(brachiopod)

(bryozoan)

DEUTEROSTOMIA (modified from Tree of Life; traits & tree after Ruppert & Barnes 1994 p. 1050-3 and Brusca & Brusca 2003 p. 875)

(asteroid echinoderm)

(enteropneust hemichordate)

     ============================ Protostomia
     |
<<===|    ====1================== Chaetognatha (arrow worms)
     |    |
     |    |===2================== lophophorates (Ph. BRYOZOA, BRACHIOPODA, etc.)
     ==D==|
          |           =========== ECHINODERMATA (starfish, urchins, sea cucumbers,etc.)
          |      ==4==|
          ===3===|    ===5======= HEMICHORDATA (acorn worms, pterobranchs)
                 |
                 ================ CHORDATA

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):

D (Deuterostomia): a) radial, indeterminate cleavage** b) coelom via enterocoely c) blastopore yields anus d) tripartite coelom ----> tripartite body plan protocoel=axocoel ----> protosome mesocoel=hydrocoel ----> mesosome metacoel=somatocoel ----> metasome e) monociliated cells** 1 (Chaetognatha): a) paired, lateral fins b) grasping spines around mouth c) ventral ganglion 2 (Lophophorates): a) mesocoelic tentacles form a lophophore b) reduction in prosome c) U-shaped gut

3: a) protocoelic nephridium (=axial complex) b) protocoel has external coelomopore c) tri-coelomate organization of larval stage** d) ciliated pharyngeal pores/gill slits e) post-anal tail f) stiffened, notochord-like structure g) gonads with separate gonoducts 4 (Ambulacraria): a) protocoelic nephridium/axial complex b) protocoel has external coelomopore c) larval similarities (echinoderm auricularia & bipinnaria resemble enteropneust tornaria larvae) 5 (Hemichordata): a) stomochord (homologous with notochord?) b) muco-ciliary pre-oral locomotory organ c) paired valved collar ducts d) ventral post-anal tail