BILATERIAN ANIMALS (modified from WWW Tree of Life; traits & tree after Ruppert & Barnes 1994 p. 1052 and Brusca & Brusca 1990 p.873).

                ==C============== coelomate protostomes (arthropods, annelids, molluscs, etc.)
          ======|
     ==P==|     ================= Platyhelminthes (flatworms, tapeworms, etc.)
     |    |
     |    =(placement uncertain)= pseudocoelomates (nematodes, rotifers, etc.)
<<===|
     |    =1===================== Chaetognatha (arrow worms)
     |    |
     ==D==|   =3================= LOPHOPHORATES (Ph. Bryozoa, Brachiopoda, etc.)
          |   |
          =2==|   =5============= Echinodermata (starfish, urchins, sea cucumbers,etc.)
              |   |
              =4==|   =========== HEMICHORDATA (acorn worms, pterobranchs)
                  =6==|
                      =========================================== TO CHORDATA ===>

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): P= PROTOSTOMIA: a) spiral, determinate cleavage b) mesoderm from mesenchyme cells c) mouth (and sometimes anus) from blastopore d) multiciliated cells e) trochophore-like larva C= COELOMATE PROTOSTOMES: a) coelom via schizocoely 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 1: a) paired, lateral fins b) grasping spines around mouth c) ventral ganglion 2: a) mesocoelic tentacles 3 (Lophophorates): a) mesocoelic tentacles form a lophophore b) reduction in prosome c) U-shaped gut

4: a) protocoelic nephridium (=axial complex) b) coelomopore connects protocoel to outside of body c) tri-coelomate organization of larval stage** 5 (Echinodermata): a) pentaradial symmetry b) endoskeleton of calcareous ossicles with unique perforated structure c) unique water vascular system with suckerless podia d) open ambulacral grooves e) mouth & anus on oral surface f) attached to substratum with aboral surface g) tripartite coelom in larva (axocoel, hydrocoel, somatocoel)** h) mesocoelic tentacles lost 6: a) ciliated (U-shaped?) gill slits b) post-anal tail c) stiffened, notochord-like structure Hemichordata: a) stomochord (homologous with notochord?) b) ciliated (U-shaped?) gill slits (Cl. Enteropneusta) c) mesocoelic tentacles form a lophophore? (Cl. Pterobranchia)

Phylum CHORDATA (tree from WWW Tree of Life; traits from Brusca & Brusca 1990 p.873).

                         =====	Cl. Larvacea (the appendicularians)
      ==1================|
      |                  =====	Cl. Ascidiacea (sea squirts)
<<=C==|
      |   ==3=================	Cephalochordata (lancelets)
      =2==|
          |              =====	Myxini (hagfish)
          ===4===========|
                         =====	Vertebrata (fish, amphibians, reptiles, birds, mammals)

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): C= CHORDATA (living classes): a) segmented myomeres b) cephalization c) notochord d) somatic post-anal tail** e) dorsal hollow nerve cord f) pharynx with ciliated U-shaped gill slits** g) endostyle (thyroid gland in vertebrates) h) protocoelic nephridium (=axial complex) lost i) mesocoel & mesocoelic tentacles lost j) metacoel lost 1 (SubPh. Urochordata): a) tadpole shaped body as adult (Larvacea) or larva (Ascidiacea) b) outer acellular tunic or temporary house c) 2 (Larvacea) or 1 (Ascidiacea) exhalent siphons or spiracles from pharynx

2: a) segmentally arranged muscles b) differentiation of neural tube c) ciliated, U-shaped gill slits** 3 (SubPh. Cephalochordata): a) buccal complex (wheel organ, vestibule, oral hood, buccal cirri) b) unusual protonephridia-like nephridia 4 (Craniata): a) thyroid gland (derived from endostyle) b) full endoskeleton with cranium c) anterior end of neural tube enlarged as brain

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