Introduction

A paradox arises from the large-scale perspective afforded by the fossil record. Phyletic evolution and adaptation appear to be ubiquitous; yet adaptation cannot always be equated with success, relative to coexisting but supposedly inferior forms. The rise of vagile shell-crunching predators in the Mesozoic was accompanied by an expected overall mechanical resistance to predation in the marine benthos (e.g., Vermeij 1977, 1983). But the response may be necessary and not sufficient to explain the many evolutionary radiations that occurred during the Mesozoic. Can we explain ammonite diversity from the point of view of predation alone? It is likely that invasion of a wide variety of habitats and lifestyles contributed more to ammonite diversity. Did the ammonites proliferate because of individual adaptation? If so, why have they not stood the test of time and survived to the present day?

The dinosaurs proliferated in the Mesozoic, coexisted with mammals for many millions of years, but eventually gave way to the mammals in the Cenozoic. Are the dinosaurs to be considered inferior to their ecological successors, the mammals? If so, one has to explain why the mammalian condition, when achieved in the Triassic, took over 100 million years to manifest itself in worldwide dominance in the early Cenozoic. Why did the dinosaurs fail to succumb immediately, if the mammals were so superior? The great time period involved in the gradual evolution of “traits” such as mammalness also invites difficult questions.