Atelomycterus marnkalha, Ian P. Jacobsen & Mike B. Bennett, 2007

Ian P. Jacobsen & Mike B. Bennett, 2007, Description of a new species of catshark, Atelomycterus marnkalha n. sp. (Carcharhiniformes: Scyliorhinidae) from north-east Australia., Zootaxa 1520, pp. 19-36 : 24-35

Atelomycterus marnkalha new species

Eastern Banded Catshark

Figs 1-7; Tables 1 and 2

Atelomycterus sp. A (Torres Strait form , not A. sp. A = A. fasciatus , Compagno & Stevens,1993): Last & Stevens, 1994: 189 (in part) (Plate 22, Figure 26.17b)

Material studied. Holotype: CSIRO H 6144.01, mature male, 386 mm TL, 16 Jan. 2004, Torres Strait, Queensland, 10°36' S, 141°36' E, 17 m.

Paratypes: 11 specimens: CSIRO H 6148-01, adult male, 397 mm TL, 31 Jan. 2004, Torres Strait, Queensland, 10°20' S, 143°33' E, 37 m ; CSIRO H 6147-01, adult male, 418 mm TL, 27 Jan. 2004, Torres Strait, Queensland, 09°27' S, 143°48' E, 10.6 m ; CSIRO H 6145-01, female, 351 mm TL, 16 Jan. 2004, Torres Strait, Queensland, 10°33' S, 141°37' E, 17 m ; CSIRO H 6149-02, immature male, 322 mm TL, 4 Dec. 2003, Whitsunday Passage, Queensland, 20°17' S, 148°53' E, 44 m ; CSIRO H 6146-01, female, 293.5 mm TL, 22 Jan. 2004, Torres Strait, Queensland, 09°36' S, 142°34' E, 11-17 m ; QM I 34023, immature male, 277 mm TL, 27 Nov. 2002, Polmaise Reef, Queensland, 23°38' S, 151°53' E, 36 m ; QM I 34022, adult female, 466 mm TL, 27 Nov. 2002, SE of Masthead Island, Queensland, 23°41' S, 151°49' E, 34-36 m ; QM I 38078, female, 324 mm TL, 13 Nov. 2005, Queensland, 21°53' S, 150°21' E, 39 m ; CSIRO H 1118-01, immature male, 300 mm TL, 4 Nov. 1987, Arafura Sea, Queensland, 10°31' S, 140°48' E, 43 m ; AMS I 15557-003, adult male, 375 mm TL, 1964, North Mornington, Queensland, 16°38' S, 140°02' E, 32 m ; AMS I 21842- 001, female, 270 mm TL, 16 Nov. 1980, Arafura Sea, Queensland, 10°37' S, 133°47' E, 60 m .

Non-type material: 11 specimens: CSIRO H 6150-01, 2 immature females, 270 and 265 mm TL, 16 Jan. 2004, Torres Strait, 10°40' S, 141°33' E, 19 m ; CSIRO H 6146-02, immature male, 190 mm TL, 22 Jan. 2004, Torres Strait, Queensland, 09°36' S, 142°34' E, 11-17 m ; CSIRO H 6149-01, 2 immature females, 284.5 and 253.5 mm TL, 1 immature male, 300 mm TL, 4 Dec. 2003, Whitsunday Passage, Queensland, 20°17' S, 148°53' E, 44 m ; CSIRO H 6151-01, female, 330 mm TL, 9 Jan. 2004, Torres Strait, Queensland, 10°36'S 143°09'E, 26 m ; CSIRO H 6152-01, immature male, 310 mm TL, 7 Dec. 2003, Swain Reefs, Queensland, 21°31' S, 151°28' E, 57 m ; QM I 38079, adult female, 459 mm TL, 14 Nov. 2005, Broad Sound Channel, Queensland, 22°07' S, 150° 19' E, 25 m ; QM I 38080, immature male, 308 mm TL, 6 Oct. 2004, Lads Passage, Queensland, 13°51' S, 144°05' E, 38 m ; QM I 38081, female, 354 mm TL, 18 Feb. 2006, Wyborn Reef, Queensland, 10°57' S, 142°53' E, 25 m .

