Functional signals in the bone microstructure of flying vertebrates and their importance in understanding the evolution of powered flight in feathered dinosaurs

Project focus

 Modern birds are maniraptoran dinosaurs, the only dinosaurian group that survived the Late Cretaceous mass extinction. Extinct maniraptorans show diverse dinosaur-bird transitional morphologies, such as a long bony tail and toothed jaws but also wings with aerodynamically adapted flight feathers, which were associated with variable aerial skills revealing the complex evolution of avian flight. Even though it is well known in modern birds that flight abilities and related skeletal and integumentary features may change drastically through ontogeny, it remains elusive how limbs develop to perform bipedal locomotion and flight in extinct ‘dinobirds’ with unknown ontogenetic stage. Since biomechanical demands associated with locomotion, as well as growth rates and ontogenetic stages are also reflected at the structural level of bone tissues, histology of bones is a powerful source of complementary information in extinct vertebrates for inferring potentially flight-related traits in an ontogenetic context.

To obtain a better understanding of the terrestrial and potential aerial skills of bird-like dinosaurs and thereby of the evolution of avian ontogenetic locomotor strategies, this project first aims to explore whether there are functional signals in the bone tissues of extant birds that reflect different capabilities of powered flight throughout ontogeny. Using thin-sectioning, polarized light microscopy and µCT-scanning techniques, we analyse the microstructure of wing and leg bones of birds that exhibit different levels of locomotor abilities at different ontogenetic stages. If osteohistological correlates of powered flight can be identified through development in modern birds, they can also be used in fossil bones to get a more detailed insight into the locomotor ontogeny of bird-like dinosaurs, and hence into hotly discussed issues like when, how many times, and in which dinosaur lineages powered flight might have evolved or disappeared secondarily. 

Keywords

 dinobirds, powered flight, osteohistology, birds, locomotor ontogeny, flight evolution

Researchers: Edina Prondvai (PI), Dominique Adriaens (co-PI)