Chlamys islandica (Müller, 1776)
MÜLLER, O. F. 1776.
Zoologiae Danicae Prodromus, seu Animalium Daniae et Norvegiae Indigenarum,
characteres, nomina, et synonyma imprimis popularium. xxxii, 281 p. Hallageriis, Havniae [Copenhagen]. [p. 248]
1776 Pecten islandicus Müller, 1776
1778 Ostrea cinnabarina Born, 1778
1784 Pecten islandicus Chemnitz, 1784 [invalid publication]
1784 Pecten rubidus Martyn, 1784 [invalid publication]
1797 Ostrea demissa Solander, 1797 [invalid publication]
1798 Chlamys islandica Röding, 1798
1798 Chlamys cinnabarina Röding, 1798
1831 Pecten pealii Conrad, 1831
1844 Pecten fabriccii Philippi 1844
1869 Pecten islandicus var. tenuis Mörch, 1869
1897 Chlamys islandica var. insculpta Verril, 1897
1897 Chlamys costellata Verrill & Bush in Verrill, 1897
1778 Ostrea cinnabarina Born, 1778
1784 Pecten islandicus Chemnitz, 1784 [invalid publication]
1784 Pecten rubidus Martyn, 1784 [invalid publication]
1797 Ostrea demissa Solander, 1797 [invalid publication]
1798 Chlamys islandica Röding, 1798
1798 Chlamys cinnabarina Röding, 1798
1831 Pecten pealii Conrad, 1831
1844 Pecten fabriccii Philippi 1844
1869 Pecten islandicus var. tenuis Mörch, 1869
1897 Chlamys islandica var. insculpta Verril, 1897
1897 Chlamys costellata Verrill & Bush in Verrill, 1897
«All of the close living relatives of Chlamys islandica occur in the northern Pacific and confusion of these taxa with true C. islandica has led to the idea that the species is circumpolar. Grau (1959) concluded that C. islandica, sensu stricto, is absent from the North Pacific proper but conceded that it may occur along the Bering Sea coasts of Alaska. MacNeil (1967), however, asserted that even these Bering Sea forms are not true C. islandica. Precisely how species boundaries should be drawn in this region has been open to widely disparate interpretations. MacNeil (1967) described many sculptural variations among fossils in Quaternary terrace deposits in Alaska as newspecies, two of which he claimed are still living, but he gave no statistical justification for his work, nor did he state sample sizes. Similarly, Skarlato (1981) named a new species related to C. islandica on the Soviet side of the Bering Sea and North Pacific without adequate conside ration of the range of variation of previo usly described taxa. My own conclusion, based on the study of museum specimens in the United States and Europe, is in close agree ment with Bernard (1983) that there are four species close to C. islandica in the northern Pacific region: Chlamys behringiana (Middendorff, 1849), C. albida (Dall in Arnold, 1906), C. rubida (Hinds, 1845), and C. hastata (Sowerby, 1842). All of these at some time during their nomenclatural history have been considered to be subspecies of C. islandica. Grau (1959) gave an adequate description of the shell morphology of these taxa, and Bernard (1983) summarized their ranges in the eastern North Pacific and eastern Bering Sea.»
WALLER,
T. R. 1991. Evolutionary relationships among commercial scallops
(Mollusca: Bivalvia: Pectinidae). In: Shumway S. E. (ed.), Scallops:
biology, ecology and aquaculture. Developments in Aquaculture and
Fisheries Science, Elsevier, Amsterdam, 21: 1-73, pls. 1-8. [p. 20]
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Chlamys islandica (Müller, 1776); T. R. Waller, 1991, Evolutionary relationships among commercial scallops, plate 1, figures 4-8.
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«Discussion.— Other names proposed for this species include Ostrea cinnabarina Born, Ostrea demissa Solander, Pecten pealeii Conrad, Pecten fabricii Philippi, Chlamys islandica var. insculpta Verrill, and Chlamys costellata Verrill and Bush. It is perhaps remarkable that Linne did not have a clear concept of this species. According to Dodge (1952, p. 178-179), the box which bears the name Ostrea pusio in Linne's collection contains a right valve of C. islandica, as well as odd valves of several other species.
