|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Bivalvia - Trigoniida - Schizodidae
|Year||Name and author|
|1884||Schizodus circularis Worthen p. 11|
|1884||Schizodus depressus Worthen p. 11|
|1890||Schizodus circularis Worthen p. 109 figs. pl. 19 f. 1|
|1890||Schizodus depressus Worthen p. 109 figs. pl. 18 f. 8, 8a|
|1915||Schizodus depressus abruptus Girty p. 99 figs. pl. 9 f. 8-12a|
|1915||Schizodus depressus circularis Girty p. 100 figs. pl. 9 f. 6|
|1975||Schizodus depressus Gordon, Jr. and Pojeta, Jr. p. E15 figs. pl. 3 f. 10-13|
|1991||Schizodus depressus Busanus and Hoare pp. 472 – 474 figs. 5.1 – 5.6|
|1993||Schizodus depressus Hoare p. 386 figs. 6.1 – 6.5|
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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.
|J. W. Busanus and R. D. Hoare 1991||Small Schizodus with variable outline of the posterior margin, ranging from nearly truncate from umbonal area to posteroventral margin to convexly curved in the dorsoposterior area and continuing as a steeply curved margin rounding rather sharply into the convex ventral margin; umbonal shoul-der pronounced to gently curved; beaks located close to midlength.
As indicated in the synonymy, Schizodus depressus is believed to have considerable variation in form. This was noted by Weller, 1916, p. 250) and Hernon (1935, p. 692). The varieties described by Girty (1915) are here considered to be no more than phenotypic expressions or preservation differences in the species.
Schizodus depressus differs from S. chesterensis Meek and Worthen (1860) by having a shorter posterior region, with a more abrupt posterior margin, and beaks located nearer to midlength; from S. prolongatus Herrick (1888b) by its less quadrate shape; from S. triangularis (Herrick, 1888a) by not having a sinuous posteroventral margin, as is also true for S. axiniformis (Portlock, 1843); and from S. equalis (de Koninck, 1886) by having a more ovate form.
|R. D. Hoare 1993||Schizodus with subovate shape and moderately low convexity; anterior and ventral margins form a continuous curve; posterior margin slightly convex dorsal to where inconspicuous umbonal carina intersects it; beaks located about one-third length from anterior margin; surface ornamented with faint growth lines; muscle scars not impressed; other internal features not observed.|