The study of the Early Cretaceous terrestrial Jehol Biota,which provides a rare window for reconstruction of a Lower Cretaceous terrestrial ecosystem,is reviewed with a focus on some of the latest progress.A newly proposed deinition of the biota based on paleoecology and taphonomy is accepted.Although the Jehol fossils are mainly preserved in two types of sedimentary rocks,there are various types of preservation with a complex mechanism that remains to be understood.New discoveries of signiicant taxa from the Jehol Biota,with an updated introduction of its diversity,conirm that the Jehol Biota represents one of the most diversiied biotas of the Mesozoic.he evolutionary signiicance of major biological groups(e.g.dinosaurs,birds,mammals,pterosaurs,insects,and plants)is discussed mainly in the light of recent discoveries,and some of the most remarkable aspects of the biota are highlighted.he global and local geological,paleogeographic,and paleoenvironmental background of the Jehol Biota have contributed to the unique composition,evolution,and preservation of the biota,demonstrating widespread faunal exchanges between Asia and other continents caused by the presence of the Eurasia–North American continental mass and its link to South America,and conirming northeastern China as the origin and diversiication center for a variety of Cretaceous biological groups.Although some progress has been made on the reconstruction of the paleotemperature at the time of the Jehol Biota,much more work is needed to conirm a possible link between the remarkable diversity of the biota and the cold intervals during the Early Cretaceous.Finally,future directions for the study of the Jehol Biota are proposed that highlight the great potential of more comprehensive and multidisciplinary studies to further our understanding of the biological and geological implications of the Jehol Lagerst¨ate. The study of the Early Cretaceous terrestrial Jehol Biota, which provides a rare window for reconstruction of a Lower Cretaceous terrestrial ecosystem, is reviewed with a focus on some of the latest progress. A newly proposed deinition of the biota based on paleoecology and taphonomy is accepted .Although the Jehol fossils are mainly preserved in two types of sedimentary rocks, there are various types of preservation with a complex mechanism that remains to be understood .New discoveries of signiicant taxa from the Jehol Biota, with an updated introduction of its diversity, conirm that the Jehol Biota one of the most diversied biotas of the Mesozoic., evolutionary signiicance of major biological groups (egdinosaurs, birds, mammals, pterosaurs, insects, and plants) is discussed mainly in the light of recent discoveries, and some of the most remarkable aspects of the biota are highlighted.he global and local geological, paleogeographic, and paleoenvironmental background of the Jehol Biota h ave contributed to the unique composition, evolution, and preservation of the biota, demonstrating widespread faunal exchanges between Asia and other continents caused by the presence of the Eurasia-North American continental mass and its link to South America, and conirming northeastern China as the origin and diversiication center for a variety of Cretaceous biological groups. Though some progress has been made on the reconstruction of the paleotemperature at the time of the Jehol Biota, much more work is needed to conirm a possible link between the remarkable diversity of the biota and the cold intervals during the Early Cretaceous. Finally, future directions for the study of the Jehol Biota are proposed that highlight the great potential of more comprehensive and multidisciplinary studies to further our understanding of the biological and geological implications of the Jehol Lagerst¨ate.