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Multicostella plena
Taxonomy
Multicostella plena was named by Cooper (1956). Its type specimen is USNM 1104036, a shell, and it is a 3D body fossil. Its type locality is Both sides of the old road in the cedar glade ΒΌ mile southeast of Friendsville, which is in a Chazyan carbonate limestone in the Arline Formation of Tennessee.
Sister species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 1956 | Multicostella plena Cooper pp. 422 - 423 figs. Plate 62, B, figures 6-14 |
| 1962 | Multicostella plena Williams p. 119 figs. P1. X, figs. 16-19, 23 |
| 2014 | Multicostella plena Candela and Harper pp. Supplement 1 |
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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.
†Multicostella plena Cooper 1956
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| G. A. Cooper 1956 | Large for the genus, somewhat variable ; wider than long with the greatest width at the hinge in well-preserved specimens ; sides nearly straight or gently rounded ; anterior margin broadly rounded ; anterior commissure varying from slightly uniplicate to slightly sulcate ; lateral commissure slightly deflected toward the brachial valve at the cardinal extremities ; brachial valve having a slightly deeper profile than the pedicle one ; cardinal extremities varying from slightly acute to slightly obtuse, occasionally slightly auriculate ; surface multicostellate, costellae narrow, elevated, about equal in width to the spaces between them ; about 8 costellae in 5 mm. at the front margin of a specimen 21 mm. long; costellae produced in several generations ; costellae crossed by strong elevated fila.
Pedicle valve unevenly convex in lateral profile, most convex in posterior half but convexity very low ; anterior half gently convex ; anterior profile broadly but slightly convex ; umbo narrowly convex, the convexity continued anteriorly as a low fold perceptible in most specimens to the front margin, in a few fairly conspicuous ; flanks bounding sulcus depressed convex ; posterolateral extremities deflected more or less strongly toward the brachial valve. Interarea moderately long, strongly apsacline. Interior with short dental plates and shallow umbonal cavities ; muscle area somewhat quadrate, gently indented anteriorly and extending about one-third the length ; pallial impressions not strongly marked. Brachial valve gently convex in lateral profile; broadly convex in anterior profile and with the median region more or less strongly indented. Umbo sulcate ; sulcus narrow and shallow to moderately deep in the posterior half, widening and shallowing, often to disappearance anteriorly; flanks bounding sulcus somewhat narrowly rounded and with short but fairly steep lateral and posterolateral slopes. Interior with short, low median ridge, short brachiophores, and stout but short cardinal process ; lateral processes occasionally developed. | |
| A. Williams 1962 | The small number of Multicostella recovered from the lower horizons of the Barr Series are closely comparable in many respects with M. plena Cooper (1956, p. 422) from the lower Porterfield. The ornamentation of both stocks is more finely multicostellate than in other species of Multicostella and ranges from 9 to 13 costeUae per 5 mm. for 3, 1, 2, 6 and 1 Scottish specimens respectively. The ventral muscle-scar, for 4 Scottish valves, averaged 32.8 ~o of the length of the pedicle valve (variance 27.0) and is only three-quarters as wide as long, for the diductor scars are not strongly divergent and the muscle-field correspondingly less quadrate than is typical of Multicostella other than that of the Porterfield species, which is also similarly proportioned. Differences include the tendency for the Scottish forms to be larger and wider (Table 15), and for the dorsal sulcus to persist in adult shells, a condition displayed by 3 of the 7 specimens in excess of 13.5 mm. long. Certainly, for the present size of samples, none of these differences is significant, and all specimens are best regarded as being closely related to M. plena. |