Holohalaelurus grennian, Brett A. Human, 2006

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 : 44-53

Holohalaelurus grennian sp. nov.

(Figs. 14-16, Table 5)

Scyliorhinus (Halaelurus) melanostigma : Norman, 1939: 9 (in part).

Holohalaelurus punctatus : Bass et al., 1975: 23 (in part); Springer, 1979: 93 (in part); Compagno, 1984b: 337 (in part); Bass, 1986: 93 (in part); Compagno, 1988: 156 (in part); Compagno et al., 1989: 54 (in part); Compagno et al., 1991: 80 (in part); Compagno, 1999: 98 (in part).

Holohalaelurus melanostigma : Compagno, 1999: 98 (in part).

Holohalaelurus spA : Compagno & Human, 2003: 12; Compagno et al., 2005: 238.

Type Series and Locality. Holotype, RUSI 13082 (previously PCH 80-28) , mature male 267mm TL, R.V. Fridtjoff Nansen station 872, 2°50’S 40°34’E, off Ras Ngomeni , Kenya, from 246m, collected by PC Heemstra, 12th December, 1980, in excellent condition (Fig. 14).

Paratypes, three specimens in three lots. BMNH 1939.5.24.5 (Fig. 15), paratype (“syntype”) in part of Scyliorhinus (Halaelurus) melanostigma Norman 1939 , juvenile female 206mm TL, John Murray Station 105 (station 105b according to depth data accompanying specimen), 5°34’24”S 39°14’06”E to 5°37’00”S 39°14’36”E, off Zanzibar , Tanzania, from 238-293m, in excellent condition. SAM 36077 (Fig. 16A), mature male 273mm TL, and SAM 36078 (Fig. 16C), juvenile male 165mm TL, R.V. Fridtjoff Nansen, off Dar es Salaam , Tanzania, from 300m, collected by G. Bianchi, 6th November - 4th December, 1982, both in excellent condition.

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.

Description. Morphometric and meristic data are given in Table 5. Holotype, mature male 267mm TL (paratypes, mature male 273mm TL, juvenile male 165mm TL, juvenile female 206mm 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, 0.30, 0.24) times the snout to first gill slit distance; mouth moderately long and relatively wide, acutely arched, buccal papillae in mouth inconspicuous, mouth width 2.24 (1.87, 3.37, 3.22, 2.50) times its length; eye slit like, eye length 2.41 (1.82, 2.50, 1.93, 2.19) times its height, distance from snout to the anterior origin of the orbit 0.59 (0.56, 0.67, 0.70, 0.63) times the snout to spiracle length; spiracle length 0.17 (0.23, 0.20, 0.34, 0.23) times the eye length; area around gill slits naked, lacking denticles; distance from snout to first dorsal fin origin 0.66 (0.64, 0.67, 0.66, 0.66) times the distance from the snout to the second dorsal fin origin; denticles on dorsal midline slightly enlarged beginning from a point level to the pectoral insertion on the dorsal midline to the first dorsal insertion; first dorsal fin length 2.10 (1.45, 2.03, 1.87, 1.85) times its height, length of the base of first dorsal fin 0.87 (0.89, 0.56, 0.62, 0.74) times the length of the base of second dorsal fin; second dorsal fin length 2.26 (2.38, 3.03, 2.24, 2.41) times its height; snout to pectoral origin length 0.52 (0.55, 0.57, 0.56, 0.55) times the snout to pelvic fin origin length; pectoral fin large and winglike, no enlarged denticles on the dorsal surface in adults, pectoral fin length 1.46 (1.48, 1.72, 1.44, 1.52) times its height; height of the pectoral fin 2.94 (3.59, 2.79, 3.25, 3.04) times the height of the pelvic fin; distance from pectoral insertion to pelvic origin 0.72 (0.76, 0.79, 0.66, 0.73) times the distance between the insertion of the second dorsal fin and the caudal fin dorsal origin; pelvic fin long and low, pelvic fin length 4.34 (5.82, 4.79, 4.88, 4.81) times its height, pelvic fin free rear tips variably fused, but never completely fused; claspers elongate with club-shaped papillae on the distal tips, clasper inner margin length 8.38 (7.80, 8.0, N/A, 8.27) times their base; snout to anal origin length 3.64 (2.90, 2.56, 2.68, 2.91) times the distance between the anal fin insertion and the origin of the ventral caudal fin; anal fin long and low, anal fin length 5.07 (4.74, 5.04, 5.88, 5.19) times its height; length of anal fin base 2.0 (1.66, 1.56, 1.86, 1.77) times the length of the second dorsal fin base; caudal dorsal margin length 1.78 (1.65, 1.48, 1.36, 1.56) times the interdorsal space, caudal ventral lobe weakly developed. Vertebral counts: 27 (28, 24, 27, 26.5) monospondylous, 50 (50, 49, 52, 50.3) precaudal diplospondylous and 27 (30, 17, 27, 25.3) caudal diplospondylous vertebrae. Dental formula: upper jaw (left) 19 (21, 20, 20, 20), symphyseal 3 (0, 1, 2, 1.5), (right) 21 (21, 19, 19, 20.0); lower jaw (left) 18 (18, 17, 19, 18.0), (symphyseal) 3 (4, 3, 0, 2.5), (right) 17 (17, 18, 22, 18.5).

