[Received by the Editor, November 24, 1958.]
The deep-water sharks Centroscymnus owstonii Garman, 1906 and C. crepidater (Bocage & Capello, 1864), known from Japan and the North Atlantic respectively, are now described from New Zealand. In both species juvenile and immature dermal denticles are strongly tridentate. Adult-type denticles in C. crepidater are moderately tridentate, but in C.x owstonii these have entire margins as in C. coelolepis. Diagnostic criteria for separating Centroscymnus from Scymnodon are reviewed; the shape and sculpture of dermal denticles are shown to be adequate criteria, while the degree of obliqueness of the lower teeth is not. On this basis Bigelow & Schroeder's (1957) acceptance of Centrophorus plunketi Waite, 1910 as a species of Centroscymnus is not tenable.
In this paper two species of the genus Centroscymnus, C. owstonii Garman, 1906 and C. crepidater (Bocage & Capello, 1864) are recorded from New Zealand waters. It is remarkable that both have previously been known only from the Northern Hemisphere, C. owstonii from Japan, and C. crepidater from the North Atlantic (Madeira, Portugal, Faroes and Iceland) They can now be regarded as bipolar species, though with some degree of caution, for their occurrence in deep-water in New Zealand (500–600 fathoms) suggests a possibility that they may range throughout the intervening tropical latitudes at depth.
The only previous record of the genus from New Zealand is based on the recent recognition by Garrick (1955) of Centrophorus waitei Thompson, 1930, as a species of Centroscymnus (this is excepting the mention of C. crepidater in Bigelow & Schroeder, 1957, p. 93, from information supplied by the author on some of the material described below). As C. waitei is known from only a single juvenile, its identification as a Centroscymnus is still open to some doubt, and it does not show the most characteristic feature of adults of the better known species—i e, the large, almost circular, concave, and mostly entire-margined dermal denticles which appear when specimens are half to two-thirds grown.
The genus has recently been reviewed by Bigelow and Schroeder (1957), resulting in the inclusion of several species previously referred to Scymnodon—i.e, C. macracanthus Regan, 1906, C. rossi (Alcock, 1898), C. plunketi (Waite, 1910) and C. crepidater. C. rossi and C. crepidater, together with those previously recognised as belonging to Centroscymnus—i.e., C. coelolepis Bocage & Capello, 1864, C. cryptacanthus Regan, 1906, C. fuscus Gilchrist and von Bonde, 1924, and C. owstonii Garman, 1906, form a reasonably compact assemblage which at the generic level is readily distinguishable from all squalid genera other than Scymnodon. The chief practical difficulty in diagnosing Centroscymnus and Scymnodon stems from the long-accepted usage of the shape of the dermal denticles as a primary generic character. In particular, the presence of entire-margined denticles with a concave outer surface has been regarded as a hallmark of Centroscymnus (and remains so), while sharks in all other respects similar, but having tridentate denticles, have been assigned to
Scymnodon. The discovery by Tortonese (1952, p. 386) and confirmed by Bigelow & Schroeder (1954, p. 47) that juvenile specimens of C. coelolepis have tridentate denticles has therefore led to considerable caution in the use of the denticles as a generic character. A further complication lies in the fact that at least one other species undoubtedly belonging to Centroscymnus, C. crepidater, has tridentate denticles even in the adult stage.
To overcome these difficulties, Bigelow & Schroeder (1957, pp. 85–87) have abandoned the use of the denticles as a primary diagnostic character, and propose instead a separation of the genera according to the lengths of the upper teeth at different regions along the jaw (those at the centre are about equal to those midway out along each side in Centroscymnus, but those midway out are longer than the centrals in Scymnodon) and the obliqueness of the lower teeth (all oblique and without a symmetrical median tooth in Centroscymnus, but symmetrical at the centre of the jaw and only weakly oblique towards the angles in Scymnodon). Because some species of Centroscymnus and Scymnodon are not well known it is not possible to evaluate completely the reliability of those tooth characters as generic criteria. That they are not in fact absolute is shown by one of the New Zealand specimens of C. crepidater recorded here, in which there is not only a symmetrical median lower tooth, but the adjacent teeth are themselves almost symmetrical and erect rather than oblique (Text-fig. 3, J). A further example is C. plunketi, also from New Zealand, which by its lower teeth should be classified as Centroscymnus, but by its upper teeth is referable to Scymnodon
In such cases as these, where there is conflict between the upper and lower teeth as diagnostic features, a further criterion is necessary, and available in the dermal denticles. Here attention should be given not only to the presence or absence of teeth on the denticle margins, as has been used in the past, but more especially to the overall shape and sculpture. In all except the most juvenile specimens of Centroscymnus the dermal denticles are subcircular in outline, and have a large and obvious circular concavity on their outer surface near the anterior end. If longitudinal ridges are also present on the outer surface the median ridge is restricted to the posterior half, or at most two-thirds, behind the concavity. (Text-fig. 2, A-C; Text-fig. 4, A.) By comparison, the denticles of Scymnodon are subovoid in outline, and have a longer median ridge which in most species extends the full length of the outer surface, so that a median concavity is either lacking or not conspicuous.
