Diversity trends through time

• 38 Triassic genera in 21.7 million years from Carnian.

  • => genus density (GD) of 1.75 genera per million years.

• 124 Jurassic genera in 61.5 million years.

  • => GD = 2.0

• 289 Cretaceous genera in 79.2 million years.

  • => GD = 3.65

• General trend in observed diversity is towards increasing diversity through time.

• Bias is partly because older fossils have more time in which to be destroyed by processes such as erosion.

Notes: