Publicly accessible
URL: http://nzetc.victoria.ac.nz/collections.html
copyright 1951, by Victoria University of Wellington
All unambiguous end-of-line hyphens have been removed and the trailing part of a word has been joined to the preceding line, except in the case of those words that break over a page.
Some keywords in the header are a local Electronic Text Collection scheme to aid in establishing analytical groupings.
Publication of this paper is assisted by a grant from the Victoria University College Publications Fund.
The G. Typhlonarke is endemic to New Zealand and is represented by two species, T. aysoni and T. tarakea. Both species are blind electric rays with concealed eyes, one dorsal fin, pelvies modified for walking or burrowing, and large electric organs with many fewer columns per organ than Torpedo. T. aysoni is circular in outline and the marginal part of the disc is thin. T. tarakea has an ovoidal disc with a thick rim. Both species are marine bottom-dwellers in shallow water.
Compared with other countries, the New Zealand elasmobranch fauna is relatively poor in both genera and species. It is all the more remarkable, then, that in the small number of skates and rays in these waters, there are two species of blind electric rays (Typhlonarke aysoni and T. tarakea). T. aysoni is a well-recognized species, but T. tarakea was regarded by Whitley (Benthobatis moresbyi Alcock Narke (Bengalichthys) impennis (Annandale Benthobatis. Morphologically both are poor swimmers. It is doubtful that the thick-disced T. tarakea could swim at all, and in this species is found the greater independence of the pelvic appendage. In both species, the radial muscles of the pelvics are more heavily represented, particularly on the free appendage, than in Torpedo fairchildi. The mouth is apparently suctorial. The eyes are concealed by uninterrupted smooth skin, but, unlike Benthobatis, our species are from shallow water.
The G. Typhlonarke was established by Waite (T. aysoni (Hamilton G. Astrape but distinct in the form of the disc, junction of the disc and pelvics, the absence of functional eyes, and the short tail. Phillipps (T. aysoni as recognized by Waite (T. tarakea. The confusion of the two species rests in the absence of functional eyes and the form of other striking features which apparently detracted attention from the quite definite distinctions between the two. Both species are blind, shallow water, obviously benthic, and with quaintly modified pelvics; but T. aysoni is circular in outline, the margin of the disc is thin, and the claspers do not reach beyond the margin of the disc. T. tarakea has an ovoidal disc with a heavy thick rim, and the claspers are visible in dorsal view. Other features common to both species, and not mentioned
Torpedo marmorata has about 450 columns per organ). Waite (Typhlonarke though an optic nerve persists. Dissection of a number of specimens of both T. aysoni and T. tarakca shows (Plate 1, Fig. J) that the eye and optic nerve are present in both species, though the eye is not visible externally, being some 2.0 mm. under the surface of the skin in the subcutaneous fascia. Very delicate fibres inserted on the eyeball apparently represent vestiges of the ocular muscles.
Disc sub-circular, its outline broken only by a notch under the tail. Eyes not discernible. Spiracles with entire edges. Tail short, with a slight lateral fold. Dorsal fin single. Anterior portion of ventrals modified for walking; posterior portion coalesced with the pectorals to form the hinder margin of the disc. Teeth confined to the anterior portion of the jaws, pavement-like, the hinder series with sharp cusps. Body naked.
Study material.—Male 354 mm. T.L., female 244 mm. T.L. Collected by trawl from Cook Strait area.
Description.—Body greatly depressed, almost circular. Skin smooth, lacking dermal denticles. Length of disc 1.4 in the total length. Greatest width of disc at level of the last gill-slit; 1.6 in the total length. Greatest depth of body at the pectoral sympysis, 8.0 in the total length. Disc very much thinner peripherally. Caudal peduncle stout and slightly compressed.
Distance from anterior edge of disc to spiracles slightly more than depth of the body. Spiracles irregularly oval, their long axes directed outwards anteriorly. Margins of the spiracles produced into a definite rim. Eyes not visible externally, though a white patch anterior to each spiracle indicates their approximate position. Eyes very small, lying 1.0 mm. to 2.0 mm. below the surface of the skin. Gill-slits small, crescentic. Distance from anterior edge of disc to first gill-slit. 4.5 in the total length. Distance between first and second slits slightly greater than that between fourth and fifth and less than that between second and third or third and fourth. Nostrils fairly closely set, their posterior valves expanded and curled round, forming a nearly complete tube. Anterior nasal valves confluent as a fleshy nasal flap expanded distally and secured between the nostrils by a thick median septum, so that its wider free end almost covers the mouth. The extension of the nostrils and nasal flap makes a distinct step in the profile. Mouth small, slightly curved, and deeply inset, almost hidden externally by the nasal flap and the greatly enlarged, deeply incised lower lips. Teeth arranged in mosaic, varying from 10/10 to 12/12 per row. The tooth plates very narrow, extending across the median part of the jaws with four to five rows of teeth functional. Teeth in the posterior rows each with a single median cusp, long and sharply pointed, directed posteriorly. Anterior teeth with cusps eroded; cusps almost lacking in the first row.
