Abstract— An exhaustive parsimony analysis of amniote phylogeny using 97 characters has substantiated the hypothesis that mammals and birds are sister groups. This deduction is further supported by parasitological and molecular evidence.

The presumed importance of “synapsid” fossils in amniote phylogeny is questioned and it is concluded that they represent a transformation series which when broken down into constit uent, monophyletic groups does not support the separation of the Mammalia from the remainder of the amniotes.

Fossil members of the Haematothermia include pterosaurs and “dinosaurs” (both stem-group birds) and Dinocephalia, Dicynodontia, Gorgonopsida and Therocephalia (all stem-group mammals). The Dromaeosauridae are the most crownward stem-group birds and the Morganucodontidae the most crownward stem-group mammals.

"Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problem which we are trying to solve.” (K. R. Popper, 1972)