Holohalaelurus Fowler 1934

Brett A. Human, 2006, A taxonomic revision of the catshark genus Holohalaelurus Fowler 1934 (Chondrichthyes: Carcharhiniformes: Scyliorhinidae), with descriptions of two new species., Zootaxa 1315, pp. 1-56 : 3-6

Holohalaelurus Fowler 1934

Halaelurus (Holohalaelurus) Fowler, 1934 : 235.

Holohaelurus : Fowler, 1967 (in Compagno, 1984b).

Type species. Scylliorhinus regani Gilchrist 1922 .

Diagnosis. See Compagno (1988) for a comprehensive description of this genus. Holohalaelurus sharks are elongate scyliorhinid catsharks with a very long caudal peduncle and caudal fin; broad depressed heads lacking an upturned snout tip; nares lacking nasal barbels; ventral sensory pores conspicuously black in H. punctatus and H. regani , probably so in other Holohalaelurus species (although not visible with preserved specimens); relatively long, acutely arched mouths that lack labial furrows, with relatively large dentition, buccal papillae present and variably developed, or inconspicuous; denticles absent around external gill slit area; trunk moderately depressed; with or without denticles conspicuously enlarged from snout, or from above pectoral fin insertion, to first dorsal fin origin; pectoral fins high, long and winglike, with or without denticles enlarged on the dorsal surface in adults; anal fin low and long; the inner margin of the pelvic fins sometimes fused together to varying degrees, although never completely, not forming a complete pelvic fin curtain; claspers elongate in mature individuals with or without a distal club of papillae; moderate to extreme sexual dimorphism of overall size, with males larger than females.

The difference in total length at different stages of maturity between species is illustrated in Figure 1. Holohalaelurus regani is the largest Holohalaelurus at all stages of maturity for both sexes, with H. favus smaller at all stages. Holohalaelurus melanostigma is only slightly smaller than H. favus and sizes between these species overlap during the earlier stages of maturity. Holohalaelurus punctatus and H. grennian are dwarves of the genus, with H. punctatus marginally larger than H. grennian . The sexual dimorphism in H. regani and H. favus is particularly apparent at maturity stage 4.

Common name. Izak sharks, Izak catsharks, or hallelujah sharks.

Remarks. Originally described as a subgenus of Halaelurus by Fowler (1934), Holohalaelurus was subsequently raised to the rank of genus by Bigelow & Schroeder (1948). Although Holohalaelurus is closely related to Halaelurus , there are sufficient differences to warrant ranking Holohalaelurus as a genus (Compagno, 1988). Smith (1949) erroneously listed the type of Holohalaelurus as Scylliorhinus punctatus (as “genotype”). It should be noted that although the date of the proceedings that Fowler published his description of Holohalaelurus is shown as 1933, the publication date is 20th January 1934, hence is the date that should be referred to for these taxa, as has been done by Compagno (1984b) and Eschmeyer (1998).

The literature fundamental to the taxonomy of this genus are those papers that describe its included species (Gilchrist, 1914; Regan, 1921; Gilchrist, 1922; Fowler, 1934; Norman, 1939), revisions of the Scyliorhinidae of the east coast of southern Africa by Bass et al. (1975), and of the Carcharhiniformes by Compagno (1988). All other systematic or taxonomic works related to this genus have been based on the work of Bass et al. (1975) as part of larger revisionary works, with minor additions or notes.

A characteristic of this genus is that males are notably larger than females (Fig. 1), particularly in H. favus and H. regani as has been noted by many authors (Bass, 1973; Bass et al., 1975; Springer, 1979; Compagno, 1988; Richardson et al., 2000; present study). This is paradoxical as it is more often the case that females grow larger than the males in chondrichthyan fishes (Bass, 1973; Bass et al., 1975; Compagno, 1988; Richardson et al., 2000). This is a possible autapomorphy for Holohalaelurus , as is the naked patch of skin immediately surrounding the external gill slits.

There are five species that belong to the genus Holohalaelurus as determined from this review. The genus Holohalaelurus is comprised of H. punctatus (Gilchrist 1914) , H. regani (Gilchrist 1922) , H. melanostigma Norman 1939 , H. favus sp. nov., and H. grennian sp. nov.

Etymology. Holohalaelurus is derived from Holos (Greek) meaning entire, referring to the lack of labial folds in this genus, and the genus Halaelurus , for which Holohalaelurus was proposed as a subgenus of by Fowler (1934).

Distribution. Although Holohalaelurus sharks have been recorded as far north as Somalia (see accounts for H. grennian and H. regani ), this study can only confirm the presence of Holohalaelurus as far north as Kenya, although it is not unlikely that Holohalaelurus , particularly H. grennian or H. melanostigma , occur north of there. It is unlikely that H. regani occurs north of the South African-Mozambique border on the African east coast, and H. punctatus and H. regani appear to be allopatric to H. grennian and H. melanostigma . The confirmed presence of H. punctatus around Madagascar suggests that this shark may also be present around other west Indian Ocean archipelagos such as the Comoros Islands, for example.

Holohalaelurus melanostigma and H. grennian are largely sympatric in the tropical western Indian Ocean, however these species appear to be segregated by depth, with H. grennian occurring in water 238m to 300m deep, whereas H. melanostigma occurs in water 607m to 658m deep. Further sampling is needed to establish if this segregation is real, as there is no evidence of depth segregation between the sympatric species H. favus , H. punctatus and H. regani off kwaZulu-Natal and Mozambique, with the possible exception to preference for egg laying habitat and juvenile habitat in those species.

Key to the species of the genus Holohalaelurus (excludes H. regani and H. favus sp. nov. juveniles)

1a. No enlarged denticles on dorsal midline of body; buccal papillae very prominent; white spot at the origin of each dorsal fin ................................................... H. punctatus

1b. Denticles on dorsal midline moderately or greatly enlarged; buccal papillae less prominent to inconspicuous; white spot variably present at dorsal fin origins, but never at both dorsal fin origins ................................................................................................... 2

2a. Anal fin base length 1.5 or less times the length of pelvic fin base; club-shaped papillae present on distal tip of clasper in males; white spots present... H. grennian sp. nov.

2b. Anal fin base length 1.8 or greater times the length of pelvic fin base; club-shaped papillae not present on distal tip of clasper in males; white spots absent ..................... 3

3a. No enlarged denticles on dorsal surface of snout; “tear line” markings present from the origin of orbit to anterior margin of snout; no enlarged denticles on dorsal surface of pectoral fins in adults ........................................................................... H. melanostigma

3b. Enlarged denticles on dorsal surface of snout present; no “tear line” markings present on snout; enlarged denticles on dorsal surface of pectoral fins in adults ...................... 4

4a. Diameter of spots less than eye diameter in adults; not forming “horseshoe” shaped markings; snout broadly rounded and not coming to a point in adults; never more than one symphyseal tooth in each of the upper and lower jaws ................. H. favus sp. nov.

4b. Diameter of pattern markings greater than eye diameter in adults; forming “horseshoe” shaped markings; snout rounded and coming to a point in adults; up to six symphyseal teeth in each of the upper and lower jaws ........................................................ H. regani