Name GEOL 104 Dinosaurs A Natural History Homework 5 Dinosaur Physiology DUE Mon Nov 27 Part I Growth Rates The curves above represent the body mass in tons of the giant crocodylian Deinosuchus line A and the ceratopsian Triceratops dashed line B both of which are found in the Montana Group deposits of the American West 1 At what age does Triceratops growth level off 2 At what age does Deinosuchus growth level off 3 Which of these reptiles grew at a rate more like a modern mammal i e fast Triceratops Deinosuchus Part II Predator Prey Ratios Robert Bakker has suggested that we can use predator prey ratios to test if an extinct community were primarily endothermic primarily ectothermic or somewhere in between The ratio represented as the percentage of the total biomass made up of carnivores would have higher values for ectotherms with their lower food requirements and lower for endotherms which need to eat constantly in order to fuel their bodies Based on theoretical and observational data ectothermic communities should have predatory prey ratios over 20 while true endotherms should be below 7 1 Name Below are values Bakker discovered for various assemblages from particular formations or localities of fossils and one modern the Serengeti These are arranged by the Amniote Radiation in which they occurred 1st Basal Synapsid Radiation Locality Pred Prey ratio Williams Ranch 26 Black Flat 28 2nd Therapsid Radiation Locality Pred Prey ratio Tapinocephalus zone 12 Daptocephalus zone 13 4th Dinosaur Radiation Locality Pred Prey ratio Morrison 3 5 Cloverly 3 7 Dinosaur Park 3 5 Hell Creek 1 9 3rd Pseudosuchian Radiation Locality Pred Prey ratio Er Ma Ying 15 Ischichuca 17 5th Mammal Radiation Locality Pred Prey ratio Wasatch 4 4 Chadron 5 4 Harrison 4 3 Serengeti 0 3 Mammals 5th Radiation are known to be endothermic Essentially all researchers agree that basal synapsids 1st Radiation were ectothermic 4 The values for the dinosaurian radiation are like basal synapsids like mammals intermediate 5 The values for the pseudosuchian radiation are like basal synapsids like mammals intermediate 6 The values for the therapsid radiation are like basal synapsids like mammals intermediate Part III Dinosaur Respiration Lungs Food is only part of metabolism Another important aspect is respiration without oxygen there isn t much metabolism Recent work by Colleen Farmer David Carrier and Elizabeth Brainerd on modern animals have revealed a lot more diversity in vertebrate respiration than previously known For example mammalian breath which uses the ribs plus a muscular diaphragm but doesn t use a throat pump is just plain weird Here is a look at some of the techniques used to get air down into the lungs Buccal pumping swallowing air used by air breathing fish and amphibians Gular pumping using an actively pumping throat used by lizards and crocodilians Costal breathing moving ribs in and out all amniotes but ribless frogs Diaphragm breathing mammals Hepatic piston liver pumping crocodilians Air Sac pumping birds 2 Name Interestingly both crocodilians and birds use their pelvic hip muscles in breathing In the figure on the previous page A is a modern alligator When the rectus abdominis muscle contracts it pulls the pubis forward pushing the liver forward and forcing air out of the lungs expiration When the ischiopubic and diaphragmatic muscles contract it pulls the liver backwards causing the lungs to expand and draw in air inspiration B shows respiration in a pigeon During inspiration the sternum rotates downward and the longissimus dorsi muscles contracts to pull the tail up together these inflate some of the air sacs in the body During expiration the infrapubic and suprapubic abdominal muscles contract to pull the sternum up and the tail down pushing air out of the sacs Below is a drawing showing the air sac system of a bird in left lateral view C I AT PT and AB are different individual air sacs you don t need to worry about that level of detail The bold arrows show how the air sacs invade the vertebrae Farmer and Carrier have extrapolated back to suggest the following as the ancestral breathing condition for archosaurs that is the condition in the common ancestor of birds and crocodilians To the left below is the primitive archosaur Euparkeria As the ischiotruncus muscle contracts it pulls the gastralia belly ribs down which would expand the lungs It seems that such a mode of breathing might be possible for primitive theropods To the right is the hypothesized breath cycle for Allosaurus 3 Name 7 Dinosaurs tend to have long pubes and ischia for archosaurs How might these skeletal changes be related to an increased lung capacity 8 Ornithischian dinosaurs lack gastralia Would it be possible for them to use the ancestral archosaur mode of breath To the left are the pelves of some advanced ornithischians so that the pubis or the pubis plus ischium can move relative to the ilium 9 A is the pelvis of Triceratops in left lateral view Like other ceratopsids but unlike more primitive ceratopsians and most other ornithischians the pubis and ischium can move together as a unit As the rectus abdominis RA muscle contacted it would have pulled the pubis and ischium forward as the ischiocaudalis contracted it would have pulled the two bones back This motion is most similar to the breathing system in birds mammals crocodilians ancestral archosaurs 10 B is the pelvis of the hadrosaur Corythosaurus Its pubis like those of many advanced ornithopods was able to rotate slightly outward When the iliopubic muscle would contract the pubis would move slightly to the sides On the drawings to the left label which of the two dorsal overhead views shows the pelvis during inspiration and which in expiration 4 Name 11 Other than advanced ornithopods and ceratopsids the pelvic elements of ornithischians are immobile If mobile pelvic elements exist to help increase the oxygen flow and an increased oxygen flow is an indication of higher metabolic rate this suggests that the metabolic rates of advanced ornithopods and ceratopsians was greater the same slower than other ornithischians Extra Credit Ceratopsids and hadrosaurids also have a specialization of the jaws that make allowed them to slice or grind food up into tiny bits What adaptation is that 12 Below is a cervical neck vertebra of the ceratosaur Carnotaurus Labels A C D and E indicate openings into the vertebral bone Similar openings are found in all theropods and in sauropods