Diaphus epipedus, 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

Diaphus epipedus sp. nov.

Fig. 8G-N

Etymology.

From epipedos (Greek) = flat, referring to the relatively shallow ventral rim, the main distinguishing character from D. metopoclampoides .

Holotype.

SMF PO 101.132 (Fig. 8G-I ), Miya River at Numa, Tsuyama City, Okayama Prefecture, Takakura FM, level MS 15, late Burdigalian, diatom zone 3A-3B.

Paratypes.

8 specimens; 6 specimens (SMF PO 101.133), same data as holotype, levels MS 15, MS 27, MS 90, j; 2 specimens (SMF PO 101.134), Osedani, Toyama City, Toyama Prefecture, Higashibessho FM, level H 21, late Burdigalian to early Langhian, diatom zone 3A-4A.

Diagnosis.

OL:OH = 1.2-1.25. Shape rounded triangular with relatively shallow ventral rim, inferior rostrum and posterior tip and broad mediodorsal bulge. Antirostrum and excisura minute. Ventral rim with 7-9 denticles. Postdorsal rim broadly concave. OCL:CCL = 1.5-1.7.

Description.

Otoliths with rounded triangular outline, relatively robust, up to 2.8 mm in length (holotype 2.5 mm); OH:OT = 3.4-3.7. Rostrum far inferior, relatively short and pointed, 10-12% of OL. Antirostrum and excisura minute. Dorsal rim with broad, rounded, pronounced mediodorsal bulge, anteriorly steeply inclined, posteriorly inclined with long depressed or concave section. Ventral rim rather shallow, regularly curved, with 7-9 medium strong denticles. Posterior rim curved, slightly projecting behind termination of cauda, its tip centrally or inframedian.

Inner face relatively flat, only slightly bent in horizontal direction. Sulcus terminating relatively far from posterior rim of otolith, straight, narrow. Ostial colliculum distinctly longer than caudal colliculum (OCL:CCL = 1.5-1.7) but only slightly wider (OCH:CCH = 1.2-1.4). Caudal pseudocolliculum distinct, about as long as caudal colliculum. Ventral furrow indistinct, sometimes not discernable, relatively close to ventral rim of otolith; dorsal depression small, ventrally marked by short crista superior. Outer face moderately convex throughout without distinct umbo, with distinct excisural furrow and few other weak and short radial furrows.

Discussion.

Diaphus epipedus is an easily recognizable otolith that shares many features, such as the shape of the dorsal rim and the robust appearance without distinct umbo on the outer face, with D. metopoclampoides (see below) but differs in the shallow ventral rim, which results in a higher ratio OL:OH of 1.2-1.25 (vs. 1.05-1.1); the relatively long ostium (OCL:CCL = 1.5-1.7 vs. 1.1-1.4); and the narrower sulcus.

Figures

Figure 8. A-F: Diaphus angulatus Ohe & Araki, 1973; A-C: SMF PO 101.130, Inabacho, Tsu City, Katada Formation, level ML 2305; D-E: SMF PO 101.131, Fuchu machi, Toyama City, Higashibessho Formation, level H 20; G-N: Diaphus epipedus sp. nov.; G-I: holotype, SMF PO 101.132, Tsuyama City, Takakura Formation, level MS 15; K-J: paratype, SMF PO 101.133, Tsuyama City, Takakura Formation, level MS 15; L-N: paratype, SMF PO 101.134, Yatsuo, Toyama City, Higashibessho Formation, level H 21; O-T: Diaphus metopoclampoides Steurbaut, 1983, SMF PO 101.135, Tsuyama City, Takakura Formation level MS 06, f; U-AB: Diaphus watatsumi sp. nov., Tsuyama City, Takakura Formation; U-X: holotype, SMF PO 101.136, level MS 52; Y-AB: paratypes, SMF PO 101.137, levels gh, j; AC-AE: Diaphus sp. 1, col. Tsuchiya, Ichishi Group.