Metacrinus rotundus is a marine animal with a fan-like crown of arms supported by a tether-like stalk. It uses the arms, which are covered in rows of feather-like appendages (pinnules), to trap food such as plankton.
Metacrinus rotundus continues growing throughout its lifetime and is able to regrow its arms and stalk if they are damaged. The stalk can be as long as 40cm in adults.