Stenobrachius ohashii, Schwarzhans & Ohe & Tsuchiya & Ujihara, 2022

Schwarzhans, Werner, Ohe, Fumio, Tsuchiya, Yuki & Ujihara, Atsushi, 2022, Lanternfish otoliths (Myctophidae, Teleostei) from the Miocene of Japan, Zitteliana 96, pp. 103-134 : 103

Stenobrachius ohashii sp. nov.

Fig. 7W

Etymology.

Named in honor of Fumitaka Ohashi (Aichi Prefecture, Japan) who collected and donated a large part of the studied otoliths and has undertaken an original thesis on the fossil contents of many of the locations covered in this study.

Holotype.

SMF PO 101.126 (Fig. 7W-Y ), Kubusu River at Kashio, Toyama City, Toyama Prefecture, Kurosedani FM, level K 5, late Burdigalian, lower part of biozone N8, probably diatom zone 3A.

Paratypes.

6 specimens: 6 specimens: 1 specimen (SMF PO 101.128), near Tesseicho Hattori, Niimi City, Okayama Prefecture, Bihoku Group, late Burdigalian, diatom zone 3A-3B; 4 specimens (SMF PO 101.127), Miya River at Numa, Tsuyama City, Okayama Prefecture, Takakura FM, levels MS 15, MS 70, h, late Burdigalian, diatom zone 3A-3B; 1 specimen (SMF PO 101.129), Osedani, Toyama City, Toyama Prefecture, Higashibessho FM, level H 21, late Burdigalian to early Langhian, diatom zone 3A-4A.

Additional material.

227 specimens: 3 specimens, Near Tesseicho Hattori , Niimi City, Okayama Prefecture, Bihoku Group ; 217 specimens, Miya River at Oda and Numa , Tsuyama City, Okayama Prefecture, Takakura FM, levels MS 04.5, MS 05, MS 05.5, MS 06, MS 15, MS 22, MS 27, MS 36, MS 52, MS 70, MS 80, MS 90, c, d, f9, f10, f40, g, gh, h, j ; 3 specimens, Kubusu River at Kashio, Toyama City, Toyama Prefecture, Kurosedani FM, level K 5 ; 4 specimens, Osedani , Toyama City, Toyama Prefecture, Higashibessho FM, level H 21 .

Diagnosis.

OL:OH = 1.0-1.15. Rostrum long, massive, with more or less rounded tip, 17-25% of OL. Excisura and antirostrum distinct. Ostium slightly longer than cauda, OCL:CCL = 1.2-1.7. Caudal pseudocolliculum distinct, as long as caudal colliculum or longer. Inner face flat; outer face convex, smooth.

Description.

A small, roundish, and moderately thick otolith reaching about 2.1 mm in length (holotype); OH:OT = 3.5-4.0. Ventral rim deeply curving, deepest at or anterior of its middle. Dorsal rim relatively shallow, somewhat irregular with distinct postdorsal angle near junction with posterior rim. Anterior rim with long, massive rostrum with usually rounded tip, 17-25% of OL. Antirostrum distinct, about half the length of rostrum. Excisura deep, usually sharp. Posterior rim variably rounded. All rims smooth.

Inner face completely flat, with moderately long, relatively narrow, straight, shallow and nearly axial positioned sulcus. Ostial colliculum shallow, slightly longer and wider than caudal colliculum (OCL:CCL = 1.2-1.7). Ventral margin of ostial colliculum sometimes flexed anteriorly. Caudal pseudocolliculum distinct, as long as caudal colliculum or anteriorly projecting. Ventral furrow distinct, positioned moderately far from ventral rim of otolith. Dorsal depression wide, occupying almost entire dorsal field, but with indistinct margins. Outer face distinctly convex, smooth.

Discussion.

The genus Stenobrachius is today known from two species in the North Pacific: S. leucopsarus Eigenmann & Eigenmann, 1890 (Fig. 7AK-AM) and S. nannochir (Gilbert, 1890) (Fig. 7AN-AO). The fossil S. ohashii differs from the otoliths of the extant S. leucopsarus in the more regularly rounded ventral and posterior rims, the deeper excisura and sharper antirostrum, and the comparatively longer ostium (OCL:CCL = 1.2-1.7 vs. 1.05-1.3). It differs from the second extant species, S. nannochir , in the longer rostrum (vs. rostrum about as long as antirostrum) and the presence of a more or less strongly developed postdorsal angle. Stenobrachius otoliths are also quite similar to certain Lampanyctus otoliths such as those of the extant L. lepidolychnus or the fossil L. tsuyamaensis described above. A consistent difference seems to be that the caudal pseudocolliculum is not reduced in length or expression in Stenobrachius as it is in most Lampanyctus species.

Figures

Figure 7. A-J: Lampanyctus lenticularis sp. nov., Tsuyama City, Takakura Formation; B-D: holotype, SMF PO 101.121, level h; A, E-J: paratypes, SMF PO 101.122, levels f, g, h, j; K-M: Lampanyctus profestus Schwarzhans, 2019, SMF PO 101.123, Tsuyama City, Takakura Formation, level MS 36; N-V: Lampanyctus tsuyamaensis sp. nov., Tsuyama City, Takakura Formation; N-P: holotype, SMF PO 101.124, level MS 15; Q-V: paratypes, SMF PO 101.125, levels MS 15, MS 36, MS 90; W-AJ: Stenobrachius ohashii sp. nov.; W-Y: holotype, SMF PO 101.126, Yatsuo machi, Toyama City, Kurosedani Formation, level K 5; Z-AB, AF-AJ: paratypes, SMF PO 101.127, Tsuyama City, Takakura Formation, levels MS 15, MS 70; AC-AD: paratype, SMF PO 101.128, Niimi City, Bihoku Group; AE: paratype, SMF PO 101.129, Fuchu machi, Toyama City, Higashibessho Formation, level H 21; AK-AM: Stenobrachius leucopsarus (Eigenmann & Eigenmann, 1890), Recent, coll. Schwarzhans, leg. Fitch, off California; AN-AO: Stenobrachius nannochir (Gilbert, 1890), Recent, NSMT-P. 63309, 36 ° 28 ' N, 141 ° 10 ' E.