Chordata 



/ 



Protochordata 



(Sea squirt) 



Ancestral 

 chordata 



Arthropoda 

 (Crayfish) 



Mollusca 

 (Snail) 







Platyhelminthes 



(Planario) 

 (Modern flotworms) 



Echinodermata 

 (Starfish) 







/ 



\y 



Ancestral 

 trochophore 



Annelida 

 (Earthworm) 



ECHINODERM- 

 CHORDATE LINE 



MOLLUSK-ANNELID- 

 ARTHROPOD LINE 





Ancestral bilateral worms 

 (Primitive flatworms) 



Coelenteratd 

 (Hydra) 



• < 



Modern protozoa 



Ancestral two-layered anima 

 (Primitive planula) 



(P 



aramecium 



Porifera 



(Sponge) 



Ancestral protozoa 

 (Plant-animals) 



607 



