Page "Sibley-Ahlquist taxonomy of birds" Paragraph 3

The classification appears to be an early example of cladistic classification because it codifies many intermediate levels of taxa: the " trunk " of the family tree is the class Aves, which branches into subclasses, which branch into infraclasses, and then " parvclasses ", superorders, orders, suborders, infraorders, " parvorders ", superfamilies, families, subfamilies, tribes, subtribes and finally genera and species.

However the classification study did not employ modern cladistic methods, as it relies strictly on DNA-DNA hybridization as the sole measure of similarity.