The habitats of bird-like (Paravian) dinosaurs

Abstract

Over the past few decades, the discovery of different feathered bird-like dinosaurs particularly from China has provided strong evidence to support the dinosaurian origin of birds. Paraves is the name of the clade of bird-like dinosaurs and includes birds and their closest relatives, the deinonychosaurs. The long and complex history of paravian evolution is an important example of vertebrate macroevolution that helps us better understand the history of life. This study focuses on the habitat characteristics of basal paravians and their links to their evolutionary history. The oldest known paravians emerged in Asia and Europe which corresponded to cold and warm environments respectively in Middle-to-Late Jurassic. However, the European record is relatively limited compared to the taxonomic diversity in Asia, which mainly clusters in northeastern China. The early emerging members from Asia were all found in lacustrine rocks deposited under a cold climate. Based on the age of the known paravians considered in this study, a cold-to-warm transition of habitat conditions is apparent. Most of the members known from Middle-to-Late Jurassic strata, particularly those from China, lived in cold environments while the paravians known from the Late Cretaceous all lived in relatively warm environments. However, if the paravian phylogenetic positions are considered, such a simple trend cannot be applied as the basalmost members of Dromaeosauridae, which is currently known only in the Late Cretaceous, were found from rocks deposited under warm environments. Although there is no information on the habitats of the inferred ancestor of dromaeosaurids, the inconsistency exemplified by dromaeosaurids reveals that the habitat preference may not follow a simple one-way transition. Furthermore, the apparent ‘late occurrence’ of the primitive members of currently known dromaeosaurids may also imply early divergence but this cannot be revealed by the fossil record at this stage.