Cladistic Taxonomy (A)

Cladistics is a school of taxonomy currently enjoying great popularity, but which also attracts criticism.

Its focus is the branching pattern that reflects common ancestry. This, cladists argue, should be the basis of classification. Similarity, "species" per se is less important.

Cladistic taxonomists would classify crocodiles, true reptiles and birds in an unexpected way, (illustrated here A).

The birds and crocodiles are more closely related to one another than either group is to the true reptiles and would therefore be classified together.

Birds and crocodiles belong to the same "clade" (A), crocodiles and true reptiles to the same "grade" (B).