The study of tempo and mode in evolution is rooted in palaeontology and begins with the fossil record, our only empirical record of character acquisition through geological time. With the growth of cladistic methods and increased sampling of die fossil record the amount of character information has exploded. An initial question of this study is how did clades acquire tiieir characters, in a relatively rapid early burst as lungfishes did, or by steady, continual change as synapsids did?