Akheilos suwartanai White, Fahmi & Weigmann, 2019

White, William T. & Weigmann, Simon, 2019, A new genus and species of catshark (Carcharhiniformes: Scyliorhinidae) from eastern Indonesia, Zootaxa 4691 (5), pp. 444-460 : 447-458

publication ID	https://doi.org/ 10.11646/zootaxa.4691.5.2
publication LSID	lsid:zoobank.org:pub:91985A86-3949-4F1B-8739-FD10B6A94907
persistent identifier	https://treatment.plazi.org/id/03C5878B-FFA2-FF98-FF73-25625649E1D5
treatment provided by	Plazi
scientific name	Akheilos suwartanai White, Fahmi & Weigmann
status	sp. nov.

Treatment

Akheilos suwartanai White, Fahmi & Weigmann , n. sp.

Ambon Catshark

Table 1 View TABLE 1 ; Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 , 6a View FIGURE 6

Holotype. MZB 18227, adult male 537 mm TL, Rumahkay , southwest of Seram Island between Seram and Ambon islands, 19 June 1984, coll. by S. Wouthuyzen.

Diagnosis. A moderately small scyliorhinid catshark with the following combination of characters: moderately long precaudal tail region (tail much longer than trunk); dorsal fins of similar size and shape; snout short and narrowly parabolic; eyes large and narrowly oval (length 5.0 times in head length), broad suborbital grooves; nostrils oblique with triangular anterior nasal flaps not reaching to mouth and distinct but low posterior nasal flaps; mouth broadly rounded, its width 1.2 times preoral length; upper and lower labial furrows well developed, uppers not reaching midpoint between mouth corner and posterior margin of nostril; jaws with ~60 upper and ~53 lower tooth rows, teeth mostly multicuspid, posterolaterals not strongly differentiated from anterolaterals; caudal fin ventral lobe low but distinct; claspers long and slender, glans elongate, long and low envelope present, cover rhipidion small without an anterior fold or tab, pseudosiphon small and slit-like; supraorbital crests present on cranium; colour pale brown with numerous rusty brown spots, small brown spots forming two indistinct saddles on dorsal surface of predorsal body, broken ocellus-like marking on side behind pectoral fins and under each dorsal fin; precaudal vertebral centra 96, total centra ~137.

Description. Morphometric measurements are given in Table 1 View TABLE 1 .

Body firm and stout, suboval in cross section at mid-trunk, laterally compressed and barely tapering posterior to cloaca; head region relatively narrow, relatively short abdominal section, long caudal section. No predorsal, interdorsal, or postdorsal ridges; no postanal ridge; no lateral ridges on caudal peduncle. Trunk much shorter than tail, distance from tip of snout to anterior cloaca 40.4% TL; pre-first dorsal-fin length 46.0% TL, pre-second dorsal-fin length 65.2% TL, ventral precaudal length 74.5% TL.

Head relatively narrow and moderately depressed, with a narrowly rounded snout in dorsoventral view, bluntly pointed in lateral view; supraorbital crests present on chondrocranium; head length 1.9 times head width at middle gill slits and 1.2 times pectoral–pelvic space; head width at level of maximum outer extent of anterior nostrils 1.4 times width at level of lateral indention of head, 1.1 times preorbital length, and 6.4% TL; head width at posterior edge of nostrils 1.5 and at mouth corners 1.9 times width at level of lateral indention of head; head width at middle gill slits 2.0 times width at level of lateral indention of head. Snout short and narrowly parabolic, its tip rounded, strongly bell-shaped in dorsoventral view with distinct lateral indention; pre-outer nostril length 1.1 times internarial width and 0.4 times interorbital width; preoral length 0.8 times mouth width and 0.9 times preorbital length; preorbital length 3.2 times in head length and 0.9 times interorbital space. Eyes large and narrowly oval, mostly lat- eral on head (only very small portion of eyes visible in dorsal view), eye length 5.0 times in head length, 13.3 times in pre-first dorsal distance, and 2.7 times eye height; nictitating lower eyelids, weak anterior eye notch, no posterior eye notch, and broad suborbital grooves present. Spiracles small, subcircular, close behind but well separated from eyes, mostly lateral on head (barely visible in dorsal view), located below midline of eye, spiracle length 5.2 times in eye length and 9.6 times in interorbital width. Gill slits relatively short, well separated, their upper ends clearly below level of lower edge of eye; gill area fully scaled, gill filaments not visible externally; first three gill openings equal in size then decreasing in size to fifth opening; fourth gill opening about level with pectoral-fin origin, fifth over anterior pectoral-fin base. Nostrils oblique, expanding diagonally inwards from snout edge, clearly not reaching level of mouth, with triangular anterior nasal flaps and low but distinct posterior nasal flaps; pre-outer nostril length 0.85 times nostril width and 0.5 times preoral snout length, nostril width 1.8 times internarial width and 0.8 times eye length. Mouth rather narrow, rounded, width 1.2 times preoral length, 0.7 times head width at mouth corners, 2.7 times in head length, and 2.5 times mouth length. Upper and lower labial furrows well developed; upper ones reaching just forward of midlength of eyes, not reaching midpoint between mouth corner and posterior margin of nostril, length of lower furrows 1.2 times length of upper ones. Tongue broad, flat and rounded, pale; denticles covering anterior portion (likely detached in preservation as easily removed); no obvious oral papillae. Roof of mouth without papillae.

