Syncomistes carcharus, Shelley & Delaval & Le, 2017

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, Zootaxa 4367 (1), pp. 1-103 : 37-41

Syncomistes carcharus , new species

( Tables 13 , 14 , S 22 & S 23 ; Figures 12 & 13 )

Corresponds to the nominated taxa code ‘ Syncomistes sp. 5’ of Shelley (2016).

English vernacular name: Sharp-toothed Grunter.

Holotype (measured): NMV A.31452-001 (176 mm SL), Upper Prince Regent at confluence with Pitta Creek, Prince Regent River , 15° 50' 56.82'' S, 125° 39' 0.41'' E. The holotype was obtained with gill nets in a deep, clear pool over sandstone substrate by J. J. Shelley and M. C. Le Feuvre, July 22, 2013.

Paratypes (measured): Two specimens, 156–170 mm SL. Paratypes were collected in line with the holotype. WAM P.34541.001 (1), 156 mm SL, WAM P.34541.002 (1), 170 mm SL, Upper Prince Regent at confluence with Pitta Creek, Prince Regent River .

Diagnosis: Likely a large Syncomistes genus based on similarity with S. moranensis , although the largest specimen caught was 176 mm SL, snorkelling observations suggest it is commonly 150–200 mm. Syncomistes carcharus sp. nov. differs from all other species within the Syncomistes complex by a combination of the following characters: jaw of adults rounded with a tapered point when viewed from below (jaw shape of juveniles unknown) ( Fig. 5b ); mouth terminal; mouth slightly oblique; teeth conical ( Fig. 6i ); longest dorsal ray> 16.7 % SL; longest dorsal spine> 13.4 % SL; pectoral fins> 22.8 % SL; upper caudal lobe> 29.9 % SL; restricted to the Prince Regent River in the Kimberley region.

Description: See Table 13 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, rays 12 (12–13); anal fin spines III, rays 9 (8–9); caudal fin rays 11+8+7+11 (11–12+8+7+10–11, n = 3); pectoral fin rays 16; pelvic fin spines I, rays 5; vertebrae 11+14 = 25; lateral line scales 50 (48–51); scales above lateral line 10 (10–11); scales below lateral line 18 (18–19); pre-dorsal fin scales 15 (14–16); cheek scale rows 5 (4–5); caudal peduncle scales 31 (31–32); gill rakers on first arch 10+19 = 29 (9–10+19 = 28–29, n = 3); opercular spines 2; preopercular spines 20 (17–24).

