Studies on New Zealand Elasmobranchii. Part XII.
The Species of Squalus from New Zealand and Australia; and a General Account and Key to the New Zealand Squaloidea* *
Squalus fernandinus Molina, 1782, diagnosed as “corpore tereti ocellato”, is referable to S. acanthias Linnaeus, 1758. Immaculate specimens currently recognised as S. fernandinus are S. blainvillii (Risso, 1826). Squalus spp. in New Zealand are S. acanthias and S. blainvillii, which occur also in Australia together with S. megalops (1 Macleay, 1882). In all three species the pelvic 1 1st dorsal region grows faster than the pelvic 1 2nd dorsal, but the rate is greatest in S. acanthias Dermal denticles from all growth stages of Squalus are identifiable to Bigelow and Schroeder's species groupings; juvenile denticles are broad tridentate in S. blainvillii but simple dagger-shaped in S. acanthias and S. megalops.
The Squaloidea is represented by ten genera and fourteen species in New Zealand. Ten of these species are widely distributed in other seas, two appear confined to Australasia, and two (Etmopterus baxteri and Scymnodalatias sherwoodi) are so far known only from New Zealand. Most are deepwater species of the continental slope. Predominantly shelf or upper slope species are S. acanthias, S. blainvillii and Oxynotus bruniensis; of these S. blainvillii has a northern distribution in New Zealand, while the other two are essentially southern species.
Proportional dimensions undergo considerable change with growth in the Squaloidea. The trunk, particularly the anterior half, is a region of accelerated growth, hence the trunk length from 5th gill-opening to caudal origin occupies 5% to 12% more of the total length in adults than in juveniles. The dorsal fins become proportionately lower and longer with growth. Within the head, the preorbital length is, proportionately, fairly stable, the preoral length and eye length decrease, and the postorbital length increases.
Most squaloid species exhibit changes in the shape, sculpture or proportions of their dermal denticles with growth. The changes are largely due to successional replacement of the denticles. Spine-like or thorn-like denticles differ little from juveniles and adults. Blade-like denticles change most, those of adult form usually lying more nearly horizontal, having additional ridging, and shorter posterior marginal teeth than denticles of juvenile form; but several exceptions occur.
The genus Squalus is represented in New Zealand by two species. These also occur in Australian waters, together with a third species. Since they were first reported the three species have been recognised under at least eleven different specific names. Most of these names have been relegated to synonymy, but the relationship of the three species with Squalus spp. elsewhere has not been made clear. It is the purpose of this paper to examine the Australasian species and to establish their identity.
Squalus, the type genus of the family Squalidae and the sub-order Squaloidea, includes those species having well developed fin spines lacking lateral grooves; caudal fin without a sub-terminal notch; a longitudinal dermal ridge along each side of the caudal peduncle; one-cusped, oblique, sectorial teeth, similar in upper and lower jaws; and nostrils of the usual selachian kind—i.e., the nostril margins are not produced as barbels. Synonyms of the genus include Flakeus Whitley, 1939 and Koinga Whitley, 1939 which were proposed for Australasian species, but
[Footnote] * This study has been assisted by grants from the Research Grants Committee of the University of New Zealand.
not Cirrhigaleus Tanaka, 1912 which Fowler (1941, p. 262) recognises as a subgenus of Squalus.
The genus is cosmopolitan and many regional species have been described, though the majority of these, like the Australasian examples, are now regarded as synonyms. The number of valid species is not yet definitely known, but four are recognisable on present information. These are, Squalus acanthias Linnaeus, 1758, S. blainvillii (Risso, 1826), S. megalops (Macleay, 1882), and S. cubensis Rivero, 1936. Decision on the status of other named species, particularly those from the southern hemisphere and the Indo-Pacific, must await critical comparison of material, though as Bigelow & Schroeder (1948, 1957) have shown it is possible to arrange them in three species groups having facies corresponding to those of S. acanthias, S. blainvillii and S. megalops-cubensis respectively. Present indications are that all named species of Squalus will fit into the above four species.
Diagnoses of the three species groups are as follows, adapted slightly from Bigelow & Schroeder (1957, p. 27), and illustrated in Text-fig. 1.
(a) S. acanthias group, the members of which generally have white spots along the upper half of the trunk, though in large specimens the spots may be faint or absent; the inner (posterior) corner of the pectoral fin rounded, the distal margin moderately concave; the 1st dorsal spine over or behind the inner corner of the pectoral, such that the distance from origin of exposed spine to 5th gill-opening is at least as long as the distance from anterior edge of eye to 5th gill-opening; the midpoint of pelvic base about midway between perpendiculars at posterior free tip of 1st dorsal fin and exposed origin of 2nd dorsal spine; the anterior nasal flap simple, triangular.
(b) S. blainvillii group, with uniform coloured members, not spotted at any stage of growth; the inner pectoral corner and distal pectoral margin as in S. acanthias group; the 1st dorsal spine over or anterior to the inner pectoral corner, such that the distance from origin of exposed spine to 5th gill-opening is not more than the distance from anterior edge of eye to 2nd gill-opening; the midpoint of pelvic base generally nearer to a perpendicular at posterior free tip of 1st dorsal fin than to one at exposed origin of 2nd dorsal spine, the anterior nasal flap complex, bilobed.
(c) S. megalops-cubensis group with members similar to those of S. blainvillii group in colour, relative positions of fins and shape of nasal flap, but differing in having the inner pectoral corner pointed, the distal pectoral margin deeply concave, and in the dermal denticles.
It should be noted that group (b), named here S. blainvillii, is named S. fernandinus in Bigelow & Schroeder (1957, p. 29), who like the other authors they refer to, regard S. blainvillii as a synonym of S. fernandinus. There is no doubt that S. blainvillii and S. fernandinus as recognised by Bigelow & Schroeder are the same species—i.e., uniform coloured forms with characters as outlined above. The use of the name S. fernandinus for these forms is of fairly long standing, dating back at least to Garman (1913, p. 195). It has been followed also by Lahille (1928, p. 326), by Fowler (1941, p. 261), by Bigelow & Schroeder (1948, p. 478), by Smith (1950, p. 60), by Bigelow, Schroeder & Springer (1953, p. 220) and many others. The New Zealand representative of the group was suggested as S. fernandinus by Richardson & Garrick (1953, p. 36). This usage is erroneous. The original account of S. fernandinus by Molina (1782, p. 229), based on material from Juan Fernandez off Chile, is not readily available, but Dr. D. E. Tucker, of the British Museum has kindly supplied me with a transcript of it. The relevant descriptive portion is as follows:
“Il Tollo, Squalus fernandinus* è una specie di Pesce cane, un poco più grande del pesce gallo, rimarchevole per due spine, che ha sul dorso, come lo Squalus
[Footnote] * Squalus pinna anali nulla, dorsalibus spinosis, corpore tereti ocellato.
Text-fig. 1.—Australasian species of Squalus, drawn from specimens of comparable size. Figs. C. F. and I are of the right nostril. Figs. A–C—Squalus acanthias, male, 540 mm, Otago, New Zealand. Figs. D-F—Squalus blainvillii, female, 545 mm, Bay of Plenty, New Zealand. Figs. G-I—Squalus megalops, female, 555 mm, Victoria, Australia.
acanthias, le qualí sono triangolari, ricurvate verso la punta, dure come l'avorio, lunghe due pollici e mezzo, e larghe in ciascuno de' lati da cinque linee.
The brief diagnosis at the end of the account, describing the body as being spotted leaves no doubt that Molina's material belongs to the S. acanthias group, for in the S. blainvillii group and the S. megalops-cubensis group there are no spots on the body at any stage of growth. The only disturbing feature in this interpretation is the dorsal spine size quoted by Molina—viz., two and a-half inches long and five lines wide. Spines of these dimensions would denote an abnormally large specimen of S. acanthias, but could be more readily attributed to the heavy-spined S. blainvillii. However, I do not regard this as a decisive factor compared with the diagnosis of the body being spotted.
Mr. W. C. Schroeder, of Woods Hole Oceanographic Institution, informs me that he and Dr. H. B. Bigelow have seen only a French version of Molina's account, published in 1789, which unfortunately omitted the diagnosis given in the originial. This suggests a possible source for other misinterpretations of the affinities of S. fernandinus. Whatever the reason, there has been considerable confusion in the literature, since some authors and particularly Jordan & Evermann (1896, p. 54), Regan (1908, p. 46), Norman (1937, p. 9) and various others following Regan and Norman correctly attributed S. fernandinus to the S. acanthias group. As is shown in the section below dealing with Australasian members of the S. acanthias group, there is little cause for believing that S. fernandinus is even specifically distinct from S. acanthias, though final decision on this must await critical comparison of material from southern South America, the type locality of S. fernandinus.
The two New Zealand species of Squalus fall into the S. acanthias and S. blainvillii groups respectively. Compared with North Atlantic specimens of about equal size, I cannot separate my material from the species S. acanthias and S. blainvillii. The Australian fauna similarly includes S. acanthias and S. blainvillii, as well as a third species, S. megalops, the last representing the S. megalops-cubensis group.
As the material available for this study covers a fairly extensive size-range, it provides an opportunity for examining the affect of growth on those features currently used for diagnosing Squalus species. In this respect I find that the dimensional feature most affected by growth is that of the position of the pelvic fin relative to the dorsal fins. In S. acanthias the pelvic fin is relatively further rearward than it is in S. blainvillii, S. megalops or S. cubensis. Various means of expressing this difference have been put forward, but not all of these have been successful (for an example see Bigelow & Schroeder, 1948, p. 453; 1957, p. 27). Some at least of the reasons for the difficulties encountered can be seen in Text-fig. 2 where eight New Zealand specimens of S. acanthias and six of S. blainvillii are compared. It can be noted that juveniles of both species have similar proportions, the pelvic fin being much nearer to the 1st dorsal than to the 2nd dorsal. Both species undergo growth change of a similar nature, the pelvic to 1st dorsal region growing at a faster rate than the pelvic to 2nd dorsal region. At the same time the interspace between the 1st and 2nd dorsal fins comes to occupy a proportionately greater percentage of the total length. The difference between the species appears to lie in a faster prepelvic growth rate in S. acanthias, with the result that middle-sized specimens of S. acanthias have the pelvic fin only slightly nearer to the 1st dorsal than to the 2nd, while in S. blainvillii this condition does not occur until adult size is reached. Further growth of S. acanthias—i.e., from middle to adult size, results in the pelvic fin coming to lie about midway between the 1st and 2nd dorsals and thus increases the difference between the two species since this more posterior position of the pelvic is not attained by S. blainvillii. From this it is obvious that any expression of the position of the pelvic fin relative to the dorsals will need qualification to cover at least small and large specimens. In this respect.
the following is suggested as a preliminary step until sufficient data are available to allow more accurate diagnoses to be made.
(a) S. acanthias: midpoint of pelvic base nearer to a perpendicular at posterior tip of 1st dorsal than to one at exposed origin of 2nd dorsal spine in juveniles and half-grown specimens, but about midway between these levels in larger specimens.
(b) S. blainvillii (and also S. megalops-cubensis): midpoint of pelvic base always nearer to a perpendicular at posterior tip of 1st dorsal than to one at exposed origin of 2nd dorsal spine.
The position of the 1st dorsal spine relative to the inner (posterior) corner of the adpressed pectoral differs strongly between S. acanthias and S. blainvillii when
specimens of equal size are compared (Text-fig. 1), but again because of growth change there is overlap in this feature when complete size-ranges are examined. Thus juveniles of S. blainvillii have the 1st dorsal spine about midway between the levels of the axil and inner corner of the pectoral, while in adults it is further rearward, about over the inner corner. In S. acanthias the spine is over the inner corner in juveniles, but well behind this level in adults. This more rearward position of the 1st dorsal spine in S. acanthias has been made use of recently by Bigelow & Schroeder (1957, p. 27), who, in characterising their species-groups, find that the distance from spine to 5th gill-opening is not less than the distance from the anterior edge of eye to 5th gill-opening in S. acanthias, but not more than that to the 2nd gill-opening in S. blainvillii, S. megalops and S. cubensis. The present study confirms their account except for newly-born S. acanthias, which may be similar to larger S. blainvillii.
Other structures undergoing considerable change with growth of the animal are the dermal denticles. In the adult these have already been shown to be specific in form by Bigelow & Schroeder (1957, fig. 3). The differences are shown here to be evident in all stages of growth as illustrated in the series of denticle forms in Text-fig. 3. The figures show that the closest similarity between the species is in the newly erupted denticles of embryos of S. blainvillii and S. megalops, but even here the denticles differ sufficiently in lateral view to be easily recognisable. Likewise the adult form denticles of S. acanthias and S. blainvillii are closely similar in outline but differ in the shape and length of the anterior prolongation of the median longitudinal ridge.
