Lilliput effect

The Lilliput effect is an observed decrease in animal body size in genera that have survived a major extinction.

[1] There are several hypotheses as to why these patterns appear in the fossil record, some of which are:[2] The term was coined in by Urbanek (1993) in a paper concerning the end-Silurian extinction of graptoloids[3] and is derived from an island in Gulliver’s Travels, Lilliput, inhabited by a race of miniature people.

Atkinson et al. (2019) coined the term Brobdingnag effect[4] to describe a related phenomenon, operating in the opposite direction, whereby new species evolving after the Triassic-Jurassic mass extinction that began the period with small body sizes underwent substantial size increases.

[5][6][7] The Lilliput effect has been noted by several authors to have occurred after the Permian-Triassic mass extinction: Early Triassic fauna, both marine and terrestrial, is notably smaller than those preceding and following in the geologic record.

[1] Taxa whose animals are larger may be evolutionarily selected against for several reasons, including[1] Stanley (1973) hypothesized that newly emerged animal taxa tend to develop at an originally small size, hence a sudden proliferation of new species would tend to produce many initially small organisms.