Diagnosis. A comparatively small Atelomycterus species (TL up to 490mm) with the following combination of characters: a relatively long snout, preoral length 4.7-5.1% TL; head length 19.3-19.9% TL, precaudal length 79.7-82.6% TL; short interdorsal space 12.2-13.9% TL; anal fin height 2.5-3.0% TL; anal fin length and anal fin base-length comparatively long 9.7-10.8 and 8.2-9.1% TL respectively. Adult claspers elongate, base broad, tapering moderately from base to tip. In adult males, clasper outer length 7.2-9.0% TL, clasper base width 20.2-22.5% of clasper outer length; clasper glans covering more than half length of entire clasper; enlarged tab on cover rhipidion. Rhipidion moderately large, concealed predominantly by large cover rhipidion and exorhipidion; psuedosiphon over half length of cover rhipidion; pseudopera large; clasper tip narrow and of moderate width, bluntly pointed. Total vertebral counts 147-153 (N=16); precaudal counts 95-99 (n=16). Colour pattern dominated by broad brownish saddles and transverse bands on tan/light brown background. Prominent dark brown to black spots and white spots on dorsal and lateral surfaces. Dark brown to black spots concentrated predominantly on saddle margins and as irregular transverse lines in inter-saddle spaces; decreasing in number post second dorsal fin. Significant numbers of small to medium sized white spots found along entire length of animal; white spots increasing in concentration towards posterior end of animal.

Description. Proportions as percentages of total length for the holotype and paratypes (11) are presented in Table 1.

Head short, length approximately equal 0.93 (0.96-1.13) to pectoral-pelvic space. Head narrow and moderately depressed; roughly trapezoidal in cross section at anterior most point of eyes. Outline of head in lateral view dorsally convex, with minor concavity in front of eyes; head with narrow parabolic outline anterior to gill openings in dorsoventral view. Preoral/snout length short 0.76 (0.67-0.84) times mouth width; broadly rounded in dorsoventral view; not or very slightly indented anterior to nostrils; snout bulbous and bluntlypointed in lateral view.

Eyes small and spindle shaped, eye length 6.75 (6.12-7.55) in head length and 3.11 (2.92-4.91) times eye height. Eyes dorsolateral on head, with lower edges well medial to horizontal head rim in dorsal view; subocular ridges strong but narrow; external eye openings with prominent anterior and posterior eye notches. Posterior notch not connected to spiracle. Nictitating lower eyelids of rudimentary type, with shallow, scaled subocular pouches and secondary lower eyelids free from upper eyelids.

Spiracles small, length 4.36 (3.28-7.54) in eye length, 0.28 (0.24-0.42) eye lengths behind and below posterior eye notch. First four gill openings substantially higher than fifth, height of fifth 0.84 (0.64-0.84) of first and 0.78 (0.58-0.81) of third; first gill slit height 11.53 (8.31-12.09) in head length and 0.58 (0.58-0.76) of eye length. Gill openings straight, undulated or slightly concave, gill filaments not visible from outside. Upper ends of gill openings about opposite lower edges of eyes, gill openings not elevated on dorsolateral surface of head. Gill-raker papillae absent from gill arches.

Nostrils with small incurrent apertures lacking posterolateral keels, broadly angular nasal flaps with narrowly rounded tips, mesonarial flaps very small and positioned well laterally on anterior nasal flaps, large excurrent apertures, no posterior nasal flap. Nostrils reaching mouth, with anterior nasal flaps partially covering upper symphysis. Anterior nasal flaps very large, meeting at midline of mouth, covering excurrent apertures. Nostril width 0.97 (0.72-0.96) in internarial space, 0.78 (0.56-0.87) in eye length, 1.32 (0.85-1.33) in first gill height and 1.23 (0.78-1.24) in third gill height.

Mouth broadly angular, small, short, mouth width 3.17 (2.73-3.40) in head length; mouth length 2.20 (2.23-2.56) in mouth width. Lower symphysis nearly reaching upper symphysis, teeth adjacent upper symphysis exposed in ventral view. Tongue moderate-sized, flat and rounded, filling most of floor of mouth. Maxillary valve narrow, not highly papillose. No large buccal papillae in mouth, palate and floor of mouth covered with buccopharyngeal denticles, except just in front of tongue. Upper labial furrows long, reaching upper symphysis or stopping just prior to upper symphysis. Lower furrows slightly longer than upper furrows; 1.09 (1.04-1.34) times upper furrows, labial cartilages large.

