Antillipecten cercadicus (Maury, 1917)
MAURY, C. J. 1917. Santo Domingo Type Sections and
Fossils. Part 1: Mollusca. Bulletins of American Paleontology, 5 (29): 166-415,
pls. 1-39. [p. 352, pl. 34, fig. 11]
C. J. Maury, 1917, plate 34.
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«Shell fan-shaped, moderately convex, fairly thick but translucent, nearly equilateral, whether equivalve or not I do not know as we found but one valve; surface sculptured with sixteen rounded, radial ribs with narrower interspaces; ribs and interspaces smooth except for fine, concentric growth lines; ears rather large, nearly equal, triangular, feebly radially threaded towards the base, otherwise smooth. Length 29, altitude 27, semidiameter 6mm. This shell is distinguished from our other Pectens by its few ribs, equilateral form and nearly equal, large ears. It has been kindly examined for us by Dr. Dall and not identified with any species in the National Museum, nor does it correspond to any of Sowerby's or Gabb's descriptions of unfigured Dominican species.
Locality.— (Exp'd' 16) Bluff 2, Cercado de Mao.» CARLOTTA JOAQUINA MAURY, 1817
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«Remarks.— Cooke (1919: 135) observed the close similarity of his new species, Pecten gardnerae, to the figure of P. cercadica provided by Maury (1917a: pl. 34, fig. 11) although noting that P. gardnerae has a narrower umbonal angle ("less spreading") and differently shaped auricles. He also noted that Maury did not mention any grouping of growth lines in her description of the left valve, a feature that Cooke found to be present on the left valve of P. gardnerae. Indeed commarginal lamellae of two orders are also present on the left-valve holotype of P. cercadica (Pl. 16, fig. 7). The differences in auricular shape are very minor when true outlines are observed by means of growth lines. Cooke's holotype and paratype are somewhat less flaring, their umbonal angles being respectively 91° and 95° compared to the 102° angle of P. cercadica, but the sculpture, microsculpture, and disk flanks of the two species are essentially identical. The weak costae in interspaces that originate on the holotype left valve of P. cercadica at a valve height of ca. 23 mm (Pl. 16, Fig. 6) are absent from the paratypic left valve of P. gardnerae, but this absence might well be due to the smaller size of the valve of P. gardnerae, which is only 22.8 mm high. The ages of P. cercadica and P. gardnerae might also be very close. Cooke (1919: 135) gave the age of P. gardnerae as Oligocene, but its type locality, USGS 3440, Santiago, Cuba, is in the area of outcrop of the La Cruz Formation, regarded by Bold (1975: 131) to be no older than Pliocene on the basis of ostracodes, particularly the presence of Radimella confragosa (Edwards, 1944). Later studies, however, have shown that the first occurrence of Radimella is earlier than the beginning of the Pliocene (Bold, 1988: 7; Saunders et al., 1986: 23).
The only specimen other than the holotype of Antillipecten cercadicus collected in the Dominican Republic is the anterior half of a right valve from locality NMB 16803 (Pl. 16, Figs 8-10). This specimen is slightly smaller (26.7 mm height) than the holotypic left valve, but by superimposing the partial right valve on the holotypic left valve, it can be seen that the anterior umbonal angle and rib patterns are identical. Comparisons.— Antillipecten cercadicus differs from A. janicoensis n. sp. in lacking well-developed secondary costae in rib interspaces. The only other species of Antillipecten known from the Neogene of the Dominican Republic that lacks such secondary costae is A. microlineatus n. sp. The latter has only 11 ribs that are broader, with more sloping sides, lacks commarginal lamellae of two orders in early ontogeny, and is inequilateral, with the posterior side extended. Antillipecten vaun wythei (Hertlein, 1933) from the La Cruz Formation, Pliocene, in the Santiago area of Cuba, resembles A. cercadicus in rib number and lack of secondary costae but diff ers in having lower, more rounded ribs that begin after an early non-ribbed smooth zone, and in lacking two orders of growth lines in rib interspaces and transverse lamellae on rib crests in early ontogeny. Evolution.— The evolutionary origin of Antillipecten cercadicus is not clear, although it is possibly descended from smooth-ribbed late Oligocene and early Miocene species of Antillipecten. Within the Upper Miocene Cercado and lower Gurabo formations of the Dominican Republic, A. janicoensis n. sp. is possibly a sister species. See comments on evolution under that species. Occurrence.— In the northern Dominican Republic, Antillipecten cercadicus is known only from the upper Cercado or lower Gurabo Formation, late Miocene, on the Río Mao. Distribution.— Outside of the Dominican Republic, Antillipecten cercadicus is known from the La Cruz Formation, Pliocene, Santiago area, Cuba, from where it was described as Pecten gardnerae by Cooke (1919). A specimen very similar to and possibly the same as A. cercadicus occurs in the lower Ponce Formation of southern Puerto Rico (USGS 21911), regarded as latest Miocene to Pliocene in age by Bold (1988: 7) in that the lower part of the formation contains the basal Radimella confragosa [ostracode] Zone.» WALLER, T. R. 2011. Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley. Bulletins of American Paleontology, 381: 1-197, pls. 1-18. [p.115]
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Antillipecten cercadicus (Maury, 1917); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic, plate 16, Figures 6-10.
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