Two other differences between the species have become apparent during the course of the study. The first of these is the pupil size, which in S. acanthias is only about ¼ of the horizontal diameter of the eye, but in S. blainvillii and S. megalops is ⅓ or ½ (Text-fig. 1). The second is the heavy-bodiedness of S. megalops compared with S. acanthias or S. blainvillii. This is also shown in Text-fig. 1 where it is obvious not only in profile but in the contour of the head. However, all three species, and particularly S. blainvillii and S. megalops, become heavier-bodied with growth. As a consequence, dimensions such as height of body or width of head, which could show the differences, tend to overlap, and hence no difference may be apparent when specimens of different total lengths are compared.
Squalus acanthias Linnaeus, 1758. Text-fig. 1, A-C; Text-fig. 3, G-N; Text-fig. 5, A-F.
This species was reported from New Zealand by Hutton (1872, p. 76) as Acanthias vulgaris Risso, 1826, a name at that time current for the white-spotted dogfish of the North Atlantic and Mediterranean which we now know as Squalus acanthias. In a later account, Hutton (1904, p. 54) listed the species as S. acanthias, as did Waite (1907, p. 8). Regan (1908, p. 46), believing that the white-spotted dogfish of southern South America, southern Australia and New Zealand differed from S. acanthias, referred it to S. fernandinus Molina, 1782, a species first described from Juan Fernandez, off Chile. As I have shown above, the type description of S. fernandinus is inadequate, but since the diagnosis includes the words “corpore tereti ocellato”, Molina's species is at least a member of the S. acanthias group. Regan regarded S. fernandinus as having a shorter snout, “praeoral length equal to or less than the distance from eye to first gill-opening, the praeocular length equal to the distance from anterior edge of eye to spiracle (more in S. acanthias, except in young examples).” Comparison of Regan's findings with data assembled on white-spotted Squalus species under various names from New Zealand, north western Atlantic, Argentina and Patagonia in Table I does not confirm the distinction of a southern circumpolar species. The data do indicate a tendency for the features cited by Regan to be affected by growth change. Thus with increase
Text-fig. 3.—Dermal denticles from several growth stages of Squalus species. All denticles are from high on the side at the level of the 1st dorsal fin. Figs. A–F—Squalus blainvillii, New Zealand. Fig. A—Embryo, 218 mm, Cape Egmont (Dom. Mus. No. 2246). Fig. B—Lateral view of denticle from Fig. A. Fig. C—545 mm, female, Bay of Plenty (Dom. Mus. No. 2759). Fig. D—923 mm female, Cook Strait (Dom. Mus. No. 2647). Figs. E–F—Apical and lateral views of denticle from Fig. D. Figs. G–M—Squalus acanthias, New Zealand. Fig. G—Embryo, 228 mm, Cook Strait (Dom. Mus. No. 2645). Fig. H—Lateral view of denticle from Fig. G. Fig. I—627 mm, male, Otago. Fig. J—772 mm, female, Queen Charlotte Sound (Dom. Mus. No. 942). Fig. K— 935 mm, female, Cook Strait (Dom. Mus. No. 1255). Figs. L–M—Apical and lateral views of denticle from Fig. K. Fig. N—1,002 mm, female, Cook Strait. Figs. O–T—Squalus megalops, Australia. Fig. O—Embryo, 228 mm, Tasmania. Fig. P—Lateral view of denticle from Fig. O. Fig. Q—370 mm, female, New South Wales (Austral. Mus. No. IB–4256). Fig. R–555 mm female, Victoria. Figs. S–T—Apical and lateral views of denticle from Fig. R.
in total length the preoral length decreases relative to the distance from eye to 1st gill-opening; likewise the distance from anterior of eye to spiracle decreases relative to the preocular length. The only data which do not fit this picture are those from Vaillant (1888), and perhaps those from Norman (1937) on Argentinian specimens, but in both cases the dimensions are extracted from illustrations in these authors. On the basis of New Zealand (and Australian) material I can find no reason for retaining S. fernandinus as a distinct species, while the close correspondence of Devincenzi's (1939) data with mine suggests that the Patagonian species which he recognises as S. lebruni is similarly S. acanthias.
|Species||Locality||Length in mm and sex||Preoral length as % of distance from eye to 1st gill-opening||Distance from ant. of eye to spiracle as % of preocular length|
|Squalus acanthias||New Zealand||228 ♂||142||80|
|Squalus acanthias (1)||Massachusetts (U.S.A)||343 ♂||149||76|
|Squalus lebruni (2)||Patagonia||420 —||122||93|
|Squalus lebruni (3)||Patagonia||470 —||114||87|
|Squalus acanthias||New Zealand||540 ♂||119||75|
|S. lebruni (4)||Argentina||600 ♂||105||88|
|S. acanthias||New Zealand||627 ♂||126||68|
|S. acanthias||New Zealand||708 ♀||108||64|
|S. acanthias||New Zealand||772 ♀||118||67|
|S. acanthias||New Zealand||800 ♀||112||62|
|S. acanthias (5)||Massachusetts (U.S.A)||815 ♀||130||71|
|S. acanthias||New Zealand||935 ♀||104||62|
|S. acanthias||New Zealand||950 ♀||120||70|
|S. acanthias||New Zealand||990 ♀||117||64|
Specimen kindly sent by W. C. Schroeder, of Woods Hole Oceanographic Institution.
From data in Devincenzi (1939, p. 5).
Data extracted from illustration in Norman (1937, fig. 2).
Data extracted from illustration in Bigelow & Schroeder (1948, fig. 87 A).
Data extracted from illustration in Vaillant (1888, Pl. 1, fig. 2).
Following Regan's (1908) account, Waite (1909), Phillipps (1921, 1927, 1928) and Thomson (1921) reported the New Zealand white-spotted dogfish as S. fernandinus, while Rendahl (1926) listed it as S. acanthias
Phillipps (1931, p. 360) rejected the name S. fernandinus for the New Zealand white-spotted dogfish and described it as a new species, S. kirki. This was based on a comparison of New Zealand material with S. fernandinus as described by Lahille (1928, p. 326) from a specimen off Argentina. But Lahille's account is not of a specimen of the S. acanthias group, but of a specimen having the features of the S. blainvillii or S. megalops-cubensis groups—i.e., the 1st dorsal spine over the middle of the inner pectoral margin, the distance from exposed origin of the 1st dorsal spine to 5th gill-opening less than the distance from anterior of eye to 1st gill-opening, and a uniform colour, without spots. It therefore follows that Phillipps's species, S. kirki, was described without reference or comparison to the S. acanthias group in which it belongs.
Whitley (1934, 1940) follows Phillipps (1931) and recognises S. kirki in Australian as well as New Zealand waters. Fowler (1941) lists it as a nominal species, since he had not seen material. Norman (1937, p. 9) synonymises S. kirki with S. lebruni (Vaillant, 1888) which he believes to be the only spotted Squalus in the
southern hemisphere. His diagnosis for S. lebruni is exactly the same as that given earlier for S. fernandinus by Regan (1908), and hence for the same reasons prevent the recognition of S. lebruni as distinct from S. acanthias. The synonymy of S. lebruni given by Norman includes, with interrogation marks, Molina's original description of S. fernandinus whose status, apparently, Norman could not definitely decide on Vaillant's (1888, p. 13) account of S. lebruni, based on seven specimens from “Baie Orange: Punta-Arenas” adds little more except that the largest specimen, 700 mm long, had upper teeth more or less tricuspid in form. However from Vaillant's description and illustrations (1888, Pl. 1, fig. 2a) it is apparent that the teeth of his largest specimen were peculiar and not seen in the other material.
The only remaining accounts of the New Zealand species are those of Richardson and Garrick (1953, p. 36) who in a provisional key to the Squalidae follow Norman in recognising S. lebruni, and Phillipps (1946, p. 14) who retains S. kirki as distinct from S. acanthias on the basis of minor differences in the teeth. The differences cited by Phillipps were made on comparison of North Atlantic and North Pacific specimens of S. acanthias with New Zealand material, but I am not able to confirm them in a similar comparison. Undoubtedly differences in the teeth are present from specimen to specimen, but these seem to cover as wide a range in New Zealand specimens as occurs in the North Atlantic and Australian specimens that I have had available.
The above resumé shows that none of the features suggested in the literature for separating the New Zealand white-spotted Squalus from its counterparts elsewhere in the southern oceans, or from the North Atlantic S. acanthias can be sustained. Moreover, comparison of my material with the excellent description of S. acanthias in Bigelow and Schroeder (1948, p. 455) and with a north-western Atlantic specimen kindly supplied by Mr. W. C. Schroeder, of Woods Hole Oceanographic Institution, has not shown any feature in dimensions, morphology or details of teeth, denticles or colour pattern in which they differ. The New Zealand species is therefore to be recognised as S. acanthias.
Through the courtesy of Mr. G. P. Whitley, Australian Museum, and Mr. A. M. Olsen, C.S.I.R.O., Tasmania, I have been able to examine Australian specimens which are likewise referable to S. acanthias. The synonymy for the Australian spotted dogfish parallels that of the New Zealand one, but should include also S. whitleyi Phillipps, 1931, which though illustrated by McCoy (1883, Pl. 75) as lacking preoral clefts is obviously S. acanthias.
The existence of two subspecies of S. acanthias in the northern hemisphere has been suggested by Lindberg & Legeza (1958, p. 1685). They recognise S. acanthias acanthias and S. acanthias suckleyi, both of which occur in the North Atlantic and North Pacific but apparently do not overlap in their distribution. S. acanthias acanthias has been found in the North Sea, Mediterranean, Black Sea, Sea of Japan, southern part of the Sea of Okhotsk, and north-eastern Japan, while S. acanthias suckleyi is recorded from California, Murman and the White Sea. The basis on which Lindberg and Legeza recognise their subspecies is the length of the anterior pectoral margin compared with the distance from the 5th gill-slit to the centre of the nostril. S. acanthias acanthias is a short-finned form, the length of the pectoral margin ranging from 60.0% to 89.9% (average 76%) of the distance from 5th gill to nostril, while S. acanthias suckleyi is long-finned, the pectoral ranging from 101.0% to 110.5% (average 106%)
To see where the New Zealand form of S. acanthias fits into this picture, measurements of ten specimens 230 mm to 990 mm long were made. These had a range of pectoral length from 65.0% to 98.0% of the distance from 5th gill-opening to nostril. This range overlies the greater part of that for the short-finned S. acanthias acanthias, but also bridges the gap between the two subspecies. It was noted that the pectoral length increased relative to the 5th gill-opening to nostril length with
growth, hence to give a clearer picture the data from the New Zealand specimens and from Lindberg and Legeza were plotted against total length (Text-fig. 4). This shows a considerable reduction in the percentage ranges of Lindberg and Legeza's subspecies when only specimens of comparable size are examined—e.g., in the sizerange 630 mm to 900 mm total length, S. acanthias acanthias has percentages of 79. 0% to 90.0% S. acanthias suckleyi 101.0% to 110.5%, and the New Zealand specimens 82.0% to 91.0%. The New Zealand specimens clearly fit to S. acanthias acanthias. However it is unfortunate that Lindberg & Legeza have so few data for S. acanthias suckleyi, particularly from specimens of smaller size. Additional data might well show even less distinction between the subspecies, or possibly invalidate them.
The distribution of S. acanthias in New Zealand is essentially southern. The species is common on the continental shelf in Cook Strait and southwards on the.
Length of anterior margin of pectoral fin as % of distance between pectoral origin and centre of nostril.
east coast, but information is lacking as to its presence on the west coast of the South Island. North of Cook Strait it ranges at least to Poverty Bay on the east coast, and possibly extends to East Cape. It is uncommon on the west coast of the North Island, but is known as far north as New Plymouth.
Its distribution elsewhere is widespread, and it or very closely related forms of the S. acanthias group are circumpolar, occurring in temperate, subarctic and subantarctic waters of all oceans. For details of the distribution see Bigelow & Schroeder (1957, p. 30).
Squalus acanthias Linnaeus, 1758.
Squalus kirki Phillipps, 1931.
Squalus whitleyi Phillipps, 1931.
(a) New Zealand: Two females 935 mm and 990 mm (Dom. Mus. No. 1255 from 40–50 fathoms, Cook Strait; three females, 950 mm to 1, 002 mm, from Castlepoint; female, 772 mm (Dom. Mus. No. 942) from Queen Charlotte Sound; three females, 708 mm (Dom. Mus. No. 2732), 800 mm (Dom. Mus. No. 2733) and 965 mm, and two males, 540 mm and 627 mm, from 20 fathoms off Otago; embryo, 228 mm (Dom. Mus. No. 2645, from female taken in Cook Strait; also numerous other specimens of all sizes, mainly from Cook Strait and Otago.
