Echinoderms certainly are "different" animals. That difference begins with the development of the embryo. At some point the deuterostomes diverged from the protostomate ancestry. The deuterostomes were still coelomate but the mode of coelom formation was different. The most striking difference between deuterostomates and protostomates is the reversal of the fate of the blastopore. The protostomate blastopore became the mouth but the deuterostomate blastopore became the anus, and the mouth developed elsewhere. As the deuterostomates were different from the protostomates, so are the two phyla of the deuterostomates different from each other. The echinoderms differ greatly from the chordates. Echinoderms, though bilaterally symmetrical as larvae, are all radially symmetrical as adults. The echinoderms are entirely marine, filling their coelom with seawater.