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<p>A new deep-water softnose skate, <i>Bathyraja nansei</i> sp. nov., is described on the basis of three adult male specimens [625–645 mm in total length (TL); 408–421 mm in disc width (DW),] collected off the Nansei Islands, southern Japan, in the Okinawa Trough. The new species is morphologically similar to <i>Bathyraja isotrachys</i> (Günther 1877), <i>Bathyraja fedorovi</i> Dolganov 1983, and <i>Bathyraja tzinovskii</i> Dolganov 1983, all sharing the following combination of characters: similar dorsal and ventral ground color (usually darkish, although whitish in <i>B. tzinovskii</i>); tail thorns not extending to the nuchal region; scapular thorn absent; nuchal thorns obscure or absent; and narrow interorbital space (usually less than 20% of head length). However, <i>B. nansei</i> differs from the above congeners in several proportions and number of tooth rows, as follows: disc width (63.9–65.7% TL in <i>B. nansei</i> vs. 55.6–64.2% TL in the other three species), disc length (76.5–77.7% DW vs. 78.0–90.4), snout to maximum disc width (42.2–47.1% DW vs. 48.6–64.7), head length (26.8–27.9% DW vs. 28.2–37.3), interorbital width (5.0–5.5% DW vs. 5.6–8.4), interspiracular width (5.6–6.1% TL vs. 6.2–7.6), preoral snout length (16.0–18.0% DW vs. 18.3–29.3), distance between 1st gill slits (11.3–12.8% TL vs. 12.8–16.1), distance between 5th gill slits (7.3–7.8% TL vs. 8.6–12.2), precaudal body length (67.8–68.2% DW vs. 69.7–88.0), tooth rows in upper jaw (36 or 37 vs. 23–33), tooth rows in lower jaw (35–39 vs. 18–31). In addition, the new species can be readily distinguished from the others by a rounded disc posterior margin (vs. almost straight), a single interdorsal thorn (vs. usually absent), and uniformly brownish colored dorsal and ventral surfaces (disc ventrum with small white spots in <i>B. fedorovi</i>, dorsal and ventral ground color whitish in <i>B. tzinovskii</i>).</p>

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Bathyraja nansei, a new deep-water softnose skate (Rajiformes: Arhynchobatidae) from the Okinawa Trough, southern Japan

  • 期刊论文

  • 发表日期：

    2025年6月21日

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  • Ryo Misawa,
  • Masato Moteki,
  • Hiromitsu Endo

摘要

A new deep-water softnose skate, Bathyraja nansei sp. nov., is described on the basis of three adult male specimens [625–645 mm in total length (TL); 408–421 mm in disc width (DW),] collected off the Nansei Islands, southern Japan, in the Okinawa Trough. The new species is morphologically similar to Bathyraja isotrachys (Günther 1877), Bathyraja fedorovi Dolganov 1983, and Bathyraja tzinovskii Dolganov 1983, all sharing the following combination of characters: similar dorsal and ventral ground color (usually darkish, although whitish in B. tzinovskii); tail thorns not extending to the nuchal region; scapular thorn absent; nuchal thorns obscure or absent; and narrow interorbital space (usually less than 20% of head length). However, B. nansei differs from the above congeners in several proportions and number of tooth rows, as follows: disc width (63.9–65.7% TL in B. nansei vs. 55.6–64.2% TL in the other three species), disc length (76.5–77.7% DW vs. 78.0–90.4), snout to maximum disc width (42.2–47.1% DW vs. 48.6–64.7), head length (26.8–27.9% DW vs. 28.2–37.3), interorbital width (5.0–5.5% DW vs. 5.6–8.4), interspiracular width (5.6–6.1% TL vs. 6.2–7.6), preoral snout length (16.0–18.0% DW vs. 18.3–29.3), distance between 1st gill slits (11.3–12.8% TL vs. 12.8–16.1), distance between 5th gill slits (7.3–7.8% TL vs. 8.6–12.2), precaudal body length (67.8–68.2% DW vs. 69.7–88.0), tooth rows in upper jaw (36 or 37 vs. 23–33), tooth rows in lower jaw (35–39 vs. 18–31). In addition, the new species can be readily distinguished from the others by a rounded disc posterior margin (vs. almost straight), a single interdorsal thorn (vs. usually absent), and uniformly brownish colored dorsal and ventral surfaces (disc ventrum with small white spots in B. fedorovi, dorsal and ventral ground color whitish in B. tzinovskii).