(b) Elsewhere: Male, 343 mm (Mus. Comp. Zool. No. 36457), Buzzards Bay, Massachusetts; three specimens, including an embryo from Tasmania, one of these Austr. Mus. No. IB. 1008; Jaws of two specimens from the English Channel (Dom. Mus. No. 2698).
|♂ 228 mm (embryo)Dm. Mus. No. 2645||♂ 540 mm||♀ 772 mm Dm. Mus. No. 942||♀ 935 mm Dm. Mus. No. 1255|
|Trunk at pectoral origin: Breadth||11.3||11.6||12.0||11.8|
|Snout Length in front of: Outer nostrils||4.6||3.5||3.5||3.7|
|Eye: Horizontal diameter||4.4||3.3||3.0||2.7|
|Nostrils: Breadth between inner corners||4.4||3.1||3.4||3.3|
|Preoral clefts: Breadth between inner corners||6.6||5.0||5.4|
|Gill-opening lengths: 1st||1.7||1.8||1.7||2.0|
|1st Dorsal fin: Vertical height||5.9||5.8||5.8||6.0|
|Length of base from origin of spine||4.8||5.0||5.3||5.7|
|2nd Dorsal fin: Vertical height||3.9||4.0||3.5||3.7|
|Length of base from origin of spine||3.1||3.1||3.5||3.7|
|Caudal fin: Upper margin||22.2||20.8||20.2||20.0|
|Lower anterior margin||11.8||10.7||10.8||10.4|
|Pectoral fin: Anterior margin||11.8||13.7||14.6||15.1|
|Distance from snout to: Eye||6.8||5.9||5.8||5.7|
|1st dorsal spine||37.2||34.5||35.4||34.7|
|2nd dorsal spine||64.8||65.0||65.6||66.2|
|Interspace between: 1st dorsal base and 2nd dorsal spine||23.6||26.3||25.3||26.2|
|2nd dorsal base and upper caudal||10.9||11.3||11.0||11.2|
|Pelvic and lower caudal||22.7||22.6||22.2||21.4|
|Distance from origin to origin of:|
|Pectoral and pelvic||26.9||31.0||33.0||35.1|
|Pelvic and lower caudal||27.5||27.0||26.8||26.2|
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Head depressed, the eye rather small and the snout profile pointed; trunk slender, slightly compressed, sometimes with a feeble dermal longitudinal ridge along the dorsal midline between the 1st and 2nd dorsal fins. The dorsal profile in front of the 1st dorsal fin more arched than the ventral. Height of trunk at origin of pectorals 1/9th of its length to origin of caudal. Length of body measured to cloaca 55.0% to 56.5% of the total length Caudal
peduncle rounded above but flat below, and with a low dermal keel each side below the mid-level; the keels extend from just behind the posterior insertion of the 2nd dorsal base to about one-quarter of the distance along the caudal axis. A shallow upper precaudal pit is present, marking the origin of the epiural lobe; no lower precaudal pit.
Dermal denticles on sides of trunk somewhat spaced so that there are interspaces between them where the skin is exposed. In the 772 mm female they are mostly spearhead shaped, with a high median spine-like ridge, and a rhomboidal base; but in addition there are some larger denticles with tridentate blades. In the 935 mm female the denticles on the side of the trunk are nearly all of the tridentate form, and are more closely arranged, particularly on the posterior half of the trunk. Elsewhere on the body the denticles differ considerably in shape and sculpture, those from the caudal axis being less strongly tridentate and with a heavier median ridge; those from the interorbital region with heavy median and lateral ridges but no lateral teeth on the obtusely pointed blades, and those from the upper and lower lips almost sessile, the ridges lacking or reduced, and the blades obtusely pointed without lateral teeth.
Head measured to 1st gill-opening 6.5 to 6.6 in the total length. Head depressed and wedge-shaped in profile so that the snout tip is pointed. The least fleshy interorbital distance 2.3 in the head. Snout contour narrow and pointed, increasing smoothly in width to the level of the gill-openings. Length of snout measured to the eye 2.7 in the head. Eye longer than high, and 2.4 to 3.0 in the preoral length. Spiracle large and placed just above the dorsal margin of the eye and behind it by a distance equal to its own length. Gill-openings almost vertical, slightly concave, and in a horizontal series anterior to the pectoral base. Lengths of the gill-openings increasing slightly from the 1st to the 5th, the latter 1.2–1.3 in the horizontal diameter of the eye. Interspaces between the gill-openings subequal, though that between the 1st and 2nd is slightly greater than any of the others. Nostrils almost transverse and placed halfway between tip of snout and mouth. Interspace between nostrils 1.9 in snout measured to eye. Each nostril subdivided into a circular lateral aperture and an ovoid medial aperture by the anterior and posterior nasal flaps. The anterior nasal flap is triangular, directed posteriorly, and external to the fleshy posterior flap. The medial margin of the anterior nasal flap is smoothly concave in most specimens, but can have a minute lobe half-way along its length in others. Mouth broad and only slightly arched, its width 1.4 in the preoral distance. Preoral clefts short, reaching less than half the distance from the angles of the mouth to the upper symphysis; posteriorly the clefts are continued by oblique furrows which extend one-third of the distance between the angles of the mouth and the 1st gill-openings.
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Teeth 12-14/11-12 in a 1,002 mm female, similar in the two jaws. Each tooth blade-like, with a base broader than high, and a single, smooth-edged, triangular cusp. The cusps are deeply notched on their lateral margins and so strongly oblique that their medial margins overlap from one tooth to the next and form a continuous cutting edge. The medial margins are slightly sinuous, especially towards the tips of the cusps which turn slightly downwards in the upper teeth, and slightly upwards in the lower teeth. In both the upper and lower jaws, the teeth at the centre of the mouth are distinctly smaller than those towards the corners; while in general the lower teeth are noticeably larger than the uppers. One or two lows of upper and lower teeth functional depending on the stage of replacement.
1st dorsal large, triangular, originating behind the level of the posterior corner of the pectoral fin by a distance not more than the horizontal diameter of the eye. The posterior insertion of the 1st dorsal base is midway between the levels of the axil of the pectoral and the origin of the pelvic in large specimens, but nearer to the origin of the pelvic in small specimens. Height of 1st dorsal equal to posterior part of its base measured from the origin of the spine, and also to the snout length measured to the eye. The 1st dorsal spine dusky-coloured, at least on its anterior surface, slightly curved, long and well exposed; its tip extending half-way up the anterior margin of the fin. Anterior and posterior margins of the 1st dorsal fin almost straight, distal margin concave and apex rounded. Length of posterior margin less than length of posterior part of base measured from origin of spine; posterior tip sharply pointed. The 2nd dorsal originating over posterior tips of the pelvics; smaller than the 1st and relatively more elongate, its height 1.7 in that of the first dorsal, and its base measured from origin of spine 1.5 in base of 1st dorsal. The distal margin strongly concave, and the posterior margin equal to or more than the length of base measured from origin of spine. 2nd dorsal spine dusky, longer than the 1st and reaching ⅔ or more of the distance to apex of fin. Caudal measured from hypural origin 5.0 in total length; epiural lobe well developed and without a subterminal notch, its upper margin almost straight, its lower margin smoothly curved, and the apex acutely rounded. Hypural lobe about half as long as the epiural, its anterior margin convex and its apex acutely rounded; angle between the posterior margin of the hypural and that of the epiural just more than a right angle and
Text-fig. 5.—Squalus acanthias, female, 935 mm (Dom. Mus. No. 1255) from New Zealand. Fig. A—Lateral view and insets of transverse sections of snout and peduncle. Figs. B and C—Dorsal and ventral views of head. Fig. D—Right nostril. Figs. E and F—Female, 1,002 mm, upper and lower teeth, right side. C=Level of cloaca.
smoothly rounded. Origin of the hypural just anterior to the epiural. Pectorals large and triangular, originating just behind the 5th gill-opening. The anterior pectoral margin smoothly convex, its length 1.7 to 2.0 times the width of the fin and just less than the distance from snout tip to 1st gill-opening; posterior margin almost straight, and distal margin distinctly concave. Anterior angle of the pectoral acutely rounded, the posterior angle just less than a right angle but smoothly rounded. Pelvics entirely anterior to the 2nd dorsal fin, shallowly triangular, their length of base about 1.5 times their height, and slightly more than the length of base of the 2nd dorsal measured from the origin of the spine. Anterior, posterior and distal margins straight, apex smoothly rounded and posterior tip sharply pointed.
Colour: Grey above, merging to brownish-white below. Two rows of white spots along the upper half of the trunk on each side, one row following the lateral line, the other nearer to the dorsal midline. Large specimens have fewer spots than small specimens, and occasionally lack them altogether. In most specimens, the lateral line row includes one spot anterior to the 1st gill-opening, two spots above the pectoral origin, one or two above the axil of the pectoral, and one to three beneath the 1st dorsal fin; behind the dorsal fin there may be further lateral line spots on juvenile specimens but they are not distinct in adults. The more dorsal row of spots includes one spot just in front of the 1st dorsal, one to four spots between the posterior tip of the 1st dorsal and the origin of the 2nd dorsal, and one or two spots between the posterior tip of the second dorsal and the origin of the caudal. In addition to the above, many specimens also have two white spots low down on the side of the trunk, one just above the 1st gill-opening, the other halfway along the base of the pectoral. In juvenile specimens the apices of the dorsal fins, and the tip of the caudal fin may be black.
Squalus blainvillii (Risso, 1826). Text-fig. 1, D-F; Text-fig. 3, A-F; Text-fig. 6, A-F
The first report of this species from New Zealand was by Regan (1914, p. 14) who recorded it as Squalus megalops (Macleay, 1882). Regan's record was based on a pregnant female taken in ten fathoms off North Cape, but apparently only the embryos were preserved. Through the courtesy of Dr. D. W. Tucker of the British Museum, I have been able to examine one of these embryos, a female 144 mm long with a large yolk-sac attached. The embryo shows the characters of S. blainvillii rather than S. megalops—i.e., the inner (posterior) pectoral corner is about a right angle, and is distinctly rounded. The identification is confirmed by the dermal denticles, for although these are only beginning to erupt on the skin from the side below the 1st dorsal fin, they are definitely tridentate as seen in a stained and cleared sample. This agrees only with S. blainvillii, for in S. megalops (and also in S. acanthias) the denticles of embryos and juveniles are dagger-shaped (Text-fig. 3).
Phillipps (1927, 1928) followed Regan in retaining the name of S. megalops, but later (1931, p. 360), on the basis of two specimens from the Hauraki Gulf, proposed this northern form as a new species, S. griffini. The description is meagre and comparison is made only with S. megalops of Australia. S. griffini is stated to differ from S. megalops by “the heavy, compressed, and unpolished appearance of the second dorsal spine,” and by having a somewhat shorter head and more rearward pelvic fins. I have examined the type of S. griffini (Dom. Mus. No. 662) and it is clearly not S. megalops, differing not only in the heavier dorsal spines, but also in having a rounded inner pectoral corner, and in the dermal denticles. It and other specimens from New Zealand that I have seen, are undoubtedly S. blainvillii, which, as I have pointed out in the introduction to this account, has been commonly but erroneously referred to S. fernandinus. S. blainvillii is a circumpolar species in both the northern and southern hemispheres, in tropical and subtropical waters as well as in the temperate region. My identification of it from New Zealand is based not only on the literature—Bigelow & Schroeder (1948, p. 456, fig. 87E) and Bigelow, Schroeder and Springer (1953, p. 220) give very good accounts of the species—but also on comparison with a specimen from the east coast of the United States of America, which was kindly sent by Mr. W. C. Schroeder, of Woods Hole Oceanographic Institution.
Recent accounts of S. blainvillii from New Zealand, with two exceptions, have been under the name S. griffini. Whitley (1940, Fig. 149) illustrates it from a New Zealand specimen for the first time, his figure being based on an illustration later used by Phillipps (1946, fig. 5). Fowler (1941) provisionally accepts it as a nominal species, while Richardson and Garrick (1953, p. 36) refer it to S. griffini but suggest it may be S. fernandinus as recognised by Bigelow and Schroeder (1948). On the other hand Norman (1937, p. 10) regards it as S. fernandezianus (Guichenot, 1848), a species apparently described from Juan Fernandez. I do not have Guichenot's account (in Gay, 1848, p. 365) but most authors refer S. fernandezianus to S. fernandinus as recognised by Bigelow and Schroeder (1948); if this identification is correct then S. fernandezianus is a synonym of S. blainvillii.