On the basis of these denticle features alone five of the nine species of Centroscymnus recognised by Bigelow & Schroeder (1957, pp. 95–96) can be readily identified as belonging to this genus. These are: C. coelolepis, C. crepidater, C. cryptacanthus, C. fuscus, and C. owstonii Of the remaining four species, C. rossi, C. macracanthus and C. waitei either have juvenile denticles not so far separable from those of Scymnodon, or else the denticles are insufficiently known to be used for generic diagnosis; the inclusion of these species in Centroscymnus on other criteria is also tentative, although C. rossi has very long preoral clefts like those of C. crepidater Such long clefts are not known in other species of either Centroscymnus or Scymnodon. The last species, C. plunketi, has denticles definitely referable to Scymnodon—a feature which, in conjunction with the condition in the upper teeth in this species where the longest teeth are midway out along the jaw, confirms that plunketi must be included in Scymnodon
With regard to the two species of Centroscymnus here recorded from New Zealand for the first time, C. owstonii agrees with all the suggested diagnostic characters for the genus, both as to the denticles and the upper and lower teeth as well. C. crepidater shows agreement with the denticle characters as modified above (even though its trunk denticles are tridentate in the adult stage), and also with the upper teeth characters. It does not, however, consistently agree in the
lower teeth, and for this reason, and also from the example of Scymnodon plunketi given above, the obliqueness of the lower teeth as a means of separating Centroscymnus and Scymnodon cannot be relied on.
The material on which these new records from New Zealand are based includes four specimens of C. crepidater from the Canterbury Museum, Christchurch, two specimens of C. crepidater from Kaikoura, and one specimen of C. owstonii also from Kaikoura. The Canterbury Museum specimens carry no data, but the way in which they have been gutted for the removal of their livers suggests that they were locally caught, and probably sent in from Kaikoura, which has been the source of several other deep-water species in the Museum. This was supported in November, 1955, when Mr. R. Baxter, experimentally line-fishing for the author, caught two more adult specimens of C. crepidater, one of them a pregnant female containing four embryos, on a long-line set in 500 fathoms a few miles south of Kaikoura. In the same locality, but a year later and in 600 fathoms, he caught the single specimen of C. owstonii
Comparison of these New Zealand specimens with those described from the Northern Hemisphere (as indicated by the proportional dimensions given in the descriptions following) shows no significant differences. The locally caught specimen of C. owstonii is considerably smaller than the Japanese holotype, and consequently shows some variation in proportions which can reasonably be attributed to its age—thus the eye is larger and the tail longer, the latter 4.0 in the total length compared with 4.4 in the holotype. The trunk is also stouter, and the pelvic-subcaudal interspace shorter. The many fewer upper teeth (39 compared with 64 in the holotype) is attributable to the same cause, for a similarly large variation occurs between juveniles and adults of C. coelolepis. Specific separation of either of these species from their northern counterparts is therefore not warranted. In the specimens of C. crepidater there is in fact more variation in proportions between the New Zealand embryos (these are late embryos and well developed) and the adults, than there is between the New Zealand adults and those from the North Atlantic.
Both of these species differ so sharply from each other, and from the only known specimen of C. waitei, that separation of them is clear-cut. There is now no possibility of either C. owstonii or C. crepidater being adult stages of C. waitei. C. crepidater is immediately distinct in its long preoral clefts, which extend so far in front of the upper jaw as to be almost confluent at the symphysis (Text-fig. 3, C). This feature is shared only with the inadequately known C. rossi of the Indian Ocean, which, as will be shown later, may possibly be a growth stage of C. crepidater.. Both C. owstonii (Text-fig. 1, C) and C. waitei have much shorter preoral clefts reaching only half or three-fifths of the distance from the angle of the jaws to the symphysis. But C. waitei is markedly short-snouted, the preoral length being only 6.9% of the total length, or less than the distance from mouth to first gill-opening. In C. owstonii the preoral length is 9.2%, and equal to the distance from the mouth to the second gill-opening. Other differences between these two species are the relative positions of the pectoral and first dorsal fins, and the second dorsal and the caudal In C. owstonii the pectoral fin when adpressed to the side of the trunk fails to reach the level of the first dorsal spine by a distance almost equal to the snout length, while in C. waitei the distance is only one-third of the snout length. The tip of the second dorsal fin in C. owstonii extends well posterior to the hypural origin and almost reaches the epiural, but in C. waitei it extends just to the hypural origin.
In addition to greatly extending the known distribution of C. owstonii and C. crepidater, the New Zealand specimens also provide further information on changes with growth of the dermal denticles. Changes in the shape and structure of successional generations of denticles are known fully only in C. coelolepis of the North Atlantic (see Bigelow & Schroeder, 1954, pp. 47–50), but similar changes
can now be reported for C. owstonii where they are as complete as those of C. coelolepis. In C. crepidater changes also occur but are of less magnitude. Adults of C. owstonii, as represented by the holotype, a male 778 mm long from Japan and figured in Garman (1913, Pl. 13, Fig. 8) have rather large denticles, with entire-margined, subcircular blades; each blade with a circular concavity on its outer surface but otherwise devoid of sculpture. These occur “on the flanks and back,” while “on those over the head, shoulder, and belly there are 3–5 weak keels” (Garman, 1913, p. 206). The smooth, concave-bladed denticles on the trunk are similar to those of adults of C. coelolepis. No other growth stages of C. owstonii have been definitely identified though Bigelow & Schroeder (1954, p. 51; 1957, p. 87) state that two small Japanese squalids, 260 mm and 287 mm long, in the Museum of Comparative Zoology, agree very closely with adults of C. owstonii and are probably referable to this species. These small, presumably juvenile specimens have tridentate denticles on their trunks.
