Abstract
Analysis of new and existing data indicates that the pattern of European Jurassic Gryphaea evolution is neither uniquely concordant with the punctuated equilibria model nor the phyletic gradualism model. Phylogeny involves significant intervals of both stasis and more or less continuous evolution (not necessarily involving the same characters and thus not necessarily representing classical gradualism). However, change may be more characteristic of Gryphaea than stable equilibrium. New data favour the idea that Lower Jurassic Gryphaea evolved from Triassic congeners, rather than early Jurassic representatives of Liostrea.
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