| They are large bivalves with thick shells, which bear numerous and finely spaced concentric lines but no radial ones. |
| It was thought that this behavior was an adaptation for desiccation resistance analogous to the closed shells of bivalves. |
| The seas were inhabited by large ammonoids like Olcostephanus, bivalves like Bruchia, and some of the early rudist reefs. |
| Marine invertebrates include ammonites, echinoderms, bivalves and crustaceans, but infaunal elements are rare. |
| This member contains abundant and diverse mid-Cretaceous shallow-marine invertebrates, including reef corals and rudist bivalves. |
| Notable is the relative rarity of bivalves and gastropods, consistent with a deeper water environment. |