Fowler's (1941, p. 260) account of S. fernandinus correctly includes Phillipps' (1928) listing of S. megalops from New Zealand, though both these accounts in fact refer to S. blainvillii. However, some of the other listings in Fowler's synonymy of S. fernandinus are not S. blainvillii but are S. acanthias or S. megalops. Examples of the S. acanthias references are: as S. fernandinus, Regan (1908) and Waite (1909), and as Acanthias vulgaris, Hector (1872). All of the references of S. megalops as S. fernandinus (except Phillipps, 1928) are in error, while those of S. brevirostris likewise refer to a member of the S. megalops-cubensis group and probably to S. megalops.
Lastly Parrott's (1958, p. 114) account of S. griffini is illustrated by a figure of S. megalops from McCulloch (1922).
Within New Zealand waters, S. blainvillii is so far known only north of Cook Strait. Its distribution thus contrasts with S. acanthias, which is essentially southern. Both are mainly shelf species. Known localities of S. blainvillii are from East Cape northwards on the east coast to North Cape; and on the west coast from Cook Strait (Kapiti Island) northwards, where it overlaps the range of S. acanthias. Its presence is suspected off the north-west corner of the South Island, but this is yet to be proved. It does, however, occur at the Chatham Islands, to the east of New Zealand, where it appears to be the only Squalus species present.
I have not been able to obtain any material of S. blainvilli; from Australian waters, but Bigelow and Schroeder (1957, p. 35) who have examined the type of S. tasmaniensis Rivero, 1936, from Tasmania, identify it as S. fernandinus (= S. blainvillii), as does Munro (1956, p. 12). There can be no doubt that S. blainvillii does occur off southern Australia; the paucity of records of it may be due to confusion with S. megalops rather than to scarcity of the species. As can be seen in Text-fig. 1, the two species are superficially very similar, though S. blainvillii is readily recognisable by its rounded inner pectoral corner compared with the pointed corner of S. megalops. Specimens of S. blainvillii that I have seen have also been darker in colour—i.e., dark or greyish brown compared with the rather pinkish-brown of S. megalops.
Finally, I have noted that although the dorsal spines, and particularly the 2nd dorsal spine, are very conspicuous and massive in S. blainvillii, they are often incomplete. Close examination shows that this is not due to damage or wear, but is pathological and exogenous. Only remnants of the spine may be left protruding from the skin even though the dorsal fin above the spine shows no sign of erosion or damage. Whatever the infective agent is that attacks the spines, the phenomenon is not confined to S. blainvillii, for I have found similarly affected spines in Centrophorus squamosus.
Squalus blainvillii (Risso, 1826)
Squalus griffini Phillipps, 1931.
Squalus tasmaniensis Rivero, 1936.
(a) New Zealand. Female, 966 mm. (Dom. Mus. No. 662), type of S. griffini, from Auckland; two females, 454 mm and 545 mm (Dom. Mus. Nos. 2760, 2759) from 75 fathoms, Bay of Plenty; three females, 923 mm to 1,008 mm (Dom. Mus. Nos. 2647, 2649 and 2646) from 20–30 fathoms, Kapiti and Foxton; one female, 1,025 mm, from 2–3 fathoms, Chatham Islands; two embryos 215 mm and 218 mm (Dom. Mus. No. 2246) from female taken off Cape Egmont; embryo 144 mm (Brit. Ant. Expd. 1910, from British Mus. 1913. 12.4.297) from 10 fathoms, North Cape.
(b) Elsewhere. Female, 323 mm (Mus. Comp. Zool. No. 39827) from 33° 31 'N. 76° 35' W.
Description. Based Mainly on Two Mature Females, 923 mm and 1,003 mm, the Latter a Melanistic Variant.
|♀ 215 mm (embryo) Dm. Mus. No. 2246||♀ 545 mm Dm. Mus. No. 2759||♀ 923 mm Dm. Mus. No. 2647||♀ 1008 mm Dm. Mus. No. 2646|
|Trunk at pectoral origin: Breadth||14.0||13.2||14.4||15.2|
|Snout length in front of: Outer nostrils||4.2||3 9||3 8||3.7|
|Eye: Horizontal diameter||5.6||4.6||4.3||4.2|
|Nostrils: Breadth between inner corners||4.9||4.9||4.4||5.0|
|Preoral clefts: Breadth between inner corners||6.3||5.9||6.1||6.5|
|Gill-opening lengths: 1st||1.8||1.6||2.2||2.0|
|1st dorsal fin: Vertical height||8.4||8.2||8.0||7.9|
|Length of base from origin of|
|2nd dorsal fin: Vertical height||5.6||5.3||4.7||4.8|
|Length of base from origin of|
|Caudal fin: Upper margin||21.8||22.4||20.6||20.8|
|Lower anterior margin||11.6||11.4||11.2||10.6|
|Pectoral fin: Anterior margin||11.6||13.6||14.3||15.4|
|Distance from snout to: Eye||7.0||6.8||5.9||6.2|
|1st dorsal spine||35.0||32.0||32.2||33.5|
|2nd dorsal spine||66.0||64.9||67.0||67.2|
|Interspace between: 1st dorsal base and 2nd|
|2nd dorsal base and upper|
|Pelvic and lower caudal||23.7||23.8||22.2||22.6|
|Distance from origin to origin of:|
|Pectoral and pelvic||24.9||27.5||31.9||30.4|
|Pelvic and lower caudal||28.8||28.6||26.2||27.7|
Head strongly depressed, the eye large and the snout profile pointed; trunk moderately stout and subcircular in section. The dorsal profile more arched than the ventral, and highest at the level of the 1st dorsal fin from where it slopes downward both anteriorly and posteriorly. Height of trunk at origin of pectoral 7.1 to 7.5 in the length to origin of caudal. Length of body measured to cloaca 54.0% of the total length. Caudal peduncle rounded above but flat below, and with a prominent dermal keel along each side below the mid-level; the keels extend from just behind the posterior insertion of the 2nd dorsal base to about one-quarter
Text-fig. 6. —Squalus blainvillii, female, 923 mm (Dom. Mus. No. 2647), from New Zealand. Fig. A—Lateral view and insets of transverse sections of snout and peduncle. Figs. B and C— Dorsal and ventral views of head. Fig. D—Right nostril. Figs. E and F —Upper and lower teeth, right side. C = Level of cloaca.
of the distance along the caudal axis. Upper and lower precaudal pits are present at the origins of the epiural and hypural lobes; the upper pit deeper and better defined than the lower.
Dermal denticles on sides of trunk closely packed and overlapping, each with a near-horizontal, sub-circular, tridentate blade arising from a rhomboidal base; each blade carries a strong median dorsal ridge which is noticeably thick at its anterior end, and a low lateral ridge along each side. Denticles from the caudal axis are less tridentate and have heavier ridges; those from the interorbital region have bluntly pointed blades and no lateral teeth, but the median and lateral ridges are much stronger; while those from the upper and lower lips lack ridges and lateral teeth.
Head measured to 1st gill-opening 5.9 to 6.0 in the total lenth. Head strongly depressed and wedge-shaped in profile so that the snout tip is pointed. The least fleshy interorbital distance 2.3 to 2.0 in the head. Snout contour broad and pointed, expanding prominently at the level of the nostrils. Length of snout measured to the eye 2.9 to 2.8 in the head. Eye large, longer than high, and 2.0 to 2.1 in the preoral length. Spiracle large, placed so that its lower margin is just below the upper margin of the eye, and its anterior margin separated from the hind corner of the eye by a distance just less than the spiracular length. Gill-openings almost vertical, slightly concave, and in a horizontal series anterior to the pectoral base. Lengths of the gill-openings increasing slightly from the 1st to the 5th, the latter 1.7 to 1.8 in the horizontal diameter of the eye. Interspaces between the gill-openings subequal, though that between the 1st and 2nd slightly greater than any of the others. Nostrils almost transverse, and placed a little closer to tip of the snout than to mouth. Interspace between nostrils 1.3 to 1.2 in snout measured to eye. Each nostril subdivided into a circular lateral aperture and an elongate ovoid medial aperture by the anterior and posterior nasal flaps. The anterior nasal flap is essentially triangular, with its pointed tip directed posteriorly; however, about halfway along its medial margin there is a small lobe also directed rearwards, so that the whole flap appears unequally bifid. The posterior nasal flap fleshy, and internal to the anterior flap Mouth broad and little arched, its width about 1.5 in the preoral distance. Preoral clefts short, reaching less than half the distance from the angles of the mouth to the upper symphysis; posteriorly the clefts are continued by oblique furrows which extend one-quarter to one-third of the distance between the angles of the mouth and the 1st gill-openings.
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Teeth 14-13/12-11 in the 923 mm female, similar in the two jaws. Each tooth blade-like, the base broader than high, and with a single, smooth-edged, triangular cusp. The cups are deeply notched on their lateral margins, and so strongly oblique that their medial margins overlap from one tooth to the next to form a continuous cutting edge. The medial margins moderately convex in outline. In both jaws, the teeth at the centre of the mouth slightly smaller than those towards the corners; the lower teeth distinctly larger than the uppers. One or two rows of upper and lower teeth functional depending on the stage of replacement.
1st dorsal large, triangular, originating about midway between the levels of the axil and posterior corner of the pectoral fin when the latter is laid back along the side of the trunk. The posterior insertion of the 1st dorsal base is slightly nearer to the level of the pectoral axil than to that of the pelvic origin in large specimens, but about midway between these levels in small specimens. Height of 1st dorsal greater than the posterior part of its base measured from the origin of the spine, and equal to distance from snout tip to midway along eye. 1st dorsal spine scarcely pigmented, straight, long and sturdy, its tip reaching at least halfway up the anterior margin of the fin. Anterior margin of 1st dorsal slightly convex, distal margin strongly concave, and posterior margin straight; apex acute, but rounded. Length of the posterior margin about 1.2 in the posterior part of the base measured from the origin of the spine; the posterior tip sharply pointed. 2nd dorsal originating by a shallow angel posterior to the rear tips of the pelvics; its height 1.8 to 1.7 in that of the 1st dorsal, and its base measured from the origin of the spine 1.5 to 1.7 in the base of the 1st dorsal. The distal margin more concave, the apex more acute, and the posterior margin equal to the length of base measured from the spine. 2nd dorsal spine slightly heavier and longer than the 1st, and dusky coloured near its base; it reaches 2/3 or more of the distance to the apex of the fin. Caudal measured from the hypural origin 4.7 to 4.8 in the total length; epiural lobe well developed and without a subterminal notch, its upper margin almost straight except for the distal portion, its lower margin somewhat sinuous, and the apex acutely rounded or bluntly pointed. Hypural lobe about half as long as the epiural, its anterior margin convex and its apex acutely rounded; the angle between the posterior margin of the hypural and that of the epiural more than a right angle and smoothly rounded. Origin of the hypural just anterior to that of the epiural. Pectorals large and triangular originating just behind the 5th gill-opening. Anterior pectoral margin slightly convex, especially distally, its length 1.3 to 1.4 times the width of the fin and much less than the distance from snout tip to 1st gill-
opening; posterior margin almost straight, and distal margin slightly concave. Anterior angle of the pectoral acutely rounded, and posterior angle less than a right angle and rounded to the same degree. Pelvics well anterior to the 2nd dorsal fin, shallowly tringular, their length of base about equal to their height or to the base of the 2nd dorsal measured from the origin of the spine. Anterior, posterior and distal margins almost straight, apex smoothly rounded, and posterior tip sharply pointed.
Colour. Brown or greyish-brown above, merging to a lighter colour below. The 1,008 mm female described above is a melanistic variant, being black dorsally merging to creamy-white below, with numerous black patches on the ventral surface; the iris of this specimen is greyish blue. Embryos have the distal margins of the dorsal fins black, as well as the proximal parts of the epiural and hypural margins.
Squalus megalops (Macleay, 1882) Text-fig. 1, G-I; Text-fig. 3, O-T.
Although S. megalops has not been reported from New Zealand, its presence in southern Australia as a common shelf species ranging to 400 fathoms (Cowper & Downie, 1957) suggests a possibility that it may yet be added to the New Zealand fauna. It is illustrated here (Text-fig. 1) for comparison with the closely similar S. blainvillii from which it differs in its heavy-bodiedness, its pointed inner pectoral corner, its dermal denticles (Text-fig. 3) and its generally lighter colour. Proportional dimensions of three of the specimens that I have seen are also given for comparison. I am indebted to Messrs. T. R. Cowper and A. M. Olsen, C.S.I.R.O., Melbourne and Tasmania respectively, and to Mr. G. P. Whitley, Australian Museum, for providing specimens of S. megalops.
