PHYLUM PLATYHELMINTHES. Clade for classes and Turbellarian orders from Nielson 1994 p. 216.

                  Cl. TUR
       ==========2a======B===========    Or. Acoela (small body size, gutless)
<<=1===|                  E 
       |   =======2c=======L=========    Or. Polycladida (large body size, multi-branched gut)
       =2b=|                L
           |   ====2e========A=======    Or. Tricladida (the planarians; 3-branched gut)
           =2d=|              R
               |   ==2g========IA====    Or. Rhabocoela (small body size, unbranched gut)
               =2f=|
                   |     ======4===== Cl. Trematoda (endoparasitic flukes)
                   ==3===|
                         |     ==6=== Cl. Monogenea (ectoparasites of aquatic vertebrates)
                         ==5===|
                               ==7=== Cl. Cestoidea (endoparasitic tapeworms)

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): 1: a) mid-ventral mouth** b) blind gut** c) protonephridia** d) coelom & blood vascular system absent** e) ciliated epidermis** f) multiciliated cells** g) epidermal gland cells extensive h) monociliated sperm, i) hermaphroditic (unclear if valid trait) j) archoopheran reproductive system 2a: a) no gut** b) simple pharynx** c) lack protonephridia d) no distinct gonads (gametes from parenchyma) 2b: a) rhabdites b) bi-ciliated sperm (present in all higher groups) c) gut cavity present d) plicate pharynx 2c: a) gut has multiple branches b) pair of anterior tentacles (some) c) multiple gonads among branches of gut 2d: a) neoopheran reproductive system (present in all higher groups) b) typical 'spiral' cleavage lost

2e: a) gut has three branches 2f: a) bulbous pharynx 2g: a) gut has single cavity (unbranched) 3: a) syncytial, non-ciliated epidermis b) terminal mouth (also some rhabdocoels) c) paired intestinal cecae 4: a) oral & mid-ventral sucker b) complex=indirect life cycle (1-2 intermediate hosts) c) anaerobic metabolism 5: a) distinct attachment hooks in larva 6: a) haptor b) simple=direct life cycle** (no intermediate hosts) 7: a) scolex b) strobila (=chain of proglottids) c) mouth & gut absent d) reproductive system repeated in each proglottid e) complex=indirect life cycle (1 or more intermediate hosts)

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