Clade for classes and Turbellarian orders from Nielson'94 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)

1: a) midventral 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) biciliated 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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