The shape of life: how much is written in stone?

Considering the enormous diversity of living organisms, representing mostly untapped resources for studying ecological, ontogenetic and phylogenetic p atterns and processes, why should evolutionary biologists concern themselve s with the remains of animals and plants that died out tens or even hundred s of millions of years ago? The reason is that important new insights into some of the most vexing evolutionary questions are being revealed st the in terfaces of palaeontology, developmental biology and molecular biology. Att empts to synthesise information from these disciplines, however, often enco unter their greatest hurdles in considerations of the radiation of the Meta zoa. Ongoing challenges relate to the origins of body plans, the relationsh ips of the metazoan phyla and the timing of major evolutionary radiations. Palaeontology not only has its own unique contributions to the study of evo lutionary processes, but provides a lynchpin for many of the emerging techn iques. (C) 2000 John Wiley & Sons, Inc.