The New Zealand specimen of C. owstonii, an immature female 584 mm long, is intermediate in size between the juveniles mentioned above and the holotype Its denticles are intermediate in character between juvenile and adult. These denticles (Text-fig. 2, A, inter) are tridentate and three-ridged, as are juvenile denticles (Text-fig. 2, A, juv.), but they are larger, wider and more circular in outline, therein approximating the form of adult denticles. They also carry the well-marked circular concavity near their anterior end, which is the most stable feature of all three stages in Centroscymnus.
Apart from the intermediate denticles, denticles of juvenile and adult types are also present on the specimen. The juvenile denticles are scattered generally among the other denticles (Text-fig. 2, A, juv.), and are obvious by their much smaller size and more strongly tridentate margins, the median tooth always being half the length of the blade or more. They are three-ridged, with the lateral ridges either very close to or on the edges of the blade. The intermediate denticles are present over most of the trunk (Text-fig. 2, A-C, inter), and are characterised not only by their larger size but by their broader, shorter teeth—the median tooth never exceeding half the length of the blade—and by their greater relative width, which gives them a more circular outline. The lateral ridges lie further in from the margins of the blade, and there may be additional smaller ridges outside the major ones. The adult denticles (or more correctly sub-adult denticles, for they are still weakly tridentate) occur only on the sides of the posterior part of the trunk (Text-fig. 2, B-C, adult), from the second dorsal fin rearwards on to the caudal axis.* They are the largest denticles of all, and differ from the others chiefly in their lack of sculpture. Their external surfaces are smooth and flat, without ridges, and carry only the large circular concavity near their anterior end. Posteriorly their margins are weakly tridentate, the median tooth being not more than one-fifth the length of the blade.
The three types of denticles resemble each other closely in the spacing of the teeth on their posterior margins, the distance between the tips of the lateral teeth being almost constant even though other dimensions of the denticles such as width and length are grossly different. The resemblance suggests that juvenile denticles could become intermediate, or intermediate become adult types by expansion of their anterior and lateral margins. Growth of this kind is, however, not feasible according to present knowledge of the method of formation of dermal denticles, where the outer layer of enamel is secreted by the ectoderm before the denticle is erupted, and cannot be added to later. The alternative interpretation, which has long been accepted, is that intermediate and adult denticles are formed in their
[Footnote] * This posterior site of origin of the adult type denticles shows some correlation with the condition in some bony fishes which Huntsman (1919, pp. 75 and 79) has shown have the sides of the caudal peduncle as one of the primary sites of scale formation.
final shape and size before erupting, and at a later stage than the juvenile or intermediate denticles which they replace, and which will eventually be shed. That this process does in fact occur is shown in the specimen of C. owstonii by removal of the denticles to expose the skin, particularly on the caudal peduncle where intermediate denticles are being replaced by those of adult type. This reveals new denticles, not yet erupted, which are forming between the existing ones, and which are of the adult type and size.
The above observations not only confirm the suggestion of Bigelow & Schroeder (1954, p. 50) that denticle succession involving differently shaped denticles takes place in C. owstonii, but indicate also the very close resemblance in this process between C. owstonii and C. coelolepis.. The resemblance includes the types of denticles involved, and also the time of appearance of the various types. In C. coelolepis adult-type denticles appear when specimens are about half-grown—ie, 500–700 mm long, a size-range which agrees well with the size of the New Zealand 584 mm specimen in which adult denticles are just apparent.
The New Zealand specimens of C. crepidater, like the North Atlantic representatives of this species, have tridentate, ridged denticles, even in mature adults. These denticles (Text-fig. 4, A-C) are circular in outline except for the teeth on the posterior margin, the median tooth being one-quarter to one-third the length of the blade. The blades carry five longitudinal ridges on their outer surface, as well as a prominent circular concavity near the anterior end. In all of these features these denticles closely resemble the intermediate-type denticles of C. owstonii (Text-fig. 2, A-C, inter) or C. coelolepis They are preceded by juvenile-type denticles as shown on embryos 250 mm to 260 mm long removed from an 895 mm New Zealand female. These juvenile denticles (Text-fig. 4, F), which have not been described before for the species, are very strongly tridentate, the median tooth being half or more of the length of the blade. The blades are three-ridged, with the lateral ridges on the margins, and are concave anteriorly Comparison of these denticles with the less tridentate forms which take their place in adult specimens shows that apart from their longer teeth they differ chiefly in the marginal position of their lateral ridges Each of these juvenile denticles is therefore equivalent to only the central half of an adult denticle, the latter having the blade extended outwards from the major lateral ridges, and usually with smaller additional lateral ridges along the extensions.
The embryos of C. crepidater mentioned above carry large yolk-sacs, which during preservation have become pear-shaped and are now 75 mm deep and 35 mm wide. The mass of yolk yet to be absorbed is considerable, but the embryos are of large size and remarkably similar in appearance and dimensions to the adult specimens. They are completely covered with denticles, and have teeth identical to those of the adults. They differ in their proportions from the adults chiefly in having relatively longer heads and tails, or conversely a shorter body section as expressed by the distance from the first gill-opening to the cloaca, which is about 41% of the total length in the embryos but 49% in the adults. The eye is proportionately larger, the mouth apparently wider, though not so in proportion to the head length, and the dorsal fins a little higher.
