|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Strophomenata - Strophomenida - Rafinesquinidae
|Year||Name and author|
|1928||Strophomena tennesseensis Willard p. 285 figs. pl. 2, figs. 17, 18,|
|1956||Rhipidomena tennesseensis Cooper pp. 870 - 872 figs. Plate 252, A, figures 1-5; plate 252, B, figures 6-14; plate 253, A, figures 1-14|
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|G. A. Cooper 1956||Shell large for the genus, varying in outline from nearly quadrate to semielliptical. Cardinal extremities deflected toward the brachial valve varying from a right angle to alate. Hinge equal to or greater than the width at the middle. Lateral margins varying from nearly straight to oblique to greatly rounded. Anterior margin narrowly to broadly rounded. Surface ornamented by fine radiating costellae of 2 sizes, i or 2 costellae separating the larger ones. On the lateral slopes, particularly anterior to the cardinal extremities, the costellae become fairly uniform in size. Finer radii increasing in size toward the anterior margin and tending toward uniformity in size along the margin. At the front margin of a specimen 33 mm. long, 25 costellae may be counted in 5 mm., but in a specimen measuring 46 mm. in length, only 16 costellae were counted in the same distance. Entire surface covered by fine concentric fila, about 8 or 9 in a millimeter at about the middle, becoming more crowded toward the front. Hinge region may or may not be marked by a few oblique wrinkles.
Adult pedicle valve with posterior half gently swollen and with gentle slopes; anterior half moderately strongly geniculated toward the pedicle valve ; geniculation of lateral portions more gentle. Angle of geniculation between 105° and 130°. Beak inconspicuous; foramen small, elongated, often at the anterior of a short groove. Interarea moderately long, apsacline. Pseudodeltidium low and inconspicuous.
Posterior half of brachial valve flattened, gently concave at the umbo ; anterior slope moderately steep ; lateral slopes steeper than the anterior one. Umbonal region sulcate, sulcus wide and shallow, extending nearly to middle of valve. I
nterior : Muscle area of pedicle valve broadly cordate ; diductor scars flabellate, separated by 2 low ridges. Adductor scars elongate elliptical in outline, located somewhat posterior to the middle of the muscle area. Delthyrial chamber filled by callus that is extended forward as far as the posterior ends of the adductor impressions.