Humpback Catshark

description

A. gibbosus Taiwan Holotype Paratypes East China Sea D 2 free lobe length 4.2 ― ― ― ...... continued on the next page TABLE 3. (Continued) A. gibbosus Taiwan Holotype Paratypes East China Sea Apristurus gibbosus is similar to Japanese A. japonicus in having a long P 1 – P 2 space, but A. gibbosus is distinct from A. japonicus in having a shorter snout (Figure 19) and a narrower internarial width (Figure 20). Apristurus gibbosus is apparently a smaller species, which matures at lengths of 40 – 45 cm TL in both sexes, and attains 57 cm TL, while A. japonicus matures at lengths of 55 – 60 cm TL, and attains more than 70 cm TL (Figure 21). This is the first report of Apristurus gibbosus from Taiwan.

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters

description

Description. Proportional measurements and meristic counts are given in Table 3. Body cylindrical, moderately slender and elongate (Figure 13). Head dorso-ventrally flattened, posterior part of body compressed laterally. Snout relatively short andbroad; its tip bell-shaped. Pre-outer nostril length 0.9 – 1.4 times internarial width. Pre-oral length 0.8 – 1.0 times pre-orbital length, 1.9 – 2.7 times internarial width, 0.8 – 1.1 times mouth width and 1.0 – 1.3 times interorbital width. Pre-orbital length 1.2 – 1.6 times interorbital length, 2.8 – 4.8 times orbit length. Internarial width slightly greater than orbit length and shorter than nostril width. Nostril expanding obliquely inward from snout edge; length about 2 / 3 of pre-inner nostril length. Nostril-mouth space about half of internarial width. Mouth broadly arched, with well developed labial furrows; upper labial furrow 1.1 – 1.6 times longer than lower one. Upper labial furrow reaching beyond midpoint between mouth corner and posterior margin of nostril. Orbit relatively large and slender, with a weak subocular fold. Spiracle small placed slightly below level of horizontal axis of orbit. Five small gill slits present; fou

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters

diagnosis

Diagnosis. A species of Apristurus with the following characters: upper labial furrows longer than the lowers; first dorsal fin slightly smaller than second dorsal fin, originating above middle of pelvic-fin base; second dorsal-fin insertion anterior to anal-fin insertion; snout relatively short and broad; tip bell-shaped; abdomen long; P 1 – P 2 space longer than anal-fin base length (ceratotrichia); pectoral-fin tip always anterior to midpoint of P 1 – P 2 space; intestinal spiral valves 16 – 21; monospondylous + precaudal diplospondylous vertebrae 37 – 43 + 25 – 31; small dermal denticles giving a velvety texture to body surface; clasper hook absent on edge of exorhipidion, posterior margin of exorhipidion lacking free posterior end; body uniformly dark to blackish brown; maturingsize at least 400 mm TL in males and 450 mm TL in females.

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters

discussion

Remarks. Apristurus gibbosus was originally described by Meng et al. (1985) based on three specimens collected from the South China Sea. This species belongs to the ‘ brunneus group’ (sensu Nakaya & Sato, 1999) of the genus Apristurus, characterized by having a considerably longer labial furrow on the upper jaw than on the lower jaw, and more numbers of spiral valves in the intestine. Apristurus gibbosus is characterized by a long P 1 – P 2 space, which is greater than the anal-fin base length (ceratotrichia) and pectoral-fin tip that does not reach the midpoint of the P 1 – P 2 space. As such, A. gibbosus is clearly distinguishable from other species of Taiwanese Apristurus by these characters. Although Meng et al. (1985) described “ dorsal outline behind eye highly convexed ” as one of the diagnostic characters of this species, this is apparently based on a transformation during fixation (personal observation of the type specimens by Nakaya).

A review of the genus Apristurus (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Taiwanese waters