Dinosaur Thermoregulation Were They “Warm Blooded”?
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Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Dinosaur thermoregulation Were they “warm blooded”? Thermogram of a lion Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Body temperature in endotherms and ectotherms Thermogram of ostriches Thermogram of a snake wrapped around a human arm Thermogram of a python held by people Thermogram of a lion Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Physiology, metabolism, and dinosaurs? Ornithopods Birds Sauropods Dromeosaurs Tyrannosaurus Ceratopsians Pachycephalosaurs Crocodilians Stegosaurs Ankylosaurs Lizards and snakes Lizards ? ? ? ? ? ? ? Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 “extant phylogenetic bracket” Using phylogenetic logic to reconstruct biology of extinct animals. Features observed in living animals can be traced back to common ancestor. This suggests that extinct clades that fall between are likely to have similar in features even if they cannot be observed directly in the fossils. Witmer, 1995 Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Thermoregulation Maintaining body temperature within limited boundaries regardless of temperature of the surrounding environment. Endotherm vs. Ectotherm Endotherms use internal metabolic heat to regulate themselves, ectotherms use external sources of heat (and cool). Mammals and birds are endotherms, most other vertebrates are ectotherms. Homeotherm vs. Poikilotherm Homeotherms have a constant body temperature, poikilotherms have a variable body temperature. Mammals are homeotherms, but so are fish that live in water of constant body temperature. Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Endothermic groups In-between groups Mammalia (mammals) Very large animals (inertial Aves (birds) homeotherms) Animals with unusual physiology (tuna are endothermic) Unknown groups Ecothermic groups Non-avian dinosaurs most fishes Amphibia Pelycosaurs (non-mammalian synapsids) Lepidosauria (lizards and snakes) Crocodilians Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Source of internal heat Anaerobic metabolism Produces lactic acid Less energy stored in ATP Aerobic metabolism Produces carbon dioxide Stores more energy in ATP Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Duration of energy output in ectotherms and endotherms Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Mechanisms for regulating body temperature Regulate production of heat by changing metabolism • shivering • torpor Regulate amount of blood at surface of body • “counter current” exchange (arteries and veins intertwine in legs and other places so that outgoing blood is cooled by returning blood and vice versa) • dilation and constriction of blood vessels (blushing, shock) Insulation • hair • feathers • subcutaneous fat Evaporative cooling • sweating • panting Behavioral regulation • sunning • moving into shade • denning • lying on cool mud or in water • Expose wing surfaces Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Behavioral thermoregulation in an ectotherm From Shine, 1991, Australian Snakes, A Natural History, Cornell. Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Changes in body temperature in ectothermic poikilotherm 95F From Shine, 1991, Australian Snakes, A Natural History, Cornell. Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Poikilotherm and variation in body temperature Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Inertial homeothermy probable in large dinosaurs Large animals retain heat because their surface area is proportionally smaller. An inertial homeotherm is an ectotherm that is so large that it cannot exchange heat across the surface fast enough to keep up with changing environment temperature. Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Metabolic rate is related to body size in ectotherms (mammals) 1.50 /hr/g) 2 1.00 0.50 0.00 -0.50 -1.00 Logmetabolic rate(O -1.50 -4.0 -2.0 0.0 2.0 4.0 Log body mass (kg) Data from Eisenberg, 1981 Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Vertebrate dietary categories Omnivore - mixed diet Frugivore - diet Herbivore - generalized specializing on fruits (only diet on plant leaves and exists after the stems Cretaceous) Granivore - diet Piscivore - carnivorous diet specializing on seeds and specializing on fish nuts Insectivore - diet specializing on insects (and sometimes other Carnivore - generalized diet invertebrates, like of flesh and fat worms) Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Energy value in different food sources Small ectotherms = high metabolic rate = high calorie diet = small animals must be insectivores and granivores Large ectotherms = lower metabolic rate = lower calorie diet = large animals can be herbivores and frugivores 700 525 350 kcal per 100 g kcal per 175 0 Insects Nuts and Seeds Meat and Fat Fruits Leaves and Grasses Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Skeletal evidence for conserving heat Turbinal bones Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Deterministic growth and physiology Deterministic growth: rapid growth to fixed adult size (birds and mammals) Indeterminate growth: slower growth with no maximum size Growth patterns are related to endothermy Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Deterministic growth in dinosaurs Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Rates of growth in dinosaurs Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Structure of mammalian bone Haversian system - blood vessels nourish osteocytes, chondrocytes, and provide minerals for bone deposition in concentric rings around the vessels Kardong 1995, Vertebrates Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Histology of fossil bone Osteons (or Haversian structures Modern bone Jurassic age plesiosaur (Martill, 1991, Bones as stones) Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Bone histology and the rate of growth in dinosaurs Padian, Horner and de Ricqlès, 2004, J. Vert. Paleo, 24: 555-571. Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Climate and ectotherms Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Titanoboa and temperature in the Paleogene Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 How big was Titanoboa? Regression of SVL on vertebra width P < 0.001, R2 = 0.7 Total body length: 12.82 m +/- 2.18 m (42 ft) Body mass: 1,135 kg (1.27 tons) Living anaconda: Record = 7 m, Average = 6.5 m An adult Ball python slithering over a Living python: Record = 9 m, Average = 6 m Titanoboa vertebra. (c) 2009, Jason J. Head (Graphic by Brady MacDonald (c) 2009, LA Times) Head, J.J., J.I. Bloch, A.K. Hastings, J.R. Bourque, E. Cadena, F. Herrera, P.D. Polly, and C.A. Jaramillo. 2009. Giant boine snake from a Paleocene Neotropical rainforest indicates hotter past equatorial temperatures. Nature, 457: 715-718. Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Global Climate for the last 65 million years Present 14 C (57.2 F) Last Glacial Maximum 9 C (48.2 F) Miocene Climatic Optimum 21 C (70 F) Eocene thermal maximum 23-26 C (73-79 F) (Zachos et al., 2001. Science, 292: 686-693) Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Titanoboa’s world (Zachos et al., 2001. Science, 292: 686-693) (© 2010, Ron Blakey, NAU Geology) Department of Geological Sciences | Indiana University Dinosaurs and their relatives (c) 2015, P. David Polly Geology G114 Climate in the Paleogene circles = no frost intolerant plants squares = palms triangles = cycads, gingers or tree ferns Eocene Metasequoia stumps, Axel Heiberg Island (photo by Greenwood) (Greenwood & Wing, 1995. Geology, 23: 1044-148. Department