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Hesperorthis australis
Taxonomy
Hesperorthis australis was named by Cooper (1956). Its type specimen is USNM 109927a, a shell, and it is a 3D body fossil.
Subspecies
Sister species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 1956 | Hesperorthis australis Cooper pp. 345 - 346 figs. Plate 49, C, figures 11-15; plate 53, A, figures 1-31 |
| 2014 | Hesperorthis australis 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.
†Hesperorthis australis Cooper 1956
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†Hesperorthis australis exitis Williams 1962
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| G. A. Cooper 1956 | Shell of medium size to small for the genus, slightly wider than long with the hinge forming the widest part or usually slightly narrower. Maximum shell width often just anterior to the hinge. Cardinal extremities varying from slightly obtuse to slightly acute. Lateral margins nearly straight and slightly oblique to very gently rounded. Anterior margin broadly rounded; the outline semielliptical. Surface costate, costae direct, narrowly rounded, and numbering 26 to 30. Interspaces occupied by several fine costellae, one of which may be stronger than the others, and by fine concentric fila. Costae seldom intercalated.
Pedicle valve with lateral profile unequally convex and with the anterior flattened ; maximum convexity located just anterior to umbo. Anterior profile subcarinate with the sloping sides forming an angle slightly less than 110°. Umbonal region somewhat swollen with the swollen portion extending to the front margin as a low fold. Lateral slopes long and fairly steep. Anterior slope long but less steep than the lateral ones. Beak slightly incurved and forming an angle of about 130° to 140°. Interarea strongly apsacline, slightly curved. Delthyrium long and narrow ; pseudodeltidium small. Brachial valve with lateral profile varying from very slightly concave to distinctly but slightly convex ; anterior profile the same. Median sulcus originating at the umbo, expanding rapidly anteriorly to more than half the width ; flanks bounding sulcus very slightly convex; posterolateral extremities nearly flat. Interarea short. Pedicle interior with deep, elongate delthyrial cavity bounded by strong receding dental plates. Teeth small with deep fossettes. Vascula media not strongly developed. Brachial interior with long brachiophores and stout cardinal process often supplemented by lateral bosses. Median ridge low and stout, reaching anterior to the middle. |