Fig. 11

Over a period of about 60 million years, the Australasian brachiopods Tegulorhynchia and Notosaria have become increasingly paedomorphic, forming an evolutionary trend in the form of a paedomorphocline. The retention of more paedomorphic features has allowed successive species to colonize increasingly shallow water. The earliest forms inhabited deep, quiet water. The species at the end of the paedomorphocline inhabits the intertidal zone. Reproduced with permission from McNamara (1997)