Climate-change-enhanced habitat diversification for the Middle Jurassic Yanliao Biota in East Asia.

The Jurassic Period was characterized by the dominance of dinosaurs and the rise of early mammals, with the Yanliao Biota (∼167-157 Ma) in East Asia notable for its exceptional fossil preservation and diverse life forms. However, the drivers of the flourishing of the Yanliao Biota remain unclear. Here, we reconstruct the palaeoclimate and habitat characteristics of the Yanliao Biota by using sedimentary facies analysis, organic carbon-isotope data, palynological records, source weathering trends and climate simulations from the Community Earth System Model CESM 1.2.2. The studied sedimentary successions are well constrained to the Middle Jurassic based on carbon-isotope stratigraphic correlation and published tuff zircon U-Pb ages. Our findings reveal a regional climate shift in the late Bathonian, transitioning from wet to sub-humid conditions, as evidenced by an increase in gymnosperm pollen, a marked decline in coal seams and reduced weathering intensity. Sedimentological evidence further supports a synchronous facies change from ever-wet fluvial-delta systems to seasonally active alluvial plains. This climate shift aligns with simulation results and coincides temporally with the initial flourishing of the Yanliao Biota. We propose that this shift, associated with lithospheric extension in the Yanliao region, increased landscape heterogeneity and habitat diversity, fostering biological evolution through ecological isolation and allopatric speciation, ultimately driving the diversification of the Yanliao Biota.