@article{20797c465f5146aca4862dabaa582071,
title = "From Anomalous Arteries to Selective Brain Cooling: Parallel Evolution of the Artiodactyl Carotid Rete",
abstract = "Terrestrial artiodactyls (even-toed ungulates) inhabit some of the world's most extreme environments, including arid deserts and high elevations. As medium-to-large-bodied mammals, artiodactyls have a suite of specialized physiologies to facilitate occupation of regions unavailable to other large mammals. One such physiology is selective brain cooling, wherein reduction of brain temperature below core body temperature has been demonstrated to reduce evaporative water loss. This physiology is enabled by an arterial heat-exchanger called the carotid rete. The ubiquity of the carotid rete throughout the clade, as well as its evolutionary history, is currently uninvestigated. Here, I use osteological correlates to survey clade-wide presence and morphology of the carotid rete, prior to conducting a preliminary evolutionary analysis. Nearly all living artiodactyls possess a carotid rete and are capable of selective brain cooling; however, major arteries supplying the rete are derived from different embryonic aortic arches on a suborder-specific basis. Ancestral character estimation infers this pattern of variation to be the result of independent evolutionary processes, suggesting carotid rete homoplasy arising via parallelism. This is a surprising finding given the role this structure plays in driving a physiology that has been implicated in mitigating artiodactylan responses to extreme environmental conditions. Future studies should incorporate extinct species represented in the fossil record to better parse between parallel and convergent mechanisms, as well as to better understand the relationship between the carotid rete, selective brain cooling, and survivorship of climate perturbation. Anat Rec, 2018.",
keywords = "Artiodactyla, ancestral character estimation, carotid rete, evolutionary, homoplasy",
author = "O'Brien, {Haley D.}",
note = "Funding Information: Abbreviations: AP = Ascending pharyngeal artery; CarFor = Carotid foramen; CR = Carotid rete; FOR = Foramen orbitorotun-dum; hICA = Homologous internal carotid artery; ICA = Internal carotid artery; MA = Maxillary artery; mFLac = Medial foramen lacerum Grant sponsor: American Museum of Natural History; Grant number: Collections Study Grant; Grant sponsor: American Society of Mammalogists; Grant number: Grants In Aid of Research; Grant sponsor: Ohio University; Grant number: Student Enhancement Award; Grant sponsor: Society for Integrative and Comparative Biology; Grant number: Grants In Aid of Research; Grant sponsor: Oklahoma State University{\textquoteright}s Center for Health Sciences, American Society of Mammalogists Grants-In-Aid, Society for Integrative and Comparative Biology Grants-In-Aid, Ohio University, and an American Museum of Natural History Collections Study grant. *Correspondence to: Haley D. O{\textquoteright}Brien, Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, 1111 W 17 Street, Tulsa, OK 74107. E-mail: haley.obrien@okstate.edu Received 1 November 2017; Revised 19 December 2017; Accepted 8 January 2018. DOI: 10.1002/ar.23987 Published online 15 October 2018 in Wiley Online Library (wileyonlinelibrary.com). Funding Information: I thank T Smith for inviting my participation in this special issue of The Anatomical Record. D. Miles, N. Stevens, A. Stigall, S. Williams, and L. Witmer provided comments and suggestions on an earlier version of this manuscript. P. Gignac, G. O'Brien, and two anonymous reviewers provided valuable insight. For access to collections, I thank R.D.E. MacPhee, E. Westwig, and E. Hoeger at the American Museum of Natural History Department of Mammalogy, J. Wible and S. MacLaren at the Carnegie Museum of Natural History, S. Musila at the National Museum of Kenya, and R. Stuckey and J. Stephenson at the Denver Museum of Nature and Science. Publisher Copyright: {\textcopyright} 2018 Wiley Periodicals, Inc.",
year = "2020",
month = feb,
day = "1",
doi = "10.1002/ar.23987",
language = "English",
volume = "303",
pages = "308--317",
journal = "Anatomical Record",
issn = "1932-8486",
publisher = "John Wiley and Sons Inc.",
number = "2",
}