Teeth in 67-78/64-70 rows; 3-5/4-5 series functional, with more series functional in adults than in young and in posterior tooth rows than anterolaterals. Lateroposterior teeth not arranged in diagonal files, no toothless spaces at symphysis. Teeth not strongly differentiated in upper and lower jaws; tooth row groups along upper and lower jaws including medials (M), anterolaterals (AL) and posteriors (P) weakly defined. Tooth formula(N=4) is:

Left P13-20 AL18-20 M3 AL17-20 P14-20 right

P14-19 AL14-18 M1 AL14-20 P14-20

or

31-38 3 33-38

31-34 1 31-35

Tooth formation tricuspid (Fig. 4); central cusp strong, well-developed and substantially longer than lateral cusps. Cusps strongly erect to semi-oblique. Upper anterolateral teeth smaller than those adjacent; cusplets of upper anterolateral teeth with well-developed transverse ridges; longer than lower. Medials smaller and weak differentiated in comparison with anterolaterals. Posterior teeth forming several rows in both jaws; distinctly smaller than anterolateral and median teeth; with low weak cusps. Sexual heterodonty absent; tooth morphology not particularly enlarged or modified in adult males.

Lateral trunk denticles below first dorsal fin moderately elongate, with weak to moderately tricuspid teardrop-shaped crowns approximately 1.5 times as long as wide (Fig. 5). Denticle crown with pair of strong medial ridges extending along almost entire length of crown and onto a strong, medial cusp; lateral cusps short and obtuse when compared to medial cusp; numerous shallow depressions present proximally, covering approximately one third to half of denticle crown, occasionally extending onto lateral cusps; shallow depressions absent between medial ridges and on medial cusp. Denticle crowns closely spaced and well-imbricated.

Pectoral fins broad and triangular in shape with rounded apices, not falcate, with broadly convex anterior margins 1.08 (1.00-1.16) times its length; weakly convex to broadly rounded posterior margins, free rear tips inner margins and narrow bases. Total area of pectoral fins less than twice the area of first dorsal fin. Origins of pectoral fins under interspace between third and forth gill openings. Apex of pectoral fin slightly anterior to its free tip when fin is elevated and appressed to body.

Pelvic fins broadly triangular; pelvic fin anterior margins nearly straight or very weakly convex; 0.74 (0.63-0.78) pectoral fin anterior margins; rounded apically, with posterior margins convex or nearly straight, free rear tips narrowly rounded and not attenuated, inner margins straight or slightly convex, not fused over claspers of adult males. Pelvic area nearly 2-3 times anal fin area.

Claspers relatively long, slightly convex and tapering on lateral edge, with a slightly undulating clasper glan (Fig. 6). Claspers of adult males extending well behind pelvic fin free rear tips, distance approximately 1.7 times pelvic fin inner margin, posterior most point of distal apex falling in front of anal fin origin by 0.77- 0.93 times anal fin base. Clasper glans moderately long, length approximately half to two thirds of outer clasper margin; distal apex blunt and without specialised clasper hooks. Dorsolateral and ventral surfaces covered with small clasper denticles, dorsomedial and posteromedial surfaces of glans (including rhipidion) and lateral strip adjacent to clasper groove naked; clasper denticles much longer than broad with anteriorly directed cusps; narrow band of low semi-upright tricuspidate denticles near tip of glans. Exorhipidion strongly differentiated, originating opposite the last third of cover rhipidion. Pseudopera present, situated below anterior end of exorhipidion and about opposite posterior end of cover rhipidion. Rhipidion present and greatly enlarged, forming a flat convex-edged blade-like structure extending over most of clasper glan length; posterior end below apex of exorhipidion. Cover rhipidion very large, formed as a distally tapering wedge with large, lobate anterior tab, extending from apopyle to apex of exorhipidion; angle between free tab and base of cover rhipidion acute; posterior end proximal to exorhipidion and rear end of the rhipidion. Anterior margin of cover rhipidion slightly convex, without obvious notch (Fig. 6). Pseudosiphon long, narrow and slitlike, extending opposite most of base of cover rhipidion; posterior end terminating anterior to exorhipidion apex. Apopyle and hypopyle connected by long clasper groove, dorsal margins fused over clasper canal.

