Halaelurus sellus, William T. White, Peter R. Last & John D. Stevens, 2007

William T. White, Peter R. Last & John D. Stevens, 2007, Halaelurus maculosus n. sp. and H. sellus n. sp., two new species of catshark (Carcharhiniformes: Scyliorhinidae) from the Indo-West Pacific., Zootaxa 1639, pp. 1-21 : 11-18

Halaelurus sellus new species

Rusty Catshark

Figs 5-8; Tables 1 and 2.

Halaelurus boesemani : Springer and D’Aubrey, 1972; Last and Stevens, 1994: 203-204 (Plate 18, Figure 26.31); Compagno, Dando and Fowler, 2005 (in part): 232. (Plate 39).

Halaelurus sp. 1 : Sainsbury, Kailola and Leyland, 1984: 24-25.

Holotype. CSIRO H 994-1 , adult male 351 mm TL, north of Dampier Archipelago , Western Australia, 19°25′ S, 116°33′ E, 126 m, 29 Oct. 1986.

Paratypes. 8 specimens: CSIRO C 4809 , female 422 mm TL, North West Shelf ; CSIRO H 1082-1 , female 423 mm TL, north of Dampier Archipelago , Western Australia, 19°31′ S, 116°16′ E, 115 m, 4 Oct. 1987 ; CSIRO T 1505 , adult male 353 mm TL, north of Port Hedland , Western Australia, 18°41′ S, 118°40′ E, 136 m, 4 June 1983 ; CSIRO T 1508 , female 384 mm TL, CSIRO T 1512 , female 380 mm TL, northeast of Port Hedland , Western Australia, 19°36′ S, 118°56′ E, 128 m, 1983 ; CSIRO T 1512-02 , 6 egg cases removed from CSIRO T 1512 ; CSIRO T 1510 , adolescent male 317 mm TL, northwest of Dampier Archipelago , Western Australia, 19°59′ S, 116°08′ E, 62 m, 14 Oct. 1983 ; CSIRO T 1511 , adult male 348 mm TL, north of Port Hedland , Western Australia, 18°25′ S, 118°55′ E, 150 m, 4 Feb. 1983 ; CSIRO T 1514 , female 392 mm TL, north of Port Hedland , Western Australia, 18°47′ S, 118°30′ E, 132 m, 4 Aug. 1983.

Other material. 14 specimens: CSIRO CA 1292 , female 331 mm TL, north of Melville Island , Northern Territory, 10°14′ S, 130°03′ E, 124 m, 8 July 1980 ; CSIRO CA 1297 , adult male 342 mm TL, CSIRO CA 1298 , female 383 mm TL, northeast of Bedout Island , Western Australia, 120 m, 20 Sep. 1980 ; CSIRO H 993-1 , adolescent male 293 mm TL, north of Port Hedland , Western Australia, 18°47′ S, 118°37′ E, 128 m, 30 Oct. 1986 ; CSIRO T 1502 , adolescent male 311 mm TL, northwest of Port Hedland , Western Australia, 19°04′ S, 117°52′ E, 122 m, 11 Oct. 1983 ; CSIRO T 1503 , female 398 mm TL, northwest of Port Hedland , Western Australia, 19°00′ S, 117°34′ E, 154 m, 6 June 1983 ; CSIRO T 1504 , female 400 mm TL, northwest of Port Hedland , Western Australia, 19°01′ S, 117°56′ E, 106 m, 2 Oct. 1983 ; CSIRO T 1506 , female 346 mm TL, north of Port Hedland , Western Australia, 18°34′ S, 118°10′ E, 164 m, 10 Oct. 1983 ; CSIRO T 1507 , adult male 379 mm TL, northeast of Port Hedland , Western Australia, 19°36′ S, 118°56′ E, 128 m, 9 Oct. 1983 ; CSIRO T 1509 , female, 343 mm TL, northwest of Dampier Archipelago , Western Australia, 19°59′ S, 116°08′ E, 62 m, 14 Oct. 1983 ; NMV A 1728 , adult male southwest of Shark Bay , Western Australia, 25°28′ S, 112°27′ E ; NTM S 12974-004 , female 375 mm TL, Arafura Sea , Northern Territory, 09°26′ S, 134°45′ E, 30 Oct. 1990 ; NTM S 13317-008 , adult male 240 mm TL, Arafura Sea , Northern Territory, 09°18′ S, 132°49′ E, 7 Nov. 1990 ; NTM S 13445-002 , adult male 326 mm TL, Arafura Sea , Northern Territory, 09°18′ S, 133°26′ E, 7 Nov. 1990.

