1.Previous
3.Next

and what is general, to use less evolutionarily freighted terminology) without reference to genealogical classifications, to avoid a circular argument. Some features have been recognized as unique to particular taxa for thousands of years (e.g., feathers for birds, or an internal bony skeleton for vertebrates), and these sorts of common-sense presence/absence characters provide a scaffold upon which the polarity of other characters can be inferred: feathered animals form a natural group; things that lack feathers are just the complement - everything

1.Previous
3.Next