A new stem group echinoid from the Triassic of China leads to a revised macroevolutionary history of echinoids during the end-Permian mass extinction

Thompson, Jeffrey R., Hu, Shi-xue, Zhang, Qi-Yue, Petsios, Elizabeth, Cotton, Laura J., Huang, Jin-Yuan, Zhou, Chang-yong, Wen, Wen and Bottjer, David J. (2018) A new stem group echinoid from the Triassic of China leads to a revised macroevolutionary history of echinoids during the end-Permian mass extinction. Royal Society Open Science, 5 (1). (doi:10.1098/rsos.171548).

Abstract

The Permian–Triassic bottleneck has long been thought to havedrastically altered the course of echinoid evolution, with theextinction of the entire echinoid stem group having takenplace during the end-Permian mass extinction. The EarlyTriassic fossil record of echinoids is, however, sparse, andnew fossils are paving the way for a revised interpretationof the evolutionary history of echinoids during the Permian–Triassic crisis and Early Mesozoic. A new species of echinoid,Yunnanechinus luopingensis n. sp. recovered from the MiddleTriassic (Anisian) Luoping Biota fossil Lagerstätte of SouthChina, displays morphologies that are not characteristic of theechinoid crown group. We have used phylogenetic analyses tofurther demonstrate that Yunnanechinus is not a member of the echinoid crown group. Thus a clade ofstem group echinoids survived into the Middle Triassic, enduring the global crisis that characterizedthe end-Permian and Early Triassic. Therefore, stem group echinoids did not go extinct during thePalaeozoic, as previously thought, and appear to have coexisted with the echinoid crown group forat least 23 million years. Stem group echinoids thus exhibited the Lazarus effect during the latest Permian and Early Triassic, while crown group echinoids did not.

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Contributors

Author: Jeffrey R. Thompson

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