It is hypothesised that the ancestor of all echinoderms was a simple, motile, bilaterally symmetrical animal with a mouth, gut and anus. This ancestral organism adopted an attached mode of life with suspension feeding, and developed radial symmetry. Even so, the larvae of all echinoderms are bilaterally symmetrical, and all develop radial symmetry at metamorphosis. Like their ancestor, the starfish and crinoids still attach themselves to the seabed while changing to their adult form.
It is hypothesised that the ancestor of all echinoderms was a simple motile bilaterally symmetrical animal with a mouth gut and anus This ancestral organism adopted an attached mode of life with suspension feeding and developed radial symmetry Even so the larvae of all echinoderms are bilaterally symmetrical and all develop radial symmetry at metamorphosis Like their ancestor the starfish and crinoids still attach themselves to the seabed while changing to their adult form