Size and Sexual Maturity. Smallest of the Holohalaelurus sharks (Fig. 1 and Table 5), the maximum size recorded for H. grennian sp. nov. is 273mm TL. Males are juvenile at 165mm TL, and mature at 267mm TL and 273mm TL. Females are presumably juvenile at 206mm TL, however this may prove to be an underestimation of the maturity status, and size at maturity is not known for females.

Colouration. Holohalaelurus grennian sp. nov. is a stunningly patterned shark (Figs. 14-16); background dorsal colouration yellow brown with many small dark brown solid spots; white spots are present but are very few in number; large white spot above pectoral insertion, about level with the gill slits; white spots occasionally in front of dorsal fin origins, but never both dorsal fin origins; dark spots extending on to the dorsal fin bases and dorsal surfaces of the pectoral and pelvic fins, where they are enlarged, particularly so on the pectoral fin, sometimes developing into 2 short stripes near the rear margin of the pectoral fin; characteristic stripe present on both dorsal fins, stripe narrow and located half way along the posterior margins, the area immediately surrounding the stripe is a pale yellow, paler than the background colouration, the remainder of the dorsal fin is the same colour as the background dorsal colouration; the caudal fin tends to have dusky patches on the hypaxial fin web and on the terminal lobe. Ventral colouration is uniformly off white to pale grey, with no markings or spots, although the black sensory pores may be present on live or fresh specimens, spots usually visible through the fin web, fin webs darker.

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. 16B), 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.

Remarks. Norman (1939) included a female specimen, referable to this taxon, in his type series of H. melanostigma Norman 1939 , probably on the basis of ontogenetic and sexual dimorphism (see Remarks for H. melanostigma ). The collection of male specimens readily referable to the female “syntype” of H. melanostigma validates the recognition of this taxon as a separate species. The species level difference is illustrated by mature males of H. melanostigma being much larger than mature males of H. grennian sp. nov. (Fig. 1, Tables 3 and 5).

Bass et al. (1975) reservedly synonymised the female “syntype” of H. melanostigma with H. punctatus and noted the differences between it and H. punctatus caught off Natal. They illustrated the characteristic markings on the dorsal fin of H. grennian sp. nov. in their figure for H. punctatus .

Springer (1979) followed Bass et al. (1975) in synonymising BMNH 1939.5.24.5 with H. punctatus , although Springer did not examine the type series of H. melanostigma . In his discussion of H. punctatus , Springer (1979) describes a 205mm immature male that was trawled off Tanzania, which is almost certainly referable to this species given his description of the dorsal fin markings. Springer did not provide a precise locality for the trawl, a station number for the trawl, the depth that the shark was caught from, and apparently did not save the specimen.

Although BMNH 1939.5.24.5 has already been included in the type series of another species, it was decided to include this specimen in the type series of H. grennian sp. nov. because it is the only female specimen available, and is therefore unique, making it worthy of being included in the type series for H. grennian .

A distinguishing feature of this species is the club-shaped papillae found on the distal tip of the clasper (Fig. 16B). 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.

Distribution. Holohalaelurus grennian sp. nov. is endemic to the equatorial western Indian Ocean, confined to four degrees of latitude off of Kenya and Tanzania, at depths of between 238m and 300m (Fig. 17). The R.V. Fridtjof Nansen collected two specimens of this species in late 1982, off Dar es Salaam, however, no coordinates were recorded on the label accompanying the specimens, and the author was unable to trace the cruise.

It is likely that H. grennian occurs north of Kenya, and may be the source of records for Holohalaelurus off of Somalia (Fraser-Brunner, 1952 in Bass et al., 1975; see also Compagno, 1986, 1984b; Compagno et al., 1991, 2005).

Etymology. The species name comes from the old English, grennian, which means grin, and is in reference to the wide, broadly arched mouth, complete with relatively large dentition, that gives this shark the appearance of an ominous grin.

Common Name. Compagno & Human (2003) proposed the common name, grinning Izak. Compagno et al. (2005) referred to this species as the east African spotted Izak.

Study material. BMNH 1939.5.24.5, designated paratype of H. grennian n. sp., also paratype (in part) of H. melanostigma Norman, 1939 , see under Type Series and Locality for details; RUSI 13802, designated holotype of H. grennian n. sp., see under Type Series and Locality for details; SAM 36077, designated paratype of H. grennian n. sp., see under Type Series and Locality for details; SAM 36078, designated paratype of H. grennian n. sp., see under Type Series and Locality for details; unpublished line illustration by Igor Sidorenko, for Dr. S.I. Usachev, Indian Ocean Fish Resources Laboratory, Southern Scientific Research Institute of Marine Fisheries and Oceanography (YugNIRO), Kurch, Crimea, USSR (probably female, maturity unknown, length unknown, collection locality unknown, not part of the type series).

To the authors knowledge, these specimens are all of the known specimens referrable to this species.