Carolinapecten Ward & Blackwelder, 1987
WARD, L. W. & B. W. BLACKWELDER. 1987. Late Pliocene and Early Pleistocene Mollusca from the James City and Chowan Rives Formations at Lee Creek Mine. In: Geology and Paleontology of the Lee Creek Mine, North Carolina, II, C. E. Ray (ed.), Smithsonian Contributions to Paleobiology, 61: 113-283, pls. 1-47. [p. 141]
«Genus Carolinapecten, new genus
TYPE.— Carolinapecten eboreus (Conrad, 1833), Pliocene, upper Yorktown beds at Suffolk, Virginia, on rhe Nansenrond River; designated herewith.
DIAGNOSIS.— Shells usually large, commonly 80 mm and as much as 150 mm in height; valves thin and of low convexity, shells ranging from distinctly left-convex ro slightly right-convex; outline of disk equilateral; disk flanks lorv and curved in plane perpendicular to commissure and to disk flanks. Disk gapes broad. Auricules about equal in length; anterior auricle with shallow byssal notch, ctenolium absent in individuals larger than about 60 mm in height; auricles of right valve with dorsal margins extending dorsally from outer ligament in distinct folds increasing in anrplitude distally, giving dorsal n.rargins a shallow V-shape appearance in plane of commissure; auricles of right valve with free margins forming acute angles at juncture with outer ligament. Ornament of approximately 20 to 25 low radial plicae and of concentric lamellae, the latter better developed in interspaces; radial costae never common on disk and arising distally in interspaces or ar sides of plicae or rarely on crests of plicae. Plicae reflected over almost entire interior of valves with sharp, approximately squared margins. Adductor scar large and only faintly expressed as a thin layer of aragonite. Auricular denticles absent to moderately strong; cardinal crura low. Ventral margin of shell with interspaces projecting ventrally to form interdigitation with opposing ribs.
DISCUSSION.— The genus Carolinapecten (type species, Carolinapecten eboreus (Conrad)) is proposed for an important group of eastern North American Pectinidae. Carolinapecten species are distinguished by their large size (adults often 80 to 150 mm in height), the thin valves of low convexity, ranging from left-convex ro slightly right-convex, ornament of approximately 20 to 25 low radial plicae, cardinal crura low, byssal notch shallow, and large specimens lacking ctenolium. Disk flanks are low and poorly demarcated, the free margins of the posterior auricles are convex in the plane of commissure lvith the posterior sinus obscure or absent.
The eboreus group was recognized by Waller (1969: 59-61) as a separate species-group on morphologic grounds and as a separate lineage. Waller stated that this group forms a discrete taxonomic unit separate from all other related groups. Although he treated the group as consisting of a single essentially monotypic species, he recognized that with further work rhe group could probably be subdivided into different taxa. Waller indicated that the eboreus group arose when the subspecies eboreus urbannaensis appeared as a splitting from the main Argopecten gibbus species-group. Although Waller retained the eboreus species-group within the genus Argopecten, we believe that the eboreus group is sufficiently distinct with respect to morphology and evolution to merit generic rank. Giver.r present evidence, we are not at all certain as ro the origin of the group; in particular, we are not convinced that the lineage is closely related evolutionarily to rhe Argopecten gibbus species-group. The earliest known specimens of the eboreus group are quite distinct (upper Miocene Eastover Formation of Ward and Blackwelder, 1980). A small unnamed pecren in the Choptank Formation of Maryland may possibly be near to the origin of the group and is related to the genus Chesapecten Ward and Blackwelder, 1975. Species belonging in the genus Carolinapecten have previously been referred to Pecten, Chlamys, Plagiocteniurn, Lyropecten, Aequipecten, and Argopecten. Argopecten is a senior synonym of PIagioctenium (Waller, 1969: 32-36). Lyropecten of Conrad, 1863, is an easrern Pacific genus with prominent, strong ribs, large cardinal crura, and a large byssal notch. Aequipecten Fischer, 1886, is an eastern Atlantic genus with species having anterior auricles longer than posterior, and the plicate disk covered with dense scabrous radial costae. Argopecten (type species, Pecten circularis Sowerby, 1835) differs substantially from Carolinapecten in being smaller in size (usually less than 70 mm high); having disk flanks steep; plicae high and rectangular in cross-section; byssal notch deep; and with quite convex valves.» LAUCK W. WARD & BLAKE W. BLACKWELDER, 1987
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Carolinapecten eboreus (Conrad); L. W. Ward & B. W. Blackwelder, 1986, Late Pliocene and Early Pleistocene Mollusca from the James City and Chowan Rives Formations at Lee Creek Mine, plate 6, figures 1-9.
