Kaparachlamys hectori (Hutton, 1873)
HUTTON, F. W. 1873. Catalogue of the Tertiary Mollusca and Echinodermata of New Zealand, in the collection of the Colonial Museum. Colonial Museum and Geological Survey Deptartment, xvi, 48 p. G. Didsbury, Gobernment Printer. Wellington. [p. 30]
1873 Pecten hectori Hutton, 1873
Kaparachlamys hectori (F. W. Hutton, 1873); A. U. E. Boreham, 1965, A revision of F. W. Hutton's pelecypod species described in the Catalogue of Tertiary Mollusca and Echinodermata, plate 6, figures 3, 5, 6.
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«106. P. hectori, sp. nov. Sub-orbicular, thin, inequivalve, both valves finely radiately striated; the margin with rather broader ribs on the inside; ears sub-equal, finely transversely striated. Height, 4.1; length, 4.6.
Localities.— Chatham Islands; Brighton; Broken River (L).» FREDERICK WOLLASTON HUTTON, 1873
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«REMARKS: Marwick (1928, p. 451) pointed out the close similarity of Pecten hectori Hutton to the eastern North American genus Placopecten, but admitted that "this resemblance might be due to convergence". Boreham (1965, p. 25) agreed that P. hectori "is remarkably similar" to Placopecten, but atributed the similarity to convergence and proposed the new genus Kaparachlamys for New Zealand Placopecten-like taxa, with P. hectori as type species. The other species included in Kaparachlamys by Boreham (1965) is Pallium mariae Finlay, 1926 (new name for Pecten semiplicata Hutton, preoccupied). The relationship of these taxa and the identity of P. mariae had troubled taxonomists for years before Boreham's revision and, although Boreham very usefully resolved the identity of P. mariae, it is concluded that the similarity of P. mariae to Kaparachlamys hectori is yet another case of convergence.
Kaparachlamys hectori resembles Placopecten and numerous other members of Waller's Tribe Palliolini in its moderately large size, its thin shell, its weak inflation, its very subdued sculpture of a large number (about 170 around the margin of large specimens, about 120 mm high) of very fine, low, closely spaced radial costellae, and the byssal notch and sinus remaining relatively shallow throughout ontogeny. The costellae produce only faint radial ridges on the interior of most of the shell, but produce prominent, wide costal carinae around the outer 10 mm or so of the interior of large specimens. The fine costellae of some right valves are grouped into low, wide, costal groups that are separafed by wider grooves than elsewhere, and a minority of small left valves have about 6-7 faintly developed plicae near the umbo, fading out at no more than 30 mm disc height. Auricles are quite coarsely and sparsely sculptured on some small specimens, but larger auricles are very finely sculptured. Auricles are relatively small on small specimens, but on large specimens, with very wide umbonal angles, auricles become very large, wide and low. All specimens of K. hectori have fine, low, closely spaced commarginal ridges in radial interspaces, and a few specimens are little-enough abraided to reveal that relatively prominent, moderately widely spaced, thin commarginal lamellae cover the entire surface of fresh shells. On one specimen (GS12164, CH/f25B, Whenuataru Tuff tip of Tarawhenua Peninsula, Pitt Island) these commarginal lamellae are particularly prominent, closely spaced, dorsally inclined, and weakly overlapping on the left posterior auricle, particularly in the depression beside the disc. Similar but much more prominent, widely spaced, weakly overlapping commarginal lamellae cover the entire surface of both valves of a single, formerly enigmatic scallop (Fig. 16b) from mainland New Zealand, and are particularly prominent on the auricles, ventrally inclined over the disc but dorsally inclined on the auricles. It seems likely that this specimen is the sole known mainland specimen referable to Kaparachlamys (GS10334, O321/f8839, coast just south of mouth of Big Bush Stream, south of Conway River, North Canterbury, collected G. Warren, March 1982; with Zygochlamys delicatula; early Nukumaruan). This single large specimen (length 110 mm, hinge length 60 mm) has similar but coarser radial costae than those of K. hectori and has a wide umbonal angle and remarkably large, wide but low auricles. Recognition of a distinctive mainland species of Kaparachlamys suppors the contention arrived at below that the similarity of. P. mariae to K. hectori is convergent. DISTRIBUTION: Kaparachlamys hectori is almost entirely limited to the Whenuataru Tuff and Onoua Limestone on northern Pitt Island, Chatham Islands (see revision of statigraphy and paleonology in Campbell et al. 1993, p. 133, p. 141, p. 148) but a few fragments are known also from an unnamed Waipipian limestone in a borehole on northern Chatham Island (GS14155, CH/f588; Campbell et al. 1993, p. 136). AGE: Waipipian, possibly in places as young as early Mangapanian.» BEU, A. G. 1995. Pliocene Limestones and their scallops. Lithostratigraphy, pectinid biostratigraphy, and paleogeography of eastern North Island late Neogene limestone. Institute of Geological & Nuclear Sciences Monograph 10. Institute of Geological and Nuclear Sciences, Ltd., Lower Hutt, New Zealand, 243 pp. [pp. 19, 20]
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Kaparachlamys hectori (Hutton); A. Beu, 1995, Pliocene Limestones and their scallops, figure 14e.
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