Evolution of Birds - Classification of Modern Species

Classification of Modern Species

See also: Sibley-Ahlquist taxonomy and dinosaur classification

The phylogenetic classification of birds is a contentious issue. Sibley & Ahlquist's Phylogeny and Classification of Birds (1990) is a landmark work on the classification of birds (although frequently debated and constantly revised). A preponderance of evidence suggests that most modern bird orders constitute good clades. However, scientists are not in agreement as to the precise relationships between the main clades. Evidence from modern bird anatomy, fossils and DNA have all been brought to bear on the problem but no strong consensus has emerged. As of the mid-2000s, new fossil and molecular data provide an increasingly clear picture of the evolution of modern bird orders, and their relationships. For example, the Charadriiformes seem to consititute an ancient and distinct lineage, while the Mirandornithes and Cypselomorphae are supported by a wealth of anatomical and molecular evidence. The understanding of the interrelationships of lower level taxa also continues to increase, particularly in the massively diverse perching bird group Passeriformes.

Bird classification and phylogenetic analysis is still under debate and requires more research. A recent 2008 study published in Science examined DNA sequences from 169 species of birds that represented all of the major extant groups. The findings may necessitate a wholesale restructuring of the avian phylogenetic tree. The findings also supported unestablished relationships between orders and confirmed disputes over particular groupings.