@article{b9b4d1fb002d4af3b9cbd47bbbc51215,
title = "Are endocasts good proxies for brain size and shape in archosaurs throughout ontogeny?",
abstract = "Cranial endocasts, or the internal molds of the braincase, are a crucial correlate for investigating the neuroanatomy of extinct vertebrates and tracking brain evolution through deep time. Nevertheless, the validity of such studies pivots on the reliability of endocasts as a proxy for brain morphology. Here, we employ micro-computed tomography imaging, including diffusible iodine-based contrast-enhanced CT, and a three-dimensional geometric morphometric framework to examine both size and shape differences between brains and endocasts of two exemplar archosaur taxa – the American alligator (Alligator mississippiensis) and the domestic chicken (Gallus gallus). With ontogenetic sampling, we quantitatively evaluate how endocasts differ from brains and whether this deviation changes during development. We find strong size and shape correlations between brains and endocasts, divergent ontogenetic trends in the brain-to-endocast correspondence between alligators and chickens, and a comparable magnitude between brain–endocast shape differences and intraspecific neuroanatomical variation. The results have important implications for paleoneurological studies in archosaurs. Notably, we demonstrate that the pattern of endocranial shape variation closely reflects brain shape variation. Therefore, analyses of endocranial morphology are unlikely to generate spurious conclusions about large-scale trends in brain size and shape. To mitigate any artifacts, however, paleoneurological studies should consider the lower brain–endocast correspondence in the hindbrain relative to the forebrain; higher size and shape correspondences in chickens than alligators throughout postnatal ontogeny; artificially {\textquoteleft}pedomorphic{\textquoteright} shape of endocasts relative to their corresponding brains; and potential biases in both size and shape data due to the lack of control for ontogenetic stages in endocranial sampling.",
keywords = "Alligator, Gallus, diffusible iodine-based contrast-enhanced computed tomography, geometric morphometrics, micro-computed tomography, neuroanatomy",
author = "Akinobu Watanabe and Gignac, {Paul M.} and Balanoff, {Amy M.} and Green, {Todd L.} and Kley, {Nathan J.} and Norell, {Mark A.}",
note = "Funding Information: We thank Ruth Elsey (Rockefeller Wildlife Refuge), Gregory Erickson (Florida State University), David Kay (Oklahoma State University CHS), Broderick Vaughan (Vaughan Gators), and Doug Warner (Charles River Laboratory) for providing and collecting alligator and chicken specimens; Morgan Hill and Henry Towbin (American Museum of Natural History) for assistance with CT imaging; and Isabelle Brenes (Saint Francis Preparatory School; currently Montana State University) for CT data processing. This study was funded by the National Science Foundation (NSF) Graduate Research Fellowship (to A.W.), NSF Division of Environmental Biology (DEB-1406849 to A.W.; DEB-1457180 to P.M.G.; DEB-1801224 to A.W., P.M.G., A.M.B., M.A.N.), EAGER (1450842 to N.J.K., 1450850 to P.M.G.), Mary R. Dawson Predoctoral Fellowship Grant through the Society of Vertebrate Paleontology (to A.W.), Jurassic Foundation (to A.W.), Macaulay Family (to M.A.N.), Richard Gilder Graduate School (to A.W.), the Division of Paleontology at the AMNH (to A.W., M.A.N.), and the Department of Anatomy and Cell Biology at Oklahoma State University, Center for Health Sciences (to P.M.G.) Funding Information: We thank Ruth Elsey (Rockefeller Wildlife Refuge), Gregory Erick-son (Florida State University), David Kay (Oklahoma State University CHS), Broderick Vaughan (Vaughan Gators), and Doug Warner (Charles River Laboratory) for providing and collecting alligator and chicken specimens; Morgan Hill and Henry Towbin (American Museum of Natural History) for assistance with CT imaging; and Isabelle Brenes (Saint Francis Preparatory School; currently Montana State University) for CT data processing. This study was funded by the National Science Foundation (NSF) Graduate Research Fellowship (to A.W.), NSF Division of Environmental Biology (DEB-1406849 to A.W.; DEB-1457180 to P.M.G.; DEB-1801224 to A.W., P.M.G., A.M.B., M.A.N.), EAGER (1450842 to N.J.K., 1450850 to P.M.G.), Mary R. Dawson Predoctoral Fellowship Grant through the Society of Vertebrate Paleontology (to A.W.), Jurassic Foundation (to A.W.), Macaulay Family (to M.A.N.), Richard Gilder Graduate School (to A.W.), the Division of Paleontology at the AMNH (to A.W., M.A.N.), and the Department of Anatomy and Cell Biology at Oklahoma State University, Center for Health Sciences (to P.M.G.) Publisher Copyright: {\textcopyright} 2018 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.",
year = "2019",
month = mar,
doi = "10.1111/joa.12918",
language = "English",
volume = "234",
pages = "291--305",
journal = "Journal of Anatomy",
issn = "0021-8782",
publisher = "Wiley-Blackwell Publishing Ltd",
number = "3",
}