Scyliorhinus comoroensis Compagno, 1988

Soares, Karla D. A. & De, Marcelo R., 2019, The catshark genus Scyliorhinus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae): taxonomy, morphology and distribution, Zootaxa 4601 (1), pp. 1-147 : 50-56

Scyliorhinus comoroensis Compagno, 1988

( Figs. 34–38 , Tab. 10 )

Common names: Comoro catshark.

Scyliorhinus comoroensis Compagno, 1988b: 603 –625 (original description, type locality: Comoro Islands); Compagno, 1999: 480 (listed); Compagno et al., 2005: 249, pl. 41 (compilation); Ebert et al., 2013a: 372, 380, pl. 51 (compilation); Weigmann, 2016: 43 (listed).

Holotype. MNHN 1984–0701 , male, 457.2 mm TL (Moroni, Comoro Islands, 400 m depth).

Additional material examined. MNHN 1991–0420 , male, 175 mm TL, female, 181.5 mm TL ( Madagascar, 13°45.8’S, 47°38.5’E, 430–700 m depth) .

Diagnosis. Scyliorhinus comoroensis differs from all congeners by presenting a color pattern with beige or cream spots (vs. light spots absent in S. cervigoni , S. garmani , S. meadi , and S. retifer ; yellow to golden in S. capensis ), predominantly larger than the spiracle (vs. predominantly smaller in S. boa , S. cabofriensis , S. canicula , S. duhamelii , S. stellaris , and S. ugoi ); pelvic apron extending to 2/3 length of pelvic inner margins (vs. extending through almost entire length of pelvic inner margins in S. canicula , S. capensis , S. duhamelii , S. torazame , and S torrei ); ventral terminal 2 cartilage absent (vs. present in all other species; clasper skeleton not examined in S. hesperius , S. garmani and S. meadi ). The following combination of characters, although less conspicuous, also helps distinguish this species: saddles prominent and darker than the background color (vs. inconspicuous in S. boa , S. cabofriensis , S. cervigoni , S. garmani , S. duhamelii , and S. torrei ); light spots when present between saddles and smaller than spiracles (vs. larger than spiracles in S. duhamelii , S. hesperius and S. torrei ); nasoral grooves absent and posterior nasal flaps situated on the posterior edge of excurrent apertures (vs. grooves present and flaps situated laterally in S. canicula and S. duhamelii ); anterior nasal flaps reaching the upper lip (vs. flaps far away from the upper lip in other species, except in S. canicula , S. cervigoni , S. duhamelii , S. garmani , and S. stellaris ); interdorsal distance 0.6–1.0 times the anal base (vs. larger than anal base in S. boa , S. cabofriensis , S. haeckelii , S. hesperius , S. meadi , S. retifer , S. torrei , and S. ugoi ); cover rhipidion of clasper covered by dermal denticles (vs. no denticles in S. boa , S. cervigoni and S. retifer ); clasper with terminal dermal cover smooth (vs. rough in S. canicula and S. capensis ); terminal 3 cartilage absent (vs. present in S. boa , S. canicula , S. capensis , S. retifer , and S. torazame ); dorsal terminal 2 cartilage elongated, 1/3 of dorsal terminal (vs. reduced and subtriangular in S. cabofriensis , S. capensis , S. cervigoni , S. haeckelii , and S. ugoi ; 1/4 of dorsal terminal in S. canicula , S. duhamelii , S. retifer , S. stellaris , and S. torrei ; same length in S. torazame ); interdorsal distance similar to the anal base (vs. larger than anal base in S. boa , S. cabofriensis , S. haeckelii , S. hesperius , S. meadi , S. retifer , S. torrei , and S. ugoi ); counts of monospondylous vertebrae 40 (vs. 44–46 in S. capensis ; 35–37 in S. duhamelii ; 48 in S. garmani ; 46–48 in S. meadi ; 43–47 in S. stellaris ; 32–37 in S. torazame ; 30–35 in S. torrei ; 38–39 in S. ugoi ); adult males at least 457 mm TL (vs. adult males larger than 500 mm TL in S. capensis , S. cervigoni , S. meadi and, S. stellaris ; 269 mm TL in S. torrei ).

