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Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies.

Abstract

Body size has thermal repercussions that impact physiology. Large-bodied dinosaurs potentially retained heat to the point of reaching dangerous levels, whereas small dinosaurs shed heat relatively easily. Elevated body temperatures are known to have an adverse influence on neurosensory tissues and require physiological mechanisms for selective brain and eye temperature regulation. Vascular osteological correlates in fossil dinosaur skulls from multiple clades representing different body-size classes were identified and compared. Neurovascular canals were identified that differentiate thermoregulatory strategies involving three sites of evaporative cooling that are known in extant diapsids to function in selective brain temperature regulation. Small dinosaurs showed similarly sized canals, reflecting a plesiomorphic balanced pattern of blood supply and a distributed thermoregulatory strategy with little evidence of enhancement of any sites of thermal exchange. Large dinosaurs, however, showed a more unbalanced vascular pattern whereby certain sites of thermal exchange were emphasized for enhanced blood flow, reflecting a more focused thermal strategy. A quantitative, statistical analysis of canal cross-sectional area was conducted to test these anatomical results, confirming that large-bodied, and often large-headed, species showed focused thermal strategies with enhanced collateral blood flow to certain sites of heat exchange. Large theropods showed evidence for a plesiomorphic balanced blood flow pattern, yet evidence for vascularization of the large antorbital paranasal air sinus indicates theropods may have had a fourth site of heat exchange as part of a novel focused thermoregulatory strategy. Evidence presented here for differing thermoregulatory strategies based on size and phylogeny helps refine our knowledge of dinosaur physiology. Anat Rec, 2019. © 2019 American Association for Anatomy.

Authors+Show Affiliations

Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Ohio Center for Ecology and Evolutionary Studies, Athens, Ohio.Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Ohio Center for Ecology and Evolutionary Studies, Athens, Ohio.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31618532

Citation

Porter, Wm Ruger, and Lawrence M. Witmer. "Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies." Anatomical Record (Hoboken, N.J. : 2007), 2019.
Porter WR, Witmer LM. Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies. Anat Rec (Hoboken). 2019.
Porter, W. R., & Witmer, L. M. (2019). Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies. Anatomical Record (Hoboken, N.J. : 2007), doi:10.1002/ar.24234.
Porter WR, Witmer LM. Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies. Anat Rec (Hoboken). 2019 Oct 16; PubMed PMID: 31618532.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Vascular Patterns in the Heads of Dinosaurs: Evidence for Blood Vessels, Sites of Thermal Exchange, and Their Role in Physiological Thermoregulatory Strategies. AU - Porter,Wm Ruger, AU - Witmer,Lawrence M, Y1 - 2019/10/16/ PY - 2018/06/28/received PY - 2019/03/22/revised PY - 2019/05/11/accepted PY - 2019/10/17/entrez PY - 2019/10/17/pubmed PY - 2019/10/17/medline KW - blood vessels KW - dinosaur KW - thermoregulatory strategy JF - Anatomical record (Hoboken, N.J. : 2007) JO - Anat Rec (Hoboken) N2 - Body size has thermal repercussions that impact physiology. Large-bodied dinosaurs potentially retained heat to the point of reaching dangerous levels, whereas small dinosaurs shed heat relatively easily. Elevated body temperatures are known to have an adverse influence on neurosensory tissues and require physiological mechanisms for selective brain and eye temperature regulation. Vascular osteological correlates in fossil dinosaur skulls from multiple clades representing different body-size classes were identified and compared. Neurovascular canals were identified that differentiate thermoregulatory strategies involving three sites of evaporative cooling that are known in extant diapsids to function in selective brain temperature regulation. Small dinosaurs showed similarly sized canals, reflecting a plesiomorphic balanced pattern of blood supply and a distributed thermoregulatory strategy with little evidence of enhancement of any sites of thermal exchange. Large dinosaurs, however, showed a more unbalanced vascular pattern whereby certain sites of thermal exchange were emphasized for enhanced blood flow, reflecting a more focused thermal strategy. A quantitative, statistical analysis of canal cross-sectional area was conducted to test these anatomical results, confirming that large-bodied, and often large-headed, species showed focused thermal strategies with enhanced collateral blood flow to certain sites of heat exchange. Large theropods showed evidence for a plesiomorphic balanced blood flow pattern, yet evidence for vascularization of the large antorbital paranasal air sinus indicates theropods may have had a fourth site of heat exchange as part of a novel focused thermoregulatory strategy. Evidence presented here for differing thermoregulatory strategies based on size and phylogeny helps refine our knowledge of dinosaur physiology. Anat Rec, 2019. © 2019 American Association for Anatomy. SN - 1932-8494 UR - https://www.unboundmedicine.com/medline/citation/31618532/Vascular_Patterns_in_the_Heads_of_Dinosaurs:_Evidence_for_Blood_Vessels,_Sites_of_Thermal_Exchange,_and_Their_Role_in_Physiological_Thermoregulatory_Strategies L2 - https://doi.org/10.1002/ar.24234 DB - PRIME DP - Unbound Medicine ER -