Octopuses belong to the class Cephalopoda within the phylum Mollusca, and they exhibit two distinct features that classify them as mollusks.
Firstly, octopuses have a soft, unsegmented body. This characteristic is a defining feature of the Mollusca phylum. Unlike many other animal groups that have hard exoskeletons or segmented bodies, the octopus’s body is flexible, allowing for a wide range of motion and adaptability in their marine environment.
Secondly, octopuses possess a mantle, which is a significant part of their physiology. The mantle is a significant part of the mollusk anatomy, covering the internal organs and producing the shell in other mollusks. Although octopuses do not have an external shell, their mantle is adapted to aid in respiration and to help propel them through water.
In summary, the soft body structure and the presence of a mantle are the two key features that classify octopuses as members of the Mollusca phylum.