Clasper skeleton with all elements present (Fig. 7). Axial cartilage connected proximally to pelvic basipterygium by single, short intermediate segment (B1) and moderately long, posteriorly tapering, dorsal beta cartilage (P). Beta cartilage with rounded anterior and posterior margins and possessing a small, central, proximal protuberance. Clasper shaft formed from axial cartilage and tightly rolled dorsal and ventral marginal cartilages. Marginal cartilages anteriorly slender and tapering; expanding posteriorly along axial cartilage. Dorsal terminal (TD) of clasper glan large, narrow and curved; ventral terminal (TV) distally expanded and spear-shaped; separated along their proximomesial by narrow, cylindrical end-style (terminal extension of axial cartilage; short free posterior ends of terminal cartilages separated by narrow gap. Accessory dorsal marginal cartilage (RD2) long, wedge shaped, tapering distally, with separate, short distal segment (RD3). Dorsal terminal 2 cartilage (TD2) large, elongate, tapering distally, extending inside rhipidion, along almost entire clasper glans from dorsal margin to end-style tip. Cartilages of exorhipidion include an elongate, anterior tapered ventral terminal 2 (TV2) cartilage and a ventral terminal 3 (TV3) cartilage tapering posteriorly; TV2 cartilage articulating with anterolateral end of TV3 cartilage and extending anteriorly to partially cover distal end of ventral margin. Short, accessory terminal cartilage (T3) present under anterior half of TD2 cartilage, partially covered by terminal extension of ventral margin; T3 well anterior to TV3-TV articulation.

First dorsal fin high, apically narrow and not falcate, with nearly straight or weakly convex anterior margin, narrowly rounded apex, weakly concave posterior margin, angular free rear tip, inner margin straight. First dorsal-fin origin at midpoint approximate of pelvic-fin bases; midpoint of base slightly anterior or opposite pelvic-fin free rear tips, insertion closer to pelvic-fin insertions than anal-fin origin; free rear tip 1.67 (1.68-2.48) times length of inner margin anterior to anal-fin origin. Fin insertion anterior to fin apex; first dorsal-fin base 1.58 (1.32-1.62) in interdorsal space, 2.09 (1.88-2.35) in dorsal caudal-fin margin, first dorsal-fin height 1.58 (1.31-1.86) in its base, first dorsal-fin inner margin 1.66 (1.64-2.06) in first dorsal-fin height, 2.63 (2.70-3.40) in its base.

Second dorsal fin similar to first dorsal fin. Second dorsal fin high, apically narrow, not falcate, equal to first dorsal fin area or marginally subequal; second dorsal-fin height 0.96 (0.91-1.21) of first dorsal-fin height, base 0.95 (0.85-1.08) of first dorsal-fin base. Second dorsal fin with slightly convex anterior margin, narrowly rounded apex, nearly straight posterior margin, bluntly pointed free rear tip, and weakly concave or straight inner margin. Second dorsal-fin origin opposite or slightly in front of anal fin midbase, insertion well behind anal-fin free rear tip; free rear tip in front of upper caudal-fin origin 0.99 (0.54-2.00) times the inner margin. Posterior margin slanting posteroventrally from apex, insertion below or slightly in front of dorsal apex. Second dorsal-fin base 0.77 (0.65-0.91) in dorsal-caudal space, second dorsal-fin height 1.74 (1.49- 4.98) in its base, second dorsal-fin inner margin 1.74 (1.85-2.03) in its height and 3.04 (2.91-3.89) in seconddorsal fin base.

Anal fin low apically broad and semifalcate, much smaller than second dorsal fin, anal-fin height 0.49 (0.52-0.62) in second dorsal-fin height and anal-fin base 0.91 (0.88-1.03) times second dorsal-fin base. Analfin anterior margin moderately convex to nearly straight, apex broadly rounded, posterior margin nearly straight, inner margin nearly straight. Anal-fin base without preanal ridges, anal-fin origin 1.80 (1.44-1.83) times its base length behind pelvic-fin insertions, free rear tips 3.72 (3.05-6.02) times anal fin inner margin length anterior to lower caudal fin origin. Anal-fin posterior margin slanting posterodorsally, anal-fin insertion posterior to apex. Anal-fin base 1.14 (0.86-1.16) in anal-caudal space, anal-fin height 3.26 (2.72-3.25) in its base; anal-fin inner margin 1.11 (1.33-2.03) in its height and 3.62 (3.69-6.07) in its base.

