Bilateria

The Bilateria are animals which are bilaterally symmetrical. They have front and a back end, an upside and downside, and a left and right side. Most animals are bilateral.

 Main subgroups 
 Deuterostomia
 Echinodermata (20,000 species, 7000 living) 
 Chordata. mostly Vertebrata  (63,000 species)
 Hemichordata
 Protostomia
 Ecdysozoa (6 to 20 million species) Erwin T.L. 1982. Tropical forests: their richness in Coleoptera and other arthropod species. Coleopterists Bulletin. 36, 74/5. See also Coevolution#Numbers of species
Nematoda (20,000 species known +many more)
Arthropoda (one to 10 million species)
 Lophotrochozoa 
Annelida (17,000 species)
Platyhelminthes (20,000+ species)
Mollusca (85,000+ species)
Brachiopoda (5,000 fossil species)
Rhombozoa
 Platyzoa
 Minor phyla (like Chaetognatha)
Numbers are approximate; extinct species numbers cannot be known for most phyla.

 Related pages 
List of animal phyla

 References 

category:Groups of phyla
Category:Animals