Description. Morphometric and meristic data of holotype and other specimens are given in Table 10 .

Body slender and cylindrical, tapering considerably posterior to cloaca ( Figs. 34 , 35 ). Prepectoral length 0.5 times the prepelvic length. Trunk shorter than tail; snout-vent length 0.6–0.7 (0.7) times vent-caudal length. Pectoral-pelvic space 1.3 (1.1) times the pelvic-anal space. Interdorsal space 2.5–2.6 (2.5) times the dorsal-caudal space ( Tab. 10 ). No interdorsal, postdorsal or postanal ridges; lateral crest on caudal peduncle absent.

Head moderately broad and depressed; head length 1.6 (1.7) times head width ( Figs. 34 , 35 ). Snout relatively short, preoral length 0.4 times mouth width and 0.7–0.8 (0.8) times smaller than preorbital length. Prenasal length 0.6–0.7 (0.6) times internarial space; preorbital length 0.9–1.0 (1.0) times interorbital space.

Eye large and slitlike, eye length 2.3–2.6 (2.8) times its height and 0.2 times smaller than head length ( Fig. 34 ). Eye dorsolateral on head, with lower edge medial to horizontal head rim in dorsal view; subocular ridge strong. Nictitating lower eyelid of rudimentary type, with shallow subocular pouch and secondary lower eyelid free from upper eyelid. Spiracle close behind but well separated from eyes, dorsolaterally on head and somewhat lower than level of eye notch. Spiracle diameter goes 3.6 (3.9) times in eye length and 7.4–7.5 (5.8) times in interorbital width.

First two gill openings about equally wide; first one twice as long as fifth. All gill openings slightly concave and not elevated on dorsolateral surface of head; gill filaments not visible externally.

Nostril with broad incurrent aperture, without nasoral groove or nasal barbel, and small and oval excurrent aperture. Anterior nasal flap large, triangular, covering posterior nasal flap and excurrent aperture, and touching the upper lip ( Fig. 36 ). Mesonarial ridge distinct but not exceeding the posterior border of the anterior nasal flap. Posterior nasal flap rectangular, situated on the posterior border of the excurrent aperture and corresponding to 1/3 of the anterior flap. Mesonarial superior and inferior flaps triangular and corresponding to 1/3 of the anterior nasal flap. Internarial distance 0.7–0.8 (0.9) times smaller than interorbital distance.

Mouth arched, moderately large and short, its length goes 1.7 times in mouth width ( Fig. 36 ). Lower labial furrow short and narrow, 3.3–3.5 (3.3) times smaller than mouth width. Dorsal labial cartilage 1.3 times the ventral cartilage; anterior tip of dorsal labial cartilage reaching the orbital process of the palatoquadrate. Tongue flat and rounded, light-colored, with oral papillae hardly detectable.

Monognathic heterodonty gradual well developed; anterior teeth abruptly larger than the parasymphysial ones and lateral teeth smaller distally, with smaller and thicker principal cusps. Sexual heterodonty not observed; only the holotype was examined. Tooth counts 25–25/21–22. Upper teeth with slightly higher principal cusps than lower ones, and striae longer and stouter. Parasymphysial and anterior teeth similar in shape and principal cusp straight; principal cusp flanked by one cusplet on each side. Lateral teeth with principal cusp slightly oblique and one cusplet on each side. Commissural teeth not examined.

Lateral trunk denticles with flat, elongated teardrop-shaped crowns, 2 times longer than wide (examination under stereomicroscope). Crown with a strong medial ridge extending its entire length onto long principal cusp and flanked by lateral ridges less prominent. Cusplets poorly developed and marginal ridges short or absent.

Pectoral base 0.7 (0.9) times mouth width. Pectoral anterior margin 2–2.1 (2.1) times its base and 2.1 (1.4) times the posterior margin. Pectoral fin skeleton not examined.

Pelvic fin triangular; pelvic anterior margin 1.3–1.5 (1.0) times the posterior margin and 1–1.1 (1.0) times the pelvic base. Pelvic inner margins of males fused by 2/3 of their extension; claspers of juveniles evident without lifting the pelvic apron.

