Biotic response to Early Cretaceous climate warming in Hebei, northern China: Implications for the phased development of the Jehol Biota

The Early Cretaceous Jehol Biota in northern China is a terrestrial lagersta center dot tte that contains exceptionally-preserved fossils, including birds, dinosaurs, pterosaurs, mammals, insects, and flowering plants. The biota underwent three developmental phases, with relatively limited biodiversity in an early phase that rapidly diversified in a middle phase; however, the relationship between this biological radiation and climate remains uncertain. In this paper, we study fossils from the early-to-middle phases of the Jehol Biota preserved in the Lower Cretaceous (middle Valanginian-lower Barremian) Dabeigou and Dadianzi formations of Hebei Province to ascertain climatic impact on biotic evolution. The occurrence of a cool to warm climate turnover during the deposition of these strata is inferred based on a synthesis of geochemical and paleontological evidence. Palae-ogeographic distribution of the middle phase of the biota is wider and positioned more southerly than that of the early phase, possibly indicating that the biota in the early and middle phases lived in boreal and temperate climate realms, respectively. Biotic diversity shows an increasing trend from the early phase to the middle phase of the Jehol Biota, closely coinciding with the cool to warm turnover of the climate. The body sizes of some taxa in the middle phase were significantly smaller than those in the early phase, which is also interpreted as a cli-matic effect. This study represents the first attempt to correlate the response of terrestrial evolution of the Jehol Biota to climate change, with a focus on Early Cretaceous paleotemperatures.