Ericsfr, CC BY-SA 4.0, via Wikimedia Commons
An octopus is a soft-bodied, eight-limbed mollusc of the order Octopoda.
The order consists of some 300 species and is grouped within the class Cephalopoda
with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally
symmetric with two eyes and a beaked mouth at the centre point of the eight limbs.
The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps.
Octopuses inhabit various regions of the ocean, including
coral reefs,
pelagic waters,and the seabed; some live in the intertidal zone and others at abyssal depths.
Octopuses have a complex nervous system and excellent sight, and
are among the most intelligent
and behaviourally diverse of all invertebrates.
[1]
The octopuses arose from the Muensterelloidea within the Vampyropoda in the Jurassic.
The earliest octopus likely lived near the sea floor (benthic to demersal) in shallow marine environments.
Octopuses consist mostly of soft tissue, and so fossils are relatively rare.
As soft-bodied cephalopods, they lack the external shell of most molluscs, including other cephalopods
like the nautiloids and the extinct Ammonoidea.
They have eight limbs like other Coleoidea, but lack the extra specialised feeding
appendages known as tentacles which are longer and thinner with suckers only at their club-like ends.
[1]
A. Pollock, Public domain, via Wikimedia Commons