Other unsegregated valves of C. islandica were in Linne's collection. The types of Lepas balanus Linne (= Balanus balanus) (Pilsbry, 1916, pl. 33, fig. 1) are attached to a fine left valve of C. islandica. Pilsbry identified the substrate valve as Pecten opercularis Linne, but whether the misidentification is his or Linne's is not clear; at least Dodge did not mention an association of C. islandica and C. opercularis in Linne's collection. No better evidence of the general confusion concerning C. islandica needs to be cited. The so-called Chlamys islandica in the northern Pacific have troubled systematists for years. While typical C. islandica belongs to the same section of Chlamys as the northern Pacific forms, the stocks have been distinct since early Pleistocene time and possibly earlier. Several authors (Arnold, 1906, pl. 45, figs. 1, 1a; Oldroyd, 1924b [1925], pl. 8, figs. 1, 2; Grant and Gale, 1931, pl. 11, figs. 1, 1a; Grau, 1959, pl. 22) have figured specimens from the Atlantic coast and Greenland with discussions of northern Pacific species referred to C. islandica. While the locality of these specimens has been clearly stated, the illustration of Atlantic rather than Pacific specimens has given an entirely false impression of the Pacific species. Several species or subspecies have been described from the northern Pacific region, based, unfortunately, on unusual or juvenile specimens. Without access to large suites of the taxa involved, it might be difficult to determine beyond all question which taxa the named species represent. I am inclined to believe that the valid species have been named, however atypical the holotypes might be. Several distinct species of Chlamys that either in whole or in part have been included in C. islandica are now living in the area between Puget Sound and Point Barrow. One type has valves of nearly equal inflation and dorsal margins of nearly equal length. The ribs range from broad and rounded to sharp and high and from moderately split to strongly split, sometimes multiple. This type includes C. rubida, the subspecies C. rubida hindsii, and a new species, C. pseudislandica. The other type has a longer anterior dorsal margin. It includes two subtypes. One has valves of nearly equal inflation and a wide range in the width of the ribs, particularly in the development of fascicular bundles; this subtype probably includes typical C. beringiana of Middendorff. The other, known from a single species, has a very weakly inflated right valve, a moderately inflated left valve, and a moderate division of the ribs on the left valve into wider primary ribs and weaker secondary and tertiary ribs; the primary ribs are not appreciably higher than the other ribs. This latter species is here named C. wainwrightensis; a possible representative of this group is living in the Okhotsk Sea (Kotaka, 1962, pl. 34, figs. 18-23; identified as C. islandica erythrocomata). Despite longstanding confusion over the point, typical C. islandica does not live in Alaskan waters or anywhere in the northern Pacific region. The species probably descended, however, from the stock of C. picoensis chinkopensis Masuda and Sawada (1961, pl. 4, figs. 6, 7) and C. imanishii Masuda and Sawada (ibid., figs. 10a-c, 11), both from the early Pliocene of Japan. Very closely related forms are here recorded from supposedly late Pliocene beds of Tugidak Island, Alaska. A related but somewhat more advanced form was described by Waterfall (1929, p. 83, pl. 5, figs. 2, 4) from the upper (early Pleistocene?) part of the Pico Formation as Pecten (Chlamys] islandicus picoensis, and (ibid., p. 84, pl. 6, fig. 4) Pecten (Chamys] venturaensis; these supposedly different species probably are identical. C. chinkopensis is here regarded as a subspecies of C. picoensis. At any rate, C. picoensis is close to the borderline morphologically between C. chinkopensis and the earliest known subspecies of C. islandica. It is not entirely clear at present, however, just how C. p. chinkopensis, C. cosibensis, and C. hanaishiensis are related. C. tjornesensis occurs in both the "Mactra" and "Cardium'' [Serripes] zones of Iceland; Askelsson (1960) indicated that the Pliocene-Pleistocene boundary is between the Mactra and Cardium zones. C. breidavikensis occurs in the uppermost fossiliferous 'bed of the Breidhavik sequence at Tjornes, Iceland, a horizon within the early part of the glacial Pleistocene. C. breidavikensis is the only one of these Icelandic species that resembles C. islandica, but