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Diagnostic Features
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- Test moderately large; low hemispherical in profile; ovate in outline.
- Apical disc disjunct with posterior ocular plates separated by two interambulacral plates from the anterior portion. Anterior plating not clearly seen in holotype, but with compact apical disc in C. ambigua and C. ovulum and with gonopores opening in ocular plates II and IV.
- Ambulacra about two-thirds the width of interambulacra at the ambitus; composed of large hexagonal plates; pores microscopic and not discernable.
- Interambulacral plates also hexagonal and large.
- Plastron meridosternous; labral plate followed by a single plate.
- Peristome small subcircular; not preserved.
- Periproct small circular, inframarginal, bounded on oral side by interambulacral plate ?6 and with about 8 plates between it and the apical disc.
- Tuberculation unknown.
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Distribution
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Lower Cretaceous (Berriasian - Albian ), Europe and Russia. |
| Name gender |
feminine |
| Type |
Dysaster hemisphericus Gras, 1848, p. 66. Holotype: Museum National d'Histoire Naturelle, Paris R62445. |
| Species Included |
- C. hemispherica (Gras, 1848); Neocomian, France.
- C. ambigua (Eichwald, 1865); Barremian, Russia.
- C. plana Szorenyi, 1965;
- C. ambayraci Lambert, 1924; Albian, ??
- C. morgani (Gauthier, 1902); Cretaceous, Iraq.
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| Classification and/or Status |
Irregularia, stem group Atelostomata; Tithoniidae.
?
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| Remarks |
It is unfortunate that the most adapical plating in the type species is not clearly discernible. However, the apical disc is undoubtedly compact with the posterior gonopores opening through ocular plates II and IV in C. ovulum and C. ambigua, as in Tithonia. Its plastron plating is close to that seen in Tithonia, but very different from that of Tetraromania.
Solovjev, A. 1971. Late Jurassic and Early Cretaceous disasterids of the USSR. Transactions of the Palaeontological Institute, Academy of Sciences of the USSR 131, 1-120, pls 1-16 [in Russian].
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