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Dinosaurs - warm or cold blooded?
Topic Started: Jan 26 2013, 11:18 PM (4,225 Views)
Varanus
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I understand that dinosaurs were warm-blooded for various reasons cited by Robert T Baker. Any reason to doubt him?
Edited by Varanus, Jan 26 2013, 11:18 PM.
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theropod
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I didn’t write greater, just great.
As I wrote, due to the numerous factors involved (starting with aerodynamics, different styles of flight or running etc.), I’m not sure how birds actually compare to other animals when performing truly comparable feats. All I know is that there are birds with amazing stamina.

Since I presume it’s aerobic capacity we are considering here, it’s important not to confuse the two things. There’s how much power an animal can produce, and how efficiently it uses it. That’s why for different locomotory styles, we see different adaptions.
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theropod
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You mean the paper about T. rex’ and Giganotosaurus’ metabolism?
http://palaeo-electronica.org/1999_2/gigan/text.pdf

Yeah, they also showed those theropods where energy-efficient compared to extant carnivores. But larger animals are generally more efficient as far as I know.
Edited by theropod, Jun 17 2014, 04:10 AM.
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Jinfengopteryx
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^Exactly this one.
The not greater was to say that the respiratory system doesn't make them superior to mammals. But as for your point on efficiency, I remember I wrote this Ursus and he didn't seem convinced:
http://carnivoraforum.com/single/?p=8429988&t=9445333
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Koolyote
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About bird stamina: The swifts are said to be capable of flying for two years without landing after leaving their nests, until they reach maturity that is, meaning they also feed, preen, sleep and even mate while in flight, now that must require extreme stamina compared to other animals. There's also the Frigate-birds which may fly months over the sea without landing.
Edited by Koolyote, Jun 17 2014, 05:58 AM.
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theropod
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My point was that such feats are not just matters of energy output, but also locomotor efficiency. Animals adapted to cover long distances one way or another will evolve adaptions to do so efficiently, so that’s a factor besides mere metabolism to consider.
For example, regardless of metabolism the built of a camel is far more efficient in terms of terrestrial locomotion than that of a crocodile, while the opposite is true in water–regardless of aerobic capacity. Or, another example, cats are endotherms, but yet have far less stamina than many other endotherms, such as canids, of comparable size, because of their built and their high percentage of anaerobic fast-twitch muscles.

So better stamina doesn’t automatically correspond to higher metabolic rates or vice versa.
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Jinfengopteryx
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I am very well aware of this that's common sense.
My point was that I used a very similar argument before (but not as well formulated), but that doesn't seem to be the explanation:

In contrast, my analysis suggests that, at the level of
the heart and convection of blood and oxygen around
the body, the capacity for VO2max and/or aerobic scope is
similar for birds and mammals and, therefore, that the
current values for the VO2max of birds and bats flying in
wind tunnels (figure 2) are likely to be maximal (Bishop
1997).



http://www.bangor.ac.uk/biology/publication_abstract.php?abstractid=000084108900006

Both, VO2 max (oxygen consumption) and aerobic scape are similar, if I got this right.

Here is something from the abstract (the quote above is from a long text block that Ursus quoted):

Quote:
 
The results show that the maximum sustainable metabolic rates of both birds and mammals are similar and scale as approximately the 0.88 +/- 0.02 power of body mass (and aerobic scope as approximately the 0.15 +/- 0.05 power), when the measurements are standardized with respect to the differences in relative heart mass and haemoglobin concentration between species.


Metabolism efficiency is not that terribly different.
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Vobby
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This is relevant:

http://theropoda.blogspot.it/2009/02/gli-uccelli-ed-il-limite-k-t.html#comment-form

it suggest that the reason for Neornithes being the only clade of dinosaurs surviving of the asteroid were their faster growth (and then reproductive) rates.
This may suggest also that I was actually wrong in considering anatomy as a decent predictor for metabolism since between some neornithes and some enantiornithes the physical differences weren't so drastic, I guess. This consideration is valid, of course, only assuming that grow rates are really good predictors for metabolism, being dictated by metabolic rates, which I still doubt.
Edited by Vobby, Jun 19 2014, 03:48 AM.
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theropod
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As you already suggested, they are probably not.
Animals can grow with very different speeds, and that depends on more than just metabolism. In birds, I could imagine it is somehow linked to flight requiring birds to grow and mature quickly.
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Vobby
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I don't know if the point is flight, the fact that several enantiornithes were flyiers may suggest otherwise. I wonder if it's even possible for a cold blooded or "mesothermic" animal to effectively fly, if not, so if enantiornithes were necessarily completely endothermic, we can safely exclude the linkage between metabolism and grow rates.
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theropod
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It may have to do with specialization for flight. Adaptions can take some time to develop, that doesn’t mean they are not advantageous. for example it took primates a fairly long time to evolve brains over 1000ml in volume, which doesn’t mean they are not important for them. Perhaps the key to neoornithine success is that they grew faster, who knows…
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Thalassophoneus
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I think they were warm-blooded. Except for Spinosaurus. It was probably warm all cold-blooded depending on what it preferred.
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Taipan
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Dinosaurs were likely warm-blooded