Diagnosis. Member of the genus Halaelurus with the following combination of characters: a relatively short, parabolic snout, preoral length 4.5-5.2% TL; predorsal length 39.1-41.8% TL, 3.4-3.8 times anal -caudal space; anal -caudal space 10.8-12.3% TL; mouth relatively short, length 2.1-2.9% TL; upper labial furrows very short (7.1-12.9 in eye length) but conspicuous; eyes of moderate size, eye length 2.9-3.3% TL; pectoral fin with a rather angular apex, anterior margin 9.6-10.7% TL, 1.5-1.9 times inner margin; anal fin of moderate size, length 9.3-10.8% TL, anterior margin 6.9-7.9% TL; adult clasper very elongate and narrow, outer length 8.1-8.8% TL, 6.3-6.5 times clasper base length, extending past the pelvic-fin free rear tip by 0.68-0.80 times pelvic-fin inner margin length, clasper tip sharply pointed; total vertebral centra 126-132, precaudal centra 79-83; dorsal surface with broad, dark brownish saddles bordered with variable, dark brown spots; spots absent from interspaces between saddles. Small adult size, attaining about 420 mm TL.

Description. Proportions as percentages of total length for the holotype and paratypes (7) are presented in Table 1.

Body tapering, anterior trunk wide and somewhat depressed; length of trunk from fifth gill openings to vent 1.13 (1.00-1.31) times head length; tail long and slender, almost circular in cross-section at second dorsal-fin insertion; no lateral keels; height 0.99 (0.99-1.30) in width at second dorsal-fin insertion, 2.83 (2.72- 3.45) in dorsal-caudal space; no postnatal ridge between anal fin base and lower caudal-fin origin; multiple weak longitudinal ridges on dorsal surface, extending from head to about second dorsal fin, usually indistinct, no other obvious lateral ridges. Head short, length 1.15 (1.01-1.18) to pectoral-pelvic space; wide and somewhat depressed, more so between eyes and ventrally; narrowly pointed, not upturned or knob-like in lateral view; in dorsoventral view anterior to gill openings narrowly parabolic; subocular ridge evident, somewhat angular. Preoral snout short, 0.83 (0.69-0.76) times mouth width; narrowly rounded with a somewhat acute apex in dorsoventral view; very shallow or no indentations adjacent to anterior of orbits.

Eyes small, spindle-shaped; dorsolateral on head, with lower edges well medial to lateral head margin in dorsal view; subocular ridge strong, relatively well defined, subequal in length to eye, almost a spiracle length from eye margin; no supraorbital crest; length 5.84 (5.25-6.08) in head length, 4.14 (4.18-5.35) times eye height. External eye openings with weak anterior and posterior notches. Nictitating lower eyelids of rudimentary type. Spiracles small, variable, subcircular to suboval, length 3.59 (2.65-3.70) in eye length, 0.15 (0.13- 0.21) eye length behind and below posterior eye notch. Gill openings straight to concave; slightly elevated on dorsolateral surface of head, upper margins slightly below lower edge of eye; anteriormost openings larger than those posterior (heights variable, first four subequal or with anteriormost taller in paratypes); fifth opening much shorter than anterior four; fourth opening over origin of pectoral fin; height of fifth 0.48 (0.39-0.57) of third; height of third 12.33 (10.49-14.39) in head, 0.47 (0.40-0.53) of eye length. Gill filaments not visible from outside. Nostrils separated from each other and not reaching mouth; very small incurrent apertures; width 1.01 (0.87-1.10) in internarial space, 1.24 (1.19-1.41) in eye length, 0.59 (0.48-0.71) in third gill-slit height. Anterior nasal flaps large, forming a right angle at apex (sometimes with a weak lobe in paratypes); posterior margin weakly corrugated to crenulate, innermost edge short of upper lip by about a tooth length; covering excurrent apertures; posterior nasal flaps present but inconspicuous, directed internally, visible when upper flap is lifted; skirt-shaped fold around excurrent aperture (nasal curtain and fold overlapping).

