PLAIN LANGUAGE SUMMARY:

This article has two purposes. One is to enable the reader to select a Family or Families from The Fossil Record 2 and plot the changes in diversity through time. If you have access to Netscape vers. 4 or Internet Explorer 4.0, or higher, you can do this from your own computer. By following the instructions set out in the article you can make many thousands of different curves and download them to your own system. You can search for higher ranks of taxa, for a variety of habitats, and for the taxa present at any interval of time.

The article's second purpose is more creative. The few curves we have made tend to show a bell shaped curve, radiating quickly to the maximum diversity and then falling slowly to extinction. This is in agreement with other observations from the fossil record. It appears that internal dynamics, as well as the limits of the ecological niche, control the evolution of the biological system, as can events from outside it. Such reasoning has enabled us to create a model to describe changes in Family diversity through time. The equation takes The Fossil Record 2 data and sets it against the niche capacity, as well as extinction and origination factors (conceived here for the first time). Our tests confirm that extinct Families diversify according to the shape of a bell curve, often exhibiting a fast rise in diversity followed by a slower fall. The model can encompass the complete evolutionary history of each group, in the unlikely event that there are to be no more mass extinction events from outside the system.

Michael C. Boulter and Dilshat Hewzulla, Palaeobiology Research Unit, University of East London, Romford Road, London E15 4LZ, UK.