Chapter objectives

• Introduce large-scale patterns of dinosaur evolution

• Develop a deeper understanding of climate in the Mesozoic Era

• Introduce a few important Mesozoic plants

• Introduce dinosaur–plant co-evolution

Dinosaurs in the Mesozoic Era

Throughout much of this book, we have considered dinosaurs as individuals; who they were, what they did, and how they did it. Now we'll step back and take a look at the large-scale ebb and flow of dinosaur evolution. Before we can do that, though, we need to think about what might be missing.

Preservation

Table 13.1 shows the distribution of dinosaurs among the continents through time. The paucity of dinosaur remains from Australia and Antarctica, however, is surely more a question of local preservation and inhospitable conditions today for finding and collecting fossils, than defining where dinosaurs actually lived. Into this mix must be factored geological preservation; some time intervals simply contain more rocks than others. For example, the terrestrial Middle Jurassic is not well represented by rocks, with the result that it artificially appears to have been a time of very low tetrapod diversity (Box 13.1, p. 278). The Late Cretaceous is rather the opposite, with the happy result that we have a rich record of Late Cretaceous dinosaurs. Several methods of estimating the completeness of fossil preservation have been developed to mitigate these problems (Box 13.2, page 280).