Zenarchopterus takaoensis, Liao & Thiel & Chang, 2024

Liao, Yun-Chih, Thiel, Ralf & Chang, Chih-Wei, 2024, Zenarchopterus takaoensis (Perciformes: Zenarchoperidae), a new estuary garfish from southwestern Taiwan, Zootaxa 5550 (1), pp. 7-16 : 8-15

publication ID	https://doi.org/ 10.11646/zootaxa.5550.1.4
publication LSID	lsid:zoobank.org:pub:4E43E65F-E6D0-4F5E-B0CD-90EE89A7A445
DOI	https://doi.org/10.5281/zenodo.14502842
persistent identifier	https://treatment.plazi.org/id/039287C4-FFE4-FF81-FF60-FA467FBCFA9F
treatment provided by	Plazi
scientific name	Zenarchopterus takaoensis
status	sp. nov.

Treatment

Zenarchopterus takaoensis sp. nov.

( FIGURES 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 , 4A–B View FIGURE 4 , 5–6A–B View FIGURE 5 View FIGURE 6 ; Tables 1–2 View TABLE 1 View TABLE 2 )

[New English name: Takao’s garfish]

[Chinese name: ḢÑĀṞü]

Zenarchopterus sp. Collette & Su, 1986: 291. ZMH 6543 View Materials , female (59.1 mm SL), Takao (Kaohsiung City), Formosa (Taiwan), Hans Sauter, V–VII 1907, date uncertain.

Holotype. ASIZP0081779 View Materials , 76.6mm SL, male; 9Apr.2023, Dongshi , Chiayi County,southwest Taiwan, 23°27'01.5"N 120°08'27.2"E, pole and line fishing, YC Liao coll. GoogleMaps

Paratypes. 7 specimens: ZMH 6543 View Materials , female, 60.4 mm SL; date uncertain, 1907, Takao (Kaohsiung City), Formosa (Taiwan), Hans Sauter, V –VII 1907. ASIZP0081778 View Materials , 2 males (69.9–76.0 mm SL), 4 females (72.5–80.0 mm SL); the same as in Holotype.

Diagnosis. A species of genus Zenarchopterus , snout length slightly longer than width, prominent stripe on middle snout absent, prominent pigmentation or dark mark on snout. Anal-fin with 9 rays that is distinct from other congener species. Sixth anal-fin not elongated or thickened in adult males; dorsal body pigmented with three longitudinal dashed lines, with oval-like dashed pigmentation on dorsal lateral series scales; anterior lateral stripe on body in dashed line, ventral body with one longitudinal dashed line ( FIGURES 4–5 View FIGURE 4 View FIGURE 5 ). No sexual dimorphism except anal papilla in adult ( FIGURE 6 View FIGURE 6 ).

Description. Proportional measurements and counts are presented in TABLE 1 View TABLE 1 . Data of the holotype are presented first, and followed by those of the paratypes in parentheses, if different.

ub and b of caudal-fin rays in parentheses indicate "unbranched" and "branched", respectively.

Single dorsal-fin, dorsal-fin short, dorsal-fin base length 6.1 (4.6–6.1) in SL; its origin behind vertical line at middle between pelvic-fin and anal-fin, dorsal-fin spine absent, with 11 (11–12) soft rays, anterior and posterior rays slightly shorter than others. Anal-fin base 18.7 (15.9–19.6) in SL; its origin behind vertical line of 5 th dorsal-fin ray base, anal-fin spine absent, with one unbranched and 8 branched soft rays, 1 st ray shortest, 5–7 th rays longer than others, 6 th ray not thickened and elongated. Caudal-fin slightly rounded or truncated, lower lob slightly acute, caudal-fin length 6.0 (5.3–6.0) in SL, caudal-peduncle depth 2.9 (2.1–3.0) in caudal-fin length, caudal-fin with 17 (17–18) soft rays. Pectoral-fin short, pectoral-fin length 7.7 (7.1–7.7) in SL, with 9 branched soft rays. Pelvic-fin short, pelvic-fin length 14.5 (13.9–15.6) in SL, with one unbranched and 8 branched soft rays; its origin before dorsal-fin. Gill rakers on 1st arch with 2 upper and 9 (6–11) lower slender fences. Vertebrae: with 30 abdominal vertebrae + 11 caudal vertebrae, total 41; with 5 anal-fin pterygiophores anterior to 1 st haemal spine.

Head length 4.4 (4.1–4.4) in SL. Eye moderate, orbital diameter 4.2 (3.8–4.4) in HL, interorbital width 3.5 (3.3–4.0) in HL. Upper jaw triangular, Snout slightly longer than width, snout width 1.1 (1.0–1.1) in snout length; lower jaw length 2.4 (2.1–2.3) in SL. Teeth on jaws small, dense. Nasal papilla short and elongate, its length about 1/2 orbital diameter. Body slender and elongated; body depth 8.0 (7.4–8.0) in SL.

