Grinning Izak Catshark

description

A distinguishing feature of this species is the club-shaped papillae found on the distal tip of the clasper (Fig. 16 B). This structure was illustrated by Compagno (1988: 153), who described it as a “ brush of papillae at clasper tip ”. Compagno (1988) stated that this structure may be absent in the Tanzanian-Kenyan representative of the punctatus group, however the opposite is true. Holohalaelurus grennian sp. nov. is the only Holohalaelurus shark with such a structure on its claspers. Although not observed on preserved specimens (Figs. 14 - 15), it is likely that H. grennian has black sensory pores on the ventral surface, as these markings have been observed to fade in specimens of H. punctatus and H. favus sp. nov. (under the name of H. regani) once preserved (Bass et al., 1975). Morphological sexual dimorphism is readily apparent in H. grennian. The head is narrower and the snout more broadly rounded in the female, compared to males (Figs. 14 - 16). Also, the spots on the female are paler, and more yellow in colouration, on the dorsal surface compared to the darker brown colouration of the males, giving an overall paler colour to the female.

A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species.

description

Description. Morphometric and meristic data are given in Table 5. Holotype, mature male 267 mm TL (paratypes, mature male 273 mm TL, juvenile male 165 mm TL, juvenile female 206 mm TL, mean of all specimens examined in Table 5, see Study material): body slender and elongate; head compressed, head width 2.63 (2.27, 2.53, 2.51, 2.46) times its height at the posterior margin of the orbit, and head width 1.90 (1.77, 2.07, 1.94) times its height at the pectoral fin origin; trunk depressed, trunk width 1.19 (1.41, 1.08, 1.67, 1.32) times its height; abdomen slightly compressed to slightly depressed, abdomen width 0.77 (0.90, 1.0, 1.14, 0.94) times its height; tail slightly depressed, tail width 1.04 (1.10, 1.33, 1.08, 1.14) times its height; caudal peduncle compressed, caudal peduncle height 1.16 (1.44, 1.33, 1.29, 1.33) times its width; ventral sensory pores not conspicuously black in preserved specimens, although likely to be so in fresh or live specimens; head long, head length 0.23 (0.25, 0.23, 0.22, 0.23) times the precaudal length; snout short, rounded and coming to a point in males, although broadly rounded and not coming to a point in females, preoral length 0.19 (0.20, 0.26, 0.3

A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species.

diagnosis

Diagnosis. A dwarf species of Holohalaelurus, H. grennian is the smallest member of the genus and is distinguished from other Holohalaelurus sharks by: denticles on dorsal midline slightly enlarged beginning from a point level to the pectoral insertion on the dorsal midline to the first dorsal insertion; enlarged denticles not present on the dorsal surface of the pectoral fin in adults; claspers with club-shaped papillae present on the distal tip, unique amongst Holohalaelurus sharks; buccal papillae inconspicuous; relatively low vertebral count, 104 total vertebrae in the holotype (108, 90, 106, mean 102.0); relatively low tooth counts, 43 upper teeth in total in the holotype (42, 40, 41, mean 41.5), 38 lower teeth in total in the holotype (39, 38, 41, mean 39.0). Covered in small dark spots on yellow-brown background, with few white spots; large white spot above pectoral fin insertion; characteristic narrow dark horizontal stripe on both dorsal fins.

A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species.

discussion

Comparison with other species. Holohalaelurus grennian has denticles on the dorsal midline slightly enlarged, less so than in H. favus and H. regani, about equally developed in H. melanostigma, and more so than in H. punctatus. No enlarged denticles on dorsal surface of pectoral fins in adults as opposed to H. regani and H. favus. Buccal papillae inconspicuous as opposed to H. punctatus and H. regani. Holohalaelurus grennian has club-shaped papillae found on the distal tip of the clasper (Fig. 16 B), unique to this species amongst Holohalaelurus sharks. Spots are not fused into bars or stripes as in H. favus and H. punctatus, however distinguishable from those two species by having spots fused into large blotches on the pectoral fins, and also bearing a distinctive stripe on each dorsal fin. White spot present above pectoral fin bases as in H. punctatus, but fewer white spots than that species. Holohalaelurus grennian is the smallest member of the genus at all stages of maturity. Holohalaelurus grennian is closest to H. punctatus in overall morphology and colouration.

A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species.