Pentidotea wonsnesenskii is a marine isopod which lives on seaweed on rocky shores along the British Columbia and Washington coastlines, as far south as San Francisco. It can be as large as 40 millimetres (1.6 in) long, with a concave (outwardly curved) tail rather than an indented tail as previously shown on this page, is usually green, but its colour is adaptable to its environment. It can often be found hiding under rockweed (Fucus gardnerii) in the intertidal zone. It is named after the Russian biologist Ilya G. Voznesensky.