TY - JOUR
T1 - Birds have paedomorphic dinosaur skulls
AU - Bhullar, Bhart Anjan S.
AU - Marugán-Lobón, Jesús
AU - Racimo, Fernando
AU - Bever, Gabe S.
AU - Rowe, Timothy B.
AU - Norell, Mark A.
AU - Abzhanov, Arhat
N1 - Funding Information:
Acknowledgements We thank R. M. Elsey and colleagues at the Rockefeller Wildlife Refuge, Louisiana Department of Wildlife and Fisheries for assistance in obtaining alligator embryos, S. Majadla for imaging assistance, C. Sánchez for constructing the SupplementaryMovie,I.Sarrisfor assistance with the R scriptpackages,andJ.B.Losos, H. E. Hoekstra, F. A. Jenkins Jr and B. Zweig for comments that improved the manuscript. B.-A.S.B. was partly funded by National Science Foundation dissertation improvement grant 1110564. J.M.-L. was supported by project BFU2008-00642.
Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2012/7/12
Y1 - 2012/7/12
N2 - The interplay of evolution and development has been at the heart of evolutionary theory for more than a century. Heterochrony-change in the timing or rate of developmental events-has been implicated in the evolution of major vertebrate lineages such as mammals, including humans. Birds are the most speciose land vertebrates, with more than 10,000 living species representing a bewildering array of ecologies. Their anatomy is radically different from that of other vertebrates. The unique bird skull houses two highly specialized systems: the sophisticated visual and neuromuscular coordination system allows flight coordination and exploitation of diverse visual landscapes, and the astonishing variations of the beak enable a wide range of avian lifestyles. Here we use a geometric morphometric approach integrating developmental, neontological and palaeontological data to show that the heterochronic process of paedomorphosis, by which descendants resemble the juveniles of their ancestors, is responsible for several major evolutionary transitions in the origin of birds. We analysed the variability of a series of landmarks on all known theropod dinosaur skull ontogenies as well as outgroups and birds. The first dimension of variability captured ontogeny, indicating a conserved ontogenetic trajectory. The second dimension accounted for phylogenetic change towards more bird-like dinosaurs. Basally branching eumaniraptorans and avialans clustered with embryos of other archosaurs, indicating paedomorphosis. Our results reveal at least four paedomorphic episodes in the history of birds combined with localized peramorphosis (development beyond the adult state of ancestors) in the beak. Paedomorphic enlargement of the eyes and associated brain regions parallels the enlargement of the nasal cavity and olfactory brain in mammals. This study can be a model for investigations of heterochrony in evolutionary transitions, illuminating the origin of adaptive features and inspiring studies of developmental mechanisms.
AB - The interplay of evolution and development has been at the heart of evolutionary theory for more than a century. Heterochrony-change in the timing or rate of developmental events-has been implicated in the evolution of major vertebrate lineages such as mammals, including humans. Birds are the most speciose land vertebrates, with more than 10,000 living species representing a bewildering array of ecologies. Their anatomy is radically different from that of other vertebrates. The unique bird skull houses two highly specialized systems: the sophisticated visual and neuromuscular coordination system allows flight coordination and exploitation of diverse visual landscapes, and the astonishing variations of the beak enable a wide range of avian lifestyles. Here we use a geometric morphometric approach integrating developmental, neontological and palaeontological data to show that the heterochronic process of paedomorphosis, by which descendants resemble the juveniles of their ancestors, is responsible for several major evolutionary transitions in the origin of birds. We analysed the variability of a series of landmarks on all known theropod dinosaur skull ontogenies as well as outgroups and birds. The first dimension of variability captured ontogeny, indicating a conserved ontogenetic trajectory. The second dimension accounted for phylogenetic change towards more bird-like dinosaurs. Basally branching eumaniraptorans and avialans clustered with embryos of other archosaurs, indicating paedomorphosis. Our results reveal at least four paedomorphic episodes in the history of birds combined with localized peramorphosis (development beyond the adult state of ancestors) in the beak. Paedomorphic enlargement of the eyes and associated brain regions parallels the enlargement of the nasal cavity and olfactory brain in mammals. This study can be a model for investigations of heterochrony in evolutionary transitions, illuminating the origin of adaptive features and inspiring studies of developmental mechanisms.
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U2 - 10.1038/nature11146
DO - 10.1038/nature11146
M3 - Article
C2 - 22722850
AN - SCOPUS:84863725587
SN - 0028-0836
VL - 487
SP - 223
EP - 226
JO - Nature
JF - Nature
IS - 7406
ER -