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Abstract
Dasyatis brevicaudatus (Hutton, 1875) is a stingray characterised by a smooth rhomboidal disc broader than long, and a tail closely subequal to the length of the disc and bearing a strong ventral fold and one or more dorsal serrated spines. D. brevicaudatus is known from New Zealand, Australia and South Africa, but records from these countries indicate confusion with a concealed second species having a slightly longer tail and possibly sharply spined teeth.
The short-tailed species of stingray in New Zealand waters was first described by Hutton in 1875 as Trygon brevicaudata, from a female specimen taken in Dunedin Harbour and measuring 76 inches in overall length but showing signs of having lost a portion of the extremity of the tail. It was obvious that only a small part of the latter was missing, for in Hutton's words, “the end of the tail of this specimen is broken off; but it is evident that it could only have extended a few inches further.” The specimen was generally similar to the larger stingrays which we now recognise as belonging to the g. Dasyatis, but was characterised by having a smooth disc broader than long, with an obtuse anterior angle; the tail subequal to the length of the disc and with a prominent keel below but no upper ridge; and the tail armed “with two serrated spines, the anterior one the smaller, and in front of these a row of large ossifications; sides of the tail with smaller stellate ossifications.”
Hutton (1872) had earlier provisionally identified a species of stingray from New Zealand waters, as Trygon thalassia, from a dried tail, 22 inches in length, in the Colonial Museum. But in 1876, in a repetition of the description of Trygon brevicaudata, Hutton states further that the tail which he provisionally identified as that of a specimen of T. thalassia, “may probably belong to a male of this (T. brevicaudata) species.”
Since then, there has been no adequate description published of a complete specimen of D. brevicaudatus from New Zealand material. Waite (1909) describes a female specimen taken by the New Zealand Government Trawling Expedition of 1907, but this specimen lacks the greater part of the tail; and Graham (1953) gives a general account of the species but uses an illustration (after McCulloch) of an Australian specimen. Some of the features described by Waite do not agree with the material used in this study, and these will be discussed later in this paper following a description of D. brevicaudatus from New Zealand material.
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McCulloch (1915, 1921, 1922), Waite (1921), and Whitley (1940), give accounts of D. brevicaudatus from Australian waters, and Smith (1949) lists the species from South Africa, but it is obvious from some of these accounts and from the illustrations that not all of the specimens described by these authors can be assigned to D. brevicaudatus. Fowler (1941) lists the complete synonymy of D. brevicaudatus.
The material used in this study includes the type specimen, at present lodged in the Otago Museum, and comprising a stuffed mount of the dorsal surface only; a female of 64 inches total length trawled from 40 fathoms off Cape Campbell by the steam trawler “Maimai” in November, 1952, complete except for a damaged nasal flap; and three dried tails from the Dominion Museum collection, the first of which is 22 inches long, labelled Col. Mus. N.Z. 186. Tail of the Sting Ray. Pres. by Rev. Mr. Stock, and is obviously the same tail as that identified by Hutton (1872) as T. thalassia; the second 28 inches long (dried skin only) and labelled J. Bollons. 18th June, 1932; and the third 11 ½ inches long and labelled Black Stingaree, Awanui. F. M. Begley. Oct. 8th, 1941. No. 822. A description of the species D. brevicaudatus from the “Maimai” specimen is as follows:
Dasyatis brevicaudatus (Hutton) 1875. Text-fig. 1, Figs. A-K. Text-fig. 2, Figs. A, B, C.
Body depressed, thick, rhomboid; anterior angle of disc obtuse and tip of snout bluntly pointed so that it scarcely breaks the outline. Head wide but not greatly distinct dorsally from disc. Snout profile concave above in lateral view. Tail stout and tapered, its length less than the length of the disc. Disc smooth, tail tuberculate and bearing a serrated spine. Length of disc (including pelvics) 1.6 in the total length, and 1.1 in its width. Greatest width of disc at level of third gill-slit and 1.5 in the total length. Greatest depth of body at pectoral symphysis, 9·0 in the total length.
Snout greater than the depth of body and 1.4 in the head as measured to the first gill slit. Interorbital 1.6 in the head and 6.0 in the width of the disc. Eyes small, lateral, partly covered dorsally by a bluntly pointed, fleshy, supraorbital lobe, and provided with a frilled pupillary flap. Length of eye 9.4 in the snout md 8·3 in the interorbital. Spiracles partly lateral, large and ovoidal, placed posterolateral to the eyes. Length of spiracles 3.0 in the snout, and 2.7 in the interorbital. Head 5·2 in the total length and 3.6 in the width of the disc, Gill-slits small, sinuous, the first slit twice the width of the 5th. Distance between the first and second slits equal to that between second and third, and slightly greater than that between third and fourth, which latter is also greater than that between fourth and fifth. Transverse distance between first slits 1·5 times that between the fifth slits and 1·3 in the head. Nostrils ovoidal, transverse, the internarial width 1.3 in the distance from anterior edge of disc to the nostrils and 2·6 in the head. Nostrils separated by a wide rectangular nasal flap, its length 2.2 in its width which is greatest anteriorly. Posterolateral corners of the lap rounded, while medially it is secured by a stout frenulum. Posterior edge of the flap just anterior to the mouth, slightly concave and with a well-demarcated, finely fimbriated margin. Mouth almost transverse, its width 3.0 in the head. Upper lip with coarse, transverse pleats laterally, lower lip irregularly and coarsely papillose. Both lips laterally bounded by incurving nasoral grooves.
