(feather star)	(starfish)	Phylum ECHINODERMATA (traits & tree after Brusca & Brusca 1990 834. additional traits from Ruppert et al. 2004 p. 926	(sea urchin)
	(brittle star)		(sea cucumber)

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

     $ some consider the Ophiuroidea to be the sister group of the Echinozoa based on the ambulacra

Back to Zool 250 tree for animal phyla or Deuterostomia.

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 (stereom) 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) g) multiple gonads** # h) spherical sperm** # i) gill pores/slits absent in adults j) mutable collagen tissue k) monociliated cells** l) dipleurula larvae** 1= Crinoidea: 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) ring canal has many stone canals e) use articulated cirri for locomotion (derived forms) f) vitellaria larvae 2: a) free living (not sessile) # b) oral surface becomes ventral c) anus becomes dorsal d) use podia (tube feet) for locomotion e) stone canal becomes ossified # f) polian vesicles (or similar) on ring canal 3= ASTEROZOA: a) body plan of five arms connected to an oral disc 4= Asteroidea: a) thick arms, broadly connected to oral disc b) eyespot at each arm tip c) podia possess suckers d) pedicellaria** (2 orders) e) paired pyloric cecae in each arm f) gonads in arms g) bipinnaria & brachilaria larvae

5= Ophiuroidea: a) snake-like arms narrowly connected to oral disc b) arm ossicles like miniature 'vertebrae' c) oral madreporite d) anus absent in adult e) ophiopleuteus larvae 6= ECHINOZOA: 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 e) podia possess calcified disc # f) podia possess secretory goblet & tuft cells # g) esophagous has internal skeleton # h) well developed hemal system 7= Echinoidea: 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) Aristotle's lantern e) secondary bilateral symmetry (some groups) f) Polian vesicles lost (replaced by Tideman's bodies) g) elongate sperm  h) echinopleuteus larvae 8= Holothuroidea: a) ossicles greatly reduced & isolated in thick dermis b) fleshy body c) elongation of body along oral-aboral axis d) oral podia modified as particle feeding tentacles e) secondary bilateral symmetry (some groups) f) paired, internal respiratory trees g) single gonad # h) auricularia larvae

# traits from Janies 2001 Can. J. Zool. 79:1232