Lampadena exima, 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

Lampadena exima sp. nov.

Fig. 6N-Q

Lampadena 2012 Lampadena sp. - Brzobohatý & Stranik: fig. 7.11.

Lampadena speculigeroides 2015 Lampadena aff. speculigeroides Brzobohatý & Nolf, 1996 - Lin et al.: fig. 2.21.

Etymology.

From eximus (Latin) = excellent, exemplary, referring to the good preservation and clear allocation of the type specimen.

Holotype.

SMF PO 101.119 (Fig. 6N-Q ); Miya River at Numa, Tsuyama City, Okayama Prefecture, Takakura FM, level MS 36, late Burdigalian, diatom zone 3A-3B.

Diagnosis

(based on holotype and measurements taken from photograph of Lin et al. 2015). OL:OH = 1.25-1.30. Rostrum massive, its length 18-22% of OL. Ventral rim broadly rounded with 6 massive denticles; dorsal rim shallow, nearly straight; posterior rim rounded. Ostium slightly inclined, slightly wider than cauda. OCL:CCL = 1.7-1.8. Caudal pseudocolliculum longer than caudal colliculum, extending forward beyond collum.

Description

(based on holotype and measurements taken from photograph of Lin et al. 2015). Thin, delicate otoliths up to 3.5 mm length (holotype 3.1 mm); OH:OT = 5.2. Rostrum broad, massive, relatively long (18-22% of OL); excisura distinct, but not deep; antirostrum short and high on anterior rim. Ventral rim regularly curving, with 6 evenly spaced, massive and robust denticles; dorsal rim shallow, flat, with distinct angle at junction with regularly curved posterior rim. Posterior rim somewhat undulating but without concavity.

Otolith flat, almost not bent along axis, resulting in nearly flat inner and outer faces. Sulcus large, wide, distinctly supramedian, reaching close to posterior rim of otolith; OL:SuL = 1.1-1.2. Ostium longer and wider than cauda, slightly inclined upwards towards anterior, with ostial colliculum opening towards anterior otolith rim. Cauda short, slightly inclined upwards towards posterior. Caudal colliculum small, OCL:CCL = 1.7-1.8. Caudal pseudocolliculum longer than caudal colliculum and extending forward further than caudal colliculum. Ventral furrow distinct, positioned distant from ventral rim; dorsal depression weak, poorly defined and small. Outer face smooth with few faint, very wide radial depressions along ventral rim.

Discussion.

Lampadena exima more closely resembles the extant L. speculigera Goode & Bean, 1896 than the coeval L. speculigeroides Brzobohatý & Nolf, 1996 from the Paratethys. It differs from L. speculigera (Fig. 6R-U ) in the more gently curving outline, particularly the ventral and posterior rims (with the latter not being concave, as is characteristic of L. speculigera ); the upward inclined ostium (vs. straight); the OCL:CCL relation (1.7-1.8 vs. 2.1-2.3); and the long caudal pseudocolliculum extending forward of the caudal colliculum (vs. similar in length and not forward extended). Lampadena exima differs from L. speculigeroides in being more compressed (OL:OH = 1.25-1.3 vs. 1.35-1.5), the shallower dorsal rim, the smaller number and more robust nature of the denticles along the ventral rim of the otolith (6 vs. 8 or indistinct undulations), and the relatively wide ostium.

Otoliths of Lampadena are among the most diverse in the myctophid genera and are relatively easy to identify. The ease with which they can be identified makes them potentially valuable for biostratigraphic purposes, but unfortunately they are also usually very rare. In any case, it is interesting to note that specimens described by Lin et al. (2015) as L. aff. speculigeroides from the Tortonian of Italy and by Brzobohatý and Stranik ( 2012) as Lampadena sp. from the Langhian of the Czech Republic seem to represent the same species as our holotype of L. exima from the late Burdigalian of Japan. This finding indicates a relatively wide distribution range and a relatively long stratigraphic range.

Figures

Figure 6. A-D: Bolinichthys higashibesshoensis sp. nov., holotype, SMF PO 101.116, Fuchu machi, Toyama City, Higashibessho Formation, level H 20; E: Bolinichthys distofax Johnson, 1975, coll. Schwarzhans, Recent, Walter Herwig R / V, station 459 - 71; F-M: Ceratoscopelus brevis sp. nov., Tsuyama City, Takakura Formation; J-M: holotype, SMF PO 101.117, level MS 15; F-I: paratypes, SMF PO 101.118, levels MS 7, MS 52; N-Q: Lampadena exima sp. nov., holotype, SMF PO 101.119, Tsuyama City, Takakura Formation, level MS 36; R-U: Lampadena speculigera Goode & Bean, 1896, Recent; R: coll. Schwarzhans, Walter Herwig R / V, 38 ° S, 54 ° W; S: MCZ 169474; T-U: MCZ 96917; V-X: Taaningichthys sp., SMF PO 101.120, Tsuyama City, Takakura Formation, level MS 27.