Scales cycloid, snout scales 7 (7–8) in 3 rows; predorsal scales 33 (33–34), arranged in two series: anterior series including 4 head scales and 9 scales directed posteriorly to middle of body, posterior series including 21 (20–21) scales directed posteriorly until dorsal-fin base; first scale covering two scale series. Second lateral scale 43 (42–45), 10 th scale covering two series. Third lateral scales starting above opercle, with 44 (40–45) scales, 8 th (7–9 th) scale covering two series. Fourth lateral scales running after pectoral-fin base, with 38 (39–40) scales. Lateral line scales trifurcated and located on lower body, 4 (3–4) scales direct upward to pectoral-fin base, 5 (3–5) scales direct anteriorly to thorax, with 41 (39–42) scales running posteriorly to caudal-fin base with additional small scales on caudal-fin membrane, 30 th (29–31 th) lateral scale located on vertical line of anal-fin start. Membrane scale on dorsal-fin, anal-fin absent. Anal papilla sexually dimorphic, anal papilla teardrop-shaped and expanded with elongated and slender projection in male, genital opening pointed at tip; anal papilla ellipse with prominent slender projection in female, genital opening at base of projection with two small flaps on two sides.

Color when fresh: Head lateral side upper half dark brown and lower part silver, lower jaw dark green and pigmented with yellow anterior end, proximal of lower jaw pigmented, maxillary pigmented, ventral lower jaw with longitudinal pigmented flap and stripe, thorax with longitudinal line and peripheral pigmentation; lower half orbital socket with dashed line, dorsal surface of orbital pigmented not extending posteriorly to vertical line of posterior eye; upper half of opercle pigmented; snout with prominent pigmentation or dark mark, extended posteriorly to middle interorbital, nasal papilla white without pigmentation, nasal socket pigmented. Body sides silver with prominent longitudinal gray stripe under dorsal-fin, starting from vertical line of first dorsal-fin ray running posteriorly to caudal-fin base, with pigmentation extending to base of caudal-fin rays; one dashed line running along lower margin of 3 rd lateral scale row, starting above pectoral-fin, running posteriorly and connecting to longitudinal stripe; belly white, area between lateral stripe and belly not pigmented. Dorsal body with three longitudinal dashed lines running posteriorly to anterior dorsal-fin, oval-like dash-like pigmentation on margin of 2 nd and on upper half of 3 rd lateral scales scattered posteriorly to dorsal-fin base until caudal-fin base; area above anal-fin base pigmented on two sides and running posteriorly to caudal-fin base; ventral body with longitudinal dash-like pigmentation between middle body to pelvic-fin. Color in preserved specimens: in ZMH 6543, body uniformly pale, lower jaw, maxillary, upper half opercle, dorsal surface of orbital, and area after interorbital prominently pigmented. Body sides with unclear longitudinal white stripe with dash-like pigmentation running posteriorly from upper pectoral-fin to caudal-fin base; dorsal body with three dashed lines running posteriorly under dorsal-fin base and to caudal-fin base; area above anal-fin base pigmented on two sides and running posteriorly to caudal-fin base; ventral body with longitudinal dash-like pigmentation between middle body and pelvic-fin. However, snout with prominent pigmentation or dark mark in all type specimens except ZMH 6543 because of absence of snout scale ( TABLE 1 View TABLE 1 ).

Distribution. Currently known only from the estuary from southwestern Taiwan. However, after an intensive collection around Taiwan, it was not seen at Kaohsiung City and Kaohsiung Harbor. The original habitats might had been destroyed and lost during the harbor construction in 1970s.

Etymology. The new species is named after the type locality “Takao”, based on the type specimen in the ZMH labeled “ Zenarchopterus sp. , Takao, Formosa, Hans Sauter, V–VII 1907 ”. “Takao” was the old name of Kaohsiung City, and “Formosa” was the old name of Taiwan during that time.

Remarks. The prominent differences between the new species and the other three congeners in this region are as follows: snout slightly longer than width, rather than wider than length as in Z. buffonis , Z. dispar , Z. dunckeri ; only 9 anal-fin rays rather than 12 in Z. buffonis , and 11–13 in others; prominent pigmentation or dark marks on snout, rather than dark stripe on middle snout in Z. buffonis , and without prominent pigmentation nor dark stripe on snout in others; dorsal body pigmented with three longitudinal dashed lines, rather than slender or bold longitudinal lines as in others; anterior longitudinal lateral stripe on body with dashed line, rather than prominent slender stripe; ventral body with one longitudinal dashed line, rather than absent in others. For more comparisons between these congeners, see TABLE 2 View TABLE 2 .

Zenarchopterus takaoensis sp. nov. is similar to Z. buffonis in that 6 th anal-fin ray and 4–5 th dorsal-fin rays are not elongated in the adult male. However, the former differs from Z. buffonis in the following ways: with prominent pigmentation or dark mark on snout, rather than prominent dark stripe on middle snout; anterior nasal papilla not pigmented, rather than pigmented in latter; anterior dorsal body with three longitudinal dashed lines running posteriorly to anterior dorsal-fin, oval-like dash-like pigmentation on margin of 2 nd and on upper half of 3 rd lateral series scales scattered posteriorly to dorsal-fin base until caudal-fin base, rather than dorsal longitudinal line slender on two sides and one bold line in middle, 2 nd and 3 rd lateral series scales pigmented entirely; dorsal-fin and anal-fin membrane not pigmented in adult, rather than pigmented in adult; 6 th anal-fin ray not thickened in adult male, rather than thickened in latter.

All the specimens of Zenarchopterus takaoensis sp. nov. were collected by pole and line fishing and were smaller than other congeners in Taiwan. The species might be difficult to collect by traditional trawling or net fishing because of its small size and lower economic value. However, it has often been overlooked or confused with other species, making it a cryptic species in Taiwan.