The following features are used as the basis of animal classification.
Level of Organization:- Identify the level of organization like cellular, tissue or a still higher level of Organization organ level of organization.
Body symmetry: Identify if the animals are asymmetrical, radially or have bilateral symmetry.
Diploblastic of triploblastic:- based on the presence of a number of embryonic layers.
Diploblastic: two embryonic layers as external ectoderm and as internal
Endoderm triploblastic: three embryonic layers as external ectoderm, middle mesoderm and inner endoderm.
Body cavity: The presence or absence of body cavity animals possessing coelom are called coelomates. Animals in which body cavity absent are called acoelomates
Segmentation: some animals show segmentation of body externally or internally
Presence of Notochord: chordates are animals with notochord and non-chordates which don’t form notochord during embryonic development.