Dinosaur Body Temperatures
Allison Chowdhury, Ashley Beckles, Sebastian Palacio, Jillian
Villeneuve, Ekatherina Shlychkov
Introduction
●  Why do we care so much about big dinosaurs?
●  Are dinosaurs endotherms or ectotherms?
●  How can we discover this?
●  Through what methods can we discover this?
Sauropods
●  Largest terrestrial animals that have ever lived
●  Importance: Understanding their physiology
poses a challenge; Were they endotherms or
ectotherms?
Why are Sauropods important?
●  A body temperature model for most dinosaurs can be determined based on
that of a Sauropods’ model
Ectoderm or Endoderm, that is the question
●  Difference between ectotherms and endotherms
○  Ectotherms derive their heat from the environment
○  Endotherms regulate their body temperature by internal metabolism
heat production
■  have higher and more stable body temperatures
●  Since 1842, it was assumed that the metabolism of dinosaurs was similar
to ectothermic reptiles
●  However, in the 1960s and 1970s, evidence began emerging that
endothermy could be more consistent with scientific observations
What are the arguments in favor of
Endothermy?
●  More consistent with observations on
○  Dinosaur behavior- inferred physical performance, estimated running speeds, and predator/
prey ratios
○  Paleogeographic distribution
○  Anatomy of nonavian dinosaurs
●  Bone histology
○  Suggests high growth rates could not be sustained by a low basal metabolic rate
What are the arguments for ectothermy?
●  Modeling heat exchange by animals in the environment led researchers to
believe that endothermic sauropods would have problems with overheating
●  Gigantothermy (inertial homeothermy)- dinosaurs could achieve high body
temperatures because of their large mass
○  Problems: these models do not work on smaller dinosaur taxa
Objective of the study
●  Determine the body temperatures of
large Jurassic dinosaurs using clumped
isotope thermometry of teeth
●  Materials analyzed from 6 sites including
Tanzania, Wyoming, Oklahoma
Clumped Isotope Thermometry
●  Based on the degree of ordering of 13 C and 18O into bonds with each other
inside a carbonate mineral lattice, they are able to determine the body
temperature within 1-2 degrees Celsius
●  The abundance of 13C-18O bonds in the carbonate component of tooth
bioapatite from modern specimens decreases with increasing body
temperature of the animal
Why is tooth enamel important
●  There are large and closely packed apatite
crystals in tooth enamel
●  Teeth are mostly inorganic
●  These qualities can allow for geochemical
signatures to be preserved for a long time
●  Geochemical: showing the results of both
chemical and geological action
What did we do with the teeth
●  First we analyzed dentin from the same teeth, bone and sparry calcites to
define diagenetic end members
●  (Sparry Calcites are a crystalline mosaic of calcite crystals)
●  Diagenetic end members: Diagenesis is the change of sedimentary rock into
another type of sedimentary rock. An endmember is a mineral at the
extreme end of a mineral series in purity.
●  Well preserved enamel should yield distinct d13C and d18O values when
compared with materials that are known to be altered or are secondary
precipitates (fig. S3).
What we did with the teeth
●  Phosphate d18O (d18OPO4) was analyzed for each specimen
●  These values were compared with d18O values of carbonate in apatite
●  Because the oxygen isotope composition of phosphate groups is thought to
be especially well preserved over geologic time scales, deviations from this
offset can be used as an indicator of alteration of the carbonate component
because of reactions with diagenetic fluids.
What did we discover from the teeth
●  Samples were identified that were clearly altered and some samples that
appear to be well preserved.
●  Tooth enamel material from the Tendaguru Beds had average body
temperatures of 38.2 T 1.0°C (1 SE) from three Brachiosaurus teeth and
33.6 T 4.0°C from two sauropod teeth of a Diplodocinae
●  Camarasaurus well-preserved teeth yielded an average temperature of 36.9
T 1.0°C.
Fossils Used
●  The fossils studied were of the following:
●  Brachiosaurus Brancai from Tendaguru Beds in
Tanzania
●  A sauropod tentatively identified as belonging to
the subfamily Diplodocinae also from Tendaguru
Beds in Tanzania
●  Camarasaurus from sites in the Morrison
Formation
Samples Analyzed
Sauropod samples were collected from various locations
What we learn from Body Mass
●  In general the Body temperatures of vertebrates reflect the combined influences of:
○  metabolism
○  size
○  environmental temperature
●  In some cases it even reflected specialized physiological strategies for heat regulation
●  As a result the data taken in isolation, places quantitative constraints on sauropod physiology,
limiting the range of possible thermoregulatory strategies.
Measured Dinosaur Body Temperatures
Comparison of measured dinosaur body
temps to a previously published model
for scaling of body temps with body
mass
Why is there a difference between what
was expected beforehand and what was
found by Gillooly
Results
●  Largest sauropods had body temperatures cooler than Gillooly model
●  Possible explanation- adult sauropods had mechanisms to prevent
excessively high body temperatures being reached so they can regulate
body temperature
○  Examples:
■  Air sac system that serves as an internal cooling system
■  Long necks and tails could have facilitated heat dissipation by increasing surface area
Wrap-Up
Sauropods sustained high metabolic rates during ontogeny to reach gigantic size
A combination of physiological and behavioral adaptations and/or a slowing of
metabolic rate prevented overheating and avoided high body temperatures
Future Questions
Could these adaptations have compensated for high internal heat production
associated with endothermy?
OR...
Did large sauropods have both heat dissipating adaptations and a low basal
metabolism to maintain their body temperatures?