Dimarzipecten Ward, 1992
WARD, L. W. 1992. Molluscan bioestratigraphy of the Miocene, middle Atlantic Coastal Plain of North America. Memoirs of theVirginia Museum of Natural History, 2: 1-159, pls. 1-26. [p. 67]
Genus Dimarzipecten, new genus
«Diagnosis.— Valves higher than long, with about 22 thin, inegularly scaled ribs. Small riblets nearly fill interspaces between ribs.
Description.— Cooke's (1919, p. 135) description of Pecten crocus characterizes the genus well and is repeated here: "Shell equivalve, inequilateral, moderately convex; about 22 round ribs separated by slightly narrower interspaces; surface of the ribs with curved imbricating spines, convex towards the umbones, and with very faint radiating striae; interspaces with sculpture of fine, close-set, concentric striae; near the ventral margin a small thread appears in each interspace; submargins depressed, omamented with small radial threads and fine concentric striae; ears moderately large, subequal, with radial, nodose riblets. Alt., 39 mm; lat., 36 mm.; diam., 14 mm." Discussion.—This taxon has a broad geographic distribution, from the West Indies to North Carolina, and a narrow, known stratigmphic range, the upper Oligocene and lower Miocene. For that reason it is an important marker species for that period. It is desirable, therefore, to give the taxon a generic name for ease of discussion, even though it is the only known species that is assigned to the new genus Dimarzipecten. Dimarzipecten crocus was originally assigned to the catch-all genus "Pecten." Dimarzipecten differs in having an only slightly convex right valve and a deeply convex left valve, while the left valve of Pecten is flat to concave and the right valve is deeply convex. Other authors, such as Tucker (1934), Rowland (1936), Mansfield (1937), and Richards and Hopkins (1960) placed the species in the genus Chlamys. The type of Chlamys is C. islandica which differs in having far more (averaging 50) thinner, bifurcating ribs, which tend to group in pairs, threes, or fours. Type information.— Type species: Based on Cooke's (1919) Pecten crocus. Type locality: "Roadside, descent to Crocus Bay, Anguilla, station 6893, also 6894 and 6995, Vaughan" (Cooke, 1919, p. 135). Stratigraphic and geographic range.— Tampa Formation (upper Oligocene and lower Miocene) and its equivalents in Florida and Georgia. Edisto Formation (upper Oligocene and lower Miocene) in South Carolina and Belgrade Formation (upper Oligocene and lower Miocene) in North Carolina.» LAUCK W. WARD, 1992
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Dimarzipecten crocus (Cooke, 1919); L. W. Ward, 1992, Molluscan bioestratigraphy of the Miocene, middle Atlantic Coastal Plain of North America, plate 24, figure 2.
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