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Virgiana mayvillensis
Taxonomy
Virgiana barrandei mayvillensis was named by Savage (1916) [Virgiana barrandei var. mayvillensis].
It was recombined as Virgiana mayvillensis by Boucot et al. (1971), Jin et al. (1996) and Jin and Copper (2000).
It was recombined as Virgiana mayvillensis by Boucot et al. (1971), Jin et al. (1996) and Jin and Copper (2000).
Synonymy list
| Year | Name and author |
|---|---|
| 1916 | Virgiana barrandei mayvillensis Savage p. 321 figs. pl. 17, figs. 3-7 |
| 1971 | Virgiana mayvillensis Boucot et al. p. 273 figs. pl. 1, figs. 5-11; pl. 6, fig. 13 |
| 1996 | Virgiana mayvillensis Jin et al. pp. 602 - 603 figs. 3g-m, 4a-h |
| 2000 | Virgiana mayvillensis Jin and Copper pp. 31 - 32 figs. Pl. 7, figs. 5-17; Text-fig. 16 |
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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.
†Virgiana mayvillensis Savage 1916
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| J. Jin and P. Copper 2000 | Shell medium to large in size, elongate oval, strongly and almost equally biconvex or with ventral valve slightly deeper than dorsal valve; average length 39.8 mm, width 33.4 mm, and thickness 24.4 mm (Text-fig. 16), with large whole specimens reaching 52.5 mm long and 46.6 mm wide. Greatest convexity located between 1/3-1/2 of length from apex; anterior half of shells more strongly broadened than posterior half in relatively large forms. Hingeline slightly curved, attaining about half shell width. Anterior commissure weakly sulcate to nearly rectimarginate.
Ventral umbo tumid, strongly convex and arched, extending up to I 0 mm above hingeline, with strongly in curved beak appressed onto opposite umbo; delthyrium obscured by incurved beak, devoid of deltidial plates; ventral sulcus or fold generally absent, except for weak median furrow present in umbonal area of some specimens. Dorsal umbo moderately to fairly strongly convex, with beak buried in delthyrial cavity of ventral valve; weak median fold present in dorsal umbonal area; anterior 2/3 of dorsal valve generally having uniform contour, lacking sulcus for fold, but medial portion becoming flattened or slightly depressed in anterior 1/3 of valve in some shells. Costae strong, rounded to subangular, covering entire surfaces of both valves, increasing anteriorly through bifurcation (more rarely through intercalation) to reach about 40-50 on each valve at anterior margin of large forms; growth lines fine, about 3-5 per I mm, interrupted by much coarser, irregularly spaced growth lamellae (Pl. 7, figs. 5-7, 9, 10, 16). Shell thick in umbonal area (up to 2.5 mm), with well-developed prismatic layer in posterior portion of ventral valve. Spondylium relatively wide, shallow, extending for about 1/3 of shell length; teeth weak to obsolete; median septum shorter than spondylium, extending for about 1/4 of shell length. Outer plates short, low, about 1/3 length of spondylium; inner plates slightly longer than outer plates; brachial processes rod-like, about 2/3 of length of spondylium;junction of brachial plates with processes smooth, without flanges. |