Mouth moderately large, very broadly arched; upper jaw horizontal at symphysis, forming a sharp angle near insertion of nasal curtain (less angular in some paratypes), posterior half of jaw almost straight, directed posterolaterally; central part of upper jaw overhanging lower jaw so that upper teeth are exposed in ventral view, edge of lower jaw similar in shape to edge of upper jaw; width 2.99 (2.55-2.95) in head length; length 2.64 (2.40-3.09) in width. Tongue large, flat, rounded anteriorly, filling most of floor of mouth (from paratype CSIRO T 1512). Labial furrows short but conspicuous; upper furrows very short, much shorter than lower furrows, 0.31 (0.25-0.55) of lower furrows. Teeth in 55/46 rows; 5/4 series functional; usually with long central cusp flanked by either one or two short cusplets on each side; lateral teeth with progressively smaller cusps; no toothless spaces at symphysis; not strongly differentiated in upper and lower jaws; medials, anterolaterals and posteriors in both jaws weakly defined; central upper anterolateral teeth largest. Tooth formula (from paratype CSIRO T 1512) is: 26-2-27 / 24-0-22.

Sexual heterodonty present; upper anterolateral teeth in the adult male holotype (CSIRO H 994-01) with slightly enlarged central cusp compared to those in the female paratype (CSIRO T 1512), teeth height 0.8-0.9 vs. 0.5-0.6 mm.

Lateral trunk denticles below first dorsal fin small (0.4-0.5 mm long), dense, strongly imbricate. Crowns mostly tricuspid, with long pungent central cusp flanked by short, sharp lateral cusps; pair of strong, converging medial ridges extending entire length of crown; pair of low but prominent ridges on lateral cusps; crown length about twice width, medial cusp about half total length of denticle.

First dorsal fin low, angled rearwards, not falcate; slightly convex anterior margin, apex broadly rounded; posterior margin sloping slightly posteroventrally from apex; free rear tip slightly rounded to angular, inner margin straight to slightly concave; insertion about opposite fin apex; origin over posterior half of pelvic-fin bases (further forward in female paratypes); insertion about opposite pelvic-fin free rear tips (well forward of free rear tips in female paratypes, free rear tip about over free rear tip of pelvic fin in female paratypes), well anterior to anal-fin origin. First dorsal-fin base 2.00 (1.71-2.20) in interdorsal space, 2.94 (2.55-3.04) in dorsal caudal-fin margin; height 1.89 (1.65-2.21) in base length; inner margin 1.86 (1.93-2.41) in height, 3.51 (3.42-4.53) in base length. Second dorsal fin low, not falcate, subequal in area and similar in shape to first dorsal fin; height 0.86 (0.72-0.98) of first dorsal-fin height, base length 1.04 (0.93-1.20) of first dorsal fin base length; anterior margin nearly straight or slightly convex, with broadly rounded apex; posterior margin sloping posteroventrally from apex; free rear tip mostly angular; inner margin straight; origin slightly forward to insertion of anal-fin (somewhat variable); insertion well posterior to anal-fin free rear tip, just posterior to second dorsal-fin apex. Second dorsal-fin base length 0.96 (0.88-1.22) in dorsal -caudal space; height 2.29 (2.04-2.62) base length; inner margin 1.88 (1.52-2.44) in height, 4.30 (3.94-5.43) in base length.

