Calycoceras guerangeri Zone
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Base: The base of the zone is immediately below the first appearance of the index species (Gale, 1995).
Top: The top of the zone is immediately above the last occurrence of the index species (Gale, 1995).
Range of index species: The zone is coincident with the total range of the index species (Gale, 1995).
Key fauna:
| Bivalvia: | Amphidonte obliquatum (locally abundant) |
| Inoceramus pictus | |
| Ammonoidea: | Calycoceras guerangeri |
| C. spp. | |
| Eucalycoceras pentagonum | |
| Thomelites spp. | |
| Echinoidea: | Holaster spp. (thin-shelled, fragmentary species) |
Faunal abundance & preservation: The zone is typically sparsely fossiliferous, and the fauna often fragmentary and poorly preserved.
Bio-markers: The middle of the zone contains a widely developed acme of the oyster Amphidonte obliquatum (Gale et al., 1999).
Age: Late Cenomanian.