Guo, W.; Tian, L.; Chu, D.; Shu, W.; Benton, M.; Liu, J.; Tong, J.

The greatest mass extinction at the end-Permian, 252 million years ago (Ma), led to a tropical dead zone on land and sea. The speed of recovery of life has been debated, whether fast or slow, and terrestrial ecosystems are much less understood than marine. Here, we show fast reestablished riparian ecosystems in low-latitude North China within as little as ~2 million years (Myr) after the end-Permian extinction. The initial ichnoassemblages in shallow lacustrine and fluvial facies of late Smithian age are monospecific, devoid of infaunalization, with apparent size reduction. In the following Spathian, newly identified medium-sized carnivores, plant stems, root traces, coupled with improved ichnological criteria and significantly increased infaunalization, suggesting a relatively complex, multi-level trophic structured riverain ecosystem had been rebuilt. Specifically, burrowing behavior had re-emerged as a key life strategy not only to minimize stressful climatic conditions, but possible to escape predation.