Lilliput effect

Trends in body size changes are seen throughout the fossil record in many organisms, and major changes (shrinking and dwarfing) in body size can significantly affect the morphology of the animal itself as well as how it interacts with the environment. 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. == Potential causes ==

Extinction of larger taxa The extinction event may have been more severe for the larger-bodied species, leaving only species of smaller-bodied animals behind. Shrinking of surviving taxa It is possible that the extinction event selectively removed larger individuals within any single lineage, without extinguishing the entire species, but leaving as survivors only the individuals with a naturally smaller body size. The smaller survivors then form the new breeding population, and pass on that trait to their descendents. Because of the selection during the extinction, compared to the previously "normal"-sized members of the species who lived before the extinction event occurred, later members of that species living after the extinction, who are descended only from the smaller survivors, would be reduced in size, constituting a "new-normal". ==References==