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Cryptothyrella ovoides

Rhynchonellata - Athyridida - Meristellidae

Taxonomy
Whitfieldella ovoides was named by Savage (1913) [= 1868. Meristella? sp. Meek and Worthen, III. Geol. Survey, vol. 3, p. 354, pI. 6, figures 4a and 4b.].

It was recombined as Cryptothyrella ovoides by Amsden (1974).

Synonyms
Synonymy list
YearName and author
1913Hindella ambigua Savage pp. 133 - 134 figs. Plate VI, figures 17 - 18
1913Whitfieldella ovoides Savage pp. 134 - 135 figs. Plate VII, figures 13, 14, and 15
1974Cryptothyrella ovoides Amsden pp. 70 - 72 figs. PI. 16, figs. 2-9; pI. 17, figs.la-lb; text-figs. 44, 45

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Eutriploblastica
Neotriploblastica
Eucoelomata
superphylumLophotrochozoa
Lophophorata
phylumBrachiopodaCuvier 1805
subphylumRhynchonelliformeaWilliams et al. 1996
RankNameAuthor
classRhynchonellataWilliams et al. 1996
orderAthyrididaBoucot et al. 1964
suborderAthyrididinaBoucot et al. 1964
superfamilyMeristelloideaWaagen 1883
familyMeristellidaeWaagen 1883
subfamilyMeristellinaeWaagen 1883
genusCryptothyrella
speciesovoides()

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
T. E. Savage 1913 The shells are biconvex, subelliptical in outline, the greatest width near the middle, the anterior margin truncate or somewhat produced. Ventral valve rather strongly arched, most convex in the umbonal region from which the surface slopes abruptly to the cardinal margins, and more gently to the sides and front; median portion of the shell depressed in a narrow shallow sinus which is deepest at the front margin, from which it extends two-thirds or more of the distance to the beak; the beak . of the ventral valve is prominent, and strongly incurved over and upon that of the dorsal valve. Dorsal valve slightly less convex than the ventral; highest along the median line, especially on the posterior half of the shell, from which the cardinal slopes are steeper than those over the lateral and antero-Iateral portions; no well defined mesial fold is present but the median portion of the valve is the most prominent from the front to near the beak, which is concealed beneath that of the ventral valve. Surface of both valves marked by lines of growth and by numerous very fine concentric striae, which appear only under a lens.
T. W. Amsden 1974The outline of this species is variable, although all specimens examined are at least slightly elongate; length/width ratio ranges from 1.02 to 1.31 (text-fig. 44; table 11). It has a subequally biconvex profile with a length/thickness ratio ranging from 1.52 to 1.77 (text-fig. 45; table 11). The ventral beak is hooked over the dorsal and in mature individuals may rest directly on the dorsal umbo (pI. 16, fig. 2c). A sulcus begins a few millimeters in front of the ventral beak and extends to the front as a shallow, narrow, indistinct furrow (pI. 16, figs. 2a, 6b, 6c). The dorsal valve commonly has no well-defined fold, although on some shells a slight fold may develop near the front (pI. 16, fig.2d). Both valves are smooth except for growth lines.

The ventral valve has dental plates which in mature individuals are partly buried in the secondarily thickened shell wall (pI. 17, fig.lb). The dorsal hinge plate is divided and rests on the thickened end of the low ridge (pI. 16, figs. 9a-9c). Thejugum is joined and directed posteriorly; the nature of the stem, if any was present, is uncertain.