it has many more ribs than the latter. Furthermore, the anterior ear of the left valve more nearly resembles that of C. harmeri Altena (pl. 24, fig. 6) and C. tauroperstriata (Sacco) (1897, pl. 1, figs. 20, 21), species related to C. multistriata (Poli) from the Mediterranean. Sacco (1897, p. 9) though C. islandica diverged from C. multistriata in post-Pliocene time. I am inclined to believe that C. breidavikensis belongs to the C. tauroperstriata group, but I have not seen any specimens that convince me that C. islandica is derived from C. breidavikensis. C. islandica appears to be much more closely related to some early Pleistocene forms in the Pacific. Roger (1939, p. 168, pl. 22, figs. 3, 4) figured a specimen from Sicilian (early glacial Pleistocene) beds of Sicily that is very similar to the two Pacific early Pleistocene subspecies, C. i kanagae and G. i. powersi. The Sicilian occurrence is both the earliest in Europe and the most southern. Presumably the species reached the Mediterranean region from the Arctic, but the exact route is not clear; the species is not known in early Pleistocene beds in either England or the Netherlands. It did not survive the early Pleistocene in the Mediterranean region. A living variant of C. islandica, (pl. 24, figs. 12, 13) from northern Iceland has some resemblance to both the typical form and C. i. kanagae. Its ribs, while slightly coarser than in either of these forms, are not as coarse as in C. pseudislandica and C. wainwrightensis, nor is its left valve more inflated as in C. wainwrightensis. Typical C. islandica occurs in late Pleistocene (or postglacial) beds at Bohuslan, Sweden, at Keykjavik, Iceland (pl. 18, fig. 8; pl. 19, figs. 2, 5), and probably in Greenland and northern Canada. All northern Atlantic records for G. islandica however, need, to be reexamined. Recent specimens from eastern North America show clearly and consistently that two distinct species are involved: one species with fine nonbif urcating ribs on both valves lives from Newfoundland northward; another species with coarse bifurcating ribs on the right valve and inequisized ribs on the left valve lives along the coast of Maine and Massachusetts. A specimen of the latter from Eastport, Maine, was figured by Grant and Gale (1931, pl. 11, figs, 1a, b); in my opinion this is typical C. pseudislandica. MacGinitie (1959, p. 155) mentioned a specimen with broad primary ribs that divide from Vadsø, Norway, suggesting that C. pseudislandica is living on both sides of the Atlantic. The same species occurs in the Clyde beds (late Pleistocene) of Scotland (Wood, 1851, pl. 5, fig. 1). Richards (1962) recorded C. islandica from beds of late Pleistocene and postglacial age from Labrador to Long Island, but it now seems likely that both C. islandica and C. pseudislandica are included among the forms so identified.» MACNEIL,
F. S. 1967. Cenozoic pectinids of Alaska, Iceland, and other nothern
regions. United States Geological Survey Professional Paper, 553: iv +
1-57, pls. 1-25. [p. 33, 34]
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Chlamys (Chlamys) islandica islandica (Müller); F. S. MacNeil, 1967, Cenozoic pectinids of Alaska, plate 18, figure 8; plate 19, figures 2, 5; plate 24, figures 12, 13.
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«Remarks: Although extra-limital, this species is included in the present paper because of the frequent references to it in literature on the eastern Pacific fauna south of the Bering Sea. Records from southern Alaska, British Columbia and Puget Sound were the result of misidentifications. Chlamys islandica varies considerably in number of ribs and in sculpture, but is quite distinct, and easily separable from its subspecies albida (Dall) and behringiana (Middendorff).
Geographical range: Arctic Ocean, except East Siberian and Leptev Seas; west coast of Norway; Iceland; Greenland; Hudson Bay; western Atlantic, from Arctic Ocean to Chesapeake Bay; Bering Sea and Aleutian Islands. Geochronological range: Plioccnc, Pleisfocene, Recent. Bathymetric range: Low tide to 150 fathoms. Ecological data: Usually found on rocky bottoms.» GRAU, G. 1959. Pectinidae of the eastern Pacific. Allan Hancock
Pacific Expeditions, 23: i-viii, 1-308, pls. 1-57. University of
Southern California Press. Los Angeles, California.
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Chlamys islandica (Müller) 1776; G. Grau, 1959, Pectinidae of the eastern Pacific, plate 22.
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