Lindapecten plurinominis (Pilsbry & Johnson, 1917)
PILSBRY, H. A. & C. W. JOHNSON. 1917. New Mollusca of the Santo Domingan Oligocene. Proceedings of the Academy of Natural Sciences of Philadelphia, 69: 150-202. [p. 193]
1917 Pecten plurinominis Pilsbry & Johnson, 1917
Pecten plurinominis Pils. and Johns.; H. A. Pilsbry, 1922, Revision of W. M. Gabb's Tertiary Mollusca of Santo Domingo, plates 45, figures 1, 2.
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«Pecten oxygonum Sby., Gabb, Trans. Amer. Philos. Soc., XV, 1873, p. 256. Not of Sowerby.
Pecten thetidis Sowerby, Dall, Trans. Wagn. Inst., Ill, p. 714. Not of Sowerby. In this scallop there are 19 rounded ribs a little wider than their intervals, over ribs and intervals there are weak radial cords bearing thin scales, near the edge of the left valve there are three of these scaly cords upon each rib and three in each interval. Submargins and ears with numerous small ribs. Ctenolium is rather long. The right valve is slightly more convex than the left.
Length and alt. 31 mm. Type No. 3230, A. N. S. P. This species resembles the recent P. fuscopurpurea Conrad in sculpture, but the ribs are not so strong and the ears are much smaller. In our opinion it cannot be either P. oxygonum or P. thetidis of Sowerby. Whether it is specifically separable from several forms found in the Canal Zone and Costa Rica is uncertain, but there are various differences which indicate at least racial distinction. Typical specimens occur in some abundance in the Bowden bed also.» H. A. PILSBRY & C. W. JOHNSON, 1917
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«Remarks.— The two patterns of scale development, trisquamous (Pl. 11, Figs 3-12) and bisquamous (Pl. 11, Figs 13-17), have not been recognized previously in Lindapecten plurinominis, but they are of particular interest because of their stratigraphic distribution. On the Río Cana, the stratigraphically lowest specimens, from the upper Cercado Formation and lower Gurabo Formation, are all of the trisquamous type (Table 17). These are followed in the interval from ca. 250-300 m above the base of the section by specimens that display a transition between the two patterns. The transition is expressed by frequent off set of the central costa on rib crests to one side or the other, with the bisquamous condition beginning in the central sector of the disk, commonly in mid-ontogeny. In samples marked transitional (Tsq/Bsq) in Table 17, some specimens retain the trisquamous condition, whereas others in the same sample have become at least partially bisquamous. Above ca. 310 m above the base of the Río Cana section, at the approximate position of the Miocene-Pliocene boundary according to Saunders et al. (1986: 23), all specimens are of the bisquamous type. A similar stratigraphic change occurs in the Río Gurabo section, where all specimens of L. plurinominis in the Cercado Formation (sensu E. Vokes, 1989: 18) are trisquamous; those near the Cercado-Gurabo boundary are transitional; the single sample in the undisputed Gurabo Formation is bisquamous. The Gurabo sample (NMB 15878) is well below the Miocene-Pliocene boundary, which was determined by Saunders et al. (1986: text-fig. 14) to be nearly 400 m above the base of the section. Specimens having the bisquamous pattern also occur stratigraphically above those with the trisquamous pattern on the Río Amina (Table 17), where the single bisquamous specimen (TU 1219, Table 17) is below the base of the Pliocene as determined by Saunders et al. (1986: 33). No definite reversals in the stratigraphic occurrence of the two sculptural patterns have been observed in any of the river sections.
The two sculptural states of Lindapecten plurinominis are interpreted to be ecophenotypes rather than chronological subspecies, because specimens are nearly identical on the basis of other characters. There is also the evidence that the occurrence of the two types is correlated more with changing lithologies determined by ecological conditions than with a particular time-stratigraphic horizon such as the Miocene-Pliocene boundary. In the Río Cana section, Saunders et al. (1986: 22) emphasized the very shallow depth of deposition of the lower part of the Cercado Formation, including assemblages of fossils indicating nearby brackish-water conditions. The finer-grained portions of the overlying Gurabo Formation indicate only slightly deeper conditions, still probably < 50 m in depth. Whereas the trisquamous form of L. plurinominis is associated with siliciclastic sand, the bisquamous form tends to be associated with finer, more calcareous sediment. By analogy with its living counterpart, L. exasperatus, the trisquamous form probably lived in association with abundant marine grasses. The bisquamous form might have lived near the outer limits of this habitat, where the reduced scaliness of its right valve could have facilitated movement on finer, softer sediment. Comparisons.-- Lindapecten plurinominis closely resembles the extant species L. exasperatus in having small, more or less equally sized scales on secondary costae on ribs and interspaces. Both species lack elongated and strongly pointed posterior auricles and are generally of only moderate convexity. The primary difference is in the number of disk plicae, commonly 20-23 (rarely 19 or 24) in L. plurinominis but commonly only 17 or 18 , rarely 19, in L. exasperatus. It is on the basis of the number of ribs (commonly 19 or 20) that Chlamys (Aequipecten) plurinominis morantensis from the Bowden beds of Jamaica is regarded in the present study as a subspecies of L. exasperatus. The bisquamous sculptural variant present in L. plurinominis has not been observed in either L. exasperatus s. s. or in L. exasperatus morantensis.
