|Basic info||Taxonomic history||Classification||Relationships|
|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Rhynchonellata - Athyridida - Meristellidae
It was recombined as Meristella crassa by Angelin and Lindström (1880); it was recombined as Meristina crassa by Williams (1951); it was recombined as Cryptothyrella crassa by Wright (1968), Boucot et al. (1972) and Isaacson et al. (1976); it was recombined as Hindella crassa by Sheehan (1977).
|Year||Name and author|
|1839||Atrypa crassa Sowerby p. 636 figs. pl. 21 f. 1|
|1839||Atrypa crassa de Sowerby and Murchison p. 636 figs. P1.21, fig. 1|
|1880||Meristella crassa Angelin and Lindström p. 21 figs. pl. 13 f. 4-8, 23-25|
|1951||Meristina crassa Williams|
|1968||Cryptothyrella crassa Wright p. 356|
|1972||Cryptothyrella crassa Boucot et al. figs. Pl. 30, figs. 1-17|
|1976||Cryptothyrella crassa Isaacson et al. pp. 1110 - 1111 figs. P1.1,figs. 13-22|
|1977||Hindella crassa Sheehan p. 34|
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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.
|P. E. Isaacson et al. 1976||Exterior.--Shell unequally ventri-biconvex; shell outline subelliptical, with subcircular cross section. Length approximately equal to twice the width. Ventral beak prominent, strongly incurved. Pedicle foramen small. Exterior smooth, with one or two distinct growth lamellae. Anterior commissure rectimarginate to faintly uniplicate. Shell material greatly thickened (up to 6 mm in large specimens) at posterior end.
Ventral interior.-Dental lamellae long, very slightly divergent, extending approximately onequarter valve length, and attached to valve floor throughout length. Pedicle muscle field deeply impressed. Paired diductor scars extend one-third valve length.
Dorsal interior.-Disjunct hinge plates rising from posterior end of myophragm, which is low, rounded, extending over one-half the valve length. Short crural plates extending ventrally from hinge plates. Cardinal process obscured. Muscle field broad, well impressed, and separated by principal myophragm and other smaller myophragms.