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Monorthis menapiae
Taxonomy
Orthis menapiae was named by Davidson (1868) [Lectotype designated by Bates (1969).]. Its type specimen is BB.31873a-b, a valve (Internal and external moulds of pedicle valve), and it is a 3D body fossil.
It was recombined as Monorthis menapiae by Bates (1969).
It was recombined as Monorthis menapiae by Bates (1969).
Synonymy list
| Year | Name and author |
|---|---|
| 1868 | Orthis menapiae Davidson p. 314 figs. pl. 16, figs. 24-28. |
| 1969 | Monorthis menapiae Bates pp. 8 - 9 figs. Pl. 2, figs. 1-13 |
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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.
†Monorthis menapiae Davidson 1868
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| D. E. B. Bates 1969 | Subquadrate biconvex Monorthis, slightly indented anteriorly, widest at a long, straight hingeline, alate, with acute cardinal angles, lateral profile convexo-plane ; pedicle valve almost flat, with well marked carinate median fold, flat or slightly concave laterally, interarea plane, strongly apsacline, short, delthyrium open; brachial valve convex, with median sulcus and swollen folds on either side, interarea shorter than the ventral one, anacline, notothyrium open; ornament of both valves multi-costellate, costellae arising by bifurcation, numbering about four per mm. at shell margins and about five per mm. at 5 mm. from the ventral umbo, growth lines visible only at shell margin where they are crowded together and imbricate ; ventral interior with receding dental lamellae, teeth blunt and prominent, with well defined crural fossettes, muscle scars extending a little beyond the delthyrial cavity, of the same type as in Hesperonomiella, with adductors and diductors expanding linearly forwards, the adductors quadrangular in outline, the diductors crescentic and extending slightly further forwards ; mantle canal system probably saccate, with divergent vascula media; dorsal interior with small elevated notothyrial platform, cardinal process a simple ridge, brachiophores stout ridges, slightly swollen at their outer ends ; sockets rounded ; muscle scars with anterior and posterior pairs the same size, both sets subcircular in outline, the anterior pair directly in front of the posterior. |