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An octopus (pl.: octopuses or octopodes [a]) is a soft-bodied, eight-limbed mollusc of the order Octopoda (/ ɒ k ˈ t ɒ p ə d ə /, ok-TOP-ə-də [3]).The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids.
The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata. [1]The class developed during the middle Cambrian, and underwent pulses of diversification during the Ordovician period [2] to become diverse and dominant in the Paleozoic and Mesozoic seas.
The common octopus (Octopus vulgaris) is a mollusk belonging to the class Cephalopoda. Octopus vulgaris is one of the most studied of all octopus species, and also one of the most intelligent. It ranges from the eastern Atlantic, extends from the Mediterranean Sea and the southern coast of England , to the southern coast of South Africa.
The evolution of the molluscs is the way in which the Mollusca, one of the largest groups of invertebrate animals, evolved. This phylum includes gastropods, bivalves, scaphopods, cephalopods, and several other groups. The fossil record of mollusks is relatively complete, and they are well represented in most fossil-bearing marine strata.
The traditional view of cephalopod evolution holds that they evolved in the Late Cambrian from a monoplacophoran-like ancestor [133] with a curved, tapering shell, [134] which was closely related to the gastropods (snails). [135] The similarity of the early shelled cephalopod Plectronoceras to some gastropods was used in support of this view.
The study was focused on early cephalopod diversification in the Late Cambrian and Ordovician, and did not discuss in detail the origin of post-Ordovician groups. The following is a simplified version of their cladogram , showing early cephalopod relationships to the order level (although various isolated families also originated during this ...
A tree of life, like this one from Charles Darwin's notebooks c. July 1837, implies a single common ancestor at its root (labelled "1").. A phylogenetic tree directly portrays the idea of evolution by descent from a single ancestor. [3]
Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopuses and the vampire squid.All living members of Octopodiformes have eight arms, either lacking the two tentacles of squid (as is the case in octopuses) or modifying the tentacles into thin filaments (as in vampire squid).