DEE BREGER / SCIENCE PHOTO LIBRARY DEE BREGER / SCIENCE PHOTO LIBRARY
Fossil pollen grain. Coloured scanning electron micrograph (SEM) of a fossilized pollen grain from the now extinct conifer Corollina or Classopollis sp. A relative abundance of these pollen grains marks a clear boundary in the fossil record. This boundary, around 195 million years ago, is now used to define the end of the Triassic period and the start of the Jurassic period in the geological timescale of Earth's history. It is thought that the loss of diversity in the plant fossil record of this time, reflected in the domination of these conifers, was caused by a mass extinction event. Magnification: x1600 at 6x6cm size.
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