Admittedly, the term "Class" is used rather loosely here. The classification of the vertebrates has been and seems to be continuing to be reworked by specialists and is further being complicated by the rules of Cladistics. I have no doubt that the names for many of the groupings (and indeed the groupings themselves) that I have used will draw criticism from somewhere. To help reduce the confusion I have tried to identify with common names, the creatures I have included in the groupings. I have not invented terms, but I am sure that not all of them reflect the latest classifications or nomenclature.

These are approximate numbers of living species, which I expect to update as newer, and/or better information comes to my attention . Two authoritative sources for current classification information are: The Taxonomy Browser of the NCBI and the Tree Of Life Project. (My principal references will follow the table.)

** = More detailed Table to follow

Principal sources:	"The Variety of Life" by Colin Tudge	Oxford University Press, 2000
	"Fishes of the World" by Joseph Nelson	Wiley & Sons, 1994
	FishBase.org
	"Walker's Mammals of the World" by Ronald Nowak	Johns Hopkins University Press, 1991
	Reptile Species Statistics Website