Retractor muscles of the pharynx are absent. Phylum Echinodermata Characteristics Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to extend and push against the ground, then relaxing to allow the feet to retract. They also contain a hydrovascular system known as the ambulacral system. Get carried away with personal biases and are not pertinent to the key issues. Date These subzones differ in physical and chemical parameters of water and sediments, which results in the presence of different species of echinoderms. This is especially apparent in starfish, brittle . examine a variety of echinoderm species such as starfish, basket star, sand dollar, and sea cucumber. check_circle Expert Answer. S Chand Publishing. Chordata is composed of two major clades: chordates and echinoderms + hemichordates bottle shaped and contains specialized respiratory.! The body consists of an aboral cup, the calyx and oral cover or roof, the tegmen, and strongly pentamerous in structures. Post Anal Tail Gills at some point in life Have supporting rod Sources Deuterostome Characteristics All the members have their mouth form second All are bilaterially symmetrical All have indeterminate and radial cleavage (b=d([55356,56826,55356,56819],[55356,56826,8203,55356,56819]))&&(b=d([55356,57332,56128,56423,56128,56418,56128,56421,56128,56430,56128,56423,56128,56447],[55356,57332,8203,56128,56423,8203,56128,56418,8203,56128,56421,8203,56128,56430,8203,56128,56423,8203,56128,56447]),!b);case"emoji":return b=d([55358,56760,9792,65039],[55358,56760,8203,9792,65039]),!b}return!1}function f(a){var c=b.createElement("script");c.src=a,c.defer=c.type="text/javascript",b.getElementsByTagName("head")[0].appendChild(c)}var g,h,i,j,k=b.createElement("canvas"),l=k.getContext&&k.getContext("2d");for(j=Array("flag","emoji"),c.supports={everything:!0,everythingExceptFlag:!0},i=0;i