======================== Platyhelminthes (flatworms, tapeworms, etc.)
        |
        |  =(branch uncertain)== pseudocoelomates (nematodes, rotifers, etc.)
     =P=|  |
     |  |  |   ================= Nemertea (ribbon worms)
     |  |  |   |
     |  ===|   |        ======== Sipuncula (peanut worms)
     |     |   |  ======|
     |     |   |  |     ======== Mollusca (snails, clams, squids, etc.)
     |     =C==|  | 
<<===|         |  |     ======== Echiura (proboscis worms)
     |         ===|     |
     |            |  =B=|  ===== Pogonophora (beard worms, vent worms)
     |            |  |  ===|
     |            =A=|     ===================================== TO ANNELIDA ===>
     |               |
     |               |  ======== Onychophora (velvet worms)
     |               ===|
     |                  ======== Arthropoda (insects, spiders, crabs, etc.)
     |
     =========================== Deuterostomia (echinoderms, chordates, etc.)

P: Protostomia C: coelomate Protostomia TRAITS SUPPORTING EACH CLADE A: a) segmented coelom b) pre-oral prostomium c) anus-bearing pygidium B: a) "annelid cross" in 64-cell embryo b) epidermal, chitinous setae in setal sacs

                         ===3=== "SubCl." Errantia (errant marine segmented worms)
       ==2==Polychaeta===|
       |                 ===4=== "SubCl." Sedentaria (sedentary marine segmented worms)
<<=1===|
       |   =====6=============== Oligochaeta (earthworms & relatives)
       |   |
       =5==|         ==8======== Acanthobdellida (primitive leech-like annelids)
           =====7====|
                     ==9======== Hirudinea (true leeches)

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): 1: a) many similar body segments each bearing a separate coelom** b) simple prostomium** c) no parapodia** d) multiciliated cells** e) chitinous setae in setal sacs** f) separate sexes, gametes from body wall (no permanent gonads)** g) segmented ventral nerve cord** h) closed circulatory system with capillaries and contractile vessels or hearts i) nephridia with nephrostome opening in segment anterior to that of the nephridiopore 2: a) extensive setae b) parapodia c) gametes from body wall (no permanent gonads)** d) complex prostomium 3: a) parapodia well developed b) pharynx with jaws (most) 4: a) parapodia reduced or absent** b) segments usually differ in form c) jaws usually absent

5: a) few setae b) simple prostomium** c) no parapodia** d) hermaphroditic e) clitellum (produces the cocoon in which eggs are laid) f) permanent gonads 6: a) calciferous glands of esophagus b) typhlosole (earthworms) 7: a) single large coelom due to loss of septae between body segments b) fixed number of body segments c) setae restricted to a few anterior segments d) posterior (and often anterior) sucker e) superficial annuli in body wall 8: a) segmented coelom in anterior-most 5 segments (no anterior sucker)** b) setae restricted to a few anterior segments** c) body of 30 segments 9: a) well-developed anterior sucker b) body of 33 or 34 segments c) coelom unsegmented d) no setae

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