Novel neuroanatomical integration and scaling define avian brain shape evolution and development

eLife

Akinobu Watanabe¹  Mark A Norell²  M Eugenia L Gold³  Paul M Gignac⁴  Amy M Balanoff⁵ 

[1] Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, United States;Division of Paleontology, American Museum of Natural History, New York, United States;Department of Life Sciences Vertebrates Division, Natural History Museum, London, United Kingdom;Division of Paleontology, American Museum of Natural History, New York, United States;Division of Paleontology, American Museum of Natural History, New York, United States;Biology Department, Suffolk University, Boston, United States;Division of Paleontology, American Museum of Natural History, New York, United States;Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Tulsa, United States;Division of Paleontology, American Museum of Natural History, New York, United States;Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, United States;

关键词: brain evolution;    geometric morphometrics;    phenotypic integration;    dinosauria;    aves;    alligator;    Chicken;    Other;   

DOI  :  10.7554/eLife.68809

来源: eLife Sciences Publications, Ltd

【 摘 要 】

How do large and unique brains evolve? Historically, comparative neuroanatomical studies have attributed the evolutionary genesis of highly encephalized brains to deviations along, as well as from, conserved scaling relationships among brain regions. However, the relative contributions of these concerted (integrated) and mosaic (modular) processes as drivers of brain evolution remain unclear, especially in non-mammalian groups. While proportional brain sizes have been the predominant metric used to characterize brain morphology to date, we perform a high-density geometric morphometric analysis on the encephalized brains of crown birds (Neornithes or Aves) compared to their stem taxa—the non-avialan coelurosaurian dinosaurs and Archaeopteryx. When analyzed together with developmental neuroanatomical data of model archosaurs (Gallus, Alligator), crown birds exhibit a distinct allometric relationship that dictates their brain evolution and development. Furthermore, analyses by neuroanatomical regions reveal that the acquisition of this derived shape-to-size scaling relationship occurred in a mosaic pattern, where the avian-grade optic lobe and cerebellum evolved first among non-avialan dinosaurs, followed by major changes to the evolutionary and developmental dynamics of cerebrum shape after the origin of Avialae. Notably, the brain of crown birds is a more integrated structure than non-avialan archosaurs, implying that diversification of brain morphologies within Neornithes proceeded in a more coordinated manner, perhaps due to spatial constraints and abbreviated growth period. Collectively, these patterns demonstrate a plurality in evolutionary processes that generate encephalized brains in archosaurs and across vertebrates.

【 授权许可】

CC BY