Caudal fin narrow, elongate and asymmetrical, with large terminal lobe, ventral lobe not developed; dorsal margin slightly undulating, 4.63 (4.29-4.67) in precaudal length. Preventral caudal-fin margin 2.34 (2.00- 2.54) in dorsal caudal-fin margin, terminal lobe 4.43 (3.48-5.11) in dorsal caudal-fin margin, subterminal margin 1.45 (1.05-1.67) in terminal margin. Dorsal caudal-fin margin without lateral undulations; proximally and distally straight, basally concave and apically straight, tip of ventral caudal fin lobe bluntly rounded.

Postventral caudal-fin margin not differentiated into upper and lower parts, margin straight to slightly concave. Subterminal notch a narrow, deep slot, subterminal margin straight to convex; terminal margin concave and sometimes notched, edges of lobe bluntly angular, tip of tail broadly rounded; terminal margin length 3.81 (3.66-5.47) times dorsal caudal-fin margin.

Vertebral counts, ratios and statistics are given in Table 2. Transition between monospondylous (MP) and diplospondylous (DP) centra on average 6 (5-7) centra behind front of pelvic girdle. Monospondylous - Diplospondylous transition hardly enlarged, not forming ‘stutter zone’ of alternating long and short centra.

Colour. In alcohol, colour light brownish above, light brown to tan colouration on ventral surfaces of head, trunk, precaudal tail and fins, bands and saddles dark brown. Broad, brown saddle-marks on head above eyes, extending ventrally to include eyes; over gills, extending ventrally to incorporate first three gill slits; over, but not including, pectoral-fin free rear tips; on abdomen well anterior of pelvic-fin origins; over pelvicfin insertions with anterior margin of saddle posterior to first dorsal-fin origin, including section of first dorsal-fin anterior margin; between dorsal-fin bases; over and including second dorsal fin, extending ventrally to include inner margin of anal fins (Figs. 1 and 2). Thinner saddle marks present in dorsal-caudal space/anal caudal space; continuing as two bands on caudal fin and one on caudal fin terminal lobe. Ventral limits of abdomen saddle-marks approximately 75% of trunk depth; caudal fin saddles continuing to ventral limits.

Secondary, thinner saddles of light brown colouration may occur over first dorsal-fin origin extending anteriorly and over second dorsal-fin origin extending anteriorly. Development and prominence of secondary saddles may vary.

Small dark brown to black spots the size of eye width or smaller, loosely arranged in lines around saddlemark margins and centre of inter-saddle spaces (strongly demarcated in dorsal view) of head and trunk, irregularly arranged on pectoral fins and dorsal fins. Brown/black spots on trunk region decreasing in number approaching second dorsal fin, black spots absent from body surfaces post-second dorsal fin free rear tip. First and second dorsal fin apices with white tips, posterior tip of caudal fin terminal lobe with small white tip, occasionally extending along terminal margin. Small white spots absent on head anterior to third gill arch, pectoral fins, pelvic fins and on dorsal surface; excluding caudal fin dorsal margin. Small white spots present on lateral surfaces post-third gill arch, irregularly arranged on the trunk, dorsal fins and caudal fin on saddlemarks and inter-saddle spaces. White spots increasing in intensity and number on posterior surfaces of animal; most pronounced on caudal-tail. Overall, white spots slightly smaller than brown/black spots and more numerous.

Distribution and habitat. The distribution of A. marnkalha specimens collected from the present survey, extends from Gladstone in Central East Queensland (22°S, 150°E) to the southern reaches of Papua New Guinea (9° S, 143° E) (Fig. 8).

Atelomycterus marnkalha specimens collected from the Great Barrier Reef and the Torres Strait were caught in a variety of environmental substrates ranging from sandy to course rubble (Great Barrier Reef Seabed Biodiversity Project). Depths of capture were from 10.6 to 74 m, with most records shallower than 50m.

Size, reproduction and diet. The total length of males and females of A. marnkalha ranged from 190- 470 and 178-484 mm TL respectively. The average mass of adult males was 92.5% of the adult females, with considerable overlap between large males and small females. The mass of adult males ranged from 182.5- 286.0 g (n=5, mean = 203.8, sd = 43.6); adult females mass range 150-386.3 g (n=4, mean = 220.3, sd = 111.2). There was a considerable overlap in the mass of juveniles and adults for both males and females in the A. marnkalha sample.

