Syncomistes trigonicus , Vari 1978
Creators: name: Shelley, James J.
name: Delaval, Aurélien
name: Le, Matthew C.
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Perciformes
Terapontidae
Syncomistes
Syncomistes trigonicus

description: Syncomistes trigonicus Vari, 1978
(Tables 25, 26, S 22 & S 23; Figures 24 & 25)
Syncomistes trigonicus, Vari 1978: 316. Neotype: Paxton et al. 1989: 536 (in part); Allen & Leggett 1990: 539 (in part); Hutchins & Smith 1991: 23 (in part); Hutchins 2001: 31 (in part); Unmack 2001: 1063 (in part); Allen et al. 2002: 239 (in part); Moore et al. 2008: 24 (in part); Morgan et al. 2011a: 17 (in part); Davis et al. 2012: 1173; Allen et al. 2017: online (in part).
Corresponds to the nominated taxa code ‘ S. trigonicus I’ of Shelley (2016).
English vernacular name: Longnose Grunter.
Neotype (measured): WAM P.25028.006 [elevated from paratype series to replace the destroyed holotype (see remarks)], 98 mm SL, caught alongside the former holotype at Wyulda Creek, a tributary of the upper Roe River, about 2 kilometers above the junction with Roe River, Western Australia, (?) 15° 34' 4.89" S, 125° 49' 12.87" E. The neotype was obtained with rotenone by G. R. Allen, August 17, 1974.
Paratypes (measured): One specimen; WAM P.25027.002 (1), 129 mm SL, Roe River, upper, large pool off main river, (?) 15° 33' 54.78" S, 125° 49' 26.31" E, August 15, 1975, obtained with seine by G. R. Allen and A. Chapman. 15° 33' 54.78"
Paratypes (not measured): Six specimens, 47–112 mm SL; WAM P.25026.002 (2), 47–112 mm SL, upper Roe River, Western Australia, (?) 15° 34' 9.08" S, 125° 49' 34.1" E, August 14, 1975, obtained with dip net by G. R. Allen; AMNH 35637 (4), 50–100 mm SL, Kennedy Creek, a tributary to the Drysdale River, (?) 16° 11' 5.45" S, 126° 25' 18.58" E, April 25, 1969, obtained with rotenone by G. J. Nelson, D. E. Rosen and W. H. Butler.
Non-type Material (measured): 31 specimens, 33.6–120 mm SL; WAM P.34542.002 (5), 37.5–115 mm SL, Lower Drysdale road crossing, Drysdale River, 15° 48' 37.3'' S, 125° 57' 9.21'' E, August 1, 2013, obtained with electrofisher and gill nets from tannin stained water over sandy/rocky substrate by J. J. Shelley and M. C. Le Feuvre; WAM P.34543.001 (5), 33.6–109 mm SL, NTM S.18108-001 (1), 56.9 mm, Upper Drysdale, Drysdale River, 15° 48' 37.32'' S, 125° 57' 9.18'' E, August 1, 2013, obtained with electrofisher and gill nets from tannin stained water over sandstone substrate by J. J. Shelley and M. C. Le Feuvre; WAM P.34544.001 (3), 59.2–115 mm SL, NMV A.31445-001 (1), 103 mm SL, NMV A.31445-002 (1), 73.6 mm SL, NMV A.31447-001 (1), 77.6 mm SL, NMV A.31447-002 (1), 76.6 mm SL, NMV A.31447-003 (1), 115 mm SL, Upper King Edward road crossing, King Edward River, 15° 22' 6.45'' S, 126° 8' 52.67'' E, June 25, 2013, obtained with electrofisher and gill nets from clear water over sandstone substrate by J. J. Shelley and M. C. Le Feuvre; NMV A.31446-001 (1), 88.5 mm SL, NMV A.31446-001 (1), 78.7 mm SL, Loonjool Creek, Morgan River, Carson River, King Edward River, 14° 52' 13.57'' S, 126° 28' 54.62'' E, August 19, 2012, obtained with gill nets from a deep, clear pool over sandstone substrate by J. J. Shelley and M. C. Le Feuvre; NMV A.31448-001 (1), 114 mm SL, NMV A.31448-002 (1), 86.3 mm, NMV A.31448-003 (1), 121 mm, NMV A.31448-004 (1), 60.7 mm SL, NMV A.31448-005 (1), 106 mm SL, NMV A.31448-006 (1), 42.2 mm SL, NMV A.31448-007 (1), 71.6 mm SL, NMV A.31448-008 (1), 67.9 mm SL, NMV A.31448-009 (1), 59.3 mm SL, NMV A.31448-010 (1), 62.8 mm, Mid Moran, Moran River, 15° 22' 33.97'' S, 125° 44' 29'' E, July 22, 2013, obtained with gill nets and electrofishing in a deep slightly turbid pool over sandstone substrate by J. J. Shelley and M. C. Le Feuvre.
