For example, birds and crocodiles derive from a common reptilian stem ancestor and are considered by cladists to be sister groups of equal rank in the taxon Archosauromorpha. Easiest and most commonly used technique today. Clarify evolution of a group 2 . Group of organisms to be studied is related by descent from a common ancestor 2 . This is controversial.
Many biologists hold that multiple new lineages can arise from a single originating population.
This is NOT an evolutionary tree showing which organism is descended from whom. All taxa go on the endpoints of the cladogram, never at nodes. All synapomorphies appear on the cladogram only once unless the character state was derived separately by evolutionary parallelism. Attempts to answer the question about the ancestry of modern birds. A very portable, usable treatment of the anatomy and evolution of dinosaurs.