Biodiversity in the Fossil Record

Biodiversity fossils

Over vast spans of geological time, evolution has resulted in the 10 to 100 million species of creatures living on Earth today.

Not all organisms or body parts are equally preserved in the fossil record. For example, most fossils are formed from just the hard or chemically resistant organic parts, such as snail shells, teeth, or the cell walls of pollen grains. Anything composed solely of soft tissues, including some whole lineages of organisms, is usually destroyed long before it can be fossilised. Some, however, leave evidence of their existence in the form of tracks and trails, for example, Zoophycos.

On top of this, certain environments and time periods are better represented in the fossil record than others. In order to understand what determines the number of species that can coexist and their rates of evolution and extinction, paleontologists use sophisticated, computer based techniques and large databases of fossil occurrences to calculate the change in biodiversity through time.

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Zealandia has by far the best Southern Hemisphere fossil record of marine animals and plants for the Cenozoic time (65–0 Ma). This record is extremely well-described in one of the most complete paleontological databases in existence.

This research indicates that Zealandia’s marine biodiversity has been approximately constant for much of the past 50 million years, with a decline over the past 5 million years. This is in marked contrast to the global pattern, which shows dramatically increasing Cenozoic biodiversity.