1.All animals (except sponges) display Bilateral or Radial Symmetry

2.The development of a coelom - a fluid filled cavity formed from the mesoderm

Some animals developed psedocoeloms- a fluid filled not formed from the mesoderm

Acoelomates do not have coeloms.

3. Development of a head was achieved by Protostomes versus Deuterostomes. Deuterostomes develop the rear end first. Protostomes develop the mouth first.

Phylum	Examples	Evolutionary Milestone
Porifera	sponges	multicellularity
Cnidaria	jellyfish, hydra, coral	tissues
Platyhelminthes	flatworms	bilateral symmetry
Nematoda	roundworms	pseudocoelom
Mollusca	clams, squids, snails	coelom
Annalida	earthworms, leeches	segmentation
Arthropoda	insects, spiders, crustaceans	jointed appendages
Echinodermata	starfish	deuterostomes
Chordata	vertebrates	notochord