Ben Creisler
A new paper:
Body size has thermal repercussions that impact physiology. Largeâbodied 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 bodyâsize 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 crossâsectional area was conducted to test these anatomical results, confirming that largeâbodied, and often largeâheaded, 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.Â
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News:
Video:
Dinosaur brain cooling strategies - Theropod ventilation of vascularized air sinus
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Big dinosaurs kept cool thanks to blood vessel clusters in their heads