Upper jaw with approximately 60 and lower jaw with about 53 diagonal rows of small teeth. Teeth similar in both jaws, mostly pentacuspidate with median cusp much longer than lateral cusps; posterolateral teeth barely differentiated from anterolateral teeth. Cutting edges of cusps without serrations.

Dermal denticles densely set and strongly overlapping. Lateral trunk denticles tricuspidate with a long, slender and acutely pointed median cusp; a small lateral cusp on each side of median cusp; two median ridges that fuse near the tip of the median cusp and reach the tip; surface almost completely covered in reticulations. No enlarged denticles on dorsal and/or ventral caudal-fin margins.

Pectoral fins large, subtriangular, non-falcate, anterior margin weakly convex, its length 2.1 times its base length and 1.3 times length of the weakly concave posterior margin, apex rounded, inner margin convex and 1.2 times pectoral base length, inner pectoral corner broadly rounded. Pectoral–pelvic space 1.3 times length of pectoral-fin anterior margin and 1.1 times interdorsal space.

Pelvic fins small, narrowly triangular with a short, mostly straight anterior margin and a long, straight posterior margin; inner margins short and straight; anterior margin 0.8 times pectoral-fin anterior margin; apex very bluntly rounded; pelvic-fin insertions just anterior to first dorsal-fin origin, pelvic posterior tips just anterior to midbase of first dorsal fin. Pelvic–anal space relatively long, 12.4% TL and 0.8 times pectoral–pelvic space.

Dorsal fins similar in size and shape. First dorsal fin small, triangular, same height as second dorsal fin, 0.9 times as long as second dorsal fin, anterior margin straight, apex bluntly rounded, posterior margin weakly concave, and inner margin straight, free rear tip angular; base length 1.2 times fin height and 0.4 times interdorsal space; first dorsal-fin origin level with anterior third of pelvic-fin free tips; first dorsal-fin insertion level with midpoint of pelvic-anal space. Second dorsal fin as high as first dorsal fin, anterior margin very slightly convex, apex narrowly rounded, posterior margin weakly concave, inner margin straight, free rear tip pointed, base length 1.4 times fin height and 0.5 times interdorsal space; second dorsal-fin origin over posterior third of anal-fin base.

Anal fin long and moderately high, with a nearly straight anterior margin, longer and very weakly concave posterior margin, and short, straight inner margin, apex somewhat angular, free rear tip narrowly pointed; base length 2.7 times fin height, 0.8 times interdorsal space, and 0.8 times pelvic–anal space; base 1.6 times longer than second dorsal-fin base. Anal–caudal space 7.9% TL, 0.8 times anal-fin base. Anal-fin origin distinctly posterior to first dorsal-fin free tip.

Caudal fin moderately long, narrow and strongly asymmetrical, its length 3.8 times fin height and 1.9 times interdorsal space; dorsal caudal margin nearly straight, no lateral undulations; upper caudal lobe very low, lower caudal lobe much deeper, preventral margin weakly convex, postventral margin moderately concave. Ventral caudal-fin origin far anterior of dorsal caudal-fin origin due to a low ridge extending anterior of ventral lobe. Ventral corner bluntly angular; terminal lobe distinct, length 5.8 times in caudal-fin length; terminal caudal margin damaged but likely moderately convex based on angle of remaining margin.