Diagnosis: A smaller species of Syncomistes (recorded up to 170 mm SL, commonly 80–130 mm SL). Syncomistes trigonicus differs from all other species within the Syncomistes complex by a combination of the following characters: lower jaw distinctly pointed when viewed from below, making a ‘V-shape’ in individuals> 65 mm (Fig. 5c), rounded in individuals <65 mm; mouth subterminal; teeth flattened, asymmetric, ‘triangleshaped’ with posterior margin angled outwards at 45° and anterior edge straight, widest point of tooth closest to mid-point, slight anteriorly pointed hook at tapered tip (Fig. 6c); jaw of adults (> 65 mm) as wide as it is long or slightly longer when viewed from below; dorsal profile straight from dorsal origin to shallow notch on upper jaw; body often with 5–6 straight dark stripes running horizontally along sides; overall colouration brown; usually 3–4 tooth rows on upper jaw and 3 rows on the lower jaw; longest dorsal fin spine usually> 11.0 % SL; longest anal fin spine usually> 13.0 % SL; 3rd or 4th dorsal ray usually longest; restricted to the Moran, Drysdale and King Edward rivers that drain the northern Kimberley Plateau.
Description: See Table 25 for a summary of meristic variation by type material and other material examined and Table S22 meristic variation across all specimens combined. Dorsal fin spines XII (XI–XIII), rays 11 (10–12); anal fin spines III, rays 8 (7–9); caudal fin rays 13+8+7+12 (9–13+8+7+9–12, n = 14); pectoral rays 15 (14–15); pelvic spines I, rays 5; vertebrae 11+14 = 25 (n = 14); lateral line scales 49 (45–54); scales above lateral line 10 (7– 12); scales below lateral line 17 (14–21); pre-dorsal scales 15 (12–19); cheek scale rows 3 (3–4); caudal peduncle scales 30 (27–34); gill rakers on first arch 10+18 = 28 (6–13+16–19 = 24–31); opercular spines 2; preopercular spines 8 (5–14).
See Table 26 for a summary of morphometric variation by type material and other material examined and Table S23 morphometric variation across all specimens combined. Smaller species of Syncomistes. Body slightly laterally compressed, dorsal profile more steeply angled than ventral profile, which is horizontal. Dorsal profile begins with concave notch behind tip of snout that rises steeply for short distance, then straight or slightly convex to inter-orbital, straight or slightly convex along nape to dorsal fin origin, convex until behind base of last dorsal ray, then horizontal to caudal fin base. Ventral profile straight or slightly convex on underside of head, straight or convex from back of head to anal fin origin, then horizontal to caudal fin base. Lateral line continuous from behind head to base of caudal fin, and approximately parallel with dorsal profile. Body depth at dorsal fin origin 27.4 (23.4–29.1) % SL; body depth at anal fin origin 25.4 (22.1–28.3) % SL; caudal peduncle length 18.8 (14.0–20.6) % SL; caudal peduncle depth 11 (10.0–11.8) % SL; pre-anus length 64.7 (57.0–68.5) % SL. Head length 29.9 (25.7– 31.4) % SL; head pointed; snout length 42.7 (32.0–48.1) % HL; upper-jaw length 31.6 (22.9–37.7) % HL; jaws equal throughout development; jaw width 31.7 (26.1–36.8) % SL; lower jaw distinctly V-shaped in adults and rounded in juveniles (<65 mm) when viewed from below, as long or longer than it is wide (Morphotype 3; Fig. 5c). Mouth subterminal with horizontal angle in lateral profile. Narrow, continuous upper lip fold, and very narrow lower lip fold that is discontinuous across the ventral midline. Upper lip