Mesopeplum convexum (Quoy & Gaimard, 1835)
QUOY, J. R. C. & J. P. GAIMARD. 1834. Zoologíe. Tome Troisème. In: J. Dumont d'Urville (1834): Voyage de Découvertes de l'Astrolabe. Paris, J. Tastu, Éditeur-Imprimeur. [p. 443, pl. 76, figs. 1-3]
1835 Pecten convexus Quoy & Gaimard, 1835
1853 Pecten roseopunctatus Reeve, 1853
1873 Pecten (Dentipecten) vellicatus Hutton, 1873
1929 Pallium kapitiensis Mestayer, 1929
1853 Pecten roseopunctatus Reeve, 1853
1873 Pecten (Dentipecten) vellicatus Hutton, 1873
1929 Pallium kapitiensis Mestayer, 1929
J. R. C. Quoy & J. P. Gaimard, 1834, plate 76.
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«Pecten, testa subaequivalvi, utrinque valde convexa, crassa, alba rubro-picta; radiis numerosissimis, glabris, rotundatis; interstitiis tenuissime striatis.
Cette coquille est équivalve, à auricules inégales, arrondie dans son contour, qui est un peu ondulé, remarquable par ses deux valves extrêmement bombées, plus que dans aucune autre espèce, la gauche un peu moins que la droite; toutes deux profondément sillonnées, ayant six larges côtes plus ou moins marquées, dont les arêtes sont rapprochées, arrondies, avec tendance à s'accoupler; leurs intervalles sont très-finement striés en travers; ce qui ne se voit bien qu'à la loupe. Quelques côtes sont divisées sur le bord seulement. Les auricules sont rugueuses et comme feuilletées. Il existe, au-dessous des plus petites, une forte dépression lunulée. Ce Peigne est blanc, ponctué de rouge, tirant sur le rosé. Intérieurement il est rosé et sillonné sur le bord. Les deux individus que nous avons eus en notre possession n'étaient pas vivants, et avaient même un peu souffert. Il est probable que dans l'état frais ils ont un ou deux demi-cercles rougeâtres. Un de nos individus avait à l'intérieur une valve rosée, et l'autre blanche. JEAN RENÉ CONSTANT QUOY & JOSEPH PAUL GAIMARD, 1835
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«Mesopeplum convexum is locally common off the four main islands of New Zealand, where it lives byssally attached on rock and bryozoan/shell substrata. The species attains exceptional size off Stewart Island, Foveaux Strait, and especially Fiordland, the largest seen being from Milford Sound (width 69 mm, M.155904). Raines and Poppe (2006, p. 85) illustrated several specimens of M. convexum reputedly trawled at 700 metres depth off the Auckland Islands. Since the species has not otherwise been recorded this deep or far south, it is likely their specimens were provided by a shell dealer with fabricated locality data.»
DIJKSTRA, H. H. & B. A. MARSHALL. 2008. The recent Pectinoidea of the New Zealand region (Mollusca: Bivalvia: Propeamusiidae, Pectinidae and Spondylidae). Molluscan Research, 28 (1): 1-88, figs. 1-70. [p. 73]
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Mesopeplum convexum (Quoy & Gaimard, 1835); H. H. Dijkstra & B. A. Marshal, 2008, The recent Pectinoidea of the New Zealand region, figure 61.
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«2. Mesopeplum convexum (Quoy & Gaimard, 1835): The living population and the very abundant early Nukumaruan specimens at Castlepoint, Wairarapa, share an apparently critical character: enormous variation in prominence of both the plicae and the radial costae. The range appears to be the same in both populations. Recent specimens are also extremely variable in colour, ranging from white to yellow and through pink and red to uniform deep magenta-purple, and are therefore clearly distinct from the Australian Recent M. fenestratum (Hedley) (= caroli) in two characters: populations of M. fenestratum are very much less variable in both coloration and sculpture than M. convexum. Almost all the large los of M. fenestratum examined in the Australian Museum, Sydney, during September 1991 have prominent plicae, have almost ecually prominent costae in all samples, and have a very consistent coloration: a white right valve and a magenta-pink left valve, the colour darker on radial costae, and particulary near the umbo, than elsewhere. No specimens that definitely can be referred o M. convexum have been seen that are older than Nukumaruan, but the origin and time of first appearance of the species are obscure at present.»