The embryos agree closely with the brief description of C. rossi (Alcock, 1898) of the Indian Ocean which, like C. crepidater, has unusually long preoral clefts reaching almost to the upper symphysis C. rossi is known only from the type specimen, a juvenile of comparable size (254 mm long). The illustrations of this species are not available to me, but according to Bigelow & Schroeder (1957, pp. 94–96) C. rossi appears to differ from adults of C. crepidater chiefly in a longer head (31% of the total length), and the lack of a subterminal notch on the caudal. In two of the New Zealand adult specimens of C. crepidater, the head length (measured from snout tip to pectoral origin) is 21.3% and 21.4% respectively, while in four
North Atlantic specimens the range is 23.7% to 24.1%. A New Zealand embryo, however, has a head length of 26.2%, a figure well above that of the adults though still short of the 31% of C. rossi (the last presumably measured from the illustration). In view of this closer correspondence between an embryo of C. crepidater and the juvenile C. rossi, further examination of the latter is desirable, not only to provide detailed comparison of all of the proportional dimensions, but also of the morphological features generally, including the denticles. Such comparison may well show that the two species are not separable.
Centroscymnus owstonii Garman 1906. (Text-fig. 1, figs. A-K; Text-fig. 2, figs. A-E).
Study Material. One immature female specimen, 584 mm long (Dom. Mus. No. 2539), lined from 600 fathoms, 7 miles south of Kaikoura by Mr. R. Baxter, in September, 1956.
Description. Proportional Dimensions in per cent of total length. (The dimensions of the holotype, extracted from the illustration in Garman, 1913, Pl. 13, Figs. 5 and 7, are given in the second column for comparison with those of the New Zealand specimen).
|♀ 584 mm||Holotype ♂|
|N.Z.||778 mm Japan|
|Trunk at pectoral origin: breadth||13.4||10.9|
|Snout length in front of: outer nostrils||2.1||2.6|
|Eye: horizontal diameter||6.0||5.0|
|Nostrils: breadth between inner corners||3.8||3.7|
|Preoral clefts: breadth between inner ends||4.6||4.6|
|Gill-opening lengths: 1st||1.7||1.5|
|1st dorsal fin: vertical height||3.2||2.8|
|length of base from origin of spine||3.1||3.3|
|2nd dorsal fin: vertical height||4.1||4.4|
|length of base from origin of spine||4.4||4.8|
|Caudal fin: upper margin||22.2||19.2|
|lower anterior margin||12.3||10.9|
|Pectoral fin: anterior margin||12.0||10.9|
|Pelvic fin: anterior margin||6.8||9.2|
|Distance from snout to: eye||5.8||5.7|
|1st gill opening||17.9||17.8|
|5th gill opening||21.7||21.4|
|origin of 1st dorsal spine||39.3||38.0|
|origin of 2nd dorsal spine||67.5||70.0|
|Interspace between: insertion of 1st dorsal base and origin of 2nd dorsal spine||26.6||28.8|
|Interspace between: 2nd dorsal and caudal||6.2||6.1|
|pelvic and subcaudal||8.0||8.7|
|Distance from origin to origin of: pectoral and pelvic||37.7||38.0|
|pelvic and subcaudal||15.7||18.1|
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Head strongly depressed, large-eyed, and the snout profile pointed, snout length in front of eye slightly less than the inter-space between the eye and the first gill-opening; trunk moderately slender and increasingly compressed posteriorly. Dorsal and ventral profiles smoothly and equally arched. Height of trunk at origin of pectorals about 1/7 of its length to origin of caudal Length of body measured to the cloaca, 65% of the total length. Caudal peduncle strongly compressed and without lateral keels or precaudal pits.
Dermal denticles of moderate size, close-set and overlapping to leave few and small interspaces, and covering the whole of the body with the exception of the axils of the fins and the margin of the lower lip. The naked axillary areas of the pectoral and pelvic fins are rather large, extending along the upper surface of each fin to its margin and embracing about one-quarter of the width of the fin. The denticles of the trunk vary in size and shape according to their location, though each has a broad, thin, near-horizontal blade, sub-circular m contour except for the posterior margin, borne on a slightly four-angled pedicel arising from a rhomboidal-shaped base. The blades are prolonged anteriorly so that they overhang the pedicel, with about one-third of their length anterior to it, and two-thirds posterior. Along
Text-Fig. 1.—Centroscymnus owstonu, New Zealand female 584 mm (Dom. Mus. No. 2539. Fig. A—Lateral view and insets of transverse sections of snout and caudal peduncle. Figs. B-C—Dorsal and ventral views of head. Fig. D—Left nostril. Figs. E-G—Right upper teeth (row numbers indicated above figures). Fig. H—Right lower teeth. Fig. 1—5th right upper tooth. Fig. J—17th right upper tooth. Fig. K—5th right lower tooth C, level of cloaca, SP, dorsal spine
the greater part of the trunk, from the head to the level of the second dorsal fin, the blades have strongly tridentate posterior margins, and are of two sizes. The larger and more recently erupted of these (Text-fig. 2, A, inter), which are in the majority, have the median tooth one-third to almost one-half of the length of the blade, while the smaller denticles (Text-fig. 2, A, juv.), which are the embryonic or early juvenile generation and hence older, have longer median teeth which are at least one-half and sometimes three-fifths the lengths of the blades Both sizes of denticle have three major sharp-topped longitudinal ridges on the external surfaces of their blades, there being a median ridge and one lateral ridge on each side. The lateral ridges extend along the whole length of the blade, terminating posteriorly at the lateral teeth Anteriorly the lateral ridges curve medially and are confluent, so that they enclose an area about three-quarters the width of the blade. The enclosed area contains a saucer-shaped depression anteriorly, the length of which is one-quarter to one-third that of the blade. The median ridge of the blade arises from the posterior edge of this depression and extends posteriorly to the tip of the median tooth Most of the larger denticles also have a low lateral ridge outside each of the large lateral ridges, and near to and parallel to the edge of the blade. At the level of the second dorsal fin, and posteriorly along the sides of the peduncle and on to the caudal axis there are again two main sizes of denticles (Text-fig. 2, B), the smaller of which correspond in size, shape, and sculpture with the large denticles from the anterior part of the trunk. The larger denticles from the rear part of the trunk (Text-fig. 2, B, adult), which are are least half as long again as the others in the same region, and larger than the denticles anywhere else on the whole fish, have the same facies as those anteriorly, but the teeth and sculpture are considerably reduced, particularly on those denticles at the extreme end of the peduncle and on the caudal axis (Text-fig. 2, C, adult) The median tooth is at most one-fifth the length of the blade, while the lateral and median ridges may be present only on the toothed portion of the blade, or lacking entirely. The external surface of each blade is therefore almost completely smooth and flat, except for the saucershaped depression anteriorly, which retains its prominence. The denticles from the head and snout are smaller than those on the anterior part of the trunk, and are tridentate with rather weak lateral teeth. They carry three main ridges, the median ridge generally extending to the anterior edge of the blade, where it joins the confluent lateral ridges. At the margins of the lips the denticles lack lateral teeth and are less sculptured than those on the remainder of the head. The upper lip denticles in particular are noticeably smooth and thin, and broadly leaf-shaped in contour.