The smallest sexually mature female was 354mm TL; although size at first maturity is possibly lower. The smallest sexually mature male was recorded at 345mm TL. Reproduction, as with the other atelomycterine species is expected to be oviparous (McKay, 1965; Compagno & Stevens, 1993; Bor et al., 2003), although no egg casings were recorded from the sample specimens.

Atelomycterus marnkalha feeds predominately on benthic invertebrates and small teleost species. Prey items found in the stomach content of A. marnkalha (n=4) included penaeid prawns, brachyuran crabs, cephalopods(Order Teuthida) and teleost species from the families Gobiidae and Platycephalidae.

Etymology. The term marnkalha originates from an indigenous Australian dialect and is the word used by the Rrumburriya clan to describe regional catshark species in the Gulf of Carpentaria. The Rrumburriya clan belong to the Yanyuwa peoples and Yanyuwa country, an expansive area encompassing the south-western coastline of the Gulf of Carpentaria, the tidal reaches of McArthur and Wearyan Rivers, and the Sir Edward Pellew Islands (Bradley et al., 2006). The Yanyuwa peoples have a close affinity to several marine animals including dugongs, turtles and elasmobranchs, which is reflected in their cultural and subsistence patterns. Yanyuwa country is where one of the first A. marnkalha specimens was recorded (Compagno & Stevens, 1994; Bradley et al., 2006). The common name Eastern Banded Catshark is in reference to the species’ geographical occurrence and colour pattern.

Comparison with other species. Atelomycterus marnkalha n. sp. is readily distinguishable from other atelomycterine species in external morphology and morphometrics, clasper structure, colouration and vertebral counts. It is most similar to the West Australian species A. fasciatus with the main morphological differences seen in the size of the anal fin (Table 1). In addition, A. marnkalha has a higher pelvic-anal to analcaudal ratio (1.65-2.38 vs. 1.33-1.59 times in A. fasciatus ) and a larger dorsal fin-caudal fin margin (17.5- 18.7 vs 16.3-17.3) (Table 1). The lateral trunk denticles of A. marnkalha lack the prominent lateral ridges seen in A. fasciatus and have clearly visible shallow depressions (Fig. 5); absent in A. fasciatus (Compagno & Stevens, 1993).

Atelomycterus marnkalha , as with A. fasciatus (Compagno & Stevens, 1993), differs from A. marmoratus and A. macleayi in having nearly straight to weakly concave dorsal fin posterior margins, slanting posterventrally from the apex. This difference is present though less pronounced when comparing A. marnkalha to A. baliensis , which has weakly falcate dorsal fins (White et al., 2005). In addition, A. baliensis , A. macleayi and A. marmoratus have relatively short preoral (POR) and prenarial (PRN) snout lengths when compared to A. marnkalha ; POR: A. baliensis 4.14-4.51, A. macleayi 3.25-3.39, A. marmoratus 4.06-4.47; PRN: A. baliensis 3.42-3.60, A. macleayi 2.46-2.55, A. marmoratus 3.18-3.63. Some overlap occurs between A. marnkalha and A. fasciatus (Table 1).

The five Atelomycterus species are clearly differentiated by the external morphology and dimensions of their claspers. Adult males of A. marmoratus have very elongate and attenuated claspers when compared to the other four species (Fig. 5; Compagno & Stevens, 1993). Mature A. macleayi males have short, very stout claspers, with the clasper structure of mature A. marnkalha , A. fasciatus and A. baliensis having intermediate characteristics; moderately stout, elongate claspers (Fig. 5; Compagno & Stevens, 1993; Fig. 6; White et al., 2005).

Claspers of mature A. marnkalha males are less tapered than A. fasciatus , and stouter than in mature A. fasciatus and A. baliensis ; clasper base width (CLB) as a percentage of clasper outer length (CLO), A. marnkalha 22.0%, A. fasciatus 17.1%, A. baliensis 15.4%. The claspers of A. marnkalha also differ from A. fasciatus in having a cover rhipidion with a straight to slightly concave anterior margin. The cover rhipidion in A. fasciatus has a distinct cover-rhipidion notch originating approximately opposite the anteriormost point of the pseudosiphon (Fig. 5A; Compagno & Stevens, 1993). The clasper structure of A. marmoratus differs from all other atelomycterine species in having glans less than half the length of the claspers outer margin.

