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Trigonarca excavata
Taxonomy
Trigonarca excavata was named by Packard (1922). Its type specimen is UCMP 12315 and is a 3D body fossil. Its type locality is UCMP loc. 2141, Santa Ana Mountains, which is in a Turonian/Coniacian marine horizon in the Ladd Formation of California.
Sister species lacking formal opinion data
Synonymy list
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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.
†Trigonarca excavata Packard 1922
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| E. L. Packard 1922 | Shell large, elongate, inequilateral; posterior margin extends nearly straight from the hinge to the pointed posterior extremity . Beaks small, widely separated, situated about one-third the distance from the anterior to the posterior end; anterior margin produced, evenly rounded front the anterior end of the hinge line to the base . A pronounced umbonal ridge extends from beak to the posterior end. Ventral margin nearly straight and not parallel to the hinge line . Posterior dorsal area broad and excavated . Surface of the shell smooth except for a few incremental lines of growth the hinge of the rjght valve with three heavy, straight, anterior teeth situated obliquely upon the hinge plate; posterior teeth, four in number, separated from anterior by six teen small nodular teeth perpendicular to hinge line. Length of type, 62+ mm.; height, 40 mm.; convexity, 25 mm. |