S. megalops was the first described of the S. megalops-cubensis group of species; consequently this name has priority should it be found that other species of the group cannot be separated from S. megalops. There seems little to distinguish the Japanese S. brevirostris Tanaka, 1917, but as I do not have comparative meterial of S. brevirostris I cannot be certain of this. The validity of S. cubensis Rivero, 1936, from Cuba, the Gulf of Mexico and southwards to Rio de Janeiro seems more likely, though it and S. megalops are strikingly similar. Bigelow & Schroeder (1957, p. 37) who have compared specimens of S. cubensis and S. megalops, reports that the former has a relatively longer 1st dorsal spine, differently shaped caudal and pectoral fins, and more rearwardly placed pelvic fins. My material of S. megalops, compared with Bigelow and Schroeder's (1948, fig. 89) figure of S. cubensis, agrees with their diagnosis in the shorter 1st dorsal spine of S. megalops, to some extent in the shapes of the fins, but not in the placing of the pelvic fins where there seems to be little difference between the two species. The comparison of more material is much to be desired.
Squalus megalops (Macleay, 1882).
Four females, 530 mm to 588 mm, from Victoria, Australia; two specimens (Austral. Mus. Nos. IB. 4256–7), one of these a female 370 mm (Austral. Mus. No. IB. 4257) from New South Wales; one late embryo and one immature specimen from off Tasmania.
General Account and Key to the New Zealand Squaloidea
The preceding account of New Zealand species of Squalus completes a revision of the known New Zealand Squaloidea. The revision is in nine parts (Garrick 1955, 1956, 1957, 1959a, 1959b, 1959c, 1960, in press, and the present account) which contribute to the continuing series “Studies on New Zealand Elasmobranchii” where they form Parts IV to XII.
|♀ 370 mm Austral Mus. No. IB. 4257||♀ 555 mm||♀ 588 mm|
|Trunk at pectoral origin: Breadth||13.5||14.2||13.7|
|Snout length in front of: Outer nostrils||3.0||3.1||3.1|
|Eye: Horizontal diameter||4.9||4.3||4.2|
|Nostrils: Breadth between inner corners||4.7||4.1||4.4|
|Preoral clefts: Breadth between inner corner,||6.1||6.0||6.3|
|Gill-opening lengths: 1st||1.9||2.3||2.0|
|1st dorsal fin: Vertical height||7.3||6.8||7.3|
|Length of base measured from origin of spine||5.3||5.4||5.6|
|2nd dorsal fin: Vertical height||4.2||4.1||3.6|
|Length of base measured from origin of spine||3.2||3.1||3.6|
|Caudal fin: Upper margin||22.1||20.7||19.6|
|Lower anterior margin||11.9||10.9||11.0|
|Pectoral fin: Anterior margin||14.3||14.6||14.9|
|Distance from snout to: Eye||5.9||5.9||5.8|
|1st dorsal spine||31.4||32.8||33.5|
|2nd dorsal spine||65.0||67.0||68.5|
|Interspace between: 1st dorsal base and 2nd dorsal spine||28.4||29.8||29.6|
|2nd dorsal base and upper caudal||11.2||10.3||10.0|
|Pelvic and lower caudal||26.2||25.2||26.1|
|Distance from origin to origin of:|
|Pectoral and pelvic||26.3||30.5||29.3|
|Pelvic and lower caudal||32.0||29.2||30.6|
It is now possible to examine the New Zealand squaloid fauna as a whole, and in the account below its composition, relationships and distribution are considered. This is followed by a key to the species. Lastly, two growth phenomena which are of considerable importance in the systematics of the Squaloidea—change with growth of dimensions, and change in the dermal denticles with successional replacement—are reviewed.
Composition of the New Zealand Squaloidea
Fourteen species of squaloid sharks, representing ten genera and four families, are so far known from New Zealand. These are as follows:—
- Oxynotus bruniensis (Ogilby, 1893).
- Squalus acanthias Linnaeus, 1758.
- Squalus blainvillii (Risso, 1826).
- Etmopterus baxteri Garrick, 1957.
- Etmopterus lucifer Jordan & Snyder, 1902.
- Centrophorus squamosus (Bonnaterre, 1788).
- Centroscymnus owstonii Garman, 1906.
- Centroscymnus crepidater (Bocage & Capello, 1864).
- Scymnodon plunketi (Waite, 1910).
- Deania calcea (Lowe, 1839).
- Dalatias licha (Bonnaterre, 1788).
- Scymnodalatias sherwoodi (Archey, 1921).
- Echinorhinus brucus (Bonnaterre, 1788).
- Echinorhinus cookei Pietschmann, 1928
Compared with previous accounts of the New Zealand squaloids, of which the most recent (other than lists only) is by Phillipps (1946), five additional species are recognised. Phillipps lists ten squaloids, but one of these, Centrophorus waitei, is now known to be a juvenile of Scymnodon plunketi. Of the remaining nine of Phillipps' species, six have been found to be synonyms, and a seventh has been placed in another genus. Thus only Scymnodon plunketi and Oxynotus bruniensis remain without nomenclatural change. To facilitate comparison of Phillipps' list with the fauna as now known, the nomenclatural changes are shown below.
|Phillipps, 1946||Present Status|
|Squalus kirki||Squalus acanthias|
|Squalus griffini||Squalus blainvillii|
|Centrophorus waitei||juvenile of Scymnodon plunketi|
|Centrophorus kaikourae||Deania calcea|
|Centrophorus nilsoni||Centrophorus squamosus|
|Dalatias phillippsi||Dalatias licha|
|Scymnodon sherwoodi||Scymnodalatias sherwoodi|
|Echinorhinus mccoyi||Echinorhinus brucus|
Additions to the fauna have been:
- Etmopterus baxteri
- E. lucifer
- Centroscymnus owstonii
- Centroscymnus crepidater
- Echinorhinus cookei
Two new species, Etmopterus baxteri and E. abernethyi, were recognised, but as more material became available E. abernethyi was found to be a growth stage of E. lucifer. A new genus, Scymnodalatias, was also recognised, but this is based on Scymnodon sherwoodi, a species previously known from New Zealand.
Relationships of the N.Z. Squaloidea
Phillipps' (1946) and Whitley (1940) regard the New Zealand and Australasian squaloids as highly endemic. Of the ten species they list in the New Zealand fauna, six are given as occurring in New Zealand only, while the remaining four are shared only with Australia. None are classed as having a widespread or cosmopolitan distribution.
Considering that the majority of the New Zealand squaloids occur in moderately deep water, and very few are shelf species, it is unlikely that a high proportion of such a mobile fauna should be restricted in its distribution. This is borne out in the present revision, where only two species, Etmopterus baxteri and Scymnodalatias sherwoodi have not been taken as yet outside New Zealand. E. baxteri is known from the continental slope, in 480–780 fathoms, so it is not unreasonable to expect that it may have a wider distribution. Scymnodalatias sherwoodi is known from one beachcast specimen, but its facies suggest it is a deep-water species.
The remaining twelve species are all more or less widespread in their distribution except for Scymnodon plunketi and Oxynotus bruniensis which appear to be confined to New Zealand and Australia.
Two species, Squalus blainvillii and Echinorhinus brucus, are virtually cosmopolitan, occurring in both the Pacific and Atlantic north and south, though not yet known off the Pacific coast of North and Central America. I have no personal experience of E. brucus in our waters, but retain it in the list only on the basis of a mounted skin in the Otago Museum labelled “Dunedin. April, 1887.” Squalus acanthias is similarly widespread but does not occur in tropical or subtropical waters.
Centrophorus squamosus, Deania calcea and Dalatias licha are known from the Pacific north and south, and from the north Atlantic, but have yet to be taken in the south Atlantic.
New Zealand species so far restricted to the Indo-Pacific are Centroscymnus owstonii, Etmopterus lucifer and Echinorhinus cookei.
The remaining species to be mentioned, Centroscymnus crepidater, has perhaps the most curious distribution, being known only from the eastern north Atlantic as well as from New Zealand. But this is unlikely to be its real distribution, and as it is a deep-water species (420–500 fathoms in New Zealand) it will almost certainly be recorded elsewhere.
Distribution in New Zealand Waters
Present information suggests that about two-thirds of the New Zealand squaloid species have their centre of abundance in depths approximating to the middle region of the continental slope—i.e., 300–600 fathoms. These depths are not worked by commercial fishermen, and only in a few regions around our coasts have they been explored experimentally with trawls or lines suitable for taking fish such as sharks. Consequently the present known distribution of our deep-water squaloid fauna corresponds to the areas where exploration has taken place, notably the eastern approach to Cook Strait and southwards to Kaikoura. Isolated captures of deep-water squaloids in shallower water elsewhere around our coasts suggests that the fauna is not limited to the known areas.
More adequate data establish three predominatly shallow water and shelf species, Squalus acanthias, S. blainvillii and Oxynotus bruniensis. These are all taken by commercial trawlers, S. acanthias in commercial quantities, S. blainvillii sparsely, and Oxynotus bruniensis uncommonly. Squalus acanthias is particularly numerous around the South Island and in Cook Strait, but in the North Island extends only to about East Cape on the east coast, and New Plymouth on the west. Squalus blainvillii has a much more northern distribution, from East Cape northwards on the east coast, and Cook Strait northwards on the west. S. blainvillii is also found at the Chatham Islands, to the east of New Zealand, where its presence shows fairly good correlation with the warm East Cape current trending from East Cape towards the Chathams, and linking the Chathams with the north east region of the North Island, where S. blainvillii also occurs.
Oxynolus bruniensis appears to favour the edge of the shelf and the upper continental slope. Its capture by commercial trawlers is nearly always an indication that they have been fishing in 80 fathoms or deeper. So far O. bruniensis is known only from about Cook Strait southwards to Otago on the east coast. Trawling in 80–100 fathoms or deeper is not uncommon elsewhere round our coasts, and particularly in the north, but has not resulted in the capture of O. bruniensis. The bizarre appearance of this species makes it unlikely that it would be overlooked in trawl catches, hence its southern distribution appears to be established.
The three depth range categories given below are the best approximation that can so far be made as to the depth ranges of the New Zealand squaloids. The species are placed in them according to what is thought to be their centre of abundance
rather than their maximum range known for New Zealand which is given in the bracketed figures following most species. Many species undoubtedly stray outside these depth-ranges; thus Scymnodon plunketi, Deania calcea and Dalatias licha are commonest in 300 fathoms and deeper, but occasionally stray into very much shallower water. The taking of eight juveniles of Centrophorus squamosus in 200 fathoms, while the adults are known only from deeper water, down to 500 fathoms, may indicate that these deep-water squaloids move inshore to give birth to their young, as do the shallow-water species whose breeding habits are better known.
The two species of Echinorhinus are not classified to range, for although all the New Zealand captures are from shallow water, records of E. brucus elsewhere cover a wide range to about 500 fathoms. Scymnodalatias sherwoodi, known from one stranded specimen, agrees with deep-water species in its uniform dark colour and large eyes. But until more specimens are taken, its habitat can only be conjectured.
Depth Ranges of New Zealand Squaloid Sharks
- (1) Shelf species (0–100 fathoms).
- Squalus acanthias
- Squalus blainvillii
- (2) Outer shelf and upper slope (80–300 fathoms).
- Oxynotus bruniensis (25–140).
- Etmopterus lucifer (100–200).
- Juveniles of Centrophorus squamosus (200).
- (3) Middle slope (300–600 fathoms).
- Etmopterus baxteri (480–780).
- Centrophorus squamosus (500).
- Centroscymnus owstonii (420–600).
- Centroscymnus crepidater (420–500).
- Scymnodon plunkeli (120–780).
- Deania calcea (40–600).
- Dalatias licha (20–480).
- Depth range not known:
- Echinorhinus brucus
- Echinorhinus cookei (35–50).
- Scymnodalatias sherwoodi.
Likely Additions to the Fauna
The Squaloidea of the world includes 17 genera and about 65 species (the exact number of species cannot be determined because many are unsatisfactorily known). The New Zealand representation of 10 genera and 14 species would, for most groups of fishes, be a satisfactory proportion, perhaps more than usually expected. However, as the Squaloidea are predominantly fishes of moderately deep-water, for the most part living on the continental slopes, the known New Zealand representation is by no means excessive. In fact, it seems more likely that additional species will be reported than the known fauna will remain at its present level. Some support is provided for this by the situation that just over half of the species at present recorded from New Zealand are known from five or less adult specimens of each. These species are listed below.
- Scymnodalatias sherwoodi (1 adult washed ashore).
- Echinorhinus brucus (1 adult).
- Echinorhinus cookei (3 adults, 3 juveniles).
- Centroscymnus owstonii (3 adults).
- Centroscymnus crepidater (4 adults with known data).
- Etmopterus baxteri (3 adults, 9 juveniles).
- Etmopterus lucifer (5 adults).
- Centrophorus squamosus (2 adults, 8 juveniles).
It has been possible to forecast with a fair degree of accuracy which of the known species will be taken in line-fishing experiments down to 700 fathoms. However, in the relatively small amount of line-fishing so far done, the catches have included, sporadically, other squaloid species new to the fauna. There is as yet no reason to suspect that the same will not continue.