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Text-Fig. 1.—D. brevicaudatus, female, 64 inches total length.
Figs. A, B, C—Lateral, dorsal and ventral views.
Figs. D, E—Lateral and dorsal views of left eye and spiracle.
Figs. F, G— Dorsal and lateral view of small, circular tubercle from side of tail.
Figs. H, I—Lateral and dorsal views of middorsal tubercle from anterior of tail.
Fig. J—Teeth from median region of upper tooth plate.
Fig. K—Ventral view of mouth and jaws, showing maxillary velum and oral papillae.
B, base of tooth; IC, incipient cusp; MV, maxillary velum; O, rugose occlusal surface; OP, oral papillae; PF, pupillary flap; SL, fleshy supraorbital lobe; SP, spiracular valve.
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[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
Teeth arranged in pavement, the rows prominently oblique. Dental formula 22–1-22/24–1-25, the tooth plates broad, extending across the whole width of the mouth, with 10 to 11 anterior rows of teeth functional. Teeth in both jaws similar, rhomboidal in outline, those in the posterior rows with a broadly rounded incipient cusp. Teeth in the anterior rows with the cusp eroded. The occlusal surface of all the teeth finely and superficially rugose. Immediately internal to the upper tooth-plate is a pendant, transverse, maxillary velum, its width little less than the width of the mouth and its height 7.0 in its width. Its lower frer edge shallowly concave and coarsely serrated with the largest serrations medial. On the floor of the mouth, behind the lower tooth-plate, are five oral papillae in a transverse series, three medial and slightly advanced, and one lateral papilla on each side.
Pectorals wide, the anterior margin of each almost straight, though convex distally where the lateral angle is a smooth steady curve. Posterior margin convex and deeply notched at the posterior insertion, the posterior angle bluntly pointed. Distance between the two pectoral insertions slightly more than the interorbital width. Origin of the pelvics slightly anterior to the insertion of the pectorals Pelvics extend a short distance behind the pectorals, their anterior margin concave the lateral margins almost straight, and the lateral and posterior angles smoothly and sharply curved. The insertion of each pelvic acutely and deeply notched.
Text-Fig. 2.—D. brevicaudatus, female. 64 inches total length. A dorsal view tail: B. lateral view tail; C. dorsal view serrated spine.
DK, dorsal keel; LT, lateral tubercle, MT. middorsal tubercle; OS, origin serrated spine; S, serrated spine; VF, ventral fold.
Tail stout, tapered, its length less than the length of the disc and 2.2 in the total length. The anterior half depressed, the posterior half compressed. Midway along its length there arises dorsally a single, posteriorly directed, stout, tapered, serrated spine, the serrations numerous, lateral, and directed anteriorly. The serrated spine is inset for the proximal one-third to one-half of its length, in a shallow naked groove, but distally it is upraised from the tail. Length of the spine about 3·0 in the length of the tail and width at its origin 2.4 in the depth of the tail at the same level. A ventral keel originates below and slightly posterior to the origin of the serrated spine and extends posteriorly to beyond the tip of the spine but falls far short of the tip of the tail. Length of the keel 2.5 in the
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length of the tail, and its greatest height at a level one-third back from its origin and equal to or less than the depth of the tail at the same level. A minute dorsal keel arises just anterior to the tip of the serrated spine and extends beyond the spine but does not reach the level of the insertion of the ventral keel. Anterior to the serrated spine, forming a middorsal row, there arc nine large spinous tubercles with a scar between the first and second indicating a tenth. Each tubercle consists of a large ovoidal base, longer than wide, its length approximating half the depth of the tail at the origin of the serrated spine, from which arises a longitudinal ridge with a flattened anterior face terminating in an erect spine over the posterior half of the base. Both base and spine bear fine radial striations. The most anterior tubercle is above the insertion of the pelvic fins, and the succeeding tubercles are at first spaced such that the distance between them approximates to, or is less than the length of their bases, while the posterior ones are more crowded and finally contiguous. The lateral surfaces of the distal two-thirds of the tail are armed with small circular tubercles with coarsely ridged bases from which arise erect, conical spines. The tubercles are not arranged in a linear fashion, but scattered irregularly, and are everywhere well spaced. Anteriorly they form a sparse band along the side of the tail, but from the level of the origin of the serrated spine they cover more and more of the dorsal and ventral aspects, so that distally they are uniformly numerous on all surfaces of the tail. A few of them, smaller than the others, are placed along the lower surfaces of the posterior third of the ventral keel. Colour (in formalin) greyish brown dorsally, with supraorbital region and tip of tail black. Inside of spiracles and rims of lateral line pores white Ventral surface creamy white, though margin of disc and the peduncle grey.