Claspers moderately long, slender, terminating level with first dorsal-fin insertion and well anterior of anal-fin origin; lateral margins nearly straight, not undulated, extending slightly more than half of their outer margin length beyond pelvic-fin free rear tips; inner margin length 11.1% TL, base width 1.5% TL. Glans somewhat elongated, length almost half clasper inner margin; tapering to a narrowly pointed tip in distal half. Ventral and lateral surfaces of clasper covered with small clasper denticles (CD); dorsal surfaces largely naked. The narrow slit-like apopyle opens the clasper groove proximally; the hypopyle ends the clasper groove distally and is detectable as a small cavity next to the rhipidion, but both are concealed by the cover rhipidion and exorhipidion; clasper groove (CG) not fused dorsally between the apopyle (AP) and hypopyle; envelope (EN) on outer lobe of glans low, elongate, and fleshy; exorhipidion (ER) on outer lobe large and fleshy, consisting of a proximal convex blade and a distal fleshy wall; no enlarged clasper denticles (clasper hooks) along inner edge of ER; rhipidion (RH) long and low; cover rhipidion (CR) relatively small, only barely concealing anterior portion of RH, without an anterior fold or tab; pseudosiphon (PS) on inner margin short and slit-like; pseudopera (PP) relatively short and partially concealed by EN and RH.

Skeletal meristics (from radiograph): monospondylous trunk vertebral centra 39, diplospondylous precaudal centra 57, total precaudal centra 96, caudal centra ~41, and total centra ~137.

Spiral intestinal valve with 8 turns.

Colour. Based on preserved holotype; fresh colour unknown. Base colour medium brown dorsally grading to pale brown on lateral and ventral surfaces. Postorbital head, body, tail and dorsal surface of paired fins covered with small, diffuse-edged rusty brown spots; spots denser on dorsal and upper lateral surfaces, sparser on lower lateral surfaces. Preorbital snout plain, without markings. Small, diffuse-edged brown spots forming two indistinct saddles on the dorsal and upper lateral surfaces, first above pectoral-fin free tips and second above pelvic-fin origin. Elongate dark brown markings forming an incomplete ocellus on lower lateral surface midway between pectoral and pelvic fins; similar markings forming half ocelli below dorsal fins; dorsal fins with medium brown blotches below free rear tip, mostly visible in dorsal view. Dark brown markings on caudal fin near dorsal origin appear to be an artefact from labelling and only present on left side of specimen. Dorsal fins mostly plain, except several rusty brown spots near bases. No markings on ventral surfaces.

Size. Only known specimen is the adult male holotype of 537 mm TL.

Distribution. Only known from the island of Ambon; depth unknown.

Stomach contents. The stomach of the holotype contained several anterior sections of a small snake eel ( Ophichthidae ). This family of eels is very diverse and thus does not help infer the depth this specimen was collected from. Although usually in shallower waters less than 100 m depth, some species can be found in deeper waters.

Etymology. Named after the first director of the Research and Development Center of Oceanology, Indonesian Institute of Sciences (LIPI) in Ambon, Atjep Suwartana.

Remarks. This species can be readily separated from the other catsharks based on its morphology and skeletal anatomy as outlined in the generic remarks above. It is most closely allied to the genus Schroederichthys from the Americas and until now was the only genus within the subfamily Schroederichthyinae. The generic remarks section above provides the characters which separate this species to the genus Schroederichthys .

Akheilos suwartanai n. sp. is closest in general morphology to the less elongated Schroederichthys species, S. bivius and S. chilensis , but can be further differentiated from these two species by the following characters: shorter labial furrows (uppers 1.3 vs. 1.9–3.7% TL, lowers 1.6 vs. 1.9–3.4% TL), smaller pelvic-fin (anterior margin 4.9 vs. 6.1–9.0% TL, height 3.7 vs. 4.4–6.8% TL), and a longer snout (pre-inner nostril length 4.4 vs. 3.0–3.6% TL). It further differs from S. bivius in having a narrower head and trunk (head width 9.2 vs. 10.1–10.5% TL, trunk width 7.5 vs. 9.3–10.4% TL) and triangular anterior nasal flaps (vs. narrow and lobate).

Akheilos suwartanai n. sp. has less vertebrae than S. bivius , S. saurisqualus and S. tenuis (total centra ~137 vs. 141–153, ~158 and 139–150, respectively). It has more total centra than S. maculatus (~137 vs. 132–135) but less precaudal centra (96 vs. 105) ( Table 1 View TABLE 1 ).