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For trilobites, variety really was the spice of life

For trilobites, variety really was the spice of life

New Scientist

Image: dctim1

It may be possible to predict the winners and losers ahead of a mass extinction – those species with the greatest variability in their appearance should be most likely to survive.

Mark Webster at the University of Chicago has shown that trilobites, an extinct group of marine arthropods, evolved most rapidly when individuals within a species had bodies that varied in size, shape or number of body segments. When this variation fell away so did the rate of evolution, which may have left the animals more susceptible to extinction by climate change.

Webster reviewed a large number of earlier trilobite studies. These showed that 70 per cent of the earliest trilobite species, which emerged around 520 million years ago during the Cambrian period, had highly variable bodies. After the Cambrian, that number dropped to 30 per cent and remained so for most of the next 250 million years, until the trilobites died out in the Permian (ScienceDOI: 10.1126/science.1142964). Read more on…