Phylum: Mollusca
The Phylum Mollusca is familiar to us as invertebrate animals, as it includes snails, clams, squid, oysters, sea-mice and tusk shells. They live in fresh water, salt water, and on land. They appeared in the Lower Cambrian period. There are eight classes in this phylum, which are represented by over 150,000 living species and over 35,000 extinct species. They have a highly developed nervous system, which may include eyes. The circulatory system has a two or three chambered heart. The respiratory system includes gills or lungs. Their digestive system includes a digestive gland. Reproduction is sexual. They have a very complete fossil record and dominated the Mesozoic and Cenozoic Eras. Three classes of mollusks are commonly found in Kansas.
Class Bivalvia (Pelecypoda) (Ordovician to Recent)
They have no head and are bivalved – two valves equal in sizes and with a hinge line. Over 26,000 species have been identified. They are commonly called clams. Common fossilized genera include: Inoceramus, Myalina, Aviculopecten, Septimyalina, and Wilkingia.
Class Bivalvia (Pelecypoda) (Ordovician to Recent)
They have no head and are bivalved – two valves equal in sizes and with a hinge line. Over 26,000 species have been identified. They are commonly called clams. Common fossilized genera include: Inoceramus, Myalina, Aviculopecten, Septimyalina, and Wilkingia.
Class Gastropoda (Cambrian to Recent)
Gastropods have a head. Their shell is not chambered, and it’s usually coiled or curved. There have been over 50,000 species identified, with 35,000 species currently living. We commonly refer to these animals as snails. Common fossilized genera in Kansas include Bellerophon, Trepospira, Pharkidonotus, Worthenia, Turritella, Straporolus, and Amphiscapha.
Gastropods have a head. Their shell is not chambered, and it’s usually coiled or curved. There have been over 50,000 species identified, with 35,000 species currently living. We commonly refer to these animals as snails. Common fossilized genera in Kansas include Bellerophon, Trepospira, Pharkidonotus, Worthenia, Turritella, Straporolus, and Amphiscapha.
Class Cephalopoda (Upper Cambrian to Recent)
Cephalopods have a head with eyes. Their shells are chambered and may be straight or spiral. Some have no shell, such as the nautilus, squids, and octopi. This class includes the extinct ammonites and nautiloids. They are also the most advanced class of the mollusks. Scaphites and Baculites were common Cretaceous cephalopods. They are usually identified by the suture pattern left by their chambers. The animal lived in the last chamber of the shell.
Cephalopods have a head with eyes. Their shells are chambered and may be straight or spiral. Some have no shell, such as the nautilus, squids, and octopi. This class includes the extinct ammonites and nautiloids. They are also the most advanced class of the mollusks. Scaphites and Baculites were common Cretaceous cephalopods. They are usually identified by the suture pattern left by their chambers. The animal lived in the last chamber of the shell.