Until more is known of the distribution of deep-water squaloids in general, and the dispersal factors limiting or allowing their movement, there is not much to be gained in speculating as to which Indo-Pacific or Atlantic species are likely to be found in New Zealand waters. The recent additions to the New Zealand fauna of the north Pacific Centroscymnus owstonii and the north Atlantic C. crepidater, and the recognition of the New Zealand Deania and Centrophorus spp. as the north Pacific-Atlantic D. calcea and C. squamosus suggest that any of the deepwater species known elsewhere could be expected.
Somewhat firmer ground is available in the likelihood of additions from the known Australian fauna, particularly from southern and south-eastern Australia. The separation in distance and latitude, and the oceanographic continuity between these areas and New Zealand suggest no barrier. Moreover, in Cowper & Downie's (1957) recent account of lining off eastern Tasmania, several species are recorded which previously were known only from New Zealand, so it does not seem unreasonable to suppose that further fishing off New Zealand would show the converse. The following list of Australian squaloids based mainly on records and depth-ranges in Whitley (1940) and Cowper & Downie (1957) covers those species thought most likely to occur, at least as stragglers, in New Zealand also.
- Squalus megalops (Macleay, 1882) (0–400 fathoms).
- Deania quadrispinosa (McCulloch, 1915) (85–400 fathoms).
- Etmopterus brachyurus Smith & Radcliffe, 1912 (130–450 fathoms).
- Centrophorus scalpratus McCulloch, 1915 (70–450 fathoms).
- Centrophorus harrissoni McCulloch, 1915 (“deep water”).
Key to the New Zealand Squaloidea
The following key, based in part on that of Bigelow & Schroeder (1957) covers all squaloid genera, including those not yet known from New Zealand. At the specific level, only New Zealand species are keyed out, but each is followed by a brief diagnosis sufficient to exclude other species. Particular attention has been given to include juveniles and adults in the key. Any squaloid which cannot be diagnosed to species in the key should be an addition to the fauna. Where this occurs, the reader is referred to the comprehensive keys in Bigelow & Schroeder (1957). General information on size, abundance, distribution and depth is given for each species, together with a reference to a full account in one of the nine parts of “Studies on New Zealand Elasmobranchii” which make up the present revision.
The key is simple to use. The numbers in brackets are alternatives. Thus for 1 (2) if there is not agreement with 1, refer to 2. Where the agreement is with 2, continue to 3 where another pair of alternatives 3 (24), is given, etc.
Key to New Zealand Squaloidea
Vertical height of 1st dorsal fin not less than 1/7 of total length; trunk noticeably subtriangular in section due to a strong ventrolateral muscle ridge along each side between pectoral and pelvic fins …. …. …. Family Oxynotidae, with one genus Oxynotus. Represented in New Zealand by O. bruniensis (Ogilby, 1893), the Prickly Dogfish, in which the 1st dorsal spine slopes a little forwards; distance
from 1st dorsal spine tip to apex of 1st dorsal fin is about equal to length of complete dorsal spine; and interspace between 1st and 2nd dorsal fins is about equal to length of 2nd dorsal base. Up to 722 mm long. Not uncommon in 60–120 fathoms, from Cook Strait to Dunedin on the east coast. Known from trawled specimens only. Occurs also off southern Australia. See Garrick, Part XI.
Vertical height of 1st dorsal fin not more than 1/12th of total length, and generally less; trunk more or less subcircular in section, with at most a weak ventrolateral muscle ridge along each side between pectoral and pelvic fins.
1st and 2nd dorsal fins each preceded by a dorsal spine which is well exposed in most but in some may be largely or wholly concealed …. …. …. Family Squalidae.
Upper teeth one-cusped.
Lower teeth similar in shape and size to upper; hypural lobe of caudal fin lacking a subterminal notch.
Anterior margin of nostril not extended as a conspicuous barbel; caudal peduncle with an obvious dorsal precaudal pit, and with a ventrolateral ridge along each side …. …. …. Genus Squalus.
Anterior nasal flap simple, triangular; distance from exposed origin of 1st dorsal spine to 5th gill-opening at least as long as distance from anterior edge of eye to 5th gill-opening …. …. …. Squalus acanthias Linnaeus, 1758, the Spotted Spiny Dogfish, which is greyish or brownish with prominent white spots along the trunk on small and middle-sized specimens, though the spots may be faint or absent on large specimens. Up to 1,200 mm long. Very common as a shelf species in Cook Strait and southwards on the east coast, but known as far north as East Cape and New Plymouth. Elsewhere a circumpolar species in both hemispheres, in temperate, subarctic and subantarctic waters. See Garrick, Part XII.
Anterior nasal flap bilobed; distance from exposed origin of 1st dorsal spine to 5th gill-opening is not more than distance from anterior edge of eye to 2nd gill-opening …. …. …. Squalus blainvillii (Risso, 1826), the Spiny Dogfish which is a uniform greyish or brownish colour without spots at any stage of growth, and which has the inner (posterior) corner of the pectoral fin rounded, and tridentate denticles. Up to at least 1,200 mm long and probably longer. A common shelf species in northern New Zealand, from Cook Strait northwards on the west coast, and East Cape northwards on the east coast, also at the Chatham Islands. Elsewhere circumpolar in both hemispheres, in tropical, subtropical and temperate water, See Garrick, Part XII.
Anterior margin of nostril extended as a conspicuous barbel which reaches behind mouth; caudal peduncle without a precaudal pit or ventrolateral ridges …. …. …. Genus Cirrhigaleus, with one species C. barbifer Tanaka, 1912 known only from two specimens off Japan. Small sharks, not unlike Squalus, but with a highly arched dorsal profile.
Lower teeth dissimilar in shape to upper, and broader; caudal fin with a subterminal notch.
Preoral length distinctly longer than distance from mouth to pectoral origin; fin spines well exposed, the 2nd much longer than the 1st …. …. …. Genus Deania. Represented in New Zealand by D. calcea (Lowe, 1839), the Shovel -nosed Spiny Dogfish in which the vertical height of the 1st dorsal fin is ⅓ to ¼ the length of the 1st dorsal base measured from the origin of the spine; the pectoral fin tips, when pressed to the sides, fall far short of the level of the 1st dorsal spine; and the dermal denticles are high, slender and antlerlike, usually four-toothed. Up to 1,100 mm long. Relatively common in 400–600 fathoms in Cook Strait and southwards to Banks Peninsula Occurs elsewhere in southern Australia, Japan, north-eastern Atlantic and the Mediterranean. See Garrick, Part XI.
Preoral length equal to or shorter than distance from mouth to pectoral origin; fin spines short, subequal, and largely or wholly concealed (except in juveniles of Centrophorus squamosus which have well exposed spines, the 2nd much longer than the 1st).
Inner (posterior) corner of pectoral fin angular or extended …. …. …. Genus Centrophorus, with a species in New Zealand waters, C. squamosus (Bonnaterre, 1788), which has scale-like, overlapping dermal denticles, the blade of each with a high median longitudinal ridge. In juvenile C. squamosus the shape of the inner pectoral corner is about a right angle, or the tip may be sharply pointed and slightly extended; in adults the tip is extended for a distance of about 1/10th of the pectoral fin length. Up to 1,400 mm long. So far known in New Zealand only from two adults (one of them lined from 500 fathoms) and several juveniles (from 200 fathoms) taken off Kaikoura. Found elsewhere off southern Australia, Japan, the Philippines and north-eastern Atlantic. See Garrick, Part VII.
Inner (posterior) corner of pectoral fin rounded.
Upper teeth midway along either side of jaw longer than those toward centre of mouth; dermal denticles of sub-adults and adults with a median longitudinal ridge extending the complete length of blade …. …. …. Genus Scymnodon, including a New Zealand species, S. plunketi (Waite, 1910), the Plunket shark in which the lower teeth are strongly oblique along the whole jaw, and there is no symmetrical median lower tooth. Up to 1,400 mm long. Common in 300–400 fathoms, but recorded from 120–780 fathoms in Cook Strait and southwards to Banks Peninsula. Also known from southern Australia. See Garrick, Part IX.
Upper teeth midway along either side of jaw not obviously longer than those toward centre of mouth; dermal denticles with a circular concavity at anterior end of blade so that a median longitudinal ridge, if present, is restricted to posterior half or two-thirds of blade …. …. …. Genus Centroscymnus.
Distance between inner corners of preoral clefts is about equal to distance between inner corners of nostrils …. …. …. Centroscymnus owstonii Garman, 1906, in which the dorsal spines are almost wholly concealed, and the length of the 1st dorsal base measured from the origin of the exposed spine tip is only ¾ that of the 2nd dorsal similarly measured. Juveniles and sub-adults of this species have tridentate, ridged dermal denticles, but in adults the denticles lack teeth and ridges. Up to 800 mm long, known in New Zealand from only three specimens 584 mm to 800 mm long, lined from 420–600 fathoms off Kaikoura. Occurs elsewhere off Japan. See Garrick, Part VIII.
Distance between inner corners of preoral clefts is about ¼ of distance between inner corners of nostrils. Centroscymnus crepidater (Bocage & Capello, 1864) in which the length of head measured to pectoral origin is 21%–26% of total length. Dermal denticles tridentate and ridged in all growth stages. Up to 900 mm long. So far known in New Zealand from eight specimens, four of these lined from 420–500 fathoms off Kaikoura. Occurs elsewhere in north-eastern Atlantic. See Garrick, Part VIII.
Upper teeth with three to nine cusps.
Lower teeth one-cusped, the cusps strongly reflexed laterally …. …. …. Genus Etmopterus including about 15 species of small, dark-coloured, deep-water sharks, many of them with luminescent organs. Two species in New Zealand as follows.
Dermal denticles on sides of trunk in random arrangement, at least on specimens more than 400 mm long; dark brown above and below with an inconspicuous longitudinal flank mark mostly above the pelvic fin …. …. …. Etmopterus baxteri Garrick, 1957, in which the dermal denticles are single spines, loose spaced and slender in juvenitles but crowded and thorn-like in adults; upper margin of caudal fin not longer than distance from snout tip to pectoral origin and usually less; interspace between rear of pelvic base and subcaudal origin is not more than half the interspace between axil of pectoral and pelvic origin; 2nd dorsal spine long and curved. The largest species of Etmopterus, reaching to 750 mm. Known only in New Zealand waters, from 12 specimens taken in 480–780 fathoms, Cook Strait and Kaikoura. See Garrick, Parts VI and XI.
Dermal denticles on sides of trunk in definite, uniserial, longitudinal rows; greyish or brownish above, black below with a conspicuous, attenuate, longitudinal flank mark above the pelvic fin but extending almost as far rearward as the posterior tip of the 2nd dorsal fin …. …. …. Etmopterus lucifer Jordan & Snyder, 1902, in which the dermal denticles are slender, single spines; and distance from tip of snout to pectoral origin is about equal to the upper caudal margin, and is not more than the interspace between the 1st and 2nd dorsal fins. A small species, up to 396 mm long. Known in New Zealand from five specimens, taken in 100–200 fathoms, Kaikoura and Bay of Plenty. Elsewhere reported from Japan, Philippines, East Indies and Natal. See Garrick, Parts VI, as E. abernethyi, and XI.
Lower teeth with three to five cusps, erect and similar to the uppers …. …. …. Genus Centroscyllium. Small to medium-sized, dark-coloured, deep-water sharks rather like Etmopterus. Some of them, at least, have luminescent areas on the skin. About five species recognised. Known from the North Atlantic, the Falkland Islands, Bay of Bengal and Arabian Gulf, Japan, Hawaii and the Eastern Pacific off Panama. Not yet known from Australia or New Zealand.
2nd dorsal fin not preceded by a dorsal spine; 1st dorsal similarly lacks a spine except in the dalatiid genus Squaliolus, which is not so far known from New Zealand.
Upper and lower teeth one-cusped and dissimilar; upper teeth narrow and raptorial; lower teeth broader and sectorial …. …. …. Family Dalatiidae.
Dermal denticles from side of trunk scale-like, their posterior margins tridentate …. …. …. Genus Scymnodalatias, with one species S. sherwoodi (Archey, 1921) based on a single specimen 803 mm long found washed ashore on New Brighton Beach, Canterbury. Upper teeth needle-like, with asymmetrically twisted cusps; lowers with high, triangular cusps; origin of 1st dorsal fin in front of middle of total length; 1st and 2nd dorsal fins brush-shaped, the 1st smaller than the 2nd. See Garrick, Part V.
Dermal denticles from side of trunk conical, thornlike, or with concave quadrate crowns.
Dermal denticles conical or thornlike, with longitudinal ridging.
