Owstonia tosaensis Kamohara

(Figures 79, 80)

Owstonia tosaensis Kamohara, 1934:301, fig. (original description; off Kochi Prefecture, Japan); Kamohara, 1935:134, fig. 3 (redescription and illustration); Shiino, 1972:116 (common name Yellowfin jawfish); Machida in Masuda et al., 1984:201, pl. 192-G (brief description, color photograph); Shin et al, 1993:436, pl. 137‒5 (brief description, color photograph); Nakabo, 2002:914 (diagnosis, in pictorial key); Endo et al., 2016: 37(comparative material 12 specimens, 112–192 mm SL, listed from Japan and Taiwan).

Material examined. 12 specimens, 99‒228 mm SL: Japan CAS 133930 (1, 133) and CAS 133934 (1, 149), Kochi Pref., Kochi, T. Kamohara; NSMT-P 54428 (1, 228), Shikoku, Kochi Pref., Kochi, Mimase Market. Taiwan ANSP 153169 (2, 100 C&S‒127), Tung-Kang, fish market, 22°23'N, 120°25'E, E. Chen, 1 Dec. 1983 ; ASIZP 66433 (1, 126), Nanfangao, Yilan, 24.5818°N, 121.8668°E, 2 Aug. 2005, Po-Feng Lee ; ASIZP 60461 (1, 173), Hengchun, Pingtung, 22°N, 120.74°E, 6 Mar. 1992, K.T. Shao . Philippines MNHN 1984‒653 (1, 111), MUSORSTOM 2, P. Fourmanoir, no other data . Western Australia CSIRO H6431‒02 (1, 148), CSIRO H6431‒03 (2, 155‒190) and USNM 427947 (1, 99), N. of Monte Bello Islands, 19°47'S, 115°18'E, 209 m, 17 May 2006 .

Diagnosis. A species of Owstonia with LL pattern type 2 that converges toward toward mid-line of nape but rarely unites to form a complete loop across nape; oblique body scale rows in mid-lateral series 44‒54; lower limb of preopercle with large, widely spaced spines (Fig. 8 K); dorsal- anal- and caudal-fins without wide white distal margins.

Description. A species of Owstonia with LL pattern type 2, consisting of a lateral line that originates from posttemporal sensory canal near anterodorsal margin of gill opening, extends upward and forms a "T" connection with horizontal section of lateral line (Fig. 6 B) that extends posteriorly just below dorsal-fin base to last ray and with the anterior section extending beyond dorsal fin and converging toward mid-line of nape but usually not united across nape (Fig. 6 F) but rarely forming a complete loop across nape (complete loop in only 1 of 10 specimens). Dorsal fin III, 23–24 (usually 23); anal fin I, 15–16; pectoral fin 19–21; gill rakers 15–19 + 28–33 = 45–51. Vertebrae: precaudal 12–13, caudal 17–18; total 29–30; anal-fin pterygiophores anterior to 1st haemal spine 4–5 (Fig. 7 C). Oblique body scale rows in mid-lateral series about 44–54; nape scaly and cheek scale rows 4–5. Lower limb margin of preopercle with 5–7 widely spaced, strong spines (Fig. 8 K). Papillae in slight depression behind tip of premaxillary ascending processes 4, arranged in 2 almost equally spaced pairs, with anterior pair the most obvious. Teeth in outer row of each premaxilla 20‒28; 0 (usually) or 1 inner tooth anteriorly. Teeth in lateral row of each dentary 10‒18, including 2−5 at anterior end that continue behind symphyseal teeth; symphyseal teeth 3‒6, short and peg-like, and with 1‒2 smaller inner teeth anteriorly. Pelvic fin probably sexually dimorphic, depressed fin extending to anal-fin soft rays 1‒5. Caudal fin lanceolate. Caudal fin 1.9‒2.2 times in SL; head 3.5‒4.7 times in SL; body depth at anal-fin origin 3.6‒4.5 times in SL.

Color pattern in alcohol: Adults with anterior part of dorsal fin uniformly pale; membrane connecting maxilla and premaxilla with prominent black stripe extending to near anterior end of premaxilla, and inner membrane covering posterior part of dentary also black. Kamohara (1934) described the life color of Owstonia tosaensis as "reddish, pale below. Anal yellowish, with two longitudinal red bands. Dorsal yellowish, with a longitudinal red band along the base. Upper half of caudal reddish, lower half yellowish." See also Fig. 79.

Proportions of 10 specimens 99–228 mm SL, as percentages of SL: predorsal length 20.7–27.1; preanal length 48.6–56.2; dorsal-fin base 60.0–71.4; anal-fin base 35.5–38.8; pelvic-fin length 28.9–41.6; caudal-fin length 45.8– 64.7; body depth at anal-fin origin 22.2–28.0; head length 21.5–28.1; upper jaw length 10.9–13.9; upper jaw depth 4.5–7.0; orbit diameter 8.4–12.2. As percentages of head length: upper jaw length 48.2–54.2; orbit diameter 34.4– 44.3.

Comparisons. Owstonia sarmiento, the only other species with LL pattern type 2, differs (characters of O. tosaensis in parentheses) in having in having fewer oblique body scale rows in mid-lateral series 27–30 (vs. 44–54) and cheek scale rows 2–3 (vs. 4–5), a different number of anal-fin rays II, 14 (vs. I, 15–16), and the anterior extension of lateral line forming a complete loop across nape (vs. typically not forming a complete loop). Excluding O. sarmiento, most species of Owstonia with III dorsal-fin spines also have fewer dorsal-fin soft rays, 19–22 (vs. 23–24).

Etymology. A combination of Tosa (former province of Japan, now Kochi Prefecture) and the Latin suffix ensis (meaning belonging to).

Distribution. (Fig. 25) Known from Japan, Taiwan, Philippines, and off Western Australia, in at least 209 m.

Remarks. Kamohara (1935) redescribed and illustrated Owstonia tosaensis based on a 350 mm specimen from Mimase, Japan. This specimen (BSKU 4230) was designated as a "neotype" by Kamohara (1961:8) but Eschmeyer et al (2016) consider the designation to be invalid.

Large adults of Owstonia tosaensis are distinctive in having dorsal fins with very elongate anterior soft rays, some exceeding the head length (Fig. 80).