Comments on this page refer to living Octopoda. for comments on extinct Octopoda see: Teudopseina and Incirrata.<br /><p>Octopods have rather short, compact bodies and only eight arms; no trace of the missing second arm pair remains even during embryonic development. Many species are benthic (bottom-living) and crawl over the ocean floor with the mouth facing the substratum. Others alternate between a benthic and a pelagic (free-swimming) habitat and some species are completely pelagic. The two suborders of Octopoda are very different in appearance but there is little doubt that it is a natural group as the monophyly of the Octopoda is supported by a large variety of characters. The Cirrata is a group of deep-sea octopods commonly known as the &quot;finned octopods&quot; due to their large, wing-like fins. The Incirrata contain the common (benthic), shallow-water octopods as well as many deep-sea benthic and pelagic species.</p> <h4>Brief diagnosis:</h4> <p>An octopodiform ...</p> <ul> <li>with one arm pair, presumaably true arms II, absent. <br /> </li> <li>with suckers on proximal halves of arms.<br /> </li> </ul>