Lampanyctus lenticularis, 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

Lampanyctus lenticularis sp. nov.

Fig. 7A-J

Etymology.

From Lampanyctus lenticularis (Latin) = lens-shaped, referring to the regular outline and small size of the otoliths.

Holoytpe.

SMF PO 101.121 (Fig. 7B-D ), Miya River at Numa, Tsuyama City, Okayama Prefecture, Takakura FM, level f9, late Burdigalian, diatom zone 3A-3B.

Paratypes.

8 specimens (SMF PO 101.122); same data as holotype, levels f9, g, h, j.

Additional material.

24 specimens; same data as holotype, levels MS 15, MS 36, MS 52, MS 70, d, f9, f40, g, gh, h, j .

Diagnosis.

Small, roundish otoliths; maximal size 1.7 mm; OL:OH = 1.05-1.15. All rims regularly curving without prominent angles. Rostrum short, slightly longer than antirostrum; excisura small. OCL:CCL = 1.3-1.6.

Description.

Small, relatively thin and nearly perfectly round otoliths with smooth rims without angles up to about 1.7 mm in length (holotype 1.55 mm). Rostrum short, rounded, only slightly longer than minute antirostrum, 7-15% of OL. Excisura small.

Inner face nearly flat and smooth, with slightly supramedian positioned, relatively narrow, shallow and straight sulcus. Ostium slightly longer and wider than cauda (OCL:CCL = 1.3-1.6). Ostial and caudal colliculi well marked but caudal pseudocolliculum often very narrow and sometimes indistinct. Ventral furrow closely following ventral rim of otolith; dorsal depression wide, but usually indistinct. Outer face slightly more convex than inner face, smooth.

Discussion.

The otoliths of most Lampanyctus species are small and unspectacular with smooth rims and hence can be easily confused with eroded juvenile otoliths of other myctophids, for instance those of Diaphus . It is therefore important to ensure that one is dealing with a sufficient number of well-preserved specimens before attempting a taxonomic classification of Lampanyctus otoliths. This is the case here. Even in light of the unspectacular nature of Lampanyctus otoliths, those of L. lenticularis stand out as particularly poor in traits. Lampanyctus lenticularis differs from the coeval L. profestus Schwarzhans, 2019 in the regularly rounded dorsal rim (vs. shallow) and the ostial colliculum being relatively little longer than the caudal colliculum (OCL:CCL = 1.3-1.6 vs. 2.0-2.5).

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.