The colouration of A. marnkalha and A. fasciatus differs from other Atelomycterus species in having dark brown-grey saddles and bands on a light grey background. Saddles may be present though less well-defined in A. baliensis and A. macleayi adults and of equal width (Compagno & Stevens, 1993; White et al., 2005). Atelomycterus macleayi , A. marmoratus and A. baliensis all have numerous, large and small dark brown to black spots covering the entire length of the dorsal surface. Spots of A. marmoratus and A. baliensis are often enlarged and merging when compared to A. macleayi . Black spots are less numerous and more defined in A. marnkalha , and least represented in A. fasciatus .

Atelomycterus marnkalha and A. marmoratus can be further differentiated from the other three species based on the presence or absence of white spots. Atelomycterus marnkalha has an irregular, though numerous, scattering of white spots across the dorsal and lateral surfaces, which intensify towards the posterior end of the animal. In comparison, the pale dorsal surfaces of A. marmoratus are dramatically reduced and form large irregular white spots on the lateral and dorsal surfaces (Compagno & Stevens, 1993). A sequence of white spots situated below the eye in A. marmoratus have also merged, forming a distinct white stripe through the gill slits. White spots are absent in A. macleayi and A. baliensis ; white spots are absent or fewer in number than black spots in A. fasciatus .

Atelomycterus macleayi and A. marmoratus have higher total centra (TC), precaudal centra (PC) and precaudal diplospondylous centra (DP) count ranges than A. marnkalha , A. fasciatus and A. baliensis (TC = 161- 183 vs. 147-163; PC = 106-132 vs. 95-110; DP = 63-85 vs. 53-69) (Compagno & Stevens, 1993; White et al, 2005). Atelomycterus marnkalha has the lowest PC count range (95-99) and the lowest minimum TC count (147-153) of the five species.

Atelomycterus macleayi and A. marmoratus apparently attain a larger size (mature males 481-619mm TL) than A. marnkalha , A. fasciatus and A. baliensis : mature males 386-418mm TL; 329-402mm TL; 433- 474mm TL respectively (Compagno & Stevens, 1993; White et al., 2005). Females of A. marnkalha attain a similar size to those of A. fasciatus and A. baliensis (Compagno & Stevens, 1993; White et al., 2005).

Atelomycterus marnkalha is found further south than A. fasciatus and A. macleayi (Compagno & Stevens, 1993; Last & Stevens, 1994), but may overlap with A. macleayi in the Gulf of Carpentaria and in the Torres Strait. Atelomycterus marmoratus and A. baliensis have not been recorded from Australian waters (Compagno & Stevens, 1993; White et al., 2005).

MDS ordination. Within the MDS ordination, A. marnkalha specimens were distributed around the central-left side of the plot, with A. fasciatus specimens, producing a relatively tight group at the top-left corner. As expected, the A. marnkalha sample plot was closer to A. fasciatus than the other three species (Fig 9). Atelomycterus baliensis and A. marmoratus were located in a relatively confined area in the lower half of the plot, indicating the two species are morphologically similar. This is consistent with results obtained by White et al. (2005). The two A. macleayi specimens were located to the right of the plot on the outer extremities.

The resulting ANOSIM demonstrated that all five species were significantly different overall (P<0.01; global R statistic = 0.826). Individual pairwise comparisons between A. marnkalha and the four other atelomycterine species all showed significant differences; A. fasciatus , A. marmoratus P<0.01; A. macleayi , A. baliensis P<0.05. The morphometric measurements identified by SIMPER as most responsible for the differences seen between A. marnkalha and A. fasciatus were the anal-caudal space (ACS) length and preanal (PAL) length. The corresponding morphometric results showed that both the ACS length and PAL length for A. marnkalha was smaller than A. fasciatus (Table 1).

The results obtained from the MDS ordination, ANOSIM, and SIMPER analysis further supports the morphometric results and the reidentification of AMS I.15557-003, CSIRO H1118-01 and AMS I.21842-001, 10°S37´S 140°02´E) as A. marnkalha . Given these samples are some of the earliest records of the species they have also been included in the type series.