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: 1-243, figs. 1-95. (New Zealand Geological Survey Paleontological Bulletin, 68). Institute of Geological and Nuclear Sciences, Ltd., Lower Hutt, New Zealand. [p. 52]
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«PI. 44 g. Mesopeplum (Mesopeplum) convexum (Quoy and Gaimard, 1835) [Pecten convexus Quoy and Gaimard 1835, p. 443; ? = Pecten burnetti Zittel 1864, p. 51; Pecten kapitiensis Mestayer 1929, p. 249; Pallium convexum; Pallium (Mesopeplum) convexum; Pallium (Felipes) convexum] (Pectinidae).
Small for family (to 60 mm high), thick and solid, well inflated, exceedingly variable in sculpture. All specimens have 4 or 5 (6 in a few specimens) prominent radial folds in disc; superimposed on and between folds are about 35 to 50 closely spaced, narrow radial costae, varying from many scarcely discernible fine threads (so shell appears almost smooth) to fewer, coarser, well raised costae of square cross-section. Two valves almost equally inflated; anterior ear of each valve much larger than posterior one; right valve with small but obvious byssal notch and short, finely toothed ctenolium. No cardinal crura or other obvious internal characters other than simple pallial line and large, circular adductor scar.
(Kaiatan?-) Duntroonian-Recent. Recent, New Zealand (types of Pecten convexus and Pecten kapitiensis); "Motupipi, Massacre Bay, Province of Nelson", i.e., Tarakohe Limestone, Tarakohe, Takaka, west of Nelson, Waitakian (type of Pecten burnetti).
The range of variation of fossil taxa is in need of further study, and the number of valid species, and their time ranges, are unclear; the above synonymy assumes that at least the most common early-mid Cenozoic form
(Mesopeplum burnetti) is part of the variation of M. convexum, but early-mid Cenozoic populations seem consistently to be relatively coarsely sculptured and could be distinct from Late Miocene-Recent populations. Modern specimens are exceedingly variable in the number and size of radial folds, the number and prominence of radial costae, the inflation and growth steps of the disc, and the shape of the disc; it seems possible that named extreme forms such as M. syagrus and M. waikohuense are also part of the variation of M. convexum. Despite the apparently functional byssal notch, adults lie unattached on clean, firm sand or gravel, offshore in about 20 to 80 m (and rarely deeper), and are the most actively swimming of modern New Zealand pectens, leaping about and "clapping" their valves actively when dredged. Fossils are common to abundant in sandstone and, particularly, coquina limestone (e.g., Castlepoint, Wairarapa, Nukumaruan; Patutahi Limestone, Gisborne, Tongaporutuan; Takaka Limestone, Tarakohe, northwest Nelson, Waitakian), rocks that formed in highenergy environments on the middle shelf. The earliest specimen of this type we are aware of is from Point Elizabeth-RapahoeBeach, north of Greymouth (Kaiata Mudstone, Kaiatan) and specimens are locally common in high-energy facies throughout New Zealand at all ages after Late Eocene time. Some similar but smaller and more finely ribbed species occur in northern New Zealand Early Miocene rocks (M. costatostriatum, M. kaiparaense, both Otaian-Altonian of Kaipara Harbour); the larger M. dendyi (early Pliocene, Chatham Islands; PI. 32b, g) is figured above.
Figured specimen (PI. 44g): (Castlecliff, Wanganui, Castlecliffian (NZGS, from old collection), left valve with tip of left ear broken, x 1.
BEU, A. G. & P. A. MAXWELL. 1990. Cenozoic Mollusca of New Zealand. New Zealand Geological Survey Paleontological Bulletin, 58: 1-518, pls. 1-57. [p. 338]
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Mesopeplum (Mesopeplum) convexum (Quoy and Gaimard); A. G. Beu & P. A. Maxwell, 1990, Cenozoic Mollusca of New Zealand, plate 44, figure g.
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