(errant polychaete)

(sedentary polychaete)

PHYLUM ANNELIDA (Tree and traits from Nielson 1995 p. 143-4, and most characters from Brusca & Brusca 1990 p. 432.)

(oligochaete)

(leech)

                         ===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)

Back to Zool 250 tree for animal phyla or Protostomia

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

1= ANNELIDA: a) many similar body segments each bearing a separate coelom** b) simple prostomium** c) peristomium: a unique pre-segment surrounding the mouth d) no parapodia** e) multiciliated cells** f) chitinous setae in setal sacs** g) separate sexes, gametes from body wall (no permanent gonads)** h) segmented ventral nerve cord** i) closed circulatory system with capillaries and contractile vessels or hearts j) nephridia with nephrostome opening in segment anterior to nephridiopore 2: a) extensive setae b) parapodia c) gametes from body wall (no permanent gonads)** d) complex prostomium 3= 'ERRANTIA': a) parapodia well developed b) pharynx with jaws (most) 4= 'SEDENTARIA': a) parapodia reduced or absent** b) segments usually differ in form c) jaws usually absent

5= CLITELLATA: 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= OLIGOCHAETA: 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= ACANTHOBDELLIDA: 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= HIRUDINEA: a) well-developed anterior sucker b) body of 33 or 34 segments c) coelom unsegmented d) no setae