Dorsal fin originating above the posterior insertion of the pectoral fin. Rectangular in shape, its height 1.5 in its basis and 2.0 in the distance from anterior edge of disc to spiracles. Posterior edge rounded and extending behind the posterior insertion of the fin. Origin of caudal just anterior to the posterior edge of the dorsal, its height slightly less than its length, outline subcircular. Pectorals completely fused into the body, their margins smoothly curved. Paired electric organs present, reniform in shape, extending from midway between the anterior edge of disc and the eyes, to midway between the pectoral and pelvic symphyses. The greatest width of each organ equal to little more than one-fourth the width of the disc. Origin of pelvics not quite half of total length, from anterior edge of disc. Anterior portion of each pelvic free, and produced into a broad flat appendage which when appressed is directed obtusely to the long axis of the body. Width of the appendage about 2.5 in its length. Posterior portion of the pelvic fused with the pectoral as an extension of the disc without any notch between it and the pectoral, though there is a short thick web separating them. Lateral margin smoothly rounded and a slight notch at the posterior insertion. Gaspers small
Colour.—Upper surface brown, darker posteriorly. Under surface creamy-brown. Underside of pelvic fin appendage almost white.
Size.—Most specimens taken are under 400 mm. in total length, though Whitley (
Distribution.—Foveaux Strait; the coast of Otago; Cook Strait; 28 to 102 fathoms.
References and Synonymy.—Astrape aysoni Hamilton, A. (T. tarakea). Typhlonarke aysoni: Waite, E. R. (
Study Material.—Male 266 mm. T.L., female 244 mm. T.L., female 206 mm. T.L. Collected by trawl from Cook Strait area.
Description.—Body greatly depressed, ovate in outline, tapering towards the peduncle. Skin smooth, lacking dermal denticles. Length of disc 1.4 in total length. Greatest width of disc at the level of the last two gill-slits, 2.0 in total length. Greatest depth of body at level of the last gill-slit, 7.5 in total length. Disc thinner peripherally but with a thick margin which is about 3.0 in the depth of the body. Caudal peduncle stout, slightly compressed.
Distance from anterior edge of disc to spiracles almost equal to the depth of body. Spiracles oval, their long axes directed outwards anteriorly. Eyes not visible externally, though a white patch anterior to each spiracle indicates their approximate position. Eyes very small, lying 2.0 mm. to 3.0 mm. below the surface of the skin in the subcutaneous fascia. Gill-slits small, crescentic. The first and fifth slits smaller than the others. Distance between first and second slits equal to that between fourth and fifth, and three-quarters to four-fifths of that between second and third or third and fourth. Nostrils very closely set, their posterior valves expanded and curled round, forming a nearly complete tube. Anterior nasal valves confluent as a fleshy nasal flap, slightly expanded distally and secured between the nostrils by a thick median septum, so that its wider free end almost covers the mouth. The extension of the nostrils and nasal flap makes a distinct step in the profile. Mouth small, slightly curved, and deeply inset, almost hidden externally by the nasal flap and the greatly enlarged, deeply incised lower lips. Teeth arranged in mosaic, 11/11 per row. Tooth plates very narrow, extending across the median part of the jaws, with four to five rows teeth functional. Teeth in the posterior rows each with a single median cusp, long and sharply pointed, directed posteriorly. Anterior teeth with cusps eroded so that in the first raw cusps are almost lacking.
One small dorsal fin originating slightly anterior to the posterior edge of the pelvics. Posterior edge rounded, extending behind the posterior insertion of the fin. Height of the fin 2.0 in its basis and 3.5 in the distance from anterior edge of disc to spiracles. Origin of the caudal just behind the posterior edge of the dorsal.
Colour.—Brownish-black above. Periphery of disc and ventral surface light brown. Lips, nostrils, and lower surfaces of the free parts of the pelvics, white. Cloacal aperture and openings of the endolymphatic ducts ringed with white.
Size.—Most specimens taken are under 300 mm. in total length, though a specimen 362mm. long was trawled off Otago Heads (Hamilton,
Distribution.—Otago Heads; Cook Strait; down to 130 fathoms.
References and Synonymy.—Astrape aysoni Hamilton. A. ((T. tarakea, not T. aysoni). Typhlonarke tarakea Phillipps, W. J. (