Fig. (1).

Phylogenetic relationships among animals (A) and echinoderms (B). (A) Echinoderms (phylum Echinodermata) are placed in the group of deuterostomes, with other species of the phyla Chordata (vertebrates, tunicates etc.) and Hemichordata. Not all phyla are included in this tree. Placozoa, Porifera, Cnidaria and Ctenophora are more basal in animals, although their phylogenetical positions are under debate. (B) The evolutionary tree based on fossil records, reconstructed from [12]. Extant echinoderms species from each class are shown as examples: from top to bottom, Oxycomanthus japonicus (Crinoidea), Astropecten scoparius (Asteroidea), Ophiothrix nereidina (Ophiuroidea), Temnopleurus reevesii (Echinoidea), and Pentacta australis armatus (Holothuroidea).