Lindapecten baitoaensis 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. 82, pl. 10, figs. 4-12]
2011 Lindapecten baitoaensis Waller, 2011
T. R. Waller, 2011, plate 10.
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Diagnosis.— Lindapecten with 17-21 simple radial plicae, rarely 24-29, with secondary costae not appearing on rib flanks until 13-15 mm Ht, then persisting through ontogeny; rib crests in late ontogeny each having central groove flanked by scaly costae; hl relatively short for Lindapecten (60-70% L).
Description.— Shell not known to exceed 35 mm Ht, higher than long in early ontogeny, becoming slightly longer than high later, acline to slightly prosocline, equilateral or with posterior slightly extended, convexity moderate, LV more convex than RV especially in early ontogeny. Disks commonly with 17-21 simple radial plicae, rarely 24-29, approximately equal in width to interspaces or slightly wider. Commarginal lamellae present in rib interspaces but not on rib crests in early ontogeny of both valves, later crossing rib crests and becoming prominent on rib crests but disappearing in interspaces; transverse scales on some LVs appearing earlier on 5 widely spaced plicae than on others. Secondary radial costae first appearing on rib flanks at 13-15 mm Ht, with minute scales forming where costae are crossed by commarginal lamellae; commarginal lamellae on rib crests later becoming irregular in trend and forming 2 scaly costae on rib crests with central groove; secondary costae in interspaces appearing at ca. 18-20 mm Ht. Disk flanks shallow, moderately sloped, with fine scaly radial costellae much finer than radials on disk but grading into radials on posterior and left anterior auricles. Auricles of moderate size relative to size of disk, anterior auricle longer than posterior, hl ca. 60-70% L; right anterior auricle with deep byssal notch, rugose byssal fasciole, prominent active ctenolium, and 4 or 5 scabrous radial costae; left anterior auricle not preserved; posterior auricles with ca. 8 scabrous primary radial costae, with finer scabrous costellae introduced by intercalation during ontogeny; posterior margins of posterior auricles each forming acute angle with dorsal margin. Right hinge dentition dominated by single prominent, laterally extended resilial tooth on each side of resilifer, bordered dorsally on each side by a socket to accommodate dorsal teeth of LV. Foliated-calcite re-entry on interior of RV extending into notch between striate and nonstriate portions of adductor scar, on LV extending ventrally to ca. ⅓ length of anterior margin of adductor scar. Etymology.— Named after the village of Baitoa on the Río Yaque del Norte, Dominican Republic. Holotype and measurements.— USNM 540987, 1 RV missing most of the anterior auricle and portions of the anterior part of the disk, 27.8 mm Ht, 25.0 mm L (incomplete), ca. 5 mm cvx (Pl. 10, Figs 4-5). Type locality.— Locality TU 1226, large bluff s on east bank of the Río Yaque del Norte, just below the village of Baitoa, and above the confluence of the Río Yaque del Norte and the Río Bao. Baitoa Formation. Collected by E. H. & H. E. Vokes, 1976. Other material.— 66 specimens from 11 localities, all from the Baitoa Formation on the Río Yaque del Norte, northern Dominican Republic (Table 15). All of the specimens are single valves. Remarks.— Although the specimen designated as the holotype is incomplete, it was selected because it displays the best preserved sculpture in late ontogeny of any of the specimens on hand. Two specimens of Lindapecten baitoaensis n. sp., NMB G17519 (locality NMB 16938) and NMB G17520 (locality NMB 16936), differ from all of the others in having anomalously high rib counts ranging from 24-29 (Pl. 10, Figs 11-12). These are small specimens, the largest having a restored height scarcely more than 10 mm. Most have smooth rib crests with commarginal lamellae in interspaces and look like members of Argopecten. That they are indeed L. baitoaensis n. sp. is indicated by the largest specimens, which develop scales on the lateral edges of lateral ribs, and the presence, in some specimens, of transverse lamellae on rib crests. They also develop scaly costellae on the disk flanks. Saunders et al. (1986: 29) commented on the part of the section that yielded the NMB samples as having "varying energy levels as suggested by frequent influxes of pebble and cobbles" and other indications of an unstable environment in very shallow water. Comparisons.— Lindapecten baitoaensis n. sp. is closest morphologically to two species from the approximately correlative Chipola and Torreya formations of Florida, Pecten (Aequipecten) chipolanus Dall, 1898, and Chlamys (Lyropecten) acanikos Gardner, 1926, respectively. All three of these species, which I now assign to Lindapecten, have similar sculpture in early ontogeny but differ in numbers of ribs and the degree of development and timing of appearance of secondary radial costae. Lindapecten chipolanus (Pl. 10, Figs 2-3) differs from L. baitoaensis n. sp. in having fewer ribs (commonly 16 or 17, rarely 15 or 18), and the secondary radials on the disk of L. chipolanus are not as well developed in late ontogeny or can be absent. Lindapecten acanikos has a narrower umbonal angle and fewer ribs than does L. baitoaensis n. sp., and the secondary costae of L. acanikos appear later in ontogeny, usually with a central costa on the rib crest, whereas in L. baitoaensis n. sp. the rib crest has a central groove. Lindapecten baitoaensis n. sp. differs from L. plurinominis, which appears later in the Dominican Republic sections in the Cercado Formation, in having late-appearing secondary radial costation, whereas in L. plurinominis and in other Lindapecten species of the Late Miocene and later strata, secondary radials and scales appear in early ontogeny. Evolution.— See preceding discussion of the genus Lindapecten. Occurrence and distribution.— Lindapecten baitoaensis n. sp. is known only from the Baitoa Formation in the northern Cibao Valley, Dominican Republic. THOMAS RICHARD WALLER, 2011
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