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T. R. Waller, 2018, Systematics and biostratigraphy of Chesapecten and Carolinapecten (Mollusca: Bivalvia: Pectinidae) in the upper Miocene and Pliocene "lower Tamiami Formation" of southwestern Florida, figure 9. Carolinapecten corpulentus n. sp., figures 9A-9D; Carolinapecten murdockensis druidwilsoni n. ssp., figures 9E-9H.
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«GENUS CAROLINAPECTEN WARD AND BLACKWELDER, 1987
Carolinapecten Ward and Blackwelder, 1987:141.
Type species.— Pecten eboreus Conrad, 1833, by original designation; Pliocene, upper Yorktown Formation at Suffolk, Virginia, on the Nansemond
River (Ward and Blackwelder, 1987: 141). Included species.— Carolinapecten includes a large number of nominal species and subspecies that are still being reviewed. The most commonly accepted species-group names, as evidenced by taxonomic treatments by Gibson (1987), Ward and Blackwelder (1987), Campbell (1993), Campbell and Campbell (1995), and Petuch (2004), include the following: bertiensis (Mansfield, 1937), darlingtonensis (Dall, 1898), eboreus (Conrad, 1833), gladensis (Mansfield, 1936), jamieae Petuch, 2004, senescens (Dall, 1898), solarioides (Heilprin, 1887), urbannaensis (Mansfield, 1929), walkerensis (Tucker, 1934), and watsonensis (Mansfield, 1936).
Revised diagnosis.— Aequipectinoid Pectinidae of large size (80–150 mm height), thin valves of low convexity, ranging from left-convex to strongly right convex, about 15–25 low radial ribs, secondary costae, if present, without scales, cardinal crura (hinge teeth herein) low, byssal notch shallow, active ctenolium absent in adults, disk flanks low and poorly demarcated, posterior margins of posterior auricles convex in plane of commissure, posterior sinus obscure or absent. (Modified from Ward and Blackwelder (1987:141.)
Geographic range.— Atlantic and Gulf of Mexico coastal plains from Virginia to Florida and eastern Mexico. See Gardner (1944:37) for Mexican occurrences.
Stratigraphic range.— Upper Miocene (Cobham Bay Member of Eastover Formation in Virginia; Bayshore Clay Member of lower Tamiami Formation) to Pleistocene Bermont Formation in Florida.
Remarks.— The new species of Carolinapecten described herein substantially enlarge the original concept of the genus. Both valves of the oldest species, Carolinapecten corpulentus n. sp., are strongly convex, and this species as well as its successor, Ca. murdockensis druidwilsoni n. sp. and n. ssp., are distinctly right-convex. These taxa, as well as two additional subspecies of Ca. murdockensis described herein, also differ from the original diagnosis of Carolinapecten in having fewer ribs (15–19).»
WALLER, T. R. 2011. Systematics and biostratigraphy of Chesapecten and Carolinapecten (Mollusca: Bivalvia: Pectinidae) in the upper Miocene and Pliocene "lower Tamiami Formation" of southwestern Florida. Bulletin of the Florida Museum of Natural History, 56 (1): 1-47, figs. 1-11. [p. 23]
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