Head measured to first gill-opening 5.5 in the total length Head depressed, and wedgeshaped in profile, so that the snout tip is pointed. The least fleshy interorbital distance about 2.0 in the head Snout strongly depressed, with a prominent dorsolateral edge on each side extending from the eye to the snout tip Contour of snout from above bluntly pointed, and increasing gradually in width to the hind level of the eyes. Length of snout measured to the eye 3.1 in the head, and equal to the horizontal diameter of the eye Eye more than twice as long as high Spiracle large, and placed just above the dorsal margin of the eye and behind it by a distance equal to its own length. The anterior margin of spiracle broadly concave, the posterior margin almost straight. Gill-openings small, almost vertical, concave, and in a horizontal series anterior to the pectoral base Lengths of the gill-openings sub-equal, the first 4.0 in the horizontal diameter of the eye, the others slightly shorter. Nostrils of moderate size, oblique, and placed well forward on the ventral surface of the snout and close to the lateral margins Interspace between the nostrils 1.5 in the snout Each nostril subdivided into a circular anterolateral aperture and a subovoid posteromedial aperture by the triangular nasal flaps which are extensions of the anterior and posterior nasal margins. The anterior nasal flap sharply pointed and external to the thick and fleshy posterior flap Mouth broad and almost straight, its width 1.4 in the preoral distance. The upper lip fimbriated, the lower lip smooth. Preoral clefts short, reaching just less than half the distance from the angles of the jaw to the upper symphysis, each of them opens into a long narrow pouch running parallel to and in front of the upper jaw, almost to the upper symphysis. Posteriorly the clefts are continued by oblique furrows which terminate halfway between the angles of the jaws and the first gill-openings.
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Teeth 19–20/18–19, dissimilar in the two jaws. The upper teeth erect, at least in the median third of each side of the jaw, where each has a single, smooth-edged, sharply-pointed, lanceolate cusp borne on a squarish bifid base. The basal portion of each cusp is constricted, and carries two flange-like ridges on its external surface. The size of the cusps, and particularly their width, increases from the centre of the jaw outwards to reach a maximum in the 4th to 6th rows, though the length of these wider cusps is not much greater than that of the central teeth. In the lateral two-thirds of each side of the jaw, the teeth become increasingly small and oblique, with shorter cusps which are obtusely notched on their lateral margins. The transition from erect to oblique cusps occurs at the 9th row on each side, but is not a strongly marked feature Three series of upper teeth functional at the centre of the jaw, two towards the angles. The lower teeth blade-like, each with a quadrangular base shallowly notched basally and bearing a single, smooth-edged, sharply-pointed triangular cusp. All the cusps
Text-Fig. 2.—Centroscymnus owstonn, New Zealand female 584 mm (Dom. Mus. No. 2539). Fig. A—Dermal denticles from high on side at level of 1st dorsal. Fig. B—Denticles from side at level of 2nd dorsal. Fig. C—Denticles from halfway along caudal axis. Fig. D—Denticle from interorbital region. Fig. E—Denticle from margin of upper lip Adult, sub-adult denticle; intermed, intermediate denticle; juv., juvenile denticle.
are notched laterally and strongly oblique, so that an almost continuous cutting edge is presented. There is no symmetrical median tooth, the first tooth on the right side slightly overlapping the first tooth on the left A single series of lower teeth functional.
