Parascombrops argyreus Gilbert & Cramer 1897
Creators: name: Schwarzhans, Werner W.
name: Prokofiev, Artem M.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Perciformes
Acropomatidae
Parascombrops
Parascombrops argyreus

description: Parascombrops argyreus (Gilbert & Cramer, 1897)
Figs. 2D, 7 B, 8E, 9B, 11D, 12E, 13B, 14A–E, 17, 27, 36, Tables 2–7
Melanostoma argyreum Gilbert & Cramer 1897: 416, pl. 39, fig. 3 (holotype: USNM 47732; off Hawaii, south of O'ahu, 21°12'N, 157°49'W, Albatross station 3472, 540– 545 m).
Synagrops argyreus: Schultz 1940: 419; Carpenter, 1999: 2437; Mundy 2005: 337; Randall 2007: 184; Prokofiev & Schwarzhans 2015: 84.
Synagrops adeni (non Kotthaus 1970): Rivaton & Bourret 1999: pl. 149, figs. 5–12 (based on otoliths).
Synagrops cf. pellucidus (non Alcock 1889): Prokofiev 2005: 717, figs. a – f.
Material examined (69 specimens). AMS I.24449-008, 3 specimens, 87–90 mm SL, northwestern shelf, Australia, 18°53’S, 116°10’E, 450 m; AMS I.42758-006, 120 mm SL, Norfolk Ridge, 32°35’S, 167°38’E, 348–362 m; BPBM 23839, 4 specimens, 97–119 mm SL, off Hawaii, 21°10’N, 157°25’W, 172 m; BPBM 23852, 2 specimens, 120–122 mm SL, off Hawaii, 21°11’N, 157°25’W, 168–194 m; BPBM 25884, 53 mm SL, off Hawaii, 21°06’N, 156°45’W; CAS 90647, 138 mm SL, off Tonga, 24°54’S, 168°21’W; CAS 90755, 4 specimens, 96–135 mm SL, off Tonga, 23°40’S, 168°00’W; IOM 1774, 2 specimens, 120–130 mm, 33°07´–33°12´S, 43°51´– 43°46´E, between 180 and 700 m; LACM 32242-33, 3 specimens, 90–118 mm SL, off Hawaii; LACM 32668-37, 3 specimens, 102–119 mm SL, off Hawaii; LACM 44728- 6, 110 mm SL, off Madagascar, 12°28’S, 48°09’E; LACM 56351-1, 3 specimens, 64–70 mm SL, off Hawaii; LACM uncatalogued, TC35-8, 13 specimens, 59–102 mm SL, off Hawaii; MNHN 1994-0014 (otolith only), off New Caledonia, 24°55’S, 168°22’E, 500–580 m; MNHN 1998-0993, 2 specimens, 99–100 mm SL, off Vanuatu, 16°33’S, 167°55’E, 602–620 m; MNHN 1998-1041, 7 specimens, 80–92 mm SL, off New Caledonia, 22°07’S, 167°10’E, 415–435 m; NMNZ P.027499, P.029229, P.029268, P.029282, P.029286, P.029346, P.029404, 12 specimens, 44–171 mm SL, Norfolk Ridge; ZMMGU 13269, 4 specimens, 122–183 mm SL, southwestern Coral Sea, 19°58’S, 151°32’E; ZMMGU 15338, 141 mm SL, off New Zealand, 35°41’S, 173°05’E; ZMUC P 44272, 122 mm SL, off Madagascar, 22°19’S, 43°06’E, 330– 335 m.
Diagnosis. Large slender-bodied species with slightly convex dorsal head profile. Anal fin II + 7. Pectoral fin with 13–16 rays, pectoral length 21.5–26% SL. Gill rakers 12–16, decreasing with size. Pseudobranchial filaments broad, (22) 26–38, increasing in number with growth. First anal-fin pterygiophore long, straight, slender, with sharp tip and not hollow. Ectopterygoid broad with 2–4 rows of denticles. Orbit diameter 9.3–12.0% SL. Posterior edge of maxillary plate distinctly concave with a lobate ventral expansion; 2–3 longitudinal ridges on preopercular lobe. Otolith moderately elongate (OL:OH = 1.65–1.9).
