Nodipecten magnificus (G. B. Sowerby I, 1835)
SOWERBY I, G. B. 1835. Characters and observations on new genera and species of Mollusca and Conchifera collected by Mr. Cuming. Proceedings of the Zoological Society of London, 3: 4-7, 49-51, 93-96, 109-110. [p. 109]
1835 Pecten magnificus Sowerby I, 1835
1835 Pecten magnificus var. α Sowerby I, 1835
1835 Pecten magnificus var. α Sowerby I, 1835
Pecten magnificus; L. A. Reeve, 1852-1853, Monograph of the genus Pecten, Conchologia Iconica, volume 8, plate 2, figure 9.
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«PECTEN MAGNIFICUS. Pect. testa subaequivalvi, aequilaterali, auriculis inaequalibus; striis radiantibus exiguis numerosissimis, radiisque tredecim, crassiusculis, rotundatis, nonnunquam subnodosis; intus alba purpureo marginata: long. 5·5, lat, 2', alt. 5·5 poll.
Variat α colore sanguineo nitente. Hab. ad Insulas Gallapagos. β, testa fusca, maculis albidis variegata. Hab. ad Insulam Platae, Columbiae Occidentalis. A single specimen of var. α was found in coral sand at a depth of six fathoms: var. β was also found in coral sand in seventeen fathoms.» GEORGE BRETTINHAM SOWERBY I, 1835
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«Contrary to the conclusions of Durham (1979) and J. T. Smith (1991a), N. magnificus is not a relict Lyropecten but rather is a species of Nodipecten that is derived from N. arthriticus (Reeve, 1853), which still lives in the eastern Pacific along mainland coasts from south of the Gulf of California (Islas Tres Marías, 21º25'N) to Paita, Peru (5ºS; J.T. Smith, 1991a). Nodipecten arthriticus, in turn, is closely related to N. subnodosus, which lives today at Santa Catalina Island, California (33º25'N), and throughout the Gulf of California as far south as La Paz, Baja California Sur (24N; J. T. Smith, 1991a, fig. 2; Coan et al., 2000, p. 243).
If N. magnificus evolved from N. arthriticus rather than from L. crassicardo, then it is not necessary to hypothesize that ‘‘the ancestor of L. magnificus presumably dispersed southeastward some 6,000 km across the North Equatorial Current during periods of weak westerly flow’’ (J. T. Smith, 1991a, p. 12). Rather, the dispersal direction may well have been northwestward to the Galápagos from the Panamic region or from northwestern South America, pathways followed by many other taxa. The phylogeny of the Lyropecten-Nodipecten clade (Fig. 3) does not closely constrain the origin of N. magnificus to a particular time interval in that the species could have originated from N. arthriticus at any time during the stratigraphic range of the latter, i.e., from late in the Miocene to the Holocene. As discussed above, Hickman and Lipps (1985) found that the oldest fossil N. magnificus is no older than Late Pliocene.» WALLER, T. R. 2007. The evolutionary and geographic origins on the endemic Pectinidae (Mollusca: Bivalvia) of the Galapagos Islands. Journal of Paleontology, 81 (5): 929–950 [p. 934]
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Phylogeny of Lyropecten Conrad, 1862 and Nodipecten Dall,
1898; T. R. Waller, 2007, The evolutionary and geographic origins on the endemic Pectinidae of the Galapagos Islands, fig. 3. |