OL:OH = 1.15. Anterior rim inclined at about 80° with depressed predorsal angle; posterior rim with weak developed postdorsal projection. Dorsal rim anteriorly depressed, straight ascending to postdorsal angle. Sulcus small, OL:SuL = 2.3–3.2, inclined at 8–10°. Sulcus reniform; 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 compressed, subrectangular, massive otoliths reaching about 1.45 mm in length (holotype). OH:OT = 2.2–2.4. Anterior rim slightly inclined, without concavity, and with short preventral angle. Predorsal angle obtuse, depressed. Ventral rim nearly straight, smooth. Dorsal rim relatively straight, anteriorly depressed and ascending to short, rounded postdorsal projection without or with very feeble postdorsal angle. Posterior rim with concavity below blunt postdorsal projection and orthogonal postventral angle.

Inner face moderately convex, with area around sulcus, interior of ventral furrow, and dorsal depression distinctly bulged. Sulcus wide, relatively shallow, centrally positioned, moderately inclined at 8–10°. OL:SuL = 2.3– 3.2; SuL:SuH = 1.8–2.0. Sulcus reniform without ostial lobe and without subcaudal iugum. Ventral furrow broad, deep, distinct, regularly curved, distant and divergent from ventral rim of otolith, connected around sulcus to narrow and deep dorsal depression. Outer face convex, more convex than inner face and very regularly shaped and smooth.

Discussion Medoborichthys renesulcis is readily distinguishable from M. podolicus by the shapes of the otolith and the sulcus, with both character states being considered as apomorphic and closer to extant otoliths of Priolepis . However, Schwarzhans et. al. (2020a) also recorded a single, incomplete otolith of Priolepis sp. from the early Badenian of Korytnica, Poland, that is similar to M. renesulcis in most aspects but has an even more reduced sulcus morphology, is distinctly thinner (OH:OT = 2.9 vs. 2.2–2.4), and shows a less strongly bulged area around the sulcus. Te pattern of this otolith is considered more advanced and representative of a true member of the genus Priolepis ; thus, the otolith indicates that the lineage was indeed present in the middle Miocene of the Paratethys.

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