Phylum Mollusca
Phylum Mollusca
Molluscs are shelled invertebrates which include snails, oysters, mussels, scallops, and clams. Molluscs are the most common group of fossils found in the Cretaceous of Delaware, totalling more than ninety percent of the fossil species described. Over seventy genera of molluscs have been described from the Marshalltown Formation, and the Mount Laurel has been reported to contain well over a hundred.
Three classes of molluscs are common as fossils: gastropods, pelecypods, and cephalopods.
Gastropoda is the scientific name for the group of animals more commonly called snails. Gastropods have a single coiled or uncoiled shell and are common fossil types in the Cretaceous sediments of the C & D canal area.
Pelecypoda is the group of molluscs referred to as the bivalves. Most pelecypods have a pair of hinged shells of generally equal size. Clams, oysters, and scallops are well-known types. Pelecypods can be abundant in the sediments of the C & D canal area.
Cephalopoda is the scientific name for the mollusc group that includes the chambered Nautilus, squid, and octopus. Two extinct types are found at the C & D canal: the Nautilus-like ammonites and the superficially squid-like belemnites. Ammonites are uncommon, especially complete specimens, but can be very useful for age determination. The belemnite species Belemnitella americana has been so abundant at some canal localities that it was named the state fossil of Delaware.