Date: May 28, 2015
Source: Stony Brook University
Summary:
Dinosaurs grew as fast as your average living mammal, according to a new research article. The article is a re-analysis of a widely publicized 2014 Science paper on dinosaur metabolism and growth that concluded dinosaurs were neither ectothermic nor endothermic -- terms popularly simplified as 'cold-blooded' and 'warm-blooded' -- but instead occupied an intermediate category.

Posted Image
A microscopic image of the thigh bone (femur) of a dinosaur shows concentric rings. Like tree rings, they formed each year in the dinosaur's bones during the season when resources were scarce. The rings represent unrecorded time, so an annual growth rate (dashed line in graph) is an underestimate relative to the true growth rate during the favorable growing season.
Credit: Scott Hartman


Dinosaurs grew as fast as your average living mammal, according to a research paper published by Stony Brook University paleontologist Michael D'Emic, PhD. The paper, to published in Science on May 29, is a re-analysis of a widely publicized 2014 Science paper on dinosaur metabolism and growth that concluded dinosaurs were neither ectothermic nor endothermic -- terms popularly simplified as 'cold-blooded' and 'warm-blooded' -- but instead occupied an intermediate category.

"The study that I re-analyzed was remarkable for its breadth -- the authors compiled an unprecedented dataset on growth and metabolism from studies of hundreds of living animals," said Dr. D'Emic, a Research Instructor in the Department of Anatomical Sciences as Stony Brook, when referring to "Evidence for mesothermy in dinosaurs."

"Upon re-analysis, it was apparent that dinosaurs weren't just somewhat like living mammals in their physiology -- they fit right within our understanding of what it means to be a 'warm-blooded' mammal," he said.

Dr. D'Emic specializes in bone microanatomy, or the study of the structure of bone on scales that are just a fraction of the width of a human hair. Based on his knowledge of how dinosaurs grew, Dr. D'Emic re-analyzed that study, which led him to the strikingly different conclusion that dinosaurs were more like mammals than reptiles in their growth and metabolism.

Dr. D'Emic re-analyzed the study from two aspects. First, the original study had scaled yearly growth rates to daily ones in order to standardize comparisons.

"This is problematic," Dr. D'Emic explains, "because many animals do not grow continuously throughout the year, generally slowing or pausing growth during colder, drier, or otherwise more stressful seasons.

"Therefore, the previous study underestimated dinosaur growth rates by failing to account for their uneven growth. Like most animals, dinosaurs slowed or paused their growth annually, as shown by rings in their bones analogous to tree rings," he explained.

He added that the growth rates were especially underestimated for larger animals and animals that live in very stressful or seasonal environments -- both of which characterize dinosaurs.

The second aspect of the re-analysis with the original study takes into account that dinosaurs should be statistically analyzed within the same group as living birds, which are also warm-blooded, because birds are descendants of Mesozoic dinosaurs.

"Separating what we commonly think of as 'dinosaurs' from birds in a statistical analysis is generally inappropriate, because birds are dinosaurs -- they're just the dinosaurs that haven't gone extinct."

He explained that re-analyzing the data with birds as dinosaurs lends more support that dinosaurs were 'warm-blooded,' not occupants of a special, intermediate metabolic category.

According to Holly Woodward, Assistant Professor in the Center for Health Sciences at Oklahoma State University, Dr. D'Emic's re-analysis is crucial to building research on the metabolism and development of dinosaurs.

"D'Emic's study reveals how important access to the data behind published results is for hypothesis testing and advancing our understanding of dinosaur growth dynamics," said Woodward.

