Argopecten nucleus (Born, 1778)
BORN, I. VON. 1778. Index Rerum Naturalium Musei Caesari Vindobiniensis. Pars I. Testacea. Vindobonae [Vienna], ex Officina Krausiana. [p. 92]
1778 Ostrea nucleus Born, 1778
Pecten nucleus Born; L. A. Reeve, 1852-1853, Conchologia Iconica, Monograph of the genus Pecten, plate 22, figure 89.
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Mus. Caes. Vindobon.
IGNAZ VON BORN, 1778
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«Additional description. – Shell up to ca. 35 mm high, solid, inflated, subequivalve, equilateral, both valves nearly equally convex, auricles slightly equal in size and shape. Both valves with 18-20 radial lirae, interstices with commarginal sculpture. Colour left valve greyish or greyish brown, right valve whitish.
Type locality. – Not indicated (Index, 1778). “Patria ignota (Testacea, 1780). Type material. – According to Brauer (1878: 23), the specimen referred to in Megerle von Mühlfeld’s catalogue is somewhat larger and does not belong to the type series. Taxonomic position. – O. nucleus Born, 1778 is currently placed in Argopecten Monterosato, 1889. Distribution. – Argopecten nucleus occurs in the tropical western Atlantic from Florida southwards to northern Brazil, and eastwards to the West Indies.» DIJKSTRA, H. H. 2009. Type specimens of Pectinidae (Bivalvia) described by Ignaz von Born (1778 - 1780). Basteria, 73: 99-116. [p. 112, 113]
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Argopecten nucleus (Born, 1778); B. K. Raines & G. T. Poppe, 2006, A Conchological Iconography, The Family Pectinidae, plate 268, figures 1-6.
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«Comparison. Argopecten nucleus differs from A. gibbus in having disk flanks that are gradational both in ornament and in curvature between the auricles and disk proper, in having more highly developed cardinal crura and auricular denticles, and in the nature and degree of coloration. Compared to A. irradians concentricus and A. irradians amplicostatus, A. nucleus is less right-convex, has right auricles that extend further dorsally from the outer ligament, has more white in the color pattern of its left valve, and has less well-defined disk flanks.
Stratigraphic range. Pleistocene?, Holocene, and living. Geographic distribution and ecology. The most commonly cited distribution of A. nucleus is through sontheastern Florida and the West Indies (Abbott, 1954, p. 368). According to the species interprctation of the present study, the species also occurs in the Caribbean off South America and in the Gulf of Mexico off Mexico. The mexican occurrence is thus far indicated by only one sample (USNM (Z) 219946, consisting of 1 articulated shell from La Barra, Mexico, presumably about 3 km north of Tampico). The northernmost sample of the species examined by the author is from the north inlet to Lake Worth, southeastern Florida, and the sonthernmost is from Venezuela (locality 89). Although specimens from throughout the West Indies and Bahamas are common in the collections examined, none is present from the Gulf coast of the North American mainland north of Tampico, Mexico. The ecology of A. nucleus is poorly known, partly because conursion with gibbus. Abbott ( 1954, p. 3ó8) reports that A. nucleus is ''not uncornmon in the Keys from low tide to a few fathoms or grass." Data on habitat are commonly only lacking with museum specimens, but all the available information on specimens definitely identified with the species from the Antilles and Florida indicates a preference for very shallow water, commonly in association with either marine grasses or algae. Specimens labeled as "Aequipecten nucleus" from the Florida Keys in depths greater than a few fathoms have all proved to be A. gibbus. Many other specimens from Biscayne Bay, Florida, and the Florida Keys (MCZ 82499, 194970, 194963), identified with A.. nucleus by other workers, are in fact A. irradians concentricus, with which A. nucleus is convergent in both rnorphology and coloration. It seems likely that the two species may be sympatric in these areas. This association of Antillean and Floridan A. nucleus with grasses or algae indicates that the young, like the young of A. irradians depend upon the plants for settlement and attachment during the byssal stage. Unlike A. gibbus, A. nucleus seldom seems to be covered with epifauna. In contrast to the Antillean and Floridan A. nucleus, representatives of the species living along the Colombian and Veneznelan coasts of South America (localities 87 through 90) are found at greater depths in warm, open marine waters (depths of 10 to 32 fathoms and bottom temperatures of 24.5ºC to 25.5ºC among four samples). A search by the author of the beaches along the Veneznelan coast in mid-1967 revealed only a few abraded shells of A. nucleus, suggesting that the species must be rare or absent in nearshore, shallow-water areas, some of which would otherwise seem to be favorable for its growth. The available information on distribution thus suggests that A. nucleus displays a shift in habitat preference between the southern Caribbean and the Antillean-Floridan region». WALLER, T. R. 1969. The evolution of Argopecten gibbus stock (Mollusca: Bivalvia), with Emphasis on the Tertiary and Quaternary Species of Eastern North America. The Paleontological Society. Memoir 3 [Journal of Paleontology, 43 (5, supplement)]: 125 pp. [p. 38, 39]
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Argopecten nucleus (Born); T. R. Waller, 1969, The evolution of Argopecten gibbus stock, plate 8, figures 5-9,
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