Phylum ECHINODERMATA (traits & tree after Ruppert & Barnes 1994 and Brusca & Brusca 1990 834)

        ==1================================= Crinoidea (sea lilies, feather stars)
<<=E====|
        |     ==3=========================== Asteroidea ('true' starfish)
        ==2===|
              |     ==5===================== Ophiuroidea (brittle stars)
              ==4===|
                    |     ==7=============== Echinoidea (sea urchins)
                    ==6===|
                          ==8=============== Holothuroidea (sea cucumbers)

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): E= ECHINODERMATA (living classes): a) pentaradial symmetry b) endoskeleton of calcareous ossicles with unique perforated structure c) unique water vascular system with suckerless podia d) open ambulacral grooves e) mouth & anus on oral surface** f) sessile; attached to substratum with aboral surface (primitively) 1: a) sessile; attached to substratum with stalk (primitively)** b) multiple arms bearing open ciliated grooves for suspension feeding c) podia lack suckers**, not used for locomotion d) use articulated cirri for locomotion (derived forms) 2: a) oral surface becomes ventral b) anus becomes dorsal c) use podia (tube feet) for locomotion 3: a) five generally thick arms broadly connected to oral disc b) open ambulacral grooves** c) podia possess suckers d) pedicellaria** (2 orders)

4: a) closed ambulacral grooves 5: a) five snake-like arms narrowly connected to oral disc b) podia lose suckers c) arm ossicles like miniature 'vertebrae' d) anus lost 6: a) arms absent b) ambulacral grooves extend from oral to aboral pole c) aboral surface restricted to small region around anus d) podia possess suckers 7: a) fusion of skeletal ossicles to form globular or discoidal test b) test covered with articulated, moveable spines; spines quite large in some taxa c) pedicellaria** (all orders) d) secondary bilateral symmetry (some groups) 8: a) ossicles greatly reduced & isolated b) fleshy body c) elongation of body along oral-aboral axis d) oral podia modified as tentacles e) secondary bilateral symmetry (some groups)

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