Birds

Modern birds arose around 60 million years ago, and are divided into two broad lineages, the Palaeognathes (including the rhea, ostrich and tinamous) and the Neognathes (all other birds). The Neognathes contain the Passeriformes (perching-birds such as blackbirds, robins etc) of which there are over 5,000 species. Within the bird class Aves there are 28 orders and, within these, around 172 families and almost 10,000 living species.  Bird taxonomy is hotly debated among zoologists. DNA sequence data has revealed unexpected relationships which are frequently challenged by new methods of analysis or larger data sets (see Hackett et al., 2008, Science, 320, 1763 - 1768). 

The first recognisably bird-like animals with feathers evolved around 150 million years ago. The best known bird fossil is Archaeopteryx lithographica, found in Bavaria, Germany in 1861. Case 22 has two Archaeopteryx fossil replicas (see right).