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Summary
(a) Species of Squalus from Australasia
(1) The genus Squalus (including Koinga and Flakeus but not Cirrhigaleus) contains three species groups—viz., S. acanthias group, S. blainvillii group and S. megalops-cubensis group. The best known and possibly only member of the S. blainvillii group has been currently recognised as S. fernandinus, but this is incorrect since the original diagnosis of S. fernandinus includes the words “corpore tereti ocellato”; hence S. fernandinus must be referred to the S. acanthias group whose members are the only Squalus species to have spots.
(II) The two New Zealand species of Squalus fall into the S. acanthias and S. blainvillii groups, and on comparison with North Atlantic specimens I am unable to separate them from S. acanthias Linnaeus and S. blainvillii (Risso). Similarly Squalus species of Australian waters are S. acanthias and S. blainvillii, plus S. megalops. S. kirki and S. whitleyi are synonyms of S. acanthias, and S. griffini is a synonym of S. blainvillii. Available data suggests that S. fernandinus and S. lebruni are also synonyms of S. acanthias. The distinction of S. cubensis from S. megalops is slight, and further examination of these is merited.
(III) Diagnostic criteria of the Squalus species groups are examined for change with growth. Proportional expressions of the position of the pelvic fin to the dorsal fins are most affected by growth since the pelvic 1 1st dorsal region grows at a faster rate than the pelvic 1 2nd dorsal. Lindberg's and Legeza's (1956) criteria for subspecies of S. acanthias are subject to growth change, and although New Zealand specimens fit to the short-finned S. acanthias acanthias there are insufficient data to validate their proposed subspecies.
(IV) Dermal denticles from all growth stages of Squalus species are identifiable to species groups. Juvenile form denticles of S. blainvillii are tridentate, but in S. acanthias and S. megalops are dagger-shaped.
(v) S. acanthias and S. blainvillii are described and illustrated; S. megalops is illustrated, and dimensions of three specimens are given.
(b) General Account of the New Zealand Squaloidea
(vi) The New Zealand squaloid fauna comprises ten genera and fourteen species—viz., Oxynotus bruniensis, Squalus acanthias, S. blainvillii, Etmopterus baxteri, E. lucifer, Centrophorus squamosus, Centroscymnus crepidater, C. owstonii, Scymnodon plunketi, Deania calcea, Dalatias licha, Scymnodalatias sherwoodi, Echinorhinus brucus and E. cookei.
(vii) Most of the New Zealand squaloid species are widely distributed in other seas. Etmopterus baxteri and Scymnodalatias sherwoodi are the only species apparently restricted to New Zealand, but they are deep-water species and likely to occur elsewhere. Of the remaining twelve species, two are shared only with Australia, one only with the North Atlantic, three only with the Indo-Pacific
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generally, while six are widespread or cosmopolitan. It is considered that many of the species have an even wider distribution than appears from current records.
(viii) Within New Zealand waters, Squalus acanthias and Oxynotus bruniensis are essentially southern species, while Squalus blainvillii is a northern species. All three are found mainly on the continental shelf and upper slope, and their distribution agrees with the disposition of surface currents. Other New Zealand squaloid species occur mainly in deeper water, and their distributional pattern is not yet known since too few areas of deep water have been investigated.
(ix) It is suggested that some deep water Australian squaloids will be found in New Zealand waters.
(x) A key is given for all genera of the Squaloidea, and for the New Zealand species; sufficient criteria are provided to exclude species new to the New Zealand fauna.
(xi) Change with growth of the proportional dimensions is examined in seven squaloid species. The data show that the trunk as a whole, but especially the anterior half, is a region of accelerated growth compared with the head and tail. The trunk length occupies from 5% to 12% more of the total length in adults than in juveniles. The dorsal fins are proportionately lower in adults, and usually longer as well than in juveniles. Within the head, the preorbital length remains proportionately, relatively constant, the eye length decreases, and the postorbital length increases with growth. The position of the mouth relative to the hind edge of eye is remarkably constant. Some examples of the effects of these growth changes are discussed.
(xii) Changes in the shape, sculpture or proportions of the dermal denticles with growth of the animal were observed in all squaloid species where sufficient material was available. Least change occurs in species with spine-like or thorn-like denticles. Most change occurs in species with blade-like denticles, and usually involves the addition of external ridging, the reduction of posterior marginal teeth, and a tendency for the blades to lie more nearly horizontal. Denticle bases usually become multiangled anteriorly. Exceptions are at the specific as well as the generic level; and similarity between juvenile form denticles does not necessarily mean similarity in the adult denticles.
Much, perhaps all, change follows from denticle replacement, which on the side of the trunk begins posteriorly and extends forward.