Glossary Main

Diversity - The total number of different genera that lived during any given time interval. This database uses "standing diversity", which includes genera that originate during, live through, or live only during the selected time interval.

Origination - The total number of genera who first appear during any given time interval.

Extinction - The total number of genera whose last appearence date is during any given time interval.

Linnaean Classification - This system is used to organize organisms and show how they are related to one another. The hierarchy is as follows:
    Kingdom
        
Phylum
            
Class
               Order
                   Family
                       Genus
                           Species

FAD - "First Appearence Datum" This is the date when a genera first appears in the fossil record.

LAD - "Last Appearence Datum" This is the date when a general last appears in the fossil record.

Relative Time - Time intervals based on "geologic time" rather than actual dates. Geologic time is divided into eons, eras, periods, epochs, and stages, producing smaller time intervals with each sucessive division. Divisions at the same level (i.e. periods) do not all represent the same amount of time.

Absolute Time - Time intervals based on numeric dates. These intervals all represent the same amount of time.

Rate - The number of genera divided by the selected time interval gives a rate. For example: An extinction of 12 genera over a span of 10 million years would give an extinction rate of 1.2 genera per million years.

Count - The total number of genera in a particular category for a particular time interval.