Description. Counts and measurements are summarized in Tables 2–7. Snout bluntly rounded; interorbital space slightly convex. Posterior edge of maxillary deeply concave with postero-dorsal and postero-ventral angles sharp and postero-ventral angle expanded backward and downward resulting in an obliquely truncated posterior expansion of the maxillary. Preopercular lobe with 2–3 longitudinal ridges; denticles of hind margin serration not extending onto crests on preopercular lobe; inner edge of preopercle with 2–6 small denticles not extending along ventral branch. Two anal-fin spines. First anal fin pterygiophore slender and almost straight, pointed, wedgeshaped, lacking a groove at anterior edge, reaching anterior margin of first haemal spine. First haemal spine narrow. Pelvic fin spine serrated along its outer edge; all other fin spines smooth. About 28–30 scales along lateral line.
Dentition. Premaxilla with a pair of canines near symphysis and additional, much smaller canine-like teeth inside the main canine tooth on each side (sometimes absent), followed posteriorly by a wide band of tiny conical teeth. Dentary with a pair of canines and a band of minute conical teeth near symphysis, followed posteriorly by a row of several small conical teeth and two to four enlarged, canine-like teeth on each side. Vomer with a triangular to V-shaped patch of granular teeth, followed posteriorly by 1–4 (usually 2 or 3) enlarged conical teeth on each side. Palatines with 2–3 rows of granular teeth, teeth of the innermost row sometimes somewhat enlarged. Ectopterygoid broad, with 2–4 rows of denticles. Tongue toothless.
Otolith morphology (n = 13). Otolith slender, elongate, thin, large, up to about 10 mm length. OL:OH = 1.65–1.9; OL:OT about 7–9. Dorsal rim with broad, obtuse medio-dorsal angle and distinct postdorsal angle close to posterior rim. Ventral rim deepest slightly in front of its middle, below collum of sulcus. Rostrum well developed, pointed; no or only weak excisura and antirostrum. Posterior rim symmetrical angular. Dorsal and posterior rims crenulated to various degrees; ventral rim mostly smooth. Inner face slightly convex with slightly supramedian positioned sulcus. Sulcus shallow, with narrow, long cauda and wide, shallow ostium. Ostium about twice as wide as cauda, with distinct colliculum. Cauda tapering, slightly deeper than ostium, slightly bent at its tip, terminating close to posterior tip of otolith. CaL:OsL = 1.05–1.25. Dorsal depression wide. Ventral furrow distinct, close to ventral rim of otolith anteriorly and bending away from it backwards towards tip of cauda. Outer face slightly concave, with fine radial furrows.
Size. Parascombrops argyreus is the largest species in the genus reaching a maximum known SL of 183 mm, i.e. about twice the size or more of the most other species (except P. mochizukii n. sp.). Small specimens are rare in collections, but we did find a few subadult specimens (53–70 mm SL) from Hawaii.
Discussion. Statistic ontogenetical correlation found that the number of gill rakers decreases with growth, while the number of pseudobranchial filaments increases. Parascombrops argyreus closely resembles P. philippinensis. Differences observed in the number of gill rakers and pseudobranchial filaments require comparison of specimens of about the same size (Fig. 27). The most reliable characters for distinguishing these two species are the oblique truncated posterior edge and the ventro-posterior expansion of the maxillary plate (Fig. 8E) (vs straight or very weakly concave, without expansion in P. philippinensis; Fig. 8A), the presence of 2–3 longitudinal ridges on the preopercular lobe (vs absence), the broad ectopterygoid with 2–4 rows of denticles (vs narrow with 1–2 rows of denticles) and the pointed tip of the first anal-fin pterygiophore without groove (vs broad tip and with groove). All these characters appear to be stable with ontogeny.
Geographic and bathymetric distribution. The distribution of P. argyreus is patchy, disjunctive and antitropical in the Indo-West-Pacific off Hawaii, in the Tasman Sea to northeastern New Zealand, and off southeast Africa, which was first recorded and discussed by Prokofiev & Schwarzhans (2015). Parascombrops argyreus does not seem to overlap geographically with P. philippinensis although it may be possible in the southwestern Pacific. Specimens examined have been caught in a depth range from 168 to 620 m. Large fossil Parascombrops otoliths were collected from the Late Pliocene of Okinawa and the south coast of Shikoku by F. Ohe, and several of those represent P. argyreus, indicating that the species was also present off Japan in geological history, unlike nowadays.
description: Published as part of Schwarzhans, Werner W. & Prokofiev, Artem M., 2017, Reappraisal of Synagrops Günther, 1887 with rehabilitation and revision of Parascombrops Alcock, 1889 including description of seven new species and two new genera (Perciformes: Acropomatidae), pp. 1-74 in Zootaxa 4260 (1) on pages 31-32, DOI: 10.5281/zenodo.571305