Despite being so numerically abundant, preservation of beetles in sediments is quite rare, and is largely limited to Lagerstatten sites. This is because beetles, like all insects, have a thin, chitinous exoskeleton with a poor preservation potential. The exception to this is preservation in amber, where minute details are preserved.
The oldest fossils of beetle-like insects are from the Lower Permian (280Ma: million years ago) of the Czech Republic and Russia. It seems that these insects began to radiate following the end-Permian mass extinction event, with the first true coleopterans appearing at about 240Ma, during the Triassic. The four coleopteran suborders appear to have been extant at this time. A dramatic increase in beetle diversity occurred during the Jurassic period, with the first appearances of many extant families. These include Gyrinidae (whirlygig beetles), Carabidae (ground beetles), Mordellidae (tumbling flower beetles), and Silphidae (carrion beetles). The Cretaceous diversification of angiosperms (flowering plants) opened up many ecological opportunities for beetles, leading to further diversification and adaptations.
A cooling trend that began in the Oligocene progressively excluded many beetle species from higher latitudes. The Pleistocene glaciation is thought to have put a halt to speciation of beetles in the temperate zones most affected by the glaciation. This is in contrast to tropical latitudes, where rapid and extensive bouts of speciation are thought to have occurred far more recently.
Author: Phil Jardine
Last updated: 21st November 2005
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