Mammalia (taxonomy)
Mammalia is a class of animal in the phylum Chordata. What it means to be a mammal has changed many times since Carl Linnaeus first defined the class. No system is accepted by everyone. McKenna & Bell (1997) and Wilson & Reader (2005) give useful recent compendiums. Many earlier ideas from Linnaeus and others are no longer used by modern taxonomists. Among these are the idea that bats are related to birds or that humans are a group outside of other living things. The field has had a recent surge in interest and modification due to the results of molecular phylogenetics.