Clasper short and cylindrical ( Fig. 37 ), extending beyond free rear tips of pelvic fins; clasper inner length 0.7 (0.6) times the pelvic anterior margin, 1.3 (2.3) times clasper outer length and 4.5 (4.4) times the clasper base. Most of clasper surface except dorsomedial surface of glans, medial border of cover rhipidion, rhipidion and terminal dermal cover, covered by dermal denticles with anteriorly directed crowns. Clasper hooks absent. Rhipidion welldeveloped, partly covered medially by a prominent exorhipidion and anteriorly by the cover rhipidion; insertion of rhipidion at anterior portion of terminal dorsal 2 cartilage and extending to the end of glans. Cover rhipidion expanded medially covering an exorhipidion expanded anteriorly and narrow posteriorly; both cover rhipidion and exorhipidion covering the clasper groove. Envelope absent; pseudosiphon poorly developed, visible only internally. Terminal dermal cover smooth and extending through 1/3 of the clasper glans, covering the posterior borders of exorhipidion and cover rhipidion.

Clasper skeleton relatively simple ( Fig. 37B ). Ventral marginal cartilage shorter than dorsal one. Ventral and dorsal terminal cartilages elongated and slightly concave dorsally; ventral terminal beginning anteriorly, but ending together with the dorsal terminal. Dorsal terminal 2 cartilage rodlike and extending through 1/3 of dorsal terminal cartilage. Terminal 3 and ventral terminal 2 cartilages absent.

First dorsal fin triangular or subrectangular, with nearly straight anterior margin, rounded apex and angular free rear tip ( Fig. 34 ). First dorsal fin origin opposite to the pelvic fin insertion; first dorsal fin insertion opposite to half-length of pelvic inner margins. Anterior margin 1.2–1.3 (1.5) times first dorsal fin base; first dorsal fin height 0.5–0.6 (0.7) times its base.

Second dorsal fin smaller than the first and triangular, sometimes subrectangular ( Fig. 34 ). Second dorsal fin origin opposite to anal midbase and insertion opposite to the posterior end of the anal fin. Anterior margin 1.1–1.2 (1.3) times base of second dorsal fin; second dorsal base 2.3 (1.5) times its height and 1.3–1.4 (1.3) times the dorsal-caudal distance. First dorsal fin 1.3–1.4 (1.1) times larger than the second dorsal fin.

Anal fin triangular, apically narrow and not falcate; anal fin base 1.4 times the second dorsal fin base. Anal fin origin opposite to the anterior third of interdorsal distance. Anterior margin nearly straight, apex narrowly rounded, free rear tip acutely pointed, and inner margin straight. Anal fin base 0.9–1.1 (1.0) times the interdorsal distance and 2.6–2.7 (2.6) times the dorsal-caudal distance. Anal fin anterior margin 1.7–1.9 (1.7) times the posterior margin; anal fin height 0.5 (0.4) times its base.

Caudal fin narrow-lobed and asymmetrical ( Figs. 34 , 35 ). Dorsal caudal lobe 1.9 (2.0) times larger than preventral lobe; subterminal caudal margin slightly greater than terminal margin. Caudal crest of enlarged denticles absent on caudal fin margins. Neurocranium not examined.

Coloration in alcohol. Body light brown presenting nine or ten saddles darker than the background color. Beige to cream spots, spiracle-sized, distributed predominantly inside saddles and, when present between the saddles, smaller than the spiracle. Dark spots absent. Belly and ventral surface of paired and anal fins without spots, cream in color.

Etymology. The specific name ‘comoroensis’ refers to the type locality, Comoro Islands.

Distribution. This species occurs in the Comoro Islands (original description) and northwestern coast of Madagascar (13°45’S, 47°38’E) ( Fig. 38 ).

Biological data. The holotype is the only known reported adult (male, 457 mm TL); the other specimens are juveniles. Conservation status ‘Data Deficient’ ( McCormack 2009).

