Hoplobrotula, Gill, 1863

Schwarzhans, Werner, Mors, Thomas, Engelbrecht, Andrea, Reguero, Marcelo & Kriwet, Jurgen, 2017, Before the freeze: otoliths from the Eocene of Seymour Island, Antarctica, reveal dominance of gadiform fishes (Teleostei), Journal of Systematic Palaeontology 15 (2), pp. 147-170 : 158

Hoplobrotula ? antipoda sp. nov.

( Figs 5A—C , 6O, P )

Material. Holotype: NRM-PZ P.15984 ( Figs 5A, B , 6O, P ). Paratype: NRM-PZ P.15985 ( Fig. 5C ).

Occurrence. Telm 5 unit; ‘ Natica horizon’, Cucullea I member, La Meseta Formation, late Ypresian, early Eocene. Site IAA 1/90, Seymour Island, Antarctica.

Etymology. Named for its occurrence on the opposite side of the globe when compared to other Eocene species of the genus, known from Europe.

Diagnosis. OL:OH = 1.75—1.95. Dorsal rim with low, broad predorsal lobe. OCL: CCL = 2.5—2.75. Sulcus and particularly ostium very narrow.

Description. Relatively small, elongate and thin otoliths up to 4 mm in length (holotype 3.9 mm long). OH:OT = 2.6. Dorsal rim rather regularly and gently curved with broad, not much expanded predorsal lobe. Ventral rim regularly curved, deepest slightly in front of its middle. Anterior tip tapering, inferior, below level of ostium; posterior tip narrow, tapering, at level of cauda. All rims smooth.

Inner face moderately convex, smooth, with very narrow, shallow, slightly supramedian sulcus. Ostium very narrow, about 2.5 to 3 times the length of cauda, reaching close to anterior rim of otolith; cauda short, slightly deepened, with rounded tip, terminating at some distance from posterior rim of otolith. Ventral margin of sulcus distinctly indented at ostial—caudal joint. Dorsal depression indistinct, small; ventral furrow faint, fading towards posterior, close to ventral rim of otolith. Outer face slightly convex, less than inner face, smooth.

Remarks. Hoplobrotula ? antipoda is a typical representative of the many small ophidiid otoliths, which are so common in the Palaeogene. It clearly differs from the species described from the Eocene of Europe such as Hoplobrotula biscaica (Sulc, 1932) , H. greenwoodi Nolf, 1980 , H. robusta Nolf, 1980 , H. melrosensis (Dante & Frizzell, 1965) , H. waltoni ( Schubert, 1916) , as well as Ampheristus toliapicus Konig, 1825 and A. lerichei (Stinton & Nolf, 1970) (see Nolf 1980, 2013 for figures) by the very narrow and long ostium and the low predorsal lobe. Otoliths of Hoplobrotuloides bartonensis ( Schubert, 1916) are similarly elongate, but differ in the absence of a predorsal lobe, the flat ventral rim and the broadly expanded posterior tip (see Nolf 1980; Schwarzhans 1981). It is possible that H.? antipoda represents yet another extinct genus related to the extant genus Hoplobrotula and the fossil Ampheristus , but a thorough review of the group would be required first. The only other species from the Eocene of the Southern Hemisphere is Ampheristus sinuocaudatus Schwarzhans, 1980 from New Zealand, which, however, shows a cauda nearly of the length of the ostium and distinctly deepened.

Otolith data suggest that ophidiiforms were one of the dominant teleost groups in the warm shallow seas, for instance in Europe during the Palaeogene. Temperate seas, such as probably existed in the middle Paleocene of Denmark or the Eocene of New Zealand and South Australia, were comparatively sparse in ophidiiform otoliths and have also yielded far fewer species. This observation is again corroborated by the finds in the Eocene of Antarctica.

Figures

Figure 5. Drawings of Eocene otoliths from Seymour Island. A—C, Hoplobrotula? antipoda sp. nov.; A, B, holotype, NRM-PZ P.15984, mirror imaged; A, inner face; B, ventral view; C, paratype, NRM-PZ P.15985, inner face. D—G, Notoberyx cionei gen. nov., sp. nov.; D—F, holotype, NRM-PZ P.15987; D, anterior view; E, inner face; F, ventral view; G, paratype, NRM-PZ P.15988, inner face. H, Centroberyx sp., NRM-PZ P.15986, mirror imaged, inner face. I, J, Acanthopterygii indet., NRM-PZ P.15990, mirror imaged; I, inner face, J, ventral view. K, L, Percoidei indet., NRM-PZ P.15992, mirror imaged; K, inner face; L, ventral view. M, N, Haemulidae? indet., NRM-PZ P.15993, mirror imaged; M, inner face; N, ventral view. O, P, Sparidae? indet., NRM-PZ P.15994, mirror imaged; O, inner face; P, ventral view. Q, R, Cepola anderssoni sp. nov., holotype, NRM-PZ P.15996, mirror imaged; Q, inner face; R, ventral view.

Figure 6. Eocene otoliths from Seymour Island. A, Argentina antarctica sp. nov., holotype, NRM-PZ P.15964, mirror imaged, inner face. B, C, Diaphus? marambionis sp. nov., holotype, NRM-PZ P.15966; B, inner face; C, ventral view. D—F, Macruronus eastmani sp. nov., holotype, NRM-PZ P.15970, mirror imaged; D, inner face; E, ventral view; F, outer face. G—I, Palimphemus seymourensis sp. nov., holotype, NRM-PZ P.15973, mirror imaged; G, inner face; H, ventral view; I, outer face. J—L, Coelorinchus nordenskjoeldi sp. nov., holotype, NRM-PZ P.15978; J, inner face; K, ventral view; L, outer face. M, N, Coelorinchus balushkini sp. nov., holotype, NRM-PZ P.15976; M, inner face; N, ventral view. O, P, Hoplobrotula? antipoda sp. nov., holotype, NRM-PZ P.15984, mirror imaged; O, inner face; P, ventral view. Q, Notoberyx cionei gen. nov., sp. nov.; holotype, NRM-PZ P.15987, inner face. R, Cepola anderssoni sp. nov., holotype, NRM-PZ P.15996, mirror imaged, inner face.