See Table 14 for a summary of morphometric variation by type material and other material examined and Table S23 morphometric variation across all specimens combined. Large species of Syncomistes . Steeply angled dorsal profile of head, runs ~45° relative to horizontal plane. Dorsal profile straight from tip of snout to occiput and further to nape above preopercle edge, convex to dorsal fin origin, convex to posterior of last dorsal ray base, then horizontal to caudal fin base. Ventral profile convex from tip of snout to base of last dorsal fin ray, then horizontal to caudal fin base. Lateral line continuous from behind head to base of caudal fin, and approximately parallel to dorsal profile. Body depth at dorsal fin origin 33.7 (32.6–35.8) % SL; body depth at anal fin origin 28.8 (25.4– 30.8) % SL; caudal peduncle length 16.0 (15.9–16.1) % SL; caudal peduncle depth 11.7 (11.3–12.1) % SL; preanus length 69.2 (67.6–70.2) % SL. Head length 34 (32.9–34.6) % SL; head pointed; snout length 39.5 (38.6–41.1) % HL; upper-jaw length 30.6 (30.4–30.7) % HL; jaws equal throughout development; jaw width 28.6 (25.9–30.4) % HL. Lower jaw rounded, tapering to slight point when viewed from below (Morphotype 2; Fig. 5b ), shape in juveniles (<65 mm SL) unknown. Mouth terminal with shallow upward angle in lateral profile. Upper lip fold thick and continuous. Lower lip less thick and discontinuous, being fleshy posteriorly and reducing gradually to no lip fold anteriorly. Teeth on outer row of upper jaw 75 (72–77) number varying with size, 4.0 (4.0–5.2) when standardised with upper jaw length; teeth on outer row of lower jaw 66 (66–88) number varying with size, 4.4 (4.0– 5.2) when standardised with upper jaw length; 6 (5–7) tooth rows behind outer row on upper jaw, and 4 (4–6) on lower jaw; teeth conical, large relative to Syncomistes , symmetrical, ‘hour glass-shaped’, wide base, tapering to narrowest point at mid-point of tooth, widening again before tapering to a sharp point (similar to Fig. 6i ); teeth fitted closely together but not overlapping, and embedded in a sturdy ‘plate-like’ jaw. Toothless medial hump present on dorsal surface at symphysis of lower jaw, not very pronounced, with teeth present on opposite region of upper jaw. Teeth rows curve inwards towards throat at posterior end of mouth in lower jaw. Orbital diameter 20.6 (19.6–21.5) % HL; inter-orbital width 26.3 (25.6–26.7) % HL; inter-orbital smooth and not scaled; post-orbital length 42.5 (42.1–43.3) % HL. Lower opercular spine 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 around 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 2 at mid-point, progressing to 3–4 rows posteriorly; 6th dorsal spine longest, length 13.6 (13.4–14.0) % SL; progressively shorter towards first and last dorsal spine; last dorsal spine fully joined to first dorsal ray by membrane; 4th dorsal ray longest (4th–5th), 17.5 (16.7–18.1) % SL; dorsal margin of rayed portion rounded to tip of last ray; dorsal fin base length 55.7 (52.7–59.8) % SL; dorsal fin length 64.2 (61.5–68.2) % SL; pre-dorsal fin length 43.7 (41.8–45.0) % SL. Anal fin origin immediately posterior to vertical plane through base of last dorsal fin spine; terminates at base of last ray; anal fin sheath scales 4 at midpoint (2 in one), progressing from 1–2 rows anteriorly to 2–4 rows posteriorly; 3rd anal spine longest (2nd–3rd), length 12.9 (11.4–14.8) % SL; 1 st anal ray longest (1s t– 2nd), length 17 (16.1–17.9) % SL; rays progressively shorter to last ray; margin of rayed portion rounded; anal fin base length 14.7 (14.2–15.2) % SL; anal fin length 24.4 (23.3–25.1) % SL; pre-anal fin length 72.4 (71.1–74.1) % SL. Caudal fin slightly emarginate; upper caudal lobe length 30.6 (29.9–31.6) % SL; middle caudal ray length 20.1 (19.1–20.7) % SL. Pectoral fin length 23.1 (22.8–23.8) % SL; pre-pectoral fin length 32.7 (32.3–33.1) % SL. Pelvic spine length 11.5 (10.6–13.0) % SL; 1 st pelvic ray longest (1st– 2nd), length 22.5 (21.2–24.1) % SL; pelvic fin length 24.5 (23.2–25.4) % SL; pre-pelvic fin length 41.4 (40.4–42.7) % SL.

Colour when fresh: Body dull gold overall with greenish sheen on head. Body darker dorsally, becomes lighter on the ventral surface. Five to six dark, wavy lines sometimes present on sides of adults: first following base of dorsal sheath; second, running from the anterior of nape to below posterior of soft dorsal ray base; third follows the lateral line ending on dorsal edge of caudal peduncle; fourth, from supracleithrum to middle of caudal base; fifth, running between the largest opercular spine and ventral edge of caudal peduncle; sixth running from dorsal edge of pectoral fin base to anus. Presence of lines highly variable and fading quickly once fish are removed from water or after death. Juvenile colours unknown.

Anal fin with a basal blotch extending posteriorly on anterior rays. Caudal fin membranes dull gold. Dorsal fin membranes dull gold with dusky blotches. Pelvic fins dusky, pectoral fins clear. A silvery or gold stripe running below eye. Scales on body have a dark posterior band of pigmentation.

