Notoberyx cionei Schwarzhans & Mors & Engelbrecht & Reguero & Kriwet 2017, sp. nov.

Notoberyx cionei sp. nov.

(Figs 5D—G, 6O)

Material. Holotype: NRM-PZ P.15987 (Figs 5D—F, 6O). Paratypes: two specimens, NRM-PZ P.15988— 15989 (Fig. 5G).

Occurrence. Telm 5 unit; ‘ Natica horizon’, Cucullea I member, La Meseta Formation, late Ypresian, early Eocene. Site IAA 2/95, Seymour Island, Antarctica.

Etymology. Named in honour of Alberto Cione (La Plata, Argentina) for his many contributions to the knowledge of fossil fishes from South America and Antarctica.

Diagnosis. OL:OH = 0.7—0.75. Dorsal rim high, broad; ventral rim deep, broad. Rostrum short, blunt, about equal length of antirostrum. CaL:OsL = 1.4—1.5. Ostium narrow, only slightly wider than cauda; cauda distinctly turned upwards.

Description. Large, robust, high-bodied, oval otoliths up to about 6 mm in length (holotype 5.8 mm long). OL:OT = 3.0. Dorsal rim high, much expanded and broad, undulating; rounded pre- and postdorsal angles close to anterior and posterior limits of dorsal rim, postdorsal angle usually somewhat pronounced. Ventral rim deep, nearly as broad and expanded as dorsal rim, but more gently curved and smooth. Anterior rim blunt, nearly vertically cut, with very short and massive rostrum not reaching beyond length of antirostrum; with broad, shallow excisura in between. Posterior rim likewise blunt and nearly vertically cut, its tip shifted dorsally above level of caudal tip.

Inner face bent along the horizontal axis, nearly straight in vertical direction. Sulcus slightly supramedian, wide, moderately deep. Ostium anteriorly opened, slightly deepened, distinctly shorter than cauda and only slightly wider. OsH:CaH = 1.15—1.3. Cauda long, bent upwards, terminating close to posterior rim of otolith, its colliculum with well-marked ventral rim. Dorsal depression wide, large, well defined towards sulcus; dorsal field with some short radial furrows near the dorsal margin. Ventral field smooth, with distinct ventral furrow very close to ventral rim of otolith. Outer face with broad central umbo.

Remarks. These highly diagnostic otoliths differs from the only congener, N. madseni from the Northern Hemisphere, in being even more compressed (OL:OH = 0.7—0.75 vs. 0.8—0.85), the ostium being slightly wider than the cauda (vs. not being wider at all) and the absence of the peculiar deepening of the rear portion of the cauda as observed in N. madseni. The latter character could possibly support placing N. madseni in a genus of its own, once more species with this morphological pattern have become known to support a further taxonomic division.

The two species here attributed to Notoberyx show a bipolar temperate distribution with one species each in the early Eocene of Antarctica and Denmark, subject, however, to further finds of these highly diagnostic otoliths. The Danish Eocene otoliths of N. madseni were exclusively found in burrow concretions of stomatopods, apparently indicating that these fishes represented their preferred prey.