Dipleurula represents an ancestral form for these primitive deuterostomes.

The first stage in all groups except the crinoids is the dipleurula, which has a row of cilia winding round its body.

Dipleurula is a hypothetical larva of the Echinoderms.

We can see that all well-known forms of larvae of Echinodermata are derived from the hypothetical dipleurula.

The Dipleurula is a bilaterally symmetrical, ciliated echinoderm larva.