Mimachlamys vokesorum 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. 35, pl. 3, figs. 6-9]
2011 Mimachlamys vokesorum Waller 2011
T. R. Waller, 2011, plate 3.
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«Diagnosis.— Mimachlamys with 22 or 23 simple, broad trigonal ribs much broader than interspaces and bearing small distally concave scales; secondary costae appearing in late ontogeny along bases of lateral ribs facing center of shell; posterior auricles much smaller than anterior and with posterior auricular margins forming obtuse angle of ca. 140° with dorsal margin.
Description.— Shell 52 mm Ht, height slightly exceeding length, strongly prosocline, biconvexity moderate with LV slightly more convex than RV, disk gapes absent. Disks with 22 or 23 primary ribs originating by 4 mm Ht from beak, rib profiles rounded-trigonal in early ontogeny, becoming more distinctly trigonal and much broader than interspaces in late ontogeny, becoming narrower and lower near disk flanks; secondary costae originating in late ontogeny along bases of rib flanks on sides of lateral ribs that face center of shell; medial costae in rib interspaces absent; narrow crests of ribs bearing very small, distally concave, irregularly spaced scales; divaricating to diagonal antimarginal microsculpture in rib interspaces ending abruptly at bases of rib flanks; ribs lacking microsculpture except for very fine growth lines; raised commarginal lamellae absent. Disk flanks lower on anterior side than on posterior, all except right anterior flank bearing fine scabrous radial costellae. Posterior auricles much smaller than anterior, with length of posterior auricle ca. 60% of length of anterior; posterior auricular margins nearly straight, forming angle of ca. 140° with dorsal margin; total hl 47% of L. Right anterior auricle with 6 strong, scabrous radial costae, broad byssal fasciole, and deep byssal notch with strong active ctenolium; left anterior auricle with nearly straight anterior margin forming acute angle with dorsal margin, bearing radial costae but number not determined because of adhering matrix; left posterior auricle bearing 4 fine, slightly scabrous, radial costellae; right posterior auricular surface obscured by matrix. Interior characters not accessible. Etymology.— Named in honor of Emily H. Vokes and the late Harold E. Vokes, who collected the holotype of this species and who contributed enormously to our knowledge of tropical American mollusks. Type material.— Holotype, USNM 540950, 1 articulated DV, 52.1 mm Ht, 50.0 mm L (Pl. 3, Figs 6-9). Type locality.— TU 1245, "Mao Adentro Limestone?," road cut 5 km south of bridge at Guayubín, on road to Sabaneta, northern Dominican Republic. Other material.—None. Remarks.— As stated above in Remarks under Caribachlamys guayubinensis n. sp., the stratigraphic position and formational assignment of the limestones in the Guayubín area are not yet resolved, but there is some indication based on the species present that these limestones might be younger than the true Mao Adentro Limestone Member of the Mao Formation along the Río Mao. Comparisons.— The only species of Mimachlamys close to M. vokesorum n. sp. is M. blowi n. sp., described above. Mimachlamys vokesorum n. sp. differs from the latter in having trigonal ribs that are broader relative to interspaces, a more flaring, prosocline shape, posterior auricular margins forming a more obtuse angle with the dorsal margin, and secondary costae in late ontogeny adjacent to lateral ribs. Evolution.— See under Mimachlamys blowi n. sp. Occurrence and distribution.— Known only from the type locality, TU 1245, in the northern Dominican Republic.» THOMAS R. WALLER, 2011
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