Lindapecten buchivacoanus buchivacoanus differs from L. plurinominis in having stronger secondary costae and scales, a narrower umbonal angle, and an early introduction of a medial costa in interspaces. Lindapecten b. falconensis is more gibbous, reaches a larger size, and has a medial groove on each rib crest rather than a medial costa. Lindapecten b. maracaibensis resembles L. b. falconensis in gibbosity and size but has a prominent medial costa in interspaces. Three closely related species, Lindapecten muscosus, L. paramuscosus n. sp., and L. cortezianus, all differ from L. plurinominis in having more pointed auricles, particularly the posterior, ribs that are more differentiated in height on the left valve (5 ribs consistently higher than in others, especially in L. muscosus and L. paramuscosus n. sp.), fewer ribs (commonly 17 or 18), and scales on rib crests that are larger than flanking scales through most of ontogeny.» 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. 87, 91, 90]
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Lindapecten plurinominis (Pilsbry & Johnson, 1917); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic, plate 11, figures 3-17.
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«Observations. — Le type de C. plurinominis se trouve dans la collection Gabb et provient de la Rép. Dominicaine. Cette espèce a été appelée Pecten thetidis G. B. Sowerby I par Gabb (1873, p. 256, fig. 23), par Guppy 1876, par Maury, 1917 et Dall, 1903. J'ai pu examiner les syntypes et le Iectotype de P. thetidis G. B. Sowerby I au British Museum (Nat. Hist.) dans la Collection Heneken, mais ils sont três différents des nôtres. Par contre, un echantillon determine Chlamys cf. thetidis est bien identique et provient du Miocène de la côte de la Rép. Dominicaine, près de Monohill-Montechristi (N. LL3572-8), ainsi que d'autres fossiles provenant des calcaires blancs de la Jamaïque, au Sud de Round Hill, Vere Clarendon (N. L88342-51).
Rapports et différences. — C. plurinominis diffère de C. acanikos Gardner (1926, pl. XI, figs. 1, 2) qui a trois files régulières de squames tandis que les files ne sont pas toujours régulières sur l'espèce antillaise. Chlamys portoricoensis Hubbard (1920, p. 87, pl. XI, figs. 2, 3) est différente par le plus grand nombre de côtes: 23 sur les figures, et une file de squames constante sur les intervalles. Pecten thetidis G. B. Sowerby I (in Cooke, 1919, p. 138, pl. 11, figs. 4 à 6) du calcaire d'Anguilla, se distingue par ses lamelles concentriques beaucoup plus développées sur la moitié supérieure de la coquille. Gisements, répartition stratigraphique et géographique. — Santo-Domingo, Caimito et Samba Hills (Cercado Fm.). Panama, Gatun Fm., Zone du Canal (Miocène moyen). Costa Rica, Miocène moyen de Valle Central, près de Turrucares. Haiti, Miocène moyen et supérieur (in Butterlin, 1960). Anguilla et Cuba, Miocène inferieur. Jamaica, Bowden beds (Miocène moyen). Guadeloupe, Colline de l'Aérodrome: gis. I (ma et mb), Gensollin: gis. V (ma et mb), ravine Poucet: gis. X (mb et mc), La Brousse: gis. R. G. 1471 (mb).» MONGIN, D. 1968. Les Pectinides du Miocène de La Guadaloupe (Antilles Francaises). Bulletins of American Paleontology, 54 (245): 471-510, pls. 40-50. [p. 478, 479]
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Chlamys plurinominis (Pilsbry et Johnson): D. Mongin, 1968, Les Pectinides du Miocène de La Guadaloupe, plate 40, figures 2a-2c.
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