more fleshy than lower lip. Lower lip fleshy posteriorly, reducing anteriorly until no fold present. Teeth on outer row of upper jaw 105 (27–136) number varying with size, 10.5 (6.7–16.7) / mm when standardise with upper jaw length; teeth on outer row of lower jaw 114 (20–151) number varying with size, also 10.5 (6.7–16.7) / mm when standardise with upper jaw length. Teeth laterally compressed, short and narrow relative to Syncomistes, asymmetric, ‘triangle-shaped’ with posterior margin angled outwards at 45° and anterior edge straight, widest point of tooth closest to mid-point, slight anteriorly pointed hook at tapered tip (Tooth Morphotype 2; Fig. 6c); teeth fitted close together and overlapping, laterally pointed in lower jaw, extending beyond outer edge of lip. Outer row of large teeth with 3 (2–4) inner rows of smaller teeth on both jaws, embedded in a jelly-like gum. Toothless medial, dorsally oriented hump present at symphysis of lower jaw, opposite toothless region of upper jaw. Orbital diameter 22.2 (17.7–27.0) % HL; interorbital width 27.3 (24.0–31.8) % HL; inter-orbital smooth and not scaled; post-orbital length 38.8 (32.5–42.9) % HL. Lower opercular spine is longer and more robust than upper opercular spine, sometimes extends beyond edge of opercular membrane; preopercular spines serrate, longest and most robust on apex of preopercle, reducing in size dorsally and anteriorly, anteriormost spine situated behind posterior edge of orbit. Intestinal pattern of adults highly convoluted; large amount of looping to left of stomach; juveniles with less convoluted pattern.
Dorsal fin origin posterior to vertical plane through pectoral fin origin, anterior to pelvic fin origin; terminates at base of last dorsal ray; dorsal fin sheath scales rows progress from 1–2 anteriorly to 2–4 posteriorly; 6th (5th–7th) dorsal spine longest, length 12.4 (10.3–14.6) % SL, progressively shorter towards first and last dorsal spines; last dorsal spine fully joined to first dorsal ray by membrane; 4th dorsal ray longest (1st–4th), length 13.4 (9.7–16.1) % SL, dorsal margin of rayed portion rounded to tip of last ray; dorsal fin base length 50.8 (47.3–55.4) % SL; dorsal fin length 56.7 (52.6–61.5) % SL; pre-dorsal fin length 38 (36.4–42.7) % HL. Anal fin origin immediately posterior to base of last dorsal fin spine; terminates at base of last ray; anal fin sheath scales 3 at mid-point (continuously between 2–4); 2nd (2nd–3rd) anal spine longest, length 14.7 (12.4–21.0) % SL; 1st (1st–2nd) anal ray longest, 15.5 (11.7–17.3) % SL; rays progressively shorter towards last ray; margin of rayed portion rounded; anal fin base length 14.2 (12.8–16.3) % SL; anal fin length 18.4 (18.4–25.0) % SL; pre-anal fin length 69.4 (60.9–73.5) % SL. Caudal fin slightly emarginate; upper caudal lobe length 22.4 (17.1–26.5) % SL; middle caudal ray length 17.2 (14.8–19.3) % SL. Pectoral fin length 18.5 (15.5–20.7) % SL; pre-pectoral fin length 29.3 (24.4–33.1) % SL. Pelvic spine length 9.4 (6.9–11.2) % SL; 2nd (1st–2nd) pelvic ray longest, length 18 (14.2–20.9) % SL, then progressively shorter; pelvic fin length 19 (16.2–21.3) % SL; pre-pelvic fin length 38.4 (32.5–43.2) % SL.
Colour when fresh: Body greenish-brown overall with a silvery sheen. Darker dorsally, fading to white along the ventral surface. A horizontal silvery white stripe running below eye to snout, and a dark spot is present on upper edge of gill cover. Scales on body have a dark posterior band of pigmentation.
