Avian tail ontogeny, pygostyle formation, and interpretation of juvenile Mesozoic specimens
| Autor: | Jingmai K. O’Connor, Susan C. Chapman, Dana J. Rashid, Nathan R. Carroll, Bino Varghese, Luis M. Chiappe, Kevin Surya, Kimball L. Garrett, Alida M. Bailleul, John R. Horner |
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| Rok vydání: | 2018 |
| Předmět: |
0106 biological sciences
0301 basic medicine Tail Time Factors Ontogeny lcsh:Medicine 010603 evolutionary biology 01 natural sciences Birds 03 medical and health sciences Extant taxon Morphogenesis Juvenile Animals Mesozoic Zhongornis lcsh:Science Multidisciplinary biology Fossils lcsh:R X-Ray Microtomography Pygostyle Feathers biology.organism_classification Evolutionary transitions Biological Evolution Cretaceous Spine Amber 030104 developmental biology Evolutionary biology lcsh:Q Chickens |
| Zdroj: | Scientific Reports, Vol 8, Iss 1, Pp 1-12 (2018) |
| ISSN: | 2045-2322 |
| Popis: | The avian tail played a critical role in the evolutionary transition from long- to short-tailed birds, yet its ontogeny in extant birds has largely been ignored. This deficit has hampered efforts to effectively identify intermediate species during the Mesozoic transition to short tails. Here we show that fusion of distal vertebrae into the pygostyle structure does not occur in extant birds until near skeletal maturity, and mineralization of vertebral processes also occurs long after hatching. Evidence for post-hatching pygostyle formation is also demonstrated in two Cretaceous specimens, a juvenile enantiornithine and a subadult basal ornithuromorph. These findings call for reinterpretations of Zhongornis haoae, a Cretaceous bird hypothesized to be an intermediate in the long- to short-tailed bird transition, and of the recently discovered coelurosaur tail embedded in amber. Zhongornis, as a juvenile, may not yet have formed a pygostyle, and the amber-embedded tail specimen is reinterpreted as possibly avian. Analyses of relative pygostyle lengths in extant and Cretaceous birds suggests the number of vertebrae incorporated into the pygostyle has varied considerably, further complicating the interpretation of potential transitional species. In addition, this analysis of avian tail development reveals the generation and loss of intervertebral discs in the pygostyle, vertebral bodies derived from different kinds of cartilage, and alternative modes of caudal vertebral process morphogenesis in birds. These findings demonstrate that avian tail ontogeny is a crucial parameter specifically for the interpretation of Mesozoic specimens, and generally for insights into vertebrae formation. |
| Databáze: | OpenAIRE |
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