Colour when preserved: Juveniles and adults uniformly dark brown to black with hints faints hints of pale colouration on the ventral surface. Brown when viewed ventrally. Lateral line is may be distinctly pale or dark brown in colouration. All fins dark brown to black. Colouration of juveniles unknown.

Distribution: See Fig. 13 . Collected from one site at the junction of Pitta Creek and the Prince Regent River in the upper portion of the Prince Regent River catchment. The species may be limited to the upper catchment, although sampling in this river is too limited to say definitively.

Ecology: Prefers deep backwaters and slow flowing stream sections. Observed shoaling in the middle of the water column with Hephaestus jenkinsi Whitley, 1945 . Found in clear waters over rocky substrates, often where algae is abundant. Was observed in highest abundance while snorkelling in Pitta Creek, 1km upstream from the confluence with the Prince Regent River.

Comparison: The mouth, jaw, and tooth morphology of Syncomistes carcharus is similar to Syncomistes moranensis , and distinct from other Syncomistes species. Distinctive features include a terminal mouth, rounded jaw with a slightly pointed tip, a thick, fleshy lip fold on the upper and lower lip, robust teeth, tooth rows curving inwards towards the throat at the posterior end of the lower jaw, a less pronounced medial hump on the lower jaw, and the presence of teeth on the upper jaw opposite the medial hump. The tooth count relative to jaw length is significantly less than in other Syncomistes . Other distinctive features are a straight dorsal profile from the tip of the snout to the occiput and a greater pre-anus length 72.4 (71.1–74.1) % SL.

Shares a similar morphology with Syncomistes moranensis . The following characters distinguish Syncomistes carcharus from Syncomistes moranensis : on average a larger relative orbital diameter 20.6 (19.6–21.5) % HL versus 18.7 (16.1–21.5) % HL and smaller head length 34 (32.9–34.7) % SL versus 31.3 (30.2–32.7) % SL, as well as larger relative fin measurements: dorsal spine length 13.6 (13.4–14.0) % SL versus 11.3 (10.3–12.2) % SL, pectoral fin length 23.1 (22.8–23.8) % SL versus 20.7 (19.5–22.5) % SL and upper caudal lobe 30.6 (29.9–31.6) % SL versus 25.4 (23.3–26.6) % SL. These differences are visually apparent.

Etymology: The specific name carcharus is Latin for sharp teeth, and refers to the robust, pointed teeth of the species, relative to other Syncomistes .

Remarks: The different dentition and mouth morphology of Syncomistes moranensis and Syncomistes carcharus resembles fishes from the genus Hephaestus (Vari 1978) . However, it retains the key diagnostic features of Syncomistes including: an enlarged, laterally flared outer row of teeth; toothless medial hump on the lower jaw opposite a groove on the upper jaw; horizontal body stripes; and a highly convoluted gut with 6 loops. Meristic counts were also typical of Syncomistes . Occurs in sympatry with Syncomistes versicolor .

Figures

FIGURE 5.

FIGURE 6.

FIGURE 12.

FIGURE 13.

Tables

TABLE 13. Summary of meristic variation in Syncomistes carcharus sp. nov. (values for number of teeth of upper and lower jaw are per mm of jaw length).