Lower teeth with regularly serrated margins …. …. …. Genus Dalatias with a single species D. licha (Bonnaterre, 1788), in which the snout is noticeably short and blunt, and the mouth has fleshy lips with a complex series of fringed crossfolds. Up to 1,800 mm long. Relatively common in Cook Strait and southwards to Otago, but also extending to East Cape on the east coast, and to Foxton on the west coast. 20–480 fathoms. Widely distributed in the North Atlantic, Mediterranean, south-east Africa, Japan and Australia. See Garrick, Part XI.
Lower teeth smooth-edged.
Origin of 1st dorsal fin is about level with axil of pectoral fin …. …. …. Genus Heteroscymnoides, with only one species, H. marleyi Fowler, 1934, based on a single newly-born specimen, 126 mm, taken off south-eastern Africa. Head long (measured to pectoral origin almost 1/3 of total length), but this is accentuated in all juveniles; caudal axis almost straight, no subterminal notch; dermal denticles triangular thorn-like, with three longitudinal ridges.
Origin of 1st dorsal fin is level with or behind posterior tips of pectoral fins when these are adpressed to side …. …. …. Genus Somniosus, the Greenland or Sleeper Sharks with four or five Northern Hemisphere species ranging from temperate to polar waters, and one Southern Hemisphere species, S. antarcticus Whitley, 1939, based on a sketch of a single specimen stranded on Macquarie Island. Size from little more than 3 feet to 21 feet; the specimen of S. antarcticus was about 8 feet long. Snout short; caudal fin large; dorsal fins subequal in size, the 1st originating near the middle of trunk; upper teeth slender, raptorial, lower teeth broad, reflexed laterally. At least one of the Northern Hemisphere species has luminescent organs.
Dermal denticles with concave quadrate crowns.
Vertical height of 2nd dorsal fin is about ⅔ the length of the 2nd dorsal base …. …. …. Genus Isistius with one pelagic species, I. brasiliensis (Quoy and Gaimard, 1824) from the tropical and subtropical belts of the Atlantic, Pacific and Indian Oceans. Luminescent. 1st dorsal placed well back in second half of body; 1st and 2nd dorsals brush-shaped, subequal; caudal fin sublunate, with definite subterminal notch; pectoral fin small, lobate; upper teeth narrow, raptorial, lower teeth broad, erect and triangular. Up to almost 500 mm long.
Vertical height of 2nd dorsal fin is only ⅛ to ¼ the length of the 2nd dorsal base.
Origin of 1st dorsal fin is well before the middle of the total length …. …. …. Genus Squaliolus with two species; S. laticaudus Smith and Radcliffe, 1912 from 170 fathoms off the Philippines, and S. sarmenti Noronha, 1926, from deep water off Madeira and from very shallow water off Arcachon, France. 1st dorsal spine present, its tip exposed or wholly buried; head pointed and long, measured to pectoral origin about of total length; 1st and 2nd dorsal fins long and low, the 1st dorsal base about half the length of the 2nd; caudal fin sublunate, without subterminal notch. Very small sharks, up to 226 mm long.
Origin of 1st dorsal fin is behind the middle of the total length …. …. …. Genus Euprotomicrus with one pelagic species, E. bispinatus (Quoy & Gaimard, 1824) recorded from the north and north-eastern Pacific, from the South Indian Ocean, and from off Campbell Island, well south of New Zealand (an early record by Hutton, 1872, of a specimen presumed to be from New Zealand, and based on a set of jaws in the Colonial Museum cannot be substantiated according to Phillipps, 1928, p. 224). Head bluntly pointed, its length to pectoral origin about ¼ of total length; 1st dorsal fin slender, brush-shaped; 2nd dorsal fin long and low; length of 1st dorsal base not more than ⅓ the length of the 2nd; caudal fin sublunate, without subterminal notch. Luminescent. Very small sharks, up to 234 mm long.
Upper and lower teeth similar, sectorial, one-cusped in juveniles but with several cusps in larger specimens …. …. …. Family Echinorhinidae, with one genus Echinorhinus, characterised by buckler-like dermal denticles carrying erect or slightly recurved spines.
Dermal denticles sparse, irregularly distributed, large, up to 15 mm or more basal diameter, often with the bases of adjacent denticles fused to give compound
bucklers 35 mm long …. …. …. Echinorhinus brucus (Bonnaterre, 1788), the Bramble Shark, growing to 12 feet long. The only confirmable New Zealand record of this species is based on a mounted skin in the Otago Museum. Known from most oceans, in shallow water to 500 fathoms. See Garrick, Part X.
Dermal denticles numerous, uniformly distributed, small, not more than 4.0 mm basal diameter, not compounded …. …. …. Echinorhinus cookei Pietschmann, 1928, the Bramble Shark, possibly growing to 14 feet. So far known in New Zealand from one large adult off Moeraki, and two adults and three juveniles from Cook Strait, taken in 35 to 50 fathoms. Elsewhere single specimens are known from off Hawaii, California, and Peru in similar depths. See Garrick, Part X.
Trends in the Change with Growth of the Proportional Dimensions in the Squaloidea
Contrasted with bony fishes, sharks have few of those characters which enable the systematist to recognise species or genera by simply counting structures. The number of gill-openings serves to distinguish two sub-orders from the remainder, while dental formulae have rather wider use within several sub-orders and particularly the Galeoidea. In the Squaloidea the number of teeth per row is generally less constant than in the Galeoidea, and is increased throughout the life of individuals of many species. Because of the lack of discernible fin rays and countable scales, shark systematists must rely mainly on morphological differences, and particularly proportional dimensions to distinguish species. Compared with differences in shape, outline or appearance, differences in proportional dimensions are readily stated or described, and therefore are used extensively. In view of this reliance on proportional dimensions it might be expected that information on the nature and extent of any change with growth of the proportional dimensions of sharks would be readily available and assembled to show the growth trends. Generally speaking this is not the case, especially in the Squaloidea, although many authors, and particularly those writing in the last few decades, do give some indication of the range of proportions in their specific descriptions. Such ranges of proportions are valuable, but unless they are qualified by information on the sizes of the specimens they refer to (and this is seldom made plain) their full value is not realised.
There would be little importance in having information on change with growth of dimensions if such change is of small extent. Judging by the paucity of references to the subject, it appears a tacit assumption by most shark systematists that change with growth is of small account. This is not supported by the present study where particular attention has been paid to growth change and where it has been found to be of considerable importance.
The following contribution to our information on growth change in sharks is based on seven species of six genera of Squaloidea, but is probably applicable in general terms to all sharks. Because of the small amount of material available for most of the species studied, the account is not regarded as definitive. Rather the aim has been to present a framework showing the main trends, which can be filled out and modified as further data become available. Methods adopted for the study have therefore been kept as simple as possible. For each species, measurements of various regions of the body were made from specimens of all sizes available, from juveniles and even embryos to the largest adults. These measurements, converted to percentages of total length, were then plotted against total length. On the assumption, following Olsen (1954, p. 391) that growth is isometric, straight lines were fitted, by eye, to the plots. Proportional dimensions, as in Table II were read from these straight lines for two size-groups only, juveniles and large adults. The size-groups are not specified in further detail because of the few data available, nor is any indication given of the scatter on the plots which was moderate but within recognisable trends.
The results, in Table II, show that the head, trunk and tail do not grow at a uniform rate, but that the trunk is a region of accelerated growth. Thus in large
|Species||Snout tip to 5th gill||5th gill to Upper Caudal Origin||Upper Caudal Origin to Tip of Tail||5th Gill to 1st Dorsal Spine||1st Dorsal Spine to Pelvic Origin||Pelvic Origin to 2nd Dorsal Spine||2nd Dorsal Spine to Upper Caudal Origin|
|J = Juveniles.||A = Large Adults.||C = Change with Growth.|
|J A C||J A C||J A C||J A C||J A C||J A C||J A C|
|Squalus acanthias||22 19 -3||57 63 +6||21 18 -3||15 16 +1||13 20 +7||14 12 -2||15 15 0|
|Squalus blainvillii||24 21 -3||55 60 +5||21 19 -2||11 12 +1||14 19 +5||16 16 0||14 13 -1|
|Etmopterus baxteri||24 20 -4||52 61 +9||24 19 -5||13 15 +2||15 22 +7||11 11 0||13 13 0|
|Centrophorus squamosus||24 20 -4||56 64 +8||20 16 -4||14 18 +4||21 24 +3||9 11 +2||12 11 -1|
|Centroscymnus crepidater||26 23 -3||50 59 +9||24 18 -6||13 15 +2||19 26 +7||8 7 -1||10 11 +1|
|Scymnodon plunketi||20 17 -3||55 65 +10||25 18 -7||15 20 +5||17 24 +7||9 8 -1||14 13 -1|
|5th Gill to 1st Dorsal Origin||1st Dorsal Origin to Pelvic Origin||Pelvic Origin to 2nd Dorsal Origin||2nd Dorsal Origin to Upper Caudal Origin|
|Dalatias licha||27 19 -8||49 61 +12||24 20 -4||11 16 +5||17 25 +8||7 4 -3||14 16 +2|
adults the trunk, measured from 5th gill-opening to upper caudal origin, comes to occupy from 5% to 6% (Squalus spp.) to 10% to 12% (Scymnodon plunketi-Dalatias licha) more of the total length than it does in juveniles.
The head and tail show a corresponding proportional decrease in length, which may be uniformly distributed between them as in Squalus acanthias and Centrophorus squamosus, or the tail may show a proportionately greater decrease than the head (more than twice as great in Scymnodon plunketi), or less frequently the head may show the greater proportional decrease (Dalatias licha)
Within the trunk itself, growth is not uniform, but is fastest anterior to the pelvic fins. In most squaloids (the exceptions being some of the Dalatiidae, and the Echinorhinidae) the 1st dorsal fin is well in advance of the pelvics, and hence the anterior portion of the interspace between the 1st and 2nd dorsal fins lies in this region of accelerated growth. As a consequence the distance from pelvic fin to 1st dorsal compared with pelvic to 2nd dorsal is an increasing ratio with increase of total length. Accelerated growth also occurs anterior to the 1st dorsal fin, to at least as far forward as the pectoral axis. This is evidenced in part by the data in Table II showing the increase in length from the 5th gill to the 1st dorsal spine. However, a better indication is given by comparison of the relative positions of the pectoral fin tip when adpressed to the side and the origin of the 1st dorsal spine or fin; in large adults the level of the 1st dorsal spine or fin is from 1% to 5% of the total length rearward of its position in relation to the pectoral fin tip in juveniles. This is not due to a marked decrease in the proportional length of the pectoral fins, for compared with the total length their length may remain reasonably constant, or more often will show a slight increase.
The relationship of height to length of base of the dorsal fins between juveniles and adults differs so markedly that it is evident that a very different growth rate operates on the vertical dimension to that on the longitudinal. Compared with total length, the bases generally show a slight relative increase in length, as would be expected in view of the accelerated growth rate of the trunk region. This is not invariable as in my material of Etmopterus baxteri the 1st dorsal base decreases relative to the total length, though the 2nd dorsal base increases. In contrast the heights of both fins either decrease or remain constant compared with the total length. The consequences are that in adults the heights of the dorsal fins relative to the lengths of the bases are less than they are in juveniles. This applies even to the 1st dorsal of E. baxteri where, although the base decreases proportional to the total length, the decrease in height is even more. Diminishing dorsal fin heights therefore appear to be a growth feature of most if not all squaloids, though the same cannot be said of the Galeoidea where at least the Mako and some carcharhinids show the reverse trend in their 1st dorsal fins.
