Decapodiformes is a superorder of Cephalopoda, which includes all species with ten limbs; the name derives from the Greek word meaning ten feet. The ten limbs are divided into eight short arms and two long tentacles. It is presumed that an ancestral coleoid had five identical pairs of limbs, and that one branch evolved a modified arm pair IV and became the Decapodiformes species. Another branch evolved and then eventually lost its arm pair II, becoming the Octopodiformes.
Young, Richard E.; Vecchione, Michael; Donovan, Desmond T. (1998). "The evolution of coleoid cephalopods and their present biodiversity and ecology". South African Journal of Marine Science20 (1): 393–420. doi:10.2989/025776198784126287.abstract