First dorsal small, elongate and brush-shaped, originating smoothly from the dorsal profile at about the level of the tip of the pectoral when the latter is adpressed to the side of the trunk. Height of first dorsal slightly more than the length of the posterior part of its base measured from the origin of the spine, and 17 in the snout. The first dorsal spine has only its extreme tip exposed, halfway along the anterior margin of the fin, and does not protrude enough to interrupt the profile Anterior, postenor, and distal margins almost straight, the apex bluntly rounded, and the posterior tip not produced. The posterior margin free from the base for a distance equal to one and one-half times the height of the fin. The second dorsal higher than the first, and more triangular in shape. Origin of the second dorsal above the middle of the pelvic base, and the tip of the second dorsal spine just posterior to the insertion of the pelvic base. The posterior tip of the second dorsal extends behind the hypural origin, and almost to the epiural origin Caudal measured from the hypural origin 40 in the total length, the epiural lobe not as well developed as the deep hypural. Height of the epiural 50 in its length, its margin almost straight. The terminal lobe convex, and separated from the hypural lobe by an obtuse subterminal notch. Origin of the hypural well anterior to that of the epiural. Height of the hypural one and one-half times that of the epiural, the lower anterior margin mostly straight, the apex bluntly pointed, and the postenor margin concave. The pectorals originate just behind the fifth gill-opening, and are twice as long as broad. Length of the pectorals, 16 in the head. The anterior margin just convex, the anterior angle bluntly pointed, and the distal and posterior margins convex. The posterior angle
broadly rounded. Length of the pectoral base equal to the greatest breadth of the pectoral. The pelvic origin well behind the posterior tip of the first dorsal, the interspace between these levels equal to the distance from the anterior edge of the eye to the second gill-opening. The size of the pelvics equal to that of the second dorsal, which they resemble in shape except for their posterior tips, which are less pointed or produced.
Colour. Uniform dark brown except for patches of white (due to lack of pigment in the dermal denticles) along the midline of the head, behind each spiracle, on the upper surface of each pectoral, and along most of the epiural lobe.
Centroscymnus crepidater (Bocage & Capello, 1864). (Text-fig. 3, figs A-N; Text-fig. 4, figs A-F).
Study Material. (a) Adults. Four female specimens, 822 mm to 895 mm long, presumably from Kaikoura, in the Canterbury Museum (one of these, of 822 mm, now Mus. Comp Zool No 39570); two female specimens, 875 mm and 895 mm long (Dom. Mus. Nos. 2536 and 2537 respectively) lined from 500 fathoms, 7 miles south of Kaikoura, by Mr R. Baxter, in November, 1955 (b) Embryos Four late embryos, one male and three females, 250 mm to 260 mm long (three of these as Dom. Mus. No. 2538), all with large yolk-sacs, taken from the female of 895 mm listed above as Dom. Mus. No. 2537.
Description. Proportional Dimensions in per cent of total length: A, female 895 mm, Canterbury Museum; B, female 895 mm (Dom. Mus. No. 2537), Kaikoura; C, female embryo, 260 mm (Dom. Mus. No. 2538), removed from specimen B; D, four females, 746 mm to 796 mm, off Iceland and the Faroes, from the University Zoological Museum, Copenhagen (dimensions of D from Bigelow & Schroeder, 1957, p. 94).
|Trunk at pectoral origin: breadth||11.1||11.0||11.0||8.3–9.3|
|Snout length in front of: outer nostrils||2.3||2.9||2.3||—|
|Eye: horizontal diameter||5.0||5.0||5.8||4.4–4.6|
|Nostrils: breadth between inner corners||3.9||3.9||4.8||3.1–3.6|
|Preoral clefts: breadth between inner ends||1.2||1.6||1.7||1.1–1.3|
|Gill-opening lengths: 1st||1.5||1.7||2.3||1.3–1.5|
|1st dorsal fin: vertical height||5.0||4.8||3.9||5.1–5.5|
|length of base from origin of spine||4.9||5.7||4.8||5.9–6.7|
|2nd dorsal fin: vertical height||5.1||5.2||4.2||4.3–5.9|
|length of base from origin of spine||5.2||6.1||5.0||6.3–6.8|
|Caudal fin: upper margin||19.1||18.7||22.7||19.0–20.7|
|lower anterior margin||12.8||11.8||12.7||10.7–13.5|
|Pectoral fin: anterior margin||12.4||10.7||10.4||11.8–13.1|
|Pelvic fin: anterior margin||7.5||8.7||—||—|
|Distance from snout to: eye||7.7||8.7||9.6||8.2–9.3|
|origin of 1st dorsal spine||37.7||37.7||38.5||—|
|origin of 2nd dorsal spine||68.7||70.0||65.5||—|
|Interspace between: insertion of 1st dorsal base and origin of 2nd dorsal spine||28.2||27.1||23.1||—|
|2nd dorsal and caudal||5.9||6.1||7.3||6.9–8.0|
|pelvic and subcaudal||7.1||8.7||8.8||7.4–8.8|
|Distance from origin to origin of: pectoral and pelvic||41.0||40.2||31.6||36.6–40.7|
|pelvic and subcaudal||15.2||17.1||14.2||15.2–17.9|
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(a) Adults. Head strongly depressed, large-eyed, and the snout profile pointed; snout length in front of eye equal to or greater than the interspace between the eye and the first gill-opening, trunk moderately slender, and increasingly compressed posteriorly. Dorsal and ventral profiles smoothly and equally arched. Height of trunk at origin of pectorals about 1/9th of its length to origin of caudal. Length of body measured to the cloaca, 67% of the total length Caudal peduncle strongly compressed, and without lateral keels or precaudal pits.
