A new microraptorine theropod from the Jehol Biota and growth in early dromaeosaurids

摘要: Fossils from the Jehol Group (Early Cretaceous, Liaoning Province, China) are integral to our understanding of Paraves, clade dinosaurs grouping dromaeosaurids, troodontids, and avialians, including living birds. However, many taxa represented by specimens unclear ontogenetic age. Without a more thorough ontogeny, evolutionary relationships significance character states within paravian may be obscured ability infer their biology restricted. We describe complete specimen new microraptorine dromaeosaur, Wulong bohaiensis gen. et sp. nov., geologically young Jiufotang Formation (Aptian) that helps solve this problem. Phylogenetic analysis recovers monophyletic Microraptorinae. Preserved in articulation on single slab, type is small exhibits osteological markers immaturity identified other archosaurs, such as bone texture lack fusion. To contextualize signal, we histologically sampled tibia, fibula, humerus compared them with samples closely related osteologically mature Sinornithosaurus. Histology shows both still growing at death, indicating an age for dinosaur about 1 year. The holotype possesses several feather types, filamentous feathers, pennaceous primaries, long rectrices, establishing growth preceded skeletal maturity full adult size some dromaeosaurids. Comparison histology taxon Sinornithosaurus indicates macroscopic signs developed after first year, but before cessation growth, demonstrating nonhistological indicators adulthood misleading when applied Anat Rec, 303:963-987, 2020. © 2020 American Association Anatomy.