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Schizodus depressus

Bivalvia - Trigoniida - Schizodidae

Synonyms
Synonymy list
YearName and author
1884Schizodus circularis Worthen p. 11
1884Schizodus depressus Worthen p. 11
1890Schizodus circularis Worthen p. 109 figs. pl. 19 f. 1
1890Schizodus depressus Worthen p. 109 figs. pl. 18 f. 8, 8a
1915Schizodus depressus abruptus Girty p. 99 figs. pl. 9 f. 8-12a
1915Schizodus depressus circularis Girty p. 100 figs. pl. 9 f. 6
1975Schizodus depressus Gordon, Jr. and Pojeta, Jr. p. E15 figs. pl. 3 f. 10-13
1991Schizodus depressus Busanus and Hoare pp. 472 – 474 figs. 5.1 – 5.6
1993Schizodus depressus Hoare p. 386 figs. 6.1 – 6.5

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Protostomia
Spiralia
superphylumLophotrochozoa
phylumMollusca
classBivalvia
Eubivalvia
subclassAutobranchia(Groblen 1894)
RankNameAuthor
infraclassHeteroconchia(Gray 1854)
UniomorphiGray 1854
UnioniGray 1854
UnionataGray 1854
orderTrigoniida(Dall 1889)
superfamilyTrigonioideaLamarck 1819
familySchizodidae
genusSchizodus
speciesdepressus

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.

Diagnosis
ReferenceDiagnosis
J. W. Busanus and R. D. Hoare 1991Small 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 1993Schizodus 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.