Anal fin low, subtriangular, subequal in area to second dorsal fin; height 0.73 (0.72-0.98) in second dorsal-fin height, base 0.96 (0.96-1.11) times second dorsal-fin base; base sometimes with a weak preanal ridge; anterior margin slightly convex or nearly straight, apex broadly rounded; posterior margin nearly straight or slightly concave, slanting strongly posterodorsally; free rear tip angular, inner margin nearly straight; origin about 1.69 (1.32-1.60) times base length behind pelvic-fin insertions; insertion well posterior to apex. Analfin base 0.68 (0.67-0.82) in anal -caudal space; height 3.00 (2.72-3.34) in base length; inner margin 1.50 (1.31-1.69) in height, 4.51 (4.24-4.86) in base length.

Pectoral fin small, somewhat lobate, apex and free rear tip broadly rounded (narrowly rounded in CSIRO C 4809); anterior margin weakly convex, 0.97 (0.88-1.01) times its length; base narrow; posterior margin weakly concave (nearly straight to convex in paratypes); inner margin slightly to moderately convex. Pelvic fin narrowly triangular; anterior margin nearly straight, 0.57 (0.54-0.72) of pectoral-fin anterior margins; apex broadly rounded; posterior margin slightly convex; free rear tip narrowly rounded, not attenuated; inner margins straight, not fused together over claspers of adult males.

Claspers of the adult male holotype elongate, very slender, nearly straight and tapering on lateral edge, not undulated; extending well behind pelvic-fin free rear tips, but terminating well anterior to anal-fin origin; tip sharply pointed, not fleshy. Most of ventral clasper with small clasper denticles with anteriorly directed cusps; dorsal and dorsomedial surface of glans largely naked. Apopyle and hypopyle connected by long clasper groove, with its dorsal margins fused over clasper canal. Lateral fold well developed, originating along length of dorsal midline and enveloping inner dorsal half of clasper; terminating distally near origin of cover rhipidion. Cover rhipidion very short, narrow, formed as distally tapering wedge with small mid-lateral tab; separated posteriorly from posterior end of external edge by a deep groove; partly posterior to exorhipidion, well ahead of the rear end of the rhipidion. Rhipidion present, large, extending along most of clasper glans; formed as a flat, blade with posterior tip beside apex of exorhipidion. Pseudosiphon absent. Pseudopera indistinct. Exorhipidion elongate, tapering distally, not flap-like, originating near posterolateral edge of cover rhipidion; a series of about 24 small clasper hooks along outer rim of hypopyle, in several rows at anterior end; apex sharply pointed.

Caudal fin narrow and asymmetrical; terminal lobe large; ventral lobe very low; dorsal margin moderately long, nearly straight with slight lateral undulations, 3.49 (3.61-3.91) in precaudal length; preventral margin nearly straight to slightly convex, 1.81 (1.75-2.04) in dorsal caudal-fin margin; tip of ventral caudal-fin lobe angular to broadly rounded; postventral margin irregular, mostly weakly concave, not well differentiated into upper and lower parts. Subterminal notch a narrow, shallow slot; margin straight, its length 1.33 (0.91-1.37) in terminal region. Terminal margin slightly convex, sometimes notched, dorsal tip broadly rounded, ventral tip somewhat angular; its length 3.62 (3.39-4.05) times dorsal caudal-fin margin.

Egg cases medium-sized, 45-51 mm in length from anterior to posterior margins (excluding horns); smooth-walls without longitudinal striations or ridges; relatively flat, its height 18.8 (16.4-20.7)% of case length; posterior width 41.2 (38.1-45.0)% of case length; lateral flanges absent. Anterior border nearly straight, broad; anterior horns small and nearly vestigial; tendrils long, wiry and tightly coiled. Posterior border narrow, concave; posterior horns moderately long, curved strongly towards each other and sometimes touching; tendrils very long, wiry, highly convoluted, tightly coiled. Egg cases, in alcohol, are uniformly golden yellow to brown in colour.

Vertebral centra 128 (126-132 in paratypes), monospondylous 32 (32-33), precaudal 83 (79-83) and caudal44 (40-43). Last few MP centra before MP-DP transition hardly enlarged, not forming ‘stutter zone’ of alternating long and short centra.