Dermal denticles moderately large, close-set and overlapping to leave few and small interspaces, and covering the whole of the body with the exception of the axils of the fins and the margin of the lower lip. The pectoral fins with rather large, naked, axillary areas extending along the upper surface of each fin to its up and parallel to its posterior margin
Text-Fig. 3.—Centroscymnus crepidater, New Zealand female 895 mm, Canterbury Museum. Fig. A—Lateral view and inset of transverse section of snout. Figs. B-C—Dorsal and ventral views of head of New Zealand female 837 mm, Canterbury Museum. Fig. D—Transverse section of caudal peduncle. Fig. E—Left nostril. Figs. F-H—Right upper teeth (row numbers indicated above figures). Fig. I—Teeth at centre of upper jaw showing a new row of teeth developing between the existing rows. Fig. J—Right lower teeth. Figs. K-L—Lateral and external views of 3rd right upper tooth. Fig. M—16th right upper tooth. Fig. N—5th right lower tooth. C = level of cloaca.
so as to embrace a little more than one-third of the area of the fin. Each denticle of the trunk region with a broad, thin, near-horizontal blade borne on a slightly four-angled pedicel that arises from a stout, essentially rhomboidal-shaped base. The blade is prolonged anteriorly so that about one-third of its length is anterior to the pedicel and the remaining two-thirds posterior. The contour of each blade is subcircular except for the posterior margin, which is interrupted by three prominent, sharply pointed teeth, a median, and one lateral on each side, separated from each other by moderately incised notches. The median tooth is longer than the lateral teeth, its length less than one-third of the length of the blade. The external surface of each blade usually with five longitudinal ridges, including a median ridge, and one large and one small lateral ridge on each side. The large lateral ridges, which are the most prominent, extend along almost the whole length of the blade, and terminate posteriorly at the tip of the lateral teeth Anteriorly these large lateral ridges curve medially and become confluent, thus enclosing an area which occupies about one-third to one-half of the width of the surface of the blade. This enclosed area is excavated anteriorly to form a saucer-shaped depression which extends about one-third of the length of the area. The median ridge which lies within the enclosed area does not extend along the full length of the latter, but arises from near to or just within the posterior edge of the depression and terminates at the tip of the median tooth. The small lateral ridges he outside and parallel to the large lateral ridges, but although their anterior ends curve medially they fail to become confluent, the area between these ends usually having two and sometimes more small, irregular, shallow depressions A few of the blades have an additional small lateral ridge outside and parallel to those already described All of the ridges are sharp-topped.
The base of each denticle is essentially rhomboidal in outline, with four major angles from each of which a major ridge rises on to the pedicel. However, the two anterior margins of the base each have one or two additional minor angles, so that these margins are scalloped, and the number of ridges rising on to the pedicel is increased by the addition of a minor ridge from each minor angle. The denticles of the head region, including the upper and lower lips, are smaller than those of the trunk and differ from them in that the posterior lateral teeth are absent and the median tooth is reduced or almost lacking. The median ridge is produced anteriorly so that in some examples it extends along the whole length of the enclosed area. The lateral ridges, particularly on the denticles from the lips, curve towards the midline of the denticle posteriorly and may almost reach the tip of the median ridge. The denticles on the tail are generally similar to those of the trunk, but have a deeper depression within the enclosed area, a shorter median ridge, and smaller teeth.
Head measured to 1st gill-opening about 5.5 in the total length. Head depressed, and wedge-shaped in profile so that the snout tip is sharply pointed. The least fleshy interorbital distance 22 in the head Snout strongly depressed and thin, with a prominent dorsolateral edge on each side extending from the eye to the snout tip. Contour of snout from above bluntly pointed at the snout up, but slightly concave just anterior to the nostrils Posterior to this level the snout rapidly widens to reach its maximum breadth, which is retained for the remainder of the snout and to about the hind level of the eyes. Length of snout measured to the eye 25 in the head, and equal to the distance from anterior of eye to the posterior edge of the spiracle. Eye large, oval, about twice as long as high, its horizontal diameter 14 in the snout Spiracle large, and placed a little above the dorsal margin of the eye and behind it by a distance equal to its own length. The anterior margin of spiracle broadly concave, the posterior margin almost straight. Gill-openings small, not quite vertical, concave, and in a horizontal series anterior to the pectoral base Lengths of the first four gill-openings subequal, each about 30 in the horizontal diameter of the eye. The 5th gill-opening distinctly longer than the others. Nostrils of moderate size, oblique, and placed well anterior on the ventral surface of the snout and close to the lateral margins. Interspace between the nostrils 20 in the snout. Each nostril subdivided into a circular, anterolateral aperture and a subovoid, posteromedial aperture by the triangular nasal flaps which are extensions of the anterior and posterior nasal margins. The anterior nasal flap with a sharply pointed tip, and external to the thick fleshy posterior flap. Mouth moderately arched and broad, its width 18 in the preoral distance. The upper lip with an irregularly fimbriated margin, and the lower lip smooth. The preoral clefts deeply incised and extremely long, so that their anterior ends are almost confluent in front of the upper jaw symphysis Posteriorly they are continued by furrows well behind the angles of the jaws. Length of each cleft and furrow 16 in the preoral distance, with ⅔ of this length anterior to the angles of the jaws, and ⅓ posterior.
