At first glance, both specimens look like octopuses, but only one of them is a true octopus. Both belong to the class Cephalopoda (molluscs with bilaterally symmetrical bodies, a large head and several arms), but are classified into different orders - the one on the left is Membranous Amphiprion (๐๐ฎ๐ฑ๐ฉ๐ช๐ฐ๐ค๐ต๐ฐ๐ฑ๐ถ๐ด ๐ฎ๐ฆ๐ฎ๐ฃ๐ณ๐ข๐ฏ๐ข๐ค๐ฆ๐ถ๐ด (Quoy & Gaimard, 1832), which belongs to the order Octopoda, commonly known as octopus; and the one on the right is Euryptidus berrei (๐๐ถ๐ฑ๐ณ๐บ๐ฎ๐ฏ๐ข ๐ฃ๐ฆ๐ณ๐ณ๐บ๐ช Sasaki, 1929), which belongs to the order Ottopoda, a type of squid.
Despite their similarities, it's not hard to tell them apart: the octopus has eight arms, no tentacles, and no internal shell or external fins. Octopuses are often called nature's most flexible animals, able to twist, elongate and shorten their bodies to fit into cracks and small spaces. In addition to 8 arms, the four-eared squid also has 2 long tentacles. The presence of the inner shell also makes their bodies harder, so they are less flexible. Additionally, they have side fins to aid in movement, but are slower than octopuses.
Both species are small mollusks no longer than 8 cm and are rare only in the Indo-Pacific region. Our specimens were collected from the beach of Wu Kai Sha in Hong Kong in the 1970s.
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