Colour. In preservative: Dorsal surface yellowish, with about 10 widely separated, rusty brown saddles; submargins of saddles demarcated by narrow, darker brown lines; lines transverse, diffuse, consisting of weakly connected spots (spots variably developed, sometimes barely visible on body), similar lines through middle of interspaces between saddles; saddles mostly subequal in breadth to their interspaces, extending to about lateral midline on tail and slightly more ventrally on trunk; no spots on yellowish background between lines on each interspace. Head with two prominent saddles, across orbito-spiracular region and between gills; anterior margin (origin) of first saddle through middle of interorbit, posterior margin (insertion) between spiracles(slightly posterior of spiracles in most paratypes), saddle extending antero-ventrally below eyes; second saddle recurved slightly posteriorly, origin through second gill slit, insertion just posterior to last gill slit (becoming more blotch-like in some paratypes); a few, small dark spots scattered over snout (~4 spots per 1 cm2). Supra-abdominal region with two similar saddles; anterior saddle originating near pectoral-fin insertion, terminating at level of its free rear tip; second saddle centered over pelvic-fin origin. Tail with 6 saddles; one saddle centered under each dorsal-fin base; slightly broader, central interdorsal saddle; narrower saddle centered on dorsal-caudal space; two broad saddles on caudal fin, anterior saddle above lower caudal lobe, narrower than posterior saddle at tail apex. Dorsal fins with evidence of rusty saddles anteriorly, paler posteriorly. Paired fins with dark bars over most of anterior half of dorsal surface, paler distally and at origin; ventral surface uniformly yellowish. Anal fin and lower lobe of caudal fin uniform yellowish.

Size. Attains a maximum size of about 420 mm TL; males reach sexual maturity at -340 mm TL; female of 380 mm TL (CSIRO T 1512) was pregnant, with three egg cases in each of the two uteri.

Distribution. Occurs off northwestern Australia from off Shark Bay (Western Australia) to the Arafura Sea (Northern Territory) (see Fig. 9).

Habitat. Demersal on the continental shelf at depths of 62-164 m.

Etymology. Derived from the Latin sella meaning saddle in allusion to the primary colouration of dark saddles on the head and body.

Comparisons. Halaelurus sellus is similar in appearance to H. buergeri , but is separable based on morphometrics and colour. Halaelurus sellus possesses very short (<1.8mm) labial furrows, similar to H. buergeri , but differs from this species in the consistency of their development (Fig. 6). The colour pattern of H. sellus differs from that of H. buergeri in having smaller and less defined (occasionally barely visible) dark spots bordering the saddle markings (Figs 5 and 10). Halaelurus sellus also differs from H. buergeri in morphometrics: first dorsal-fin height 3.8-4.3 vs. 4.9-5.1% TL; eye length 2.9-3.3 vs. 3.4-4.3% TL, 4.1-5.3 vs. 8.8-11.0 times eye height; anterior nasal flap length 1.2-1.7 vs. 0.6-0.9% TL; pectoral-fin inner margin length 5.6-6.5 vs. 4.5-5.2% TL; preorbital length 4.9-5.8 vs. 4.4-4.9% TL, 3.5-4.3 vs. 5.6-7.0 times anterior nasal flap length.

The two new species described here, H. maculosus and H. sellus , not only differ remarkably in colour pattern, but also in several morphometric and meristic characters: pectoral-fin anterior margin length 10.8-11.7 in H. maculosus vs. 9.6-10.7% TL in H. sellus ; anal-fin size (length 11.0-12.2 vs. 9.3-10.8%TL, base length 9.0-10.2 vs. 7.6-8.9% TL); adult clasper outer length 7.3-7.5 vs. 8.1-8.8% TL, 4.4-5.0 vs. 6.2-6.5 times clasper base length, extending past pelvic-fin free tip by 0.2-0.4 vs. 0.7-0.8 times pelvic-fin inner margin length; slightly differing numbers of precaudal vertebrae, 79-83 (mostly 81-83) vs. 81-89 (mostly 83-85). Halaelurus maculosus also differs in snout shape having a more broadly rounded snout tip than H. sellus (Figs 2 and 6).