Cyclopecten hoskynsi (Forbes, 1844)
FORBES, E. 1844. Report on the Mollusca and Radiata of the Aegean Sea, and on their distribution, considered as bearing on Geology. Report of the thisteenth meeting of the British Association for the Advancment of Science; held at Cork in August 1883, p. 130-193. John Murray, London. [p. 192]
1814 Pecten hoskynsi Forbes, 1844
1846 Pecten imbrifer Lovén, 1846
1869 Pecten mammillatus Sars, 1869 [nomen nudum]
1873 Pecten pustulosus Verrill, 1873
1879 Pleuronectia difformis Seguenza, 1880
1881 Pecten lucidus Haren Noman, 1881
1878 Pecten hoskynsi var. major Leche, 1878
1897 Cyclopecten subimbrifer Verrill & Bush in Verrill, 1897
1898 Pecten imbrifer var. lamellosa Posselt & Jensen, 1898
1912 Pecten imbrifer var. minor Jensen, 1912
1846 Pecten imbrifer Lovén, 1846
1869 Pecten mammillatus Sars, 1869 [nomen nudum]
1873 Pecten pustulosus Verrill, 1873
1879 Pleuronectia difformis Seguenza, 1880
1881 Pecten lucidus Haren Noman, 1881
1878 Pecten hoskynsi var. major Leche, 1878
1897 Cyclopecten subimbrifer Verrill & Bush in Verrill, 1897
1898 Pecten imbrifer var. lamellosa Posselt & Jensen, 1898
1912 Pecten imbrifer var. minor Jensen, 1912
Pecten Hoskynsi Forbes; A. E. Verrill, 1882, Catalogue of marine Mollusca added to the Fauna of New England during the past ten years, plate 44, figura 11.
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«P. testâ minutâ (aequivalvi), orbiculari, albâ, pellucidâ, costis longitudinalibus distantibus squamosis, squamis vesiculosis.
Lat. 0 2/12. Region VIII. Asia Minor.» EDWARD FORBES, 1844
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«Type material
Syntype, National Museums of Scotland, Edinburgh, reg. no. 1976.5.31904. Type locality
Off Piscopi [ = Tilos], Sporades, Greece, 366 m depth (restricted by Smaldon et al. 1976:51). Distribution
Arctic to tropical, eastern and western Atlantic, from Svalbard and northern Greenland southwards to Massachusetts (USA) (Abbott 1974: 445, as Cyclopecten pustulosus) in the West Atlantic and southwards to the Cape Verde Islands in the East Atlantic, in 82–2064 m (Dijkstra & Goud 2002: 41; Locard 1898). BIOICE material alive at 77 stations in 125–1314 m (Map 1). Description
Shell (Figures 1E,F, 5B,C) up to ca. 24 mm high, usually smaller, fragile, transparent to opaque, somewhat higher than long, flattened, left valve slightly more convex than right valve, anterior auricles larger and longer than posterior ones. Prodissoconch (Figure 2H), length ca. 180 μm, colour whitish. Left valve (Figures 9C, 10G) sculptured with broad, radially arranged vesicles and small secondary interstitial vesicles commencing in late growth stage or, usually damaged, so only curved lamellae remain, sculpture sometimes nearly absent. Commarginal lamellae usually present near ventral margin, sometimes absent. Anterior auricle with prominent commarginal lamellae and some radial rows of vesicles, posterior auricle similarly but more weakly sculptured. Right valve (Figures 9D, 10H) with closely spaced commarginal lamellae. Auricles rather small, anterior one more prominent sculptured with small vesicles or lamellae. Internally sometimes with rudimentary riblets commencing in late growth stage and extending towards the submarginal area. Byssal notch small, ctenolium lacking. Remarks
Arctic and northern specimens (SMNH, ZMC), have usually been identified as Cyclopecten imbrifer, and resemble Mediterranean C. hoskynsi in shape and sculpture, although larger (up to ca. 24 mm in height in high arctic areas, ca. 15 mm in northern Iceland; continuously smaller southwards, usually 6–7 mm in the Mediterranean). We cannot find any additional difference and the variation in sizes looks like a cline with BIOICE material of intermediate size. The names Cyclopecten pustulosus and Cyclopecten subimbrifer were based on specimens from the northwestern Atlantic with unusually prominent vesicles on the ribs in pustulosus and weak concentric lamellae and small vesicles in subimbrifer (see Jensen 1912 and Schiøtte 1989). Ockelmann (1959) separated four species in this group, Cyclopecten imbrifer (arctic), C. subimbrifer (West Atlantic), C. pustulosus (West Atlantic) and Cyclopecten sp. A. (from the Faroes), but also SEM examination of sculpture and larval shells from extreme localities failed to reveal any persisting differences. Among congeneric species only those from the northern hemisphere have vesicles on the left valve. Cyclopecten carlottensis Bernard, 1968, known from the north-eastern Pacific, differs from C. hoskynsi in having coarser commarginal lamellae on the right valve and more closely set rows of pustules on the left one. Also the rows of pustules are usually more prominent than in C. hoskynsi. This species is morphologically very similar to the north-western Atlantic form of C. hoskynsi named C. pustulosus (now considered a synonym of hoskynsi). Another resembling species is Cyclopecten davidsoni (Dall, 1897), from Alaska, distinguishable from C. hoskynsi by having a more sturdily built shell, often abruptly increasing the convexity of the valves close to the margin (flattened in C. hoskynsi), and by having narrower radial rows of crowded vesicles.» DIJKSTRA, H. H., A. WARÉN & G. GUDMUNDSSON. 2009. Pectinoidea (Mollusca: Bivalvia) from Iceland. Marine Biology Research, 5: 207-243, figs. 1-20. [p. 217, 218]
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Cyclopecten hoskynsi (Forbes, 1844); H. H. Dijkstra, A. Warén & G. Gudmundsson, 2009, Pectinoidea (Mollusca: Bivalvia) from Iceland, figures 1E, 1F, 5B, 5C.
