Medoborichthys, 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 : 14-15

Genus Medoborichthys n. gen.

Type species: Medoborichthys renesulcis n. sp.

Etymology Referring to the Medobory barrier reef complex of late Badenian to early Sarmatian s.l. age in western Ukraine.

Diagnosis An otolith of the family Gobiidae , supposedly belonging to the Priolepis Lineage , with the following combination of diagnostic characters. Otolith size small, up to slightly over 1.5 mm in length. Otolith shape horizontal rectangular to subrectangular. Anterior and posterior rims straight to slightly inclined. Inner and outer faces nearly equally convex or outer face more strongly though. Sulcus relatively short (OL:SuL = 2.0–3.2), wide, smoothened sole-shape or reniform, with low or without ostial lobe, without subcaudal iugum, inclined at 8–15°. Ventral furrow regularly curved, distant and diverging from ventral rim of otolith, connected around sulcus to distinct dorsal depression. Area around sulcus distinctly bulged.

Discussion At first glance, the otoliths of Medoborichthys resemble those of several different lineages. Te otolith shape and characteristics resemble otoliths of the Gobius mustus complex described above, but Medoborichthys otoliths differ in the lack of a subcaudal iugum, the reduced sole-shaped or reniform sulcus, the shape of the ventral furrow, and the distinctly bulged area around the sulcus. Otoliths of the Ponto-Caspian genus Capsiosoma resemble Medoborichthys in the shape of the otolith, the reduced sulcus shape, and the lack of a subcaudal iugum but show neither the deep ventral furrow and dorsal depression nor the bulged area around the sulcus. Medoborichthys resembles otoliths of the Priolepis Lineage , particularly of the genus Priolepis (see Schwarzhans et al., 2020a for photos of extant species), in the reduced sulcus shape, the lack of a subcaudal iugum, and the ventral furrow curving at a distance from the ventral rim of the otoliths and being connected to the dorsal depression and the bulged area around the sulcus. It differs in the less reduced sulcus, particularly in M. podolicus n. sp., and the less narrowed dorsal depression, which in extant species almost forms a continuous furrow connected to the ventral furrow. Tis character state could be regarded as plesiomorphic in respect to the modern genera of the lineage. Extant members of the Priolepis Lineage are also mostly associated with reefoidal environments. Due to the uncertainties concerning the sulcus shape, we allocate Medoborichthys only tentatively to the Priolepis Lineage.

Species Two species, both from the late Badenian of western Ukraine in the back-reef facies of the Medobory barrier reef: Medoborichthys podolicus n. sp. and Medoborichthys renesulcis n. sp.