Growth Changes in the Head
Growth changes in the longitudinal dimensions of the head are comparatively extensive, but tend to be masked by the smallness of the scale if they are examined in relation to the total length. Accordingly head dimensions in Table III are given as percentages of the head length measured to the 5th gill-opening. These were prepared in a similar manner to those of Table II. They show, as might be expected, a relative decrease with growth in the horizontal diameter of the eye, ranging from 3% to 9% of the head-length, but in most species between 5% to 7%. This slowing down of the growth rate of the orbital region is accompanied by accelerated growth of the postorbital region, where the increase may be mainly in the interspace between the rear edge of eye and the 1st gill-opening (Etmopterus baxteri and Scymnodon plunketi), or between the 1st and 5th gill-openings (Dalatias licha), or more or less uniformly distributed. The interspace between the rear margin of eye and the spiracle scarcely varies. In the preorbital region as a whole,
|Species||Snout Tip to Outer Nostril||Snout Tip to Ant. Edge Eye||Horizontal Diameter of Eye||Snout Tip to Mouth||Rear Edge of Eye to 1st Gill-opening||1st Gill-opening to 5th Gill-opening|
|J = Juveniles.||A = Large Adults.||C = Change with Growth.|
|J A C||J A C||J A C||J A C||J A C||J A C|
|Squalus acanthias||19 19 0||30 30 0||20 14 -6||45 39 -6||34 36 +2||16 20 +4|
|Squalus blainvillii||17 18 +1||29 29 0||23 20 -3||47 41 -6||32 32 0||16 19 +3|
|Etmopterus baxteri||9.5 8.5 -1||30 26 -4||26 19 -7||49 40 -9||28 37 +9||16 18 +2|
|Centrophorus squamorus||15 16 +1||24 26 +2||30 25 -5||47 42 -5||32 33 +1||14 16 +2|
|Scymnodon plunketi||4 6 +2||22 19 -3||26 21 -5||38 30 -8||34 41 +7||18 19 +1|
|Dalatias licha||4 6 +2||15 15 0||22 13 -9||30 23 -7||43 44 +1||20 28 +8|
the growth rate is much more constant than in the postorbital region, though my data do show some decrease in the preorbital length in Etmopterus baxteri and Scymnodon plunketi, and in most of the species examined a slight increase in the distance from snout tip to nostrils. The position of the mouth shows a strong correlation with the rear edge of the eye, these two levels remaining unchanged relative to each other even though the rear edge of the eye becomes proportionately further forward with growth. Some indication of the correlation is shown in Table III by the figures for the distance from snout tip to mouth, which diminish
with growth to about the same extent as do those for the horizontal diameter of the eye. Other than this stability beween rear edge of eye and mouth (and rear edge of eye and spiracle) the most stable level in the head is the anterior margin of the eye.
The above outline of growth changes from juveniles to adults of some squaloids shows that in terms of total length (or head length) the changes rarely exceed 10% and are mostly much less. Fortunately it is not often that a systematist is called upon to compare specimens of juvenile age with adults, so that in the usual run of meterial the growth changes encountered will be less than those given here. This does not mean that the changes will be minor or insignificant because it is in their interaction that their greatest affect is seen. It is common practice to equate one portion of the body against another to arrive at a proportion thought to be distinctive for the species concerned. This will be valid for all sizes only if the two regions concerned have equivalent growth rates. Where this is not so, as for example head or tail length expressed in terms of trunk length, the proportions of juveniles or immature specimens will differ considerably from those of adults because of the general tendency for the trunk to increase its length at a faster rate than the head or tail. The differences will be especially marked if the proportion is in terms of the anterior half of the trunk where the greatest accelerated growth occurs. In most squaloids the interspace between the dorsal fins lies largely in this region, and proportions based on the dorsal interspace or the 1st dorsal to pelvic interspace are not uncommonly given. Text-fig. 2 (in the preceding account of Squalus spp. in New Zealand) showing the 1st dorsal to pelvic length compared with the pelvic to 2nd dorsal length of Squalus acanthias and S. blainvillii illustrates the changes likely to be encountered. However, even in the posterior part of the trunk, where growth change is less obvious, interaction of growth rates can be important. Examples of this are given in Garrick, Part XI, on the indetification of species of Etmopterus from New Zealand waters. Growth changes in the head region offer the same problems, as can be seen in Table I in the preceding account of Squalus spp.
Despite these difficulties in their use, proportional dimensions will and must remain one of the shark systematists' most important criteria. But further study of them is greatly merited if they are to reach their highest value.
Dermal Denticle Changes in the Squaloidea
Until recently most shark systematists would have endorsed the opinion of Sakamoto (1930, p. 61) that the “placoid scale serves as a good systematic criterion when taken together with other characters”. However, since Tortonese's (1952, p. 386) discovery that the dermal denticles of juvenile Centroscymnus coelolepis differ greatly in shape from those of adults, there has been some caution in the use of dermal denticles as specific or generic characters. The present situation is understandable; more surprising is the fact that it has only so recently been generally recognised in the Squaloidea. In the Galeoidea, denticle changes have been known for more than 40 years, especially from Radcliffe (1916, p. 257) who described in detail differences in the shape of the denticles on specimens of some Carcharhinus spp. of different ages, and noted similar variation in species of Sphyrna and Pristis. Denticle changes occur when one generation of denticles is successively replaced by another generation. In other words the changes are possible because dermal denticles do not persist throughout the life of an individual shark, as do the scales of bony fishes, but are shed and replaced, apparently several times. Observations on this kind of replacement in “Centrina” and “Scyllium”
were reported as early as 1861 by Steenstrup (p. 688) while Hertwig (1874, p. 358) also noted that new dermal denticles are formed between an existing generation of denticles.
Within the Squaloidea, Jordan and Hubbs (1925, p. 107) briefly describe denticle changes in Centroscymnus owstonii, but their findings appear to have been overlooked by later writers. Bigelow and Schroeder (1954, p. 47, fig. 2) amplify Tortonese's account of similar changes in Centroscymnus coelolepis, and suggest (p. 50) that the same situation occurs in C. owstonii. More recently (1957, p. 14) they note that denticle changes take place in Oxynotus spp. and describe changes (p. 48, fig. 3) in the denticles of Etmopterus princeps.
In the present revision of the New Zealand squaloids, denticle changes involving differences in shape, sculpture or proportions between juveniles and adults were observed in 11 of the 14 species examined. For the remaining three species (Etmopterus lucifer, Dalatias licha and Scymnodalatias sherwoodi), an insufficient range of material was available. In many of the species, the changes involved are not great, but they are included here to show the universality of the phenomena, and also to give some indication of the trends of the changes. It should be noted that change in size was not regarded as a criterion, insofar as adults of all species have larger denticles than juveniles, though there is no direct proportion between total length and denticle size.
Species showing the least changes in their denticles are those with spine-like or thorn-like denticles—e.g., Etmopterus baxteri, Echinorhinus brucus and E. cookei. In Etmopterus baxteri (and also in E. princeps as noted by Bigelow and Schroeder [1957, p. 48]) juvenile form denticles are slender and bristle-like, but are replaced by stouter, thorn-like denticles in adults. In Echinorhinus brucus, strongly ridged bucklers with deeply indented margins appear to be the juvenile form, and are succeeded by finely ridged bucklers with more nearly entire margins; similar but less contrasting forms appear in juveniles and adults of E. cookei (Garrick, Part X).
Species with blade-like dermal denticles show a greater variety of changes, though with one or two exceptions they follow trends similar to those observed by Radcliffe (1916) in the carcharhinids. These are that the blades of adult form denticles have additional longitudinal ridges on their external surfaces, and reduction of the teeth on the posterior margins. There might be added for the Squaloidea the trend for the blades of adult denticles to lie more nearly horizontal compared with the near vertical or steeply directed blades of juvenile denticles. Good examples of these trends are seen in Centrophorus squamosus, Centroscymnus crepidater and Scymnodon plunketi (in Garrick, Parts VII, VIII and IX respectively). Exceptions are in Centroscymnus owstonii (Garrick, Part VIII) where longitudinal ridging is reduced and lost in adult denticles, in Oxynotus bruniensis and Deania calcea (Garrick, Part XI) where additional teeth are acquired posteriorly or posterolaterally on the blades, and also in O. bruniensis where adult form denticles are directed more steeply from the skin than juvenile denticles. Another trend common to the genera with blade-like denticles mentioned here, but not including Squalus spp., is for the anterior margins of the denticle bases to become multi-angled. This is accompanied by the development of additional ridges extending from the angles on to the pedicle. In comparison the denticle bases of Squalus spp. remain rhomboid even in adults, and have only the four major ridges extending on the pedicle.
Despite the above trends, considerable variation is shown in the nature of the changes between different species. It is of particular interest (and value also to the systematist) that the variation can occur even in species of the same genus. A striking example is seen in Centroscymnus spp. where C. coelolepis and C. owstonii show a complete elimination of the longitudinal ridges and the posterior marginal teeth in adult form denticles, while in C. crepidater these features remain strongly developed (Garrick, Part VIII). In all three species the juvenile denticles are
very similar. Likewise in three Squalus spp. examined (Text-fig. 3), two of them, S. acanthias and S. megalops, agree in their juvenile form denticles but differ widely in their adult denticles; the third species, S. blainvillii, contrasts in its juvenile denticles, but shows agreement with S. acanthias in its adult denticles.
Squalus spp. are also unusual in that although their adult form denticles are horizontal blades with a very high median longitudinal ridge, their juvenile form denticles show little development of the horizontal blade (except in S. blainvillii) but strong development of the median ridge (Text-fig. 3). In species of the other genera examined, the horizontal blade is well developed in juvenile denticles, and in Scymnodon plunketi there is initially no median ridge though it becomes progressively stronger as replacement denticles appear.
The above observations were mostly made on the denticles from the side of the trunk below the 1st dorsal fin, an area long regarded as standard. However, during the study it became apparent that examination of only the standard area could be misleading in specimens of critical size—i.e., those about one-third grown. In such specimens the denticles are still mostly of juvenile form, except on the side of the caudal peduncle. Replacement of denticles on the side of the trunk appears to begin posteriorly, and to progressively advance forwards. Jordan and Hubbs (1925, p. 107) came to the same conclusion after examining Japanese specimens of Centroscymnus owstonii, but I was not aware of their account when describing (1959 b; 1959 c) this phenomenon in New Zealand specimens of C. owstonii and also Scymnodon plunketi. Actually earlier replacement begins on the dorsal midline at the anterior ends of the bases of the dorsal fins and of the epiural lobe of the caudal, and also between these fins in a longitudinal area parallel to and alongside the mid-dorsum. In this respect there is fairly close correspondence between the sites of origin of the denticles of the embryo and the sites of the first replacing denticles of each later generation. However, as the mid-dorsal denticles often have different facies from those on the side of the trunk as a whole, it is perhaps better that they be disregarded in denticle change studies (in Squalus acanthias the first mid-dorsal denticles to erupt in the embryo are tridentate, whereas on the side of the trunk there are one or more generations of spear-head shaped denticles before tridentate forms appear).
There can be little doubt that with further study of denticle changes, the value of denticles as systematic criteria will show a considerable increase. This will require, as pointed out by Radcliffe (1917, p. 26) the assembly and examination of skin samples as a normal routine, but compared to many procedures this requires little time or effort. The result should well exceed Radcliffe's opinion (p. 27) “that these (dermal denticles) are not an open sesame by which all sharks may be readily identified, but that in a troublesome group they are an aid”.
In addition to the problems of relationships which stem from changes in the dermal denticles, other problems are also apparent. Present knowledge of the structure and development of dermal denticles does not recognise further growth of the denticles once they are erupted. This means that any change in the shape or structure of the denticles throughout the life of an individual must be interpreted in terms of denticle replacement. Such changes are numerous in some species, and examinations of a series of specimens, even to near maximum size, gives a picture of continual increase in denticle size or continual change in shape. Accordingly denticle replacement must occur at a matching pace, even in the larger specimens. With some species, support can be given to this view, for in Squalus spp. and Dalatias licha newly erupted denticles, not yet pigmented, are evident even on near-maximum size specimens. On the other hand, Bigelow and Schroeder (1954, p. 50) in their study of Centroscymnus coelolepis observe that “the uniformity in size and shape of the denticles on adults, and the regularity with which they are arranged, suggest that the ovoid ones that first develop on specimens a little more
than half-grown represent the final generation, which persists throughout the later life of the individual concerned.” Even more conflicting is the view of Ford (1921, p. 494) who discusses the eruption of denticles in embryos of Scyliorhinus canicula and S. stellaris and describes large denticles with a “single medium dorso-ventrally flattened cusp” which at a later stage “have apparently developed into normal tricuspid scales”. Obviously the question of whether growth can follow eruption or not cannot yet be said to be answered with certainty.
A more fundamental problem lies in the elucidation of the cause and mechanism for denticle changes. Periodic shedding and replacement of integumentary structures is not uncommon in many vertebrate groups. But progressive change in the nature of the integumentary structure with each replacement throughout the greater part of the life of the individual does not appear to be demonstrated elsewhere.
(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
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.
The material for this revision has come from many sources. Where possible I have acknowledged it throughout the text, but I would like to thank again, collectively, all the fishermen, museum and university staff-members, and the many others who have contributed to the study. I am particularly grateful to the University of New Zealand Research Grants Committee for their continued assistance with finance for expermental line-fishing in deep water; such fishing has brought to light not only the greater part of the new or rare material described throughout the study, but has also provided the larger range of material necessary for broader studies on growth change, distribution and related topics.
I am grateful also to my colleagues whose accounts of elasmobranchs elsewhere have provided the basis for comparison and determination of my material. In this respect it is particularly fitting to mention Dr. H. B. Bigelow and Mr. W. C. Schroeder, whose recent accounts of North Atlantic species have cleared the way for workers in other regions.
Lastly, I would thank Professor L. R. Richardson, of this department, whose encouragement and advice throughout the study have been a very real assistance.
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J. A. F. Garrick, M.Sc.,
Dept. of Zoology,
Victoria University of Wellington,
P. O. Box 196,