Owstonia similis, Smith-Vaniz, William F. & Johnson, David, 2016

Smith-Vaniz, William F. & Johnson, David, 2016, Hidden diversity in deep-water bandfishes: review of Owstonia with descriptions of twenty-one new species (Teleostei: Cepolidae: Owstoniinae), Zootaxa 4187 (1), pp. 1-103 : 84-86

Owstonia similis new species

( Figure 75 )

Holotype. MNHN 2014–1766, 89 mm SL, Madagascar, 14°29'25"S, 47°26'4"E, beam trawl in 347–448 m, R/ V Miriky sta. 3291, 14 Jul. 2009.

Diagnosis. A species of Owstonia with LL pattern type 1; dorsal fin III, 21; anal fin I, 14; oblique body scale rows in mid-lateral series 52‒56; lower limb margin of preopercle without spines; dorsal fin anteriorly with several of the interradial membranes mostly black.

Description. A species of Owstonia with LL pattern type 1, consisting of a simple lateral line that originates from posttemporal sensory canal near anterodorsal margin of gill opening, curves upward and backward then continues posteriorly just below dorsal-fin base to soft ray 16. Dorsal fin III, 21; anal fin I, 14; pectoral fin 22/21; gill rakers 10 + 22/23. Vertebrae: precaudal 11, caudal 17, total 28; anal-fin pterygiophores anterior to 1st haemal spine 2. Oblique body scale rows in mid-lateral series 52–56; nape scaly and cheek scale rows 6. Lower limb margin of preopercle without spines. Papillae in slight depression behind tip of premaxillary ascending processes difficult to discern with absolute certainty, but they appear to be in two closely spaced rows with 3 large, almosttouching papillae in anterior row and 2 smaller papillae on opposite ends of the posterior row. Teeth in outer row of each premaxilla 10/13; no inner teeth anteriorly. Teeth in lateral row of each dentary 10/8; symphyseal teeth 3, spike-like, and with 1 smaller inner tooth anteriorly. Pelvic fin short, depressed fin extending only to anus. Caudal fin lanceolate. Caudal fin 2.5 times in SL; head 2.9 times in SL; body depth at anal-fin origin 3.4 times in SL.

Color pattern in alcohol: Dorsal fin interradial membranes between spine 2 and soft ray 3 with heavy concentration of melanophores and anal fin with interradial membranes between posterior 5 soft rays also with heavy concentration of melanophores; membrane connecting maxilla and premaxilla with prominent black stripe extending about 3/4 length of premaxilla, and inner membrane covering posterior part of dentary pale. Life coloration unknown.

Proportions of 89 mm SL holotype as percentages of SL: predorsal length 31.4; preanal length 64.3; dorsal-fin base 60.0; anal-fin base 28.4; pelvic-fin length 23.5; caudal-fin length 39.6; body depth at anal-fin origin 29.4; head length 34.1; upper jaw length 19.1; upper jaw depth 9.7; orbit diameter 14.8. As percentages of head length: upper jaw length 56.0; orbit diameter 43.5. Head length 2.9 times in SL; body depth at anal-fin origin 3.4 times in SL.

Comparisons. Owstonia melanoptera , O. psilos and O. scottensis have many of the diagnostic characters of O. similis but differ (characters of O. similis in parentheses) as follows: O. melanoptera is most similar to O. similis but has lateral line ending below dorsal-fin soft rays 7 or 8 (vs. 16), more gill rakers 13‒14 + 25 (vs. 10 + 22‒23) and interradial membranes of posterior anal-fin soft rays unpigmented (vs. interradial membranes of posterior analfin soft rays with heavy concentration of melanophores); O. psilos has fewer oblique body scale rows in mid-lateral series, ca. 32 (vs. 52–56), more gill rakers 12–14 + 24–27 = 36–40 (vs. 10 + 22–23), membrane connecting maxilla and premaxilla typically pale with a few scattered melanophores or a pale incomplete stripe (vs. continuous black stripe present), and dorsal fin with interradial membranes between spine 3 and soft rays 4 or 5 mostly black (vs. black between spine 2 and soft ray 3); O. scottensis has fewer oblique body scale rows in mid-lateral series, 40‒45 (vs. 52‒56), more total gill rakers, 40‒43 (vs. 32‒33), dorsal fin pale anteriorly (vs. mostly black between spine 2 and soft ray 3); and inner membrane covering posterior part of dentary dark (vs. pale).

Etymology. From the Latin similis (like), in reference to similarity of the holotype to other species with a black blotch anteriorly in the dorsal fin, especially to O. melanoptera . An adjective.

Distribution. ( Fig. 27 ) Known only from the Madagascar type locality, where trawled in 347– 448 m.

Remarks. We cannot entirely eliminate the possibility that the total number of gill rakers (32–33) in the 88.6 SL holotype of O. similis compared to those (37–38) in the much larger, 116.2 SL, holotype of O. melanoptera is correlated with body size. However, in Owstonia species with relatively low numbers of total gill rakers, gill rakers usually increase only slightly by the time specimens have obtained a size of about 80 mm SL.

Figures

FIGURE 27. Distributions of selected species of Owstonia based on specimens examined.

FIGURE 75. Owstonia similis, holotype, MNHN 2014 – 1766, 89 mm SL, Madagascar. Photograph by Sandra J. Raredon.