Teeth 38/16-1-16 in the 895 mm specimen from Canterbury Museum, and dissimilar in the two jaws. The upper teeth erect, at least in the median third of each side of the jaw where each has a single, smooth-edged, sharply-pointed, lanceolate cusp borne on a wide, rectangular, bifid base. The basal portion of the cusp is considerably constricted and carries two short, curved, flange-like ridges on its external surface. The teeth in the lateral two-thirds of each side of the upper jaw are increasingly oblique, each tooth with a short, triangular cusp which is obtusely notched on its lateral margin and has a slight shoulder on each side
where it joins the base. The size of the upper teeth increases slightly from the centre of the jaw towards the middle third on each side, but then decreases rapidly towards the angles. The transition from the erect, lanceolate cusps to the oblique, notched cusps is abrupt, occurring at about the 8th row from the centre on each side of the jaw. Three series of teeth functional at the centre of the jaw, two towards the angles. In this 895 mm female from the Canterbury Museum, the number of rows of teeth is in the process of being increased, as indicated by two incipient new rows of small teeth at the centre of the jaw, and at the level of the developing and as yet non-functional series of teeth. One of these new rows is at the centre of the jaw, and the other is between the 1st and 2nd rows of the left side. In both cases the new teeth have lanceolate cusps but ovoidal bases which readily distinguish them from the established teeth. The lower teeth blade-like, each with a quadrangular base shallowly notched basally, and bearing a single smooth-edged, sharply-pointed triangular cusp. Each cusp is slightly oblique, and the degree of obliqueness increases in the teeth towards the angles of the jaws. The cutting edges of the cusps are curved rather than straight, and the cusps are notched laterally where they join their bases. A symmetrical median tooth with a lateral notch on each side of the cusp is present on one of the specimens. There is a single, compact series of teeth functional, with the lateral margin of the base of each tooth slightly overlapping its neighbour.
First dorsal brush-shaped, of moderate size with a long base, and originating smoothly from the dorsal profile a little anterior to the level of the posterior insertion of the pectoral. Height of 1st dorsal equal to the length of the posterior part of its base measured from the origin of the spine, and 14 in the snout. The anterior margin interrupted ⅔ of the way along its length by the 1st dorsal spine, which arises obliquely and projects for a distance equal to or slightly less than the length of the spiracle Anterior to the spine the 1st dorsal margin is shallowly concave, but posterior it is straight or just convex, and continues smoothly over the apex. The distal margin straight to convex, and the posterior tip pointed and free from the base for a distance just greater than the height of the fin. The 2nd dorsal just higher than the 1st and with the apex better defined and almost bluntly pointed Origin of the 2nd dorsal above the pelvic origin, and the tip of the 2nd dorsal spine above or just anterior to the insertion of the pelvic base. The posterior tip of the 2nd dorsal extends well posterior to the tips of the pelvics and also to the hypural origin, but just fails to reach the epiural origin. Caudal measured from the hypural origin 44 in the total length, the epiural lobe little developed in contrast to the rather deep hypural lobe. Height of the epiural lobe 60 in its length, and its margin barely convex. The terminal lobe truncate or slightly convex, and separated from the hypural lobe by an obtuse subterminal notch. The hypural lobe originates considerably anterior to the epiural, its height is almost twice that of the epiural lobe, and its lower anterior margin concave at its origin but convex towards the apex which
Text-Fig. 4.—Centroscymnus crepidater, New Zealand female 895 mm, Canterbury Museum. Figs. A-C—Dermal denticles from high on the side at the level of the 1st dorsal. Fig. A—External view. Fig. B—Median vertical longitudinal section Fig C—apical view. Fig. D—Denticle from interorbital region. Fig. E—Denticle from caudal fin. Fig. F—New Zealand male embryo 252 mm (Dom. Mus. No. 2538), denticles from high on the side at the level of the 1st dorsal.
is bluntly pointed. The posterior margin is concave. The pectorals originate just posterior to and near the lower level of the 5th gill-openings, and are twice as long as broad. Length of the pectorals 17 in the head, so that when adpressed to the sides they just fail to reach the level of the exposed tip of the 1st dorsal spine. The anterior margin a little convex, the anterior angle rounded, and the distal and posterior margins strongly convex and not separated by a distinct posterior angle. Length of the pectoral base equal to the greatest breadth of the pectoral. The pelvics originate well posterior to the posterior tip of the 1st dorsal, the interspace between these levels equal to the distance from the anterior corner of the eye to the pectoral origin. The size of the pelvics equal to that of the dorsal fins, though the pelvic base is much shorter, being equal to the length of the snout. The shape of the pelvics similar to that of the 1st dorsal, with the anterior and distal margins a little convex and the apex smoothly rounded. The posterior tip sharply pointed and terminating below the posterior insertion of the 2nd dorsal base.
Colour. Uniform dark brown, but with a golden sheen to the denticles when freshly caught.
(b) Embryos. Description of the late embryos as for adults, except as given below; based chiefly on female of 260 mm, carrying a yolk-sac 75 mm deep and 35 mm wide.
Length of body measured to the cloaca 61.5% of the total length.
Dermal denticles thin, flexible, and very easily rubbed off. Over the whole of the body they are large, close-set and overlapping to leave few and small interspaces. Naked axillary areas of the fins as in the adults, but with rather more of the extremities of the fins bare of denticles. Each denticle of the trunk region with a horizontal blade which is strongly tridentate, the median tooth is very sharply pointed, longer than the lateral teeth and half or more of the length of the blade. Anteriorly the external surface of each blade is excavated as a shallow depression similar to that in the adult denticles. There is also a median longitudinal ridge originating at the posterior edge of the depression and extending to the tip of the median tooth, and a lateral ridge on each side. The lateral ridges form a raised rim along the sides of the blade, are confluent anteriorly where they border the depression on the blade, and terminate posteriorly at the tips of the lateral teeth.
Head measured to first gill-opening, 4.5 in the total length. Length of snout measured to the eye, 2.3 in the head Horizontal diameter of eye, 1.4 in the snout.
Teeth 20–18/16–16 in the 252 mm male, and identical to those of the adults However, none of the series of lower teeth are in a functional position, but instead are still placed on the inner face of the lower jaw.
Caudal measured from the hypural origin 3.7 in the total length. Length of the pectorals 2.2 in the head.
Colour: Uniform dark brown.