Other formats

    Adobe Portable Document Format file (facsimile images)   TEI XML file   ePub eBook file  

Connect

    mail icontwitter iconBlogspot iconrss icon

The Spatangid Echinoids of New Zealand

Spatangus thor n. sp. Plates 1, 3, 5

Spatangus thor n. sp. Plates 1, 3, 5 .

Diagnosis: As in the key above.

Holotype: A perfect specimen collected by Mr Thor Nielsen in 1959 from the western oyster beds of Foveaux Strait, south-west of Bluff, nearer Stewart Island than Bluff, 16–19 fathoms (29–34m), and now deposited in the Zoology Museum, Victoria University of Wellington. This is the largest specimen so far taken. Length, 134mm; breadth, 121mm; height, 78mm. Plastron: length, 64mm; breadth, 34mm. Subanal plastron with two pores on either side; bilobate; length, 28mm; breadth, 37mm. Subanal fasciole broad, 3–5mm wide.

Paratype: (a boiled test, devoid of spines) now in the collection of Mrs Beryl Nielsen, of Bluff. Length, 125mm; breadth, 117mm; height, 70mm. Plastron: length, 66mm; breadth, 32mm. Subanal plastron: length, 24mm; breadth, 38mm. The subanal fasciole, though broad, is much less so than on the holotype, 1.5–2mm wide.

The test in both specimens is robust. That of the paratype is perforated by two injuries, evidently made at the time of collection, but the shell remains otherwise intact. The pore-pairs are more widely separated, and more deeply sunken, in the paratype than in the type, indicating that this character is variable. The pedicellariae are rare, and seem to occur only in the adoral region. Only tridentate pedicellariae were observed; they are of the broad, short type, commonly occurring in the genus. (Text-fig. 1.) They range from 0.7–1.0mm in length, and are purple in colour.

Text-fig. 1.—Spatangus thor n. sp., holotype. A, large tridentate pedicellaria, of broad type, from adoral region. B, smaller example of same type, also from adoral region. C, subanal fasciole, with included and excluded pores.

Text-fig. 1.—Spatangus thor n. sp., holotype. A, large tridentate pedicellaria, of broad type, from adoral region. B, smaller example of same type, also from adoral region. C, subanal fasciole, with included and excluded pores.

The subanal fasciole (Text-fig. 1, C) is broad and ribbon-like, and encloses 2 pore-pairs on either side, a third pore lying just outside the fasciole on either side.

Discussion

The species is evidently most closely related to Spatangus pallidus H. L. Clark, 1908, which, with S. lutkeni A. Agassiz, 1872, falls in the same section of the genus page 4 (all three species having no anterolateral interamb-tubercles). From lutkeni the present species (like pallidus) is distinguished by its conspicuous keel on the plastron. From pallidus, as also from lutkeni, the present species is distinguished by its subambital periproct, fully visible from below, and also by its much greater size. Both pallidus and lutkeni are Japanese species, from the continental shelf. To no other known species does thor exhibit any obvious relationship, but it is important to note, as set out in the key above, that several characters are shared with the following species, to which it is evidently related; most important of these must be the subambital position of the periproct.

The species is named for its collector, Thor Nielsen, through whose efforts specimens were secured for examination; the specific name is treated as an indeclinable nominative in apposition, as permitted by the Code. Spatangus thor, as can be seen from, the illustrations of the holotype, and from the measurements cited, is the largest and most splendid species of its genus ever discovered; its unheralded arrival in my laboratory a few months ago caused much astonishment and prompted the preparation of this paper dealing with all known New Zealand spatangids. So far as can be ascertained from published records, the largest known

Explanation of Plates 1 to 6

Plate 1

Fig. 1.—Spatangus beryl n sp., holotype (in the Zoology Museum, Victoria University of Wellington), in left lateral aspect. Length, 127mm; height, 75mm. Coll. B. Smith, Foveaux Strait, ca. 30m.

Fig. 2.—Spatangus thor n. sp., holotype (in the Zoology Museum, Victoria University of Wellington), in left lateral aspect. Length, 134mm. Height, 78mm. Coll. Thor Nielsen, Foveaux Strait, 29–34m.

Fig. 3.—Spatangus multispinus Mortensen, in right lateral aspect. Length, 72mm. Height, 36mm. Cook Strait, VUZ Station 53, 250–350 fathoms (460–540m).

Plate 2

Fig. 4.—Spatangus multispinus Mrtsn., adoral aspect of specimen 74mm long; Cook Strait, VUZ Station 53, 250–350 fathoms (460–540m).

Fig. 5.—Spatangus multispinus Mrtsn., aboral aspect of another specimen, 72mm long, from same locality as Fig. 4.

Plate 3

Fig. 6.—Spatangus thor n. sp., holotype, in aboral aspect. Length, 134mm. Breadth, 121mm. Foveaux Strait, 29–34m.

Fig. 7.—Spatangus thor n. sp., holotype, in adoral aspect.

Plate 4

Fig. 8.—Spatangus beryl n. sp., holotype, in adoral aspect. Length, 127mm. Breadth, 120mm. Foveaux Strait, ca. 30m.

Fig. 9.—Spatangus beryl n. sp., holotype, in aboral aspect.

Plate 5

Fig. 10.—Spatangus beryl n. sp., paratype (ex Noel Johnson), left petals and interamb (enlarged ca. 1.2 times).

Fig. 11.—Spatangus beryl n. sp., paratype (in Beryl Nielsen collection), right petals and interamb (enlarged ca. 1.2 times).

Fig. 12.—Spatangus thor n. sp., holotype (Victoria University of Wellington, ex Thor Nielsen collection), left petals and interamb (reduced to ca. five-sixths natural size).

Fig. 13.—Spatangus beryl n. sp., paratype (in Dorothy Grantham collection, ex Thor Nielsen), right petals and interamb (ca. natural size).

Fig. 14.—Suspected hybrid Spatangus thor x beryl, in the Dominion Museum, Wellington (ex Olga Sansom collection from Foveaux Strait). Left petals and interambs. The total length of the specimen is ca. 126mm, and the portion shown is ca. natural size.

Fig. 15.—Spatangus multispinus Mrtsn., right petals and interamb. Enlarged about 2 diameters.

Plate 6

Fig. 16.—Paramaretia peloria (H. L. Clark), aboral aspect of a New Zealand specimen (from near Taiaroa Heads, coll. Patricia M. Ralph; length, —mm; breadth, —mm; height

Fig. 17.—Paramaretia peloria (H. L. Clark). Same specimen, in adoral aspect.

page break page 5

species hitherto reported is Spatangus capensis, of which Mortensen (1951) cited a "magnificent specimen measuring 125 × 120 × 68mm".