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# of Described Species: 700 (but more than 10,000 extinct species!) First Appearance: Middle Cambrian Habitats: Marine, in the water column and on the sea floor Shapes: Squids and octopuses and animals like these with shells Feeding Types: Hunting carnivores |
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Cephalopods (literally 'head foot') are dorso-ventrally elongated, have well-developed
sense organs and large brains and are thought to be the most intelligent of all invertebrates.
Nearly all are predatory and most are very active swimmers. A few taxa are benthic, drifters or
medusa-like, and some are detritus feeders. All are active carnivores in marine benthic and
pelagic habitats from nearshore to abyssal depths.
Cephalopods are thought to have evolved from monoplacophoran-like ancestors. Septa formed at the apex as the animal grew and withdrew into a newly formed body chamber. The old chambers are gas-filled and provide buoyancy for the organism. The foot was modified into a funnel that provided jet propulsion for movement. |
Giant squid (Architeuthis) are the largest invertebrates, up to 21 m in length. The cephalopods include the largest living as well as largest extinct molluscs: ammonite shells range to over 2 m across and body sizes of living squid range up to 8 m with tentacles exceeding 21 m in length. The smallest cephalopods are around 2cm in length. |
