Temporal framework for the Yanliao Biota and timing of the origin of crown mammals
Zhiqiang Yu, Haibing Wang, Chi Zhang, Liping Dong, Magdalena H. Huyskens, Zexian Cui, Paige Cary, Yankun Di, Yuri Amelin, Gang Li, Qiuli Li, Xiaoping Xia, Chenglong Deng, Yuan Wang, Huaiyu He, Qing‐Zhu Yin
Abstract
Establishing the temporal sequence of the Middle-Late Jurassic Yanliao Biota is essential as it anchors the timing of many key evolutionary innovations in vertebrates. Lack of sufficiently reliable high-precision ages of fossil-bearing horizons hinders our ability to reconstruct the tempo and mode of vertebrate evolution. Here, we frame a temporal sequence of Yanliao Biota with precise age constraints for iconic vertebrates, proposing that the major vertebrate-bearing strata span from 164 Ma to 157 Ma in age. The increasing ecological diversity of mammaliaforms is well illustrated by the Middle-Late Jurassic Yanliao Biota and Early Cretaceous Jehol Biota. Incorporation of the updated temporal frameworks in Bayesian tip-dated mammaliaform phylogeny reveals that Triassic haramiyidans are separate from Jurassic taxa and unrelated to crown Mammalia. Tip-dated phylogeny supports a long-fuse model for mammal evolution, featured by a Late Triassic root and Middle-Late Jurassic interordinal diversification of crown Mammalia, showing consistency with molecular-based timetrees in divergence timing.