Suckers, on the other hand, are generally thought to have evolved only once, although they’ve developed to look quite different in modern squid and octopuses. Octopus suckers are flexible and versatile; they can grab and manipulate small objects in addition to suctioning onto larger ones. Squid suckers are more rigid but their suction is much stronger; they sit on stalks like umbrellas blown inside out, and they often contain little rings of teeth as hard as fingernails.
