ABSTRACT
Biogeography is a scienti‘c discipline that is concerned with the geographic distribution of organisms across the earth (Upchurch et al., 2006). Thus it is essentially a question of spatial arrangement of biodiversity across a range of scales. At the broadest scale, biodiversity is spatially heterogeneous, but not randomly distributed. This nonrandom pattern has led to the suggestion of some ‘law-like’ mechanisms explaining observed distributional patterns. Well-known examples are latitudinal diversity gradients and Bergmann’s law; the causal mechanism(s) involved in the generation of these patterns remains the topic of intense study in the modern biota (see Gaston and Blackburn, 2000 and references therein). Palaeontology, in common with other branches of the earth sciences, tends to adopt an approach of methodological uniformitarianism; preferring to invoke causes observable at the present time before seeking extraordinary explanations for observed evolutionary patterns. Jackson and Erwin (2006) discussed a number of studies designed to detect whether macroecological patterns can be identi‘ed in the fossil record. However, the evolutionary history of clades and their differential and more or less predictable responses to changes in the biological and physical environment are a major factor in the generation of biodiversity.