Remarks. This species was described in detail by Compagno (1988b), who offered meaningful comparisons with all other Scyliorhinus species he considered valid. Compagno (1988b) grouped S. comoroensis with congeners that have light spots on a darker background, dark saddles and that lack small dark spots, in particular S. capensis , S. torazame , S. torrei and S. hesperius ; he further stated that the latter species was closest to S. comoroensis , even though it occurs in the Atlantic (Central America), and can be separated from it by color pattern. Compagno (1988b) went to great lengths to separate S. comoroensis from S. capensis , the geographically nearest congener, as he believed they were very distinct in many features including clasper skeleton. The re-description of S. comoroensis here substantially agrees with the original description, with the addition of two juvenile specimens recently captured that extend its geographic range to Madagascar ( Fig. 35 ). These juvenile specimens present a slightly darker background color than the holotype.

Figures

FIGURE 34. Holotype of Scyliorhinus comoroensis Compagno, 1988, MNHN 1984–0701, male, 457.2 mm TL (Moroni, Comoro Islands). A, dorsal view; B, lateral view. Scale bar = 20 mm.

FIGURE 35. Scyliorhinus comoroensis, dorsal view; A, MNHN 1991–0420, male, 175 mm TL (Madagascar); MNHN 1991–0420, female, 181.5 mm TL (Madagascar). Scale bar = 20 mm.

FIGURE 36. Scyliorhinus comoroensis; ventral view of head, MNHN 1984–0701, male, 457.2 mm TL (Moroni, Comoro Islands). Scale bar = 20 mm.

FIGURE 37. Clasper of Scyliorhinus comoroensis, MNHN 1984–0701, 457.2 mm TL (Moroni, Comoro Islands). Modified from Compagno (1988b). A, external morphology; B, skeleton. crh, cover rhipidion; end, endstyle; erh, exorhipidion; hp, hipopyle; rd, dorsal marginal cartilage; rh, rhipidion; rv, ventral marginal cartilage; td, dorsal terminal cartilage; td2, dorsal terminal 2 cartilage; tdc, terminal dermal cover; tv, ventral terminal cartilage. Scale bar = 10 mm.

FIGURE 38. Map showing the geographic distribution of Scyliorhinus comoroensis based on material examined in this study. Black star indicates the type locality.

Tables

TABLE 10. Morphometric and meristic data of Scyliorhinus comoroensis and S. garmani. Total length (TL) in mm, other measurements as percentages of TL.

Characters	Scyliorhinus comoroensis		Scyliorhinus garmani
	Holotype	MNHN 1991-0420 (2 specimens)	Holotype
Total length (TL)	457.2	175.0–181.5	267.2
Precaudal length	74.8	70.2–74.8	78.6
Eye-spiracle length	1.1	1.2–1.4	1.2
Prenasal length	3.5	3.7–4.4	3.1
Preoral length	5.3	5.2–5.8	4.5
Preorbital length	6.7	6.6–7.9	5.6
Prespiracular length	11.2	10.2–11.5	9.1
Prebranchial length	15.9	14.5–15.5	13.0
Head length	20.5	20.6–20.7	18.0
Prepectoral length	18.7	19.0–19.3	15.7
Prepelvic length	38.9	36.1–36.9	37.5
Snout-vent length	44.2	40.0–40.3	45.1
Vent-caudal length	59.7	60.3–62.3	54.9
Pre-first dorsal length	46.2	42.7–44.5	42.1
Interdorsal distance	10.9	10.7–11.7	8.2
Dorsal-caudal distance	4.3	4.2–4.5	5.5
Pectoral-pelvic distance	14.2	13.4–13.8	17.3
Pelvic-anal distance	12.3	10.2–10.7	9.7
Anal-caudal distance	6.3	5.4–6.0	4.5
Interorbital distance	6.4	7.5–8.1	7.0
Internarial distance	5.8	5.7–5.8	4.3
Mouth length	4.7	5.1–5.5	4.3
Mouth width	8.2	8.6–9.5	7.2
Lower labial furrow length	2.5	2.6–2.7	2.1
Eye length	4.0	3.9	3.0
Eye height	1.4	1.5–1.7	1.5
Spiracle length	1.1	1.0–1.1	0.7

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