	Holotype	Paratypes (N = 2)
Character		Mode	Mean	Min.	Max.	S.D.
DS	12	12.0	12.0	12.0	12.0	0.00
DR	13	12.0	12.0	12.0	12.0	0.00
AS	3	3.0	3.0	3.0	3.0	0.00
AR	8	8.5	8.5	8.0	9.0	0.71
PecR	16	16.0	16.0	16.0	16.0	0.00
PelS	1	1.0	1.0	1.0	1.0	0.00
PelR	5	5.0	5.0	5.0	5.0	0.00
UUCR	11	11.5	11.5	11	12	0.00
UBCR	8	8	8	8	8	0.00
LBCR	7	7	7	7	7	0.00
LUCR	10	11	10.5	10	11	0.71
LLSc	50	49.5	49.5	48.0	51.0	2.12
LD	10	10.5	10.5	10.0	11.0	0.71
LA	18	18.5	18.5	18.0	19.0	0.71
PDSc	16	15.0	15.0	14.0	16.0	1.41
DSSc	2	2.0	2.0	2.0	2.0	0.00
ASSc	2	4.0	4.0	4.0	4.0	0.00
CScR	4	5.0	5.0	5.0	5.0	0.00
CPSc	31	31.5	31.5	31.0	32.0	0.71
GRup	10	10.0	10.0	10.0	10.0	0.00
GRlow	19	19.0	19.0	19.0	19.0	0.00
GRtot	28	29.0	29.0	29.0	29.0	0.00
PcV	11	11	11	11	11	0.00
CV	14	14	14	14	14	0.00
TV	25	25	25	25	25	0.00
LDR	4	4.5	4.5	4.0	5.0	0.71
LDS	6	6.0	6.0	6.0	6.0	0.00
LAR	1	1.5	1.5	1.0	2.0	0.71
LAS	2	2.5	2.5	2.0	3.0	0.71
LPR	1	1.5	1.5	1.0	2.0	0.71
Tup	3.9	4.5	4.5	4.5	4.6	0.05
Tlow	4.0	4.6	4.6	4.0	5.2	0.84
TRup	6	6.5	6.5	6.0	7.0	0.71
TRlow	4	5.0	5.0	4.0	6.0	1.41
OS	2	2.0	2.0	2.0	2.0	0.00
PS	19	20.5	20.5	17.0	24.0	4.95

TABLE 14. Morphometric variation in Syncomistes carcharus sp. nov. (values are percentages of denominators inratios, except for SL).

	Holotype	Paratypes (N = 2)
Character		Mean			Min.	Max.	S.D.
SL (mm)	175.7	163.3			156.6	170.0
BDd / SL	32.6	34.2			32.7	35.8	2.16
BDa / SL	25.4	30.5			30.1	30.8	0.55
CPL / SL	15.9	16.0			16.0	16.0	0.00
CPD / SL	11.3	11.8			11.6	12.1	0.34
HL / SL	34.7	33.7			32.9	34.4	1.04
OD / HL	20.5	20.6			19.6	21.5	1.33
IoW / HL	25.6	26.7			26.6	26.7	0.08
PoL / HL	42.5	42.5			42.9	42.1	0.52
SnL / HL	41.1	38.7			38.6	38.8	0.14
JLup / HL	30.7	30.5			30.4	30.5	0.08
JW / HL	29.4	28.2			25.9	30.4	3.21
PDFL / SL	45.0	43.1			41.8	44.4	1.81
PPecL / SL	33.1	32.4			32.3	32.7	0.28
PPelL / SL	42.7	40.7			40.4	40.9	0.37
PAL / SL	67.6	70.0			69.7	70.2	0.40
PAfL / SL	71.1	73.0			71.9	74.1	1.52
DFBL / SL	59.8	53.7			52.7	54.7	1.42
DFL / SL	68.2	62.2			61.5	63.0	1.06
DFRL / SL	17.9	17.4			16.7	18.1	1.01
DFSL / SL	13.4	14.0			13.98	13.98	-
AFBL / SL	14.2	14.9			14.6	15.2	0.48
AFL / SL	23.3	24.9			24.7	25.1	0.24
AFSL / SL	12.6	13.1			11.4	14.8	2.36
AFRL / SL	16.1	17.4			16.9	17.9	0.71
PecL / SL	22.8	23.3			22.8	23.8	0.66
PelL / SL	25.4	24.1			23.2	24.9	1.18
PelSL / SL	10.9	11.8			10.6	13.0	1.72
PelRL / SL	22.2	22.6			21.2	24.1	2.05
CLLup / SL	30.2	30.8			29.9	31.6	1.18
CLLmid / SL	20.6	19.9			19.1	20.7	1.11