Antillipecten microlineatus 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. 117, pl. 17, figs. 1-3]
2011 Antillipecten microlineatus Waller, 2011
T. R. Waller, 2011, plate 17.
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«Diagnosis.— Antillipecten with thin, prosocline, inequilateral shell, RV more convex than LV, disk with 9-11 broad, rounded ribs that are nearly trigonal in profi le in early ontogeny, rounded with sloping sides in later ontogeny, evenly spaced except for two anteriormost ribs on each valve, which are narrower and more closely spaced; surface smooth and glossy except for microscopic close-set growth lines throughout ontogeny.
Description.— Shell of medium size, restored ca. 45 mm Ht, prosocline, inequilateral with posterior extended, biconvexity low with RV more convex than LV, umbonal angle 94º. Ribs on disks nearly trigonal in early ontogeny, becoming narrowly rounded with gently sloping sides later, 11 on RV, 9 on LV, evenly spaced and approximately as broad as interspaces except for anteriormost two ribs on each valve, which are narrower and lower; secondary radial costae absent, commarginal lamellae of close-set decatopectinine type throughout ontogeny; surface very smooth, somewhat glossy. Anterior disk flanks low but very steep and somewhat inturned, without radial costellae or antimarginal sculpture, possessing only fine growth lines; posterior disk fl anks not preserved. Auricles not preserved except for proximal end of byssal notch, which was apparently deep with active ctenolium of small teeth. Hinge and interior characters not accessible because of hard matrix between valves. Etymology.— Named with reference to the microscopic commarginal lineations that cover the disk surfaces. Holotype and measurements.— NMB G17535, 1 articulated DV lacking posterodorsal part and most of anterior auricles, restored 45 mm Ht, restored 48 mm L, biconvexity 10.8 mm (Pl. 17, Figs 1-3). Type locality.— Locality NMB 15893, 150 m above base of section, Cercado Formation, Río Gurabo, Dominican Republic. Th e only other pectinid from this locality is Mimachlamys blowi n. sp. Other material.— None. Remarks.— Saunders et al. (1986: 46) described the lithology at this locality as "silt with corals" and indicated that its stratigraphic position is disconformably just below the massive conglomerate that they regarded (p. 15) as marking the base of the Gurabo Formation. They stated "The coral bed at some localities ... contains colonies of (?) poritids almost in position of growth with breakage only due to compaction in situ. A coral thicket of poritids with some more massive heads and with common algal balls seems to have been the environment here" (Saunders et al., 1986: 15). Th e coral bed thickens at NMB 16184, just above 16185 (the microsample equivalent of NMB 15893), as illustrated in their pl. 1, fig. 3. Normally an incomplete specimen lacking auricles would not be considered adequate as the sole basis for the description of a new species. In this case, however, the nature of the microsculpture and ribbing are so distinctive, and so unlike anything known from the Neogene of the Dominican Republic or elsewhere in the tropical American region, that I am confident that it is a new species. Comparison.— Antillipecten microlineatus n. sp. differs from all other species in the genus in having a low number of broad, nearly trigonal ribs lacking secondary radial costae. Evolution.— Nothing can be said about the phylogenetic status of this species until more material is recovered. Occurrence and distribution.— The species is known only from the type locality at the top of the Cercado Formation, late Miocene in age.» THOMAS RICHARD WALLER, 2011
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