The Carnian Pluvial Episode and dinosaurs

Fossil Tracks and the Rise of the Dinosaurs

The Economist reports on a period when dinosaurs became the prevalent animal group. You will all, of course, be familiar with the Carnian Pluvial Episode (234 to 232m years ago in the Triassic). In this period the climate went from dry, to wet, to dry again four times over the course of 2m years. The best evidence for this period is found in marine rocks and, of course, dinosaurs are land animals.

The authors of the paper which has inspired The Economist's article use the peculiar geology of the Dolomites. Here there are deposits with fossil tracks which can be precisely dated. There are three groups of tracks (grouped by age) and these straddle the Carnian Pluvial Episode.

The earliest group had no dinosaur tracks, the middle ones were 40% dinosaur and the youngest 90%. 

it would seem that the stress caused by the pluvial episode was good for the dinosaurs, less so for the dicynodonts and rhynchosaurs. But the stress at the end of the Cretaceous was enough to kill off the dinosaurs. Which makes a nice story.

Fossil tracks from the Dolomites