This project built up a digital database of foot for birds, with a large sample size of ~90 species across the phylogeny. Digits were segmented and landmarked separately to reveal the most comprehensive and real morphology of foot, thus allows us to address questions about the character evolution and the ecological indications of this important structure, using quantitative methods such as geometric morphometric analyses. The results indicate that the ungual digits and the last non-ungual digits might be the most significant indicators for habits in the foot. The manuscript resulted from this work is under preparation and will be submitted soon. To make the most use of these data and inspire more related future research, all the CT scanning data has been uploaded and made freely available online via Morphosource (www.morphosource.org). The newly segmented 3D models, the landmark data and the R codes will be publicly archived once the manuscript gets published soon.
The project was also expanded to apply these relevant techniques to other structures such as the skull and mandible of both extant and extinct birds. High-resolution synchrotron tomography was conducted on an exquisitely preserved new skull of Jeholornis - one of the earliest-diverging birds, providing a near-complete cranial reconstruction. The possibility that Jeholornis was granivorous was excluded, based on morphometric analyses of the mandible and cranium, and comparisons with the 3D alimentary contents of extant birds. This provides the earliest evidence for fruit consumption in birds, and indicates that birds may have been recruited for seed dispersal during the earliest stages of the avian radiation. This work has been published in eLife (
https://elifesciences.org/articles/74751(opens in new window)).
Based on the data produced above, we also provided a detailed description of the cranial osteology of Jeholornis, confirming the overall plesiomorphic morphology of the skull, with the exception of the more specialized rostrum. Evidence of sensory adaptation suggested that olfaction was an important aspect of Jeholornis ecology. The digitally reconstructed scleral ring suggests a strongly diurnal habit, supporting the hypothesis that early-diverging birds were predominantly active during the day. This work has been published in Zoological Journal of the Linnean Society (
https://academic.oup.com/zoolinnean/article/198/1/93/6768673(opens in new window)).
Following research about the diet of Jeholornis combined our geometric morphometric results from above work and the study of phytoliths, providing evidence of Jeholornis consuming angiosperm leaves of the clade Magnoliales. These results lend further support for early ecological connections among the earliest birds and angiosperms. This work has been published as a preprint in Research Square (
https://www.researchsquare.com/article/rs-2557852/v1(opens in new window)) and has been accepted in Nature Communications.
Despite the stem taxon Jeholornis, this project also investigated the ecology of another important Early Cretaceous avian lineage – Enantiornithes. Drawing inferences from both avian bill proportions and variations in the dental morphology of extinct and extant taxa, we provided quantitative data to support the hypothesis that the Longipterygidae were animalivorous, with greater support for insectivory. This work has been published in PeerJ (
https://peerj.com/articles/15139/(opens in new window)).
This project also made effort to disseminate transferable skills of the quantitative analyses pipeline, i.e. 3D imaging and reconstruction, geometric morphometrics and statistical comparative analysis, to other especially Chinese researchers. Besides the presentations in the international conferences, we have been invited and published an introduction and protocol of geometric morphometrics in a Chinese textbook, while this expertise has been eagerly anticipated in Chinese vertebrate palaeontology (
https://bio-protocol.org/exchange/protocoldetail?id=1010664&type=1(opens in new window)).
Together with all these scientific publications, media release and relevant conference presentations have been made to spread the project results through the whole project period.