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«The Plio-Pleistocene fossils described by Philippi (1844) as Pecten antiquatus and P. fimbriatus, based on right and left valves, respectively, have hitherto been considered as synonyms of Cyclopecten hoskynsi (Forbes, 1844) (e.g. Jeffreys 1879; Sabelli & al. 1991). However, Philippi states the presence of 12-14 internal riblets and a size range of 7.6-8.7 mm (3.5-4 german lines), as in our material. Cyclopecten antiquatus can be distinguished from C. hoskynsi, known from the Mediterranean Sea and adjacent eastern Atlantic (Fig. 10D-I), by more numerous radial lines of smaller vesicles. Cyclopecten hoskynsi is somewhat smaller in size and quite homogeneous in sculpture with 10-17 radial sets of large vesicles on the left valve. It lacks internal riblets or, if present, these are seen only in large valves (i.e. >6 mm) and near the shell margins. Cyclopecten imbrifer (Loven, 1846), from the Arctic and boreal eastern Atlantic (Fig. 10A-C), is a closely related species, which is larger in size (up to Ca 25 mm high) and consistently lacks the internal riblets (relevant material examined in SMNH and ZMUC). It has a weaker sculpture of numerous irregularly spaced radial vesicles, or more rarely only commarginal lamellae, without vesicles [= C. imbrifer var. lamellosus (Posselt, 1898)].
Cyclopecten pustulosus (Verrill, 1873) from the northwestern Atlantic also belongs to this species group. It is larger, up to C. 25 mm high, with more prominent vesicular sculpture and sometimes with internal riblets. Verrill & Bush, in Verrill 1897 introduced the name Cyclopecten subimbrifer based on C. hoskynsi sensu Verrill, 1882 (non Forbes), from the northwestern Atlantic, which is more similar to C. imbrifer. Jensen (1912: 25) treated both as ecomorphological forms of C. imbrifer, and showed that sculpture is very variable. He also enumerated C. imbrifer var. major (Leche, 1878) and C. imbrifer var. minor (Jensen, 1912: 25) from southwest Iceland. Both are also forms of C. imbrifer.» DIJKSTRA, H. H. & S. GOFAS. 2004. Pectinoidea (Bivalvia: Propeamussiidae and Pectinidae) from some northeastern Atlantic seamounts. Sarsia, 89: 33-78, figs. 1-22. [p. 47]
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Cyclopecten hoskynsi (Forbes, 1844); H. H. Dijkstra & S. Gofas, 2004, Pectinoidea (Bivalvia: Propeamussiidae and Pectinidae) from some northeastern Atlantic seamounts, figures 10D-10I; Cyclopecten imbrifer (Loven, 1846), figures 10A-10C.
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«Nous ne pouvons juger de cette espèce que d'après les bonnes figures de Sars, et celles de P. difformis SEGUENZA.
C'est encore une espèce abyssale, méditerranéenne, atlantique et nordique. Il semble, fait assez curieux, que sa taille augmente en allant du Sud au Nord. En Méditerranée, elle atteint 4 à 5 mm., tandis que Dautzenberg et Fischer (1910, Campagne arctique du Prince d'Orléans, p. 12), signalent la variété major LECHE, qui a 20 mm. Elle correspond exactement à l'espèce précédente par son contour. Les différences essentielles sont à rechercher dans l'ornementation. Chez Ch. Hoskynsi, la valve droite est pourvue de cordonnets concentriques étroits, pointillés, de plus en pIus fortement en allant vers le bord palléal. A la valve gauche, il y a de 10 à 18 cordons radiaires de tubercules, dont la taille augmente en allant vers le bord palléal, et en forme de petits mamelons ponctués à leur surface. L'oreille antérieure, est seule ornée de petits filets divergents, et son bord supérieur est finement denticulé. La face interne est lisse; certains parlent seulement de côtes internes, très difficiles à distinguer. Répartition géographique et stratigraphique.— A l'état fossile, celle espèce ne nous est connue que du Pliocène de Monosterace et Reggio, sous le nom de P. difformis SEGUENZA.»
ROGER, J. 1939. Le genre Chlamys dans les formations néogènes de l'Europe. Conclusions générales sur la répartition géographique et stratigraphique des Pectinidés du Tertiare Récent. Mémoires de la Société Géologique de France [Nouvelle série], 17 (2-4): 1-294, pls. 1-28. [p. 221, 222]
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Pleuronectia difformis n. sp.; G. Seguenza, 1880, Le Formazione Terziarie nella Provincia di Reggio (Calabria), plate 16, figures 45, 45a, 45b.
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