Body colouration is sometimes interrupted by 5–6 dark, slightly wavy, almost straight, lines on the body of juveniles and adults, although stripes are more prominent in juveniles: first following base of dorsal sheath; second, running from the anterior of nape to below posterior of soft dorsal ray base; third running from posttemporal to dorsal edge of caudal peduncle; fourth, follows the lateral line, starting at anterior base of dorsal fin and ending at posterior base; fifth, from supracleithrum to middle of caudal base; sixth, running between the largest opercular spine and ventral edge of caudal peduncle. Lines generally fade in adults (SL 70–90 mm). Lines also fade quickly once fish are removed from the water or after death.
Dorsal fin membranes mostly dusky with clear edges. In some cases, membranes of spinous dorsal dusky for the basal three-quarters, black at the tips, and membranes of soft dorsal fin dusky, interrupted by a dark horizontal stripe running the length of the fin, close to the base. Anal fin with a dark basal blotch extending posteriorly on anterior rays. Caudal fin membranes brownish with clear edges. Pelvic and pectoral fins clear.
Colour when preserved: Adults uniformly dark brown to grey with hints of pale colouration becoming more dominant towards the ventral region. Mostly pale brown when viewed ventrally. Lateral line is distinctly pale in colouration. All fins uniformly dark brown. Black blotch sometimes present on anal fin. Juvenile colouration is same as adults, although some specimens retain horizontal stripes when preserved, which are as described in the ‘Colouration when fresh’ section. Overall colouration fades from darker to lighter the longer the specimen is preserved.
Distribution: See Fig. 25. Occurs throughout the Drysdale River, King Edward River and Moran River catchments in the northern Kimberley region, Western Australia.
Ecology: Prefers shallow fast flowing sections of creeks and rivers where they dart between the cover of larger boulders and rock ledges. Found in clear and slightly turbid waters, over rocky substrates, often where algae is abundant. Recorded in water temperatures up to 32 °C. Adults may form shoals around deep snags, sometimes mixed with S. rastellus. Juveniles predominantly reside in riffle habitat. Individuals sexually mature at 60–70 mm and breed during the wetseason. Eggs are medium size (~ 2 mm) and non-adhesive. Diet primarily consists of filamentous algae that is scraped off rocks with its modified teeth.
Comparison: Broadly similar morphological grouping to Syncomistes kimberleyensis and S. wunambal based their shallow body depth, the presence of a short notch behind the upper lip, a straight dorsal profile between the notch and the dorsal fin during all stages of development, and an extended V-shaped jaw in adults that is longer than it is wide (lower U-shaped in juveniles <65 mm).
Very similar in appearance to S. wunambal, but on average it has three teeth rows in the upper and lower jaw of adults, rather than two as in S. wunambal, and the mean relative lengths of the longest dorsal fin spine 12.4 (10.3– 14.6) % SL versus 10.7 (10.0–11.5) % SL and longest anal fin spine 14.7 (12.4–21.0) % SL versus 12.7 (11.2–13.7) % SL are greater than in S. wunambal. Furthermore, colouration is dark-brown across its range, whereas S. wunambal is distinctly golden in colour.
Etymology: The name trigonicus means triangle in Latin, in reference to the appearance of the lower jaw when viewed from below (Vari 1978).
Remarks: Syncomistes wunambal from the Mitchell River is a new species from within the range of S. trigonicus, described in this review. Syncomistes trigonicus is found in sympatry with S. bonapartensis, S. moranensis and S. rastellus.
The holotype of S. trigonicus was allowed to dry out while on loan and is no longer extant (Hutchins & Smith 1991; see under Remarks for S. butleri). Following correspondence with the original author of the description, Richard Vari (October 2013), and Glen Moore, Curator of Fishes, Western Australian Museum (November 2016) where the type material had been held, we determined that no photographs or x-rays remain for the holotype. In order to stabilised the name S. trigonicus we designated a neotype, selected from topotypic material in the paratype series.
description: Published as part of Shelley, James J., Delaval, Aurélien & Le, Matthew C., 2017, A revision of the grunter genus Syncomistes (Teleostei, Terapontidae, Syncomistes) with descriptions of seven new species from the Kimberley region, northwestern Australia, pp. 1-103 in Zootaxa 4367 (1) on pages 68-74, DOI: 10.11646/zootaxa.4367.1.1, http://zenodo.org/record/1125303