Paraleptopecten 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. 91]
«Genus PARALEPTOPECTEN n. gen.
Type species.— Chlamys (Aequipecten) bavayi Dautzenberg, 1900, Recent, Caribbean and tropical western Atlantic, from the Caribbean coast of Central America, throughout the Antilles, and southward to Uruguay (Abbott, 1974; and data from USNM collections).
Diagnosis.— Shells small, rarely exceeding 25 mm Ht, acline to moderately prosocline, Ht and L equal or with L slightly exceeding Ht, cvx of articulated shells low to moderate, ranging from equiconvex to slightly right-convex. Auricles large relative to size of disk, total hl approximately equal to L in both juveniles and adults; anterior auricle long and narrow, with anterior extremity commonly projecting beyond anterior extremity of disk throughout ontogeny; byssal notch deep, fl oored by prominent active ctenolium with 4-7 teeth; posterior auricles with straight or slightly sigmoidal posterior margin commonly forming acute angle with dorsal margin. Radial plicae on disk of LV commonly of uneven height and width, with 5 major plicae separated by 2-4 minor plicae; plicae of RV commonly of even height but with major interspaces deeper and wider, corresponding to interlocking major ribs of LV; less commonly plicae of both valves even in height and spacing but having angular profi les and commonly fringed by cuspate, tightly curved (distally concave) commarginal lamellae. Right anterior auricle with strong, closely spaced radial costae, right posterior auricle commonly with more widely spaced costellae that can be as strong as on anterior auricles and persist through ontogeny. Hinge dentition of RV weakly developed, consisting of very narrow, barely distinguishable dorsal teeth adjacent to ligament groove and very low, poorly demarcated resilial teeth. Commarginal lamellae commonly prominent throughout ontogeny, tending to form deep cusps on rib flanks, especially on major ribs.
Etymology.— The prefix para- is combined with Leptopecten to indicate probable phylogenetic closeness of the new genus to Leptopecten.
Remarks.—The fossil and R cent species that are included in Paraleptopecten n. gen. are listed in Appendix 3. Although Leptopecten and Paraleptopecten n. gen. are both aequipectinine genera, it is likely that they have independent origins on opposite sides of the Americas, an idea that was previously suggested by Ward & Blackwelder (1987: 140). As previously discussed under Leptopecten, the oldest members of that genus are in the late Oligocene or early Miocene in the eastern Pacific region. In contrast, the oldest undoubted species of Paraleptopecten n. gen., P. pirabensis (Ferreira, 1960), occurs in the Pirabas Formation of Brazil, dated as Early Miocene. Also in the same formation is a species that Ferreira (1960: 152) called "Chlamys (Leptopecten) cf. latiaurata (Conrad, 1837)." Based on Ferreira's figures, which show angular ribs and densely costate auricles, this species is likely also in Paraleptopecten n. gen.
Another Early Miocene lineage that is less likely to be in the ancestry of Paraleptopecten n. gen. is represented by Pecten burnsi Dall, 1898, of the Chipola Formation of Florida, Pecten (aff . Aequipecten) quirosensis Harris in Hodson et al., 1927, of the late Early Miocene La Rosa Formation of the state of Zulia, Venezuela, and possibly Pecten agronomica Maury, 1925b, of the Early Miocene Pirabas Formation of Brazil. All of these species are strongly right convex, with even plicae. Although their posterior auricles are large and Paraleptopecten-like, they do not have particularly deep byssal notches. Furthermore, their ctenolium consists of very fine teeth on an out-turned flange of the disk flank, unlike the coarse-toothed, more elongate ctenolium of Paraleptopecten n. gen. The P. burnsi lineage is possibly related more closely to the P. perplanus stock, abundant in the Oligocene of the southeastern United States (see Glawe, 1969), a relationship previously suggested by Dall (1898: 720). The species-level taxonomy of Paraleptopecten n. gen. of the Late Miocene to Early Pleistocene is confused and in need of revision, in part because past authors have not fully appreciated the degree to which rib patterns vary. Using the method of encoding rib patterns explained in the Materials and Methods section, I have identified 17 rib patterns on the disks of LVs of extant P. bavayi in the Smithsonian (USNM) collection of Recent mollusks (Table 18). Specimens of P. olgensis (Mansfi eld, 1939) from the middle Pliocene of Florida, raised herein to species rank, falls within the range of variation of P. bavayi in terms of the rib pattern of the LV but differs from all living P. bavayi in lacking single medial costae in the interspaces of the RV. Paraleptopecten olgensis also has a narrower umbonal angle in early ontogeny and only one minor plica between the outermost major rib and shoulder of the disk flank on the anterior and posterior of the LV. Paraleptopecten leonensis (Mansfield, 1932) of the Pliocene Jackson Bluff Formation of Florida resembles P. olgensis in umbonal angle and lack of single medial costae, but diff ers in having only 11 ribs on the LV in the pattern /r R r R r Rc r R r R r\. Paraleptopecten wendelli (Tucker, 1934), from the upper Pliocene to lower Pleistocene Caloosahatchee Formation of Florida and the Waccamaw Formation of South Carolina, differs from P. olgensis mainly in having a single medial costae in each interspace originating in mid-ontogeny. Some species of Paraleptopecten n. gen. lack the differential rib height and spacing on their LVs but have other characteristics typical of the genus, namely plicae of angular profile commonly with the rib flanks slightly undercut and covered by well-developed cuspate lamellae. In terms of rib pattern, a new species of Paraleptopecten n. gen. (in Appendix 3 as P. sp. b), from the Late Miocene Savaneta Glauconitic Sandstone Member of the Springvale Formation of Trinidad, is remarkably similar to P. biolleyi of the tropical eastern Pacific (Grau, 1959: 116) and probably reflects seaways between the Caribbean and tropical eastern Pacific that were open at that time. Although Paraleptopecten n. gen. extended as far north as Virginia during the Pliocene, at present it is unknown in Florida and is restricted to more tropical regions, mainly in the Antilles and along the coasts of Central and South America. Geographic range.— Extant in Caribbean and the tropical western Atlantic from the Lesser Antilles to Uruguay, and in the eastern Pacific from southern California to Ecuador, at depths from shallow subtidal to ca. 200 m; fossil in the western Atlantic from North Carolina to Brazil, Lower Miocene to Pleistocene, and in the eastern Pacific from southern California to Mexico, Upper Miocene to Recent. See Appendix 3 for details.
Stratigraphic range.— Lower Miocene to Recent on the eastern side of the Americas, Upper Miocene to Recent on the western side.»
THOMAS RICHARD WALLER, 2011
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Paraleptopecten bavayi (Dautzenberg, 1900); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley, plate 11, figure 18.
Chlamys (Aequipecten), Bavayi, n. sp.; P. Dautzenberg, 1900, Croisières du yacht Chazalie dans l'Atlantique. Mollusques, plate 10, figures 2, 2, 2a.
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