Lindapecten paramuscosus Waller, 2011
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. 83, pl. 10, figs. 1-2]
2011 Lindapecten paramuscosus Waller 2011
T. R. Waller, 2011, plate 10.
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«Diagnosis.— Lindapecten with pointed posterior auricles, plicae of LV differentiated in height with 5 higher and with coarser scales than others, scales on narrow rib crests larger than scales on secondary costae, commarginal lamellae prominent in interspaces, foliated-calcite re-entry on interior extensive, bordering the entire ventral margin of adductor scars in mature specimens.
Description.— Shell not known to exceed 26 mm Ht, Ht exceeding L in juveniles, equal to L in mature specimens, acline to slightly prosocline, equilateral, cvx moderate, LV more convex than RV throughout ontogeny. Disks with 17-21 plicae, most commonly 18-20, rounded to trigonal in profile, broader than interspaces on RV, narrower than interspaces on LV; 5 plicae commonly higher in elevation on LV and with coarser primary scales on crests than adjacent plicae. Commarginal lamellae in interspaces raised and prominent through most of ontogeny, gradually fading out in late ontogeny generally at > 20 mm Ht. Scales present on rib crests in early ontogeny, remaining higher than scales formed on secondary costae on rib flanks and interspaces in later ontogeny. All disk flanks with fine scabrous costellae. Right anterior auricle with deep byssal notch floored by active ctenolium with 3 or 4 teeth, byssal fasciole deeply sigmoidal in cross section with raised part adjacent to disk flank rugose, auricular surface with 4 or 5 scabrous radial costae; other auricles pointed, with deep sinuses and 7 or 8 scabrous radial costae; anterior hinge line longer than posterior (ahl/phl = 1.22 on holotype), total hl ca. 80% L. Right hinge dentition consisting of single dorsal tooth on each side of resilifer and a broader, higher resilial tooth drawn out laterally, commonly indented proximally giving appearance of an intermediate tooth in addition to resilial tooth. Foliated-calcite re-entry on both valves extensive, completely bordering ventral margin of adductor scar at Ht as small as 15 mm, in small shells re-entry expanding from both anterodorsal side of adductor scar and posteroventral side, later merging to completely border ventral margin of scar. Etymology.— The prefix para- is combined with muscosus to indicate morphological proximity to Lindapecten mucosus. Type material.— Holotype, USNM 540990, 1 RV, 20.8 mm Ht, 20.6 mm L(Pl. 10, Figs 13-16). Type locality.— Locality TU 1225: Banks of Arroyo La Sabirma on west side of the Río Mao, upstream from Mao Adentro and downstream from Cercado de Mao, ca. 11 km by (winding) road or 8 km by airline south of Mao. Gurabo Formation, probably early Pliocene in age. Other material.— 69 specimens, all but one of which are single valves, from 24 localities in the Cibao Valley, northern Dominican Republic (Table 16). Remarks.— In contrast to Lindapecten plurinominis, which lives inshore commonly associated with marine grasses, L. paramuscosus n. sp. lived off shore, probably associated with patch reefs or coral build-ups near the shelf edge. This is indicated by its common association with deepwater pectinids, notably Argopecten thetidis and Gurabopecten uniplicatus n. gen., n. sp., and the deep-water bivalve Dimya sp. These associations, including transported coral debris, are particularly evident in the Río Gurabo section near the Miocene-Pliocene boundary, just below the level at which Saunders et al. (1986: 16) determined that the depth of deposition rapidly deepened. The morphology of L. paramuscosus n. sp. remains constant through the areas sampled. Comparisons.— Lindapecten paramuscosus n. sp. closely resembles two other species, L. cortezianus, an extinct species of the late Miocene and Pliocene of the tropical eastern Pacific, and L. muscosus, an extant species traceable back to the late Pliocene in the tropical western Atlantic. All three species commonly have 17-20 scaly plicae and secondary costae, with the primary scales on rib crests larger than the other scales during at least early and mid-ontogeny. The posterior auricles of all three species are pointed, with the overall trend of the posterior auricular margins forming an acute angle with the dorsal margin. Lindapecten paramuscosus n. sp., however, is clearly separable on the basis of its prominent raised commarginal lamellae in the rib interspaces of both valves and in its extensive foliated-calcite re-entry, which in mature specimens passes completely under the adductor scar (Pl. 10, Fig. 16). Aside from these differences, L. paramuscosus n. sp. is remarkably close to L. cortezianus in having narrow rib crests with narrow primary scales as well as an ontogenetic shift from primary scales that are distinctly larger than the scales on secondary costae to a state in late ontogeny in which all scales are small. However, L. paramuscosus n. sp. is closer to L. muscosus in the nature of its byssal fasciole. In both species, the fasciole is deeply sigmoidal in cross section, the raised part adjacent to the disk flank being rugose. In L. cortezianus, the byssal fasciole is arched but not rugose. Specimens that Cooke (1919: 139) identified as Pecten (Aequipecten) thetidis from Anguilla and Cuba belong in the genus Lindapecten, not in Argopecten thetidis (see preceding discussion of that species). The Cuban specimen (USNM 167072 from USGS 5255, Santiago, Cuba, La Cruz Formation, Pliocene) is a small right valve (17.0 mm Ht) that differs from his illustrated specimens from Anguilla (Anguilla Formation, middle Miocene) in having a distinctly narrower umbonal angle and relatively larger primary scales on rib crests compared to secondary scales. The Cuban specimen appears to be L. paramuscosus n. sp. based on these characters as well as its prominent commarginal lamellae in interspaces and thick foliated-calcite re-entry extending below the striate adductor scar on the shell interior. The three Anguilla specimens illustrated by Cooke (1919: pl. 11, figs 4-6) have secondary sculpture more like that on Early and Middle Miocene L. chipolanus and are clearly not the same species as the Cuban specimen. Evolution.— Lindapecten paramuscosus n. sp. lies phylogenetically between L. cortezianus of the eastern Pacific, which first appears in the late Miocene, and the extant species L. muscosus of the western Atlantic, which as far as can be determined first appeared in the late Pliocene. The synapormorphy that ties L. paramuscosus n. sp. with L. muscosus is the nature of the byssal fasciole described above. Occurrence and distribution.— In the Dominican Republic, Lindapecten paramuscosus n. sp. is apparently limited to the Gurabo Formation, ranging in age from very late Miocene into the early Pliocene. The species has not been observed outside of the Dominican Republic.» THOMAS RICHARD WALLER, 2011
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