Stalix yanoi, Wada & Suzuki & Kobayashi & Senou, 2025

Wada, Hidetoshi, Suzuki, Toshiyuki, Kobayashi, Hirozumi & Senou, Hiroshi, 2025, Two New Jawfishes, Stalix albonotata sp. nov. and S. yanoi sp. nov., from the Ryukyu Islands, Japan (Perciformes: Opistognathidae), Bulletin of the Kanagawa Prefectural Museum (Natural Science) 54, pp. 205-217 : 212-215

Stalix yanoi sp. nov.

(New English name: Yano’s Jawfish; new standard Japanese name: Sarashi-kaeruamadai)

( Figs. 1B, 5, 6B, 7B, 8B; Table 1)

Holotype. KPM-NI 5503 , 37.4 mm SL, adult, Uehara , Iriomote-jima Island , Yaeyama Islands, Ryukyu Islands, Japan, 16 m depth, 16 November 1998, hand net, collected by K. Yano.

Paratype. OMNH-P 52945 , 34.0 mm SL, adult, Uehara , Iriomote-jima Island , Yaeyama Islands, Ryukyu Islands, Japan, 18 m depth, 18 August 1999, hand net, collected by K. Yano.

Diagnosis. A species of Stalix with the following combination of characters: dorsal fin with 11 soft rays; pectoral fin with 21 or 22 soft rays; longitudinal scale rows 45–48; gill rakers on first gill arch 13 or 14 + 23 or 24 = 36 or 37; orbit diameter 10.7–11.5 % of SL; two sensory pores (I4 and I5) present on posterior half of interorbital space; first 2 mandibular pores (M1 and M2) well-spaced, fifth pore (M5) with single opening ( Fig. 1B); lateral line terminating below second to fourth dorsal fin soft ray base (dorsal fin element 13.5–14.5); distal incision of 3rd to 5th dorsal-fin spines moderate ( Fig. 6B; see Smith-Vaniz, 1989: fig. 1); anteroventral surface of upper lip smooth ( Fig. 7B); body uniformly whitish-green covered with slight brown pigmentation; lateral surface of head with several gray roughly irregular blotches; dorsal-fin membrane whitish-green, lacking any notable patterns or markings when fresh ( Fig. 4A, B); anterior gular region unpigmented (chin and area adjacent to anterior two mandibular pores with a few scatted melanophores) ( Fig. 8B).

Description. Data for holotype presented first, followed by paratype data in parentheses if different. Counts and measurements given in Table 1. Characters given in diagnosis not repeated.

Body elongate, laterally compressed. Upper profile of head rounded. Dorsal profile rising from snout tip to fifth dorsal-fin spine base, thereafter gradually lowering to end of dorsal-fin base. Ventral profile lowering from lower-jaw tip to pelvic-fin origin, subsequently parallel to body axis until middle of anal-fin base. Ventral contour of posterior half of anal-fin base slightly rising. Dorsal and ventral profiles of caudal peduncle parallel. Mouth large, slightly oblique, posterior margin of maxilla reaching vertical through first (second) preopercular pore (P1 or P 2 in Fig. 1B); posterior end of maxilla truncate with small, terminally positioned supramaxilla.Anterior nostril tubular, posterior nostril vertically ovate, simple. Both jaws with conical teeth, ca. 6 rows anteriorly, becoming uniserial posteriorly; premaxilla with outer row of stout, slightly hooked teeth anteriorly, becoming smaller posteriorly; 3 irregular rows of smaller teeth and a few slightly enlarged symphyseal teeth behind anterior outer row; dentary with an outer row of stout straight teeth anteriorly, becoming smaller posteriorly; 3 (2) irregular rows of smaller teeth anteriorly behind outer row. Vomer and palatines toothless.

Dorsal fin origin above posterior tip of gill membrane; dorsal profile of dorsal fin rising from origin to tip of ninth (eighth) soft ray; posteriomost part of soft-rayed portion rounded; all soft rays branched, except first soft ray simple, eighth longest, last two joined basally; first to sixth (fifth) dorsal-fin spines transversely forked distally, posterior forks successively shallower and more narrow; distal margin of anterior dorsal-fin membrane somewhat thickened and expanded dorsally to accommodate spine configuration, forming a pronounced lateral fold on each side of fin. Anal fin origin below last dorsal-fin spine base; ventral profile of anal fin lowering from origin to tip of seventh soft ray (eighth); posteriomost part of soft-rayed portion rounded; all soft rays branched, except first soft ray simple, eighth (ninth) longest, last two joined basally. Caudal fin rounded; 3 + 3 procurrent rays and 8 + 8 segmented rays (including 6 + 6 = 12 branched rays), 11 + 11 = 22 rays in total. Pectoral fin rounded, rays of upper portion slightly longer than those of lower portion. Pelvic fin semi-falcate; single spine and 5 soft rays, second soft ray longest, first and second segmented rays unbranched, thickened.

