Lampanyctus tsuyamaensis, Schwarzhans & Ohe & Tsuchiya & Ujihara, 2022
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publication ID |
https://dx.doi.org/10.3897/zitteliana.96.83571 |
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publication LSID |
lsid:zoobank.org:pub:5B10FFF6-0407-4E09-B986-F931635E9BCC |
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persistent identifier |
https://treatment.plazi.org/id/8C5C8DA1-66AA-4B95-971B-4960EE692871 |
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taxon LSID |
lsid:zoobank.org:act:8C5C8DA1-66AA-4B95-971B-4960EE692871 |
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treatment provided by |
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scientific name |
Lampanyctus tsuyamaensis |
| status |
sp. nov. |
Lampanyctus tsuyamaensis sp. nov.
Fig. 7N-V View Figure 7
Etymology.
Named after Tsuyama City, the type-locality, Okayama Prefecture in western Honshu, Japan.
Holotype.
SMF PO 101.124 (Fig. 7N-P View Figure 7 ), Miya River at Numa, Tsuyama City, Okayama Prefecture, Takakura FM, level MS 15, late Burdigalian, diatom zone 3A-3B.
Paratypes.
6 specimens (SMF PO 101.125); same data as holotype, levels MS 15, MS 36, MS 90.
Additional material.
11 specimens; same data as holotype, levels MS 15, MS 27, MS 36, f40 .
Diagnosis.
OL:OH = 0.85-0.92. Ventral rim deeply curving, deepest anterior of its middle. Anterior rim slightly inclined, almost straight from broad, inferior rostrum to predorsal angle with minute excisura and antirostrum. Inner face flat, outer face convex, smooth. OCL:CCL = 1.2-1.5.
Description.
A small, very high-bodied, robust and thick otolith reaching about 1.5 mm in length (holotype); OH:OT = 3.4-3.7. Ventral rim deeply curving, deepest anterior of its middle, curving backwards into a steeply rounded posterior rim. Dorsal rim relatively shallow and nearly flat with distinct postdorsal angle at junction with posterior rim, somewhat irregular. Anterior rim steeply inclined at 75-85° (with sulcus oriented horizontal), nearly straight from distinct, rounded and inferior rostrum to minute antirostrum and predorsal angle at junction with anterior rim. Excisura minute. All rims smooth.
Inner face completely flat, with long, relatively wide, straight, shallow and slightly supramedian positioned sulcus. Ostial colliculum shallow, slightly longer and distinctly wider than caudal colliculum (OCL:CCL = 1.2-1.5; OCH:CCH = 1.25-1.5). Caudal pseudocolliculum as long as caudal colliculum. Ventral furrow distinct, positioned far from ventral rim of otolith. Dorsal depression wide, occupying almost entire dorsal field, but with indistinct margins. Outer face distinctly convex, smooth.
Discussion.
Lampanyctus tsuyamaensis resembles L. popoto Schwarzhans, 2019 from the early Miocene of New Zealand and L. latesulcatus Nolf & Steurbaut, 1983 from the late Miocene of Italy but can be readily distinguished from both species by the more high-bodied shape, which is also expressed in the OL:OH ratio of 0.85-0.92 (vs. 0.95-1.05 and> 1.0, respectively). Another distinctive character is the straight, inclined anterior rim and the asymmetrical ventral rim. The known otoliths of extant species of Lampanyctus are usually also less high-bodied, with the exceptions of L. lepidolychnus Becker, 1967 and L. macdonaldi (Goode & Bean, 1896). Otoliths of L. lepidolychnus (see Smale et al. 1995 for figures) differ in the less inclined anterior rim, a more distinct development of a broad excisura, and a more regularly rounded dorsal rim, while those of L. macdonaldi are among the very few myctophid otoliths with fused colliculi (note that the specimens of L. macdonaldi figured in Smale et al. 1995 are erroneously identified). In contrast, the otoliths of the genus Nannobrachium Günther, 1887, which is commonly synonymized with Lampanyctus , are even more compressed and high-bodied with a near rectangular outline and the sulcus almost reaching the posterior rim of the otolith.
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