Phylum vertebrata: New concepts based ... Much of how organisms are classified depends on their shared characteristics. ... Ambulacraria, above Echinodermata and Hemichordata.

Echinoderms are found in ocean ecosystems worldwide, from rocky shores to the deep sea. Animals in this phylum are characterized by radial symmetry as adults, with body parts that repeat around an ...

Its extreme characteristics suggest that this common ancestor -- one the creature shares with its sister phyla, echinoderms and hemichordates, as well as chordates -- did not have a brain or ...

COCKBAIN1 has suggested an extension of the suture-line theory2 of the origin and significance of pentamerism in the phylum Echinodermata, which depends primarily on the fact that all modern ...