Dr. D'Emic hopes that his study will also spur new research into when, why, and how pauses or slowdowns in growth are recorded in bones, which may have implications in the development of other species and in the study of bone diseases such as osteoporosis.



http://www.sciencedaily.com/releases/2015/05/150528140937.htm





Journal References:
M. D. D’Emic. Comment on “Evidence for mesothermy in dinosaurs”. Science, 2015 DOI: 10.1126/science.1260061

ABSTRACT
Grady et al. (Reports, 13 June 2014, p. 1268) suggested that nonavian dinosaur metabolism was neither endothermic nor ectothermic but an intermediate physiology termed “mesothermic.” However, rates were improperly scaled and phylogenetic, physiological, and temporal categories of animals were conflated during analyses. Accounting for these issues suggests that nonavian dinosaurs were on average as endothermic as extant placental mammals.

http://www.sciencemag.org/content/348/6238/982.2

J. M. Grady, B. J. Enquist, E. Dettweiler-Robinson, N. A. Wright, F. A. Smith. Evidence for mesothermy in dinosaurs. Science, 2014; 344 (6189): 1268 DOI: 10.1126/science.1253143

ABSTRACT
Were dinosaurs ectotherms or fast-metabolizing endotherms whose activities were unconstrained by temperature? To date, some of the strongest evidence for endothermy comes from the rapid growth rates derived from the analysis of fossil bones. However, these studies are constrained by a lack of comparative data and an appropriate energetic framework. Here we compile data on ontogenetic growth for extant and fossil vertebrates, including all major dinosaur clades. Using a metabolic scaling approach, we find that growth and metabolic rates follow theoretical predictions across clades, although some groups deviate. Moreover, when the effects of size and temperature are considered, dinosaur metabolic rates were intermediate to those of endotherms and ectotherms and closest to those of extant mesotherms. Our results suggest that the modern dichotomy of endothermic versus ectothermic is overly simplistic.

http://www.sciencemag.org/content/344/6189/1268
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Taipan
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Sun-warmed dinosaurs may have been surprisingly good sprinters
Some had the ability to warm themselves by drawing heat from the sun


Date: October 13, 2015
Source: University of California - Los Angeles
Summary:
Were dinosaurs really fast, aggressive hunters like the ones depicted in the movie 'Jurassic World'? Or did they have lower metabolic rates that made them move more like today's alligators and crocodiles? New research indicates that some dinosaurs, at least, had the capacity to elevate their body temperature using heat sources in the environment, such as the sun.

Posted Image
This is an artist's rendering of oviraptorid theropods.
Credit: Doyle Trankina and Gerald Grellet-Tinner

Were dinosaurs really fast, aggressive hunters like the ones depicted in the movie "Jurassic World"? Or did they have lower metabolic rates that made them move more like today's alligators and crocodiles? For 150 years, scientists have debated the nature of dinosaurs' body temperatures and how those temperatures influenced their activity levels.

New research by UCLA scientists indicates that some dinosaurs, at least, had the capacity to elevate their body temperature using heat sources in the environment, such as the sun. They also believe the animals were probably more active than modern-day alligators and crocodiles, which can be active and energetic, but only for brief spurts.

The researchers also found evidence that other dinosaurs they studied had lower body temperatures than modern birds, their only living relatives, and were probably less active.

The research is published in the journal Nature Communications.

Led by Robert Eagle, a researcher in the department of earth, planetary and space sciences in the UCLA College, the scientists examined fossilized dinosaur eggshells from Argentina and Mongolia. Analyzing the shells' chemistry allowed them to determine the temperature at which the eggshells formed -- information that had not been previously known.

"This technique tells you about the internal body temperature of the female dinosaur when she was ovulating," said Aradhna Tripati, a co-author of the study and a UCLA assistant professor of geology, geochemistry and geobiology. "This presents the first the direct measurements of theropod body temperatures."

The Argentine eggshells, which are approximately 80 million years old, are from large, long-necked titanosaur sauropods, members of a family that include the largest animals to ever roam Earth. The shells from Mongolia's Gobi desert, 71 million to 75 million years old, are from oviraptorid theropods, much smaller dinosaurs that were closely related to Tyrannosaurus rex and birds.

Sauropods' body temperatures were warm -- approximately 100 degrees Fahrenheit, according to the study. The smaller dinosaurs had substantially lower temperatures, probably below 90 degrees.

Warm-blooded animals, or endotherms, produce heat internally and typically maintain their body temperature, regardless of the temperature of their environment; they do so mainly through metabolism. Humans and other mammals fