Upper Cambrian – Recent
Cephalopoda is an extant class of fast-moving nektonic carnivores
Characteristics of the Class
- Internal or external shell
- Numerous tentacles
- The shell is divided into numerous compartments which are connected by a siphuncle
Treatise on Invertebrate Paleontology, Part K, Vol. 3 (1964):
- Mollusks of the class Cephalopoda are agile, bilaterally symmetrical, predacious carnivores that have achieved a structural complexity and metabolic efficiency without peer among unsegmented invertebrates. The class is represented in the modern marine fauna by some 650 species of octopuses, squids, cuttlefishes, argonauts, and Nautilus, the only living form with an external shell. The class also includes more than 10,000 fossil species informally termed nautiloids and bactritids, ammonoids, and coleoids.