Body covered with cycloid scales except head, nape, pectoral-fin base, thorax, and areas between dorsal-fin base and lateral line, and immediately behind pelvic fins naked; each fin scaleless.

Cephalic sensory pores well-developed ( Fig. 1B). Infraorbital system with relatively large pores, opening usually single; anteriormost pore (I1) located just below anterior nostril; three sensory pores (I8, I9 and I10) on junction of infraorbital system located behind posterodorsal edge of orbit; posteriormost pore (I15) oval, located on just front of lateral line origin.

Vertebrae 10 + 16; single supraneural present, positioned just before neural spine of second precaudal vertebrae.

Coloration when fresh ( Fig. 4A, B). Most parts of head and body whitish-green with slight brown pigmentation; thorax, abdomen and pectoral-fin base white; fine brown pigmentation on dorsal surface of head, and tips of both jaws; lateral surface of head with several gray, roughly irregular blotches. Anal, pectoral and pelvic fins whitish-green. Caudal fin pale yellowish-green, except anterior half grayish-green.

Coloration in alcohol ( Fig. 4C). Head and body generally pale brown; whitish, grayish and greenish coloration of fresh specimens generally faded, although brownish coloration remains, especially anteriorly on head.

Comparisons. Stalix yanoi can be distinguished from all other congeners by the total number of gill rakers on the first gill arch (36 or 37 in S. yanoi vs. 40–42 in S. albonotata , 34 or fewer in other species) ( Table 1; Smith-Vaniz, 1989, 2022; Shinohara, 1999, 2006; Prokofiev, 2015; Allen & Erdmann, 2012, 2024). The former is most similar to Stalix eremia Smith-Vaniz, 1989 , currently known from a single specimen collected from Papua New Guinea ( Smith-Vaniz, 1989; Allen & Erdmann, 2024), the two species sharing several morphological characters as follows: dorsal fin with 11 spines and 11 soft rays, first 5–7 dorsal-fin spines transversely forked distally; anal fin with 2 spines and 11 soft rays; pectoral fin with 21 or 22 rays; lateral line terminating below second to fourth dorsal fin soft ray base (dorsal fin element 13–14.5); longitudinal scale rows 44–49; body moderately deep, 19.1–21.4 % of SL; anteroventral margin of upper lip smooth; first 2 mandibular pores well-spaced, fifth pore with single opening; body uniformly golden-brown or whitish-green with slight brown pigmentation; and anterior gular region unpigmented ( Figs. 1B, 4–5, 6–8B; Table 1; Smith-Vaniz, 1989; Allen & Erdmann, 2024). However, S. yanoi differs from S. eremia in having 35–37 gill rakers on the first gill arch (vs. 33 or 34 in S. eremia ), well-developed cephalic sensory pores, two sensory pores (I4 and I5) on posterior half of interorbital space (vs. relatively poor, single pore), and no notable pattern or markings on the dorsal fin when fresh (vs. a narrow, bright blue basal stripe) ( Figs. 1B, 4–5; Table 1; Smith-Vaniz, 1989; Allen & Erdmann, 2024).

Etymology. The specific name and English common name are named in honor of Mr. Korechika Yano (Dive Service YANO), who has kindly supported our ichthyofaunal research in the Ryukyu Islands. The standard Japanese name is a combination of “Sarashi”, which means white cloth in Japanese and refers to the whitish body of the species, and “Kaeruamadai”, the common Japanese name for members of the genus Stalix .

Distribution and habitat. Currently collected only from the Iriomote-jima Island, Ryukyu Islands, Japan, the present specimens having been found in an inner bay (silty sand bottom).

Remarks. Both of the new species conform to the generic characteristics of Stalix sensu Smith-Vaniz (1989) (see Introduction), except with regard to gill raker numbers on the first gill arch. Whereas the currently recognized valid species of Stalix have 22–34 total gill rakers on the first gill arch, S. albonotata and S. yanoi have 40–42 and 36–37 gill rakers, respectively ( Table 1; Smith-Vaniz, 1989, 2022; Shinohara, 1999, 2006; Prokofiev, 2015; Allen & Erdmann, 2012, 2024). In fact, within the family Opistognathidae , total gill raker numbers range widely, from 19–47 in Opistognathus and from 38–65 in Lonchopisthus ( Smith-Vaniz and Walsh, 2017; Smith-Vaniz, 2023), indicating that the number of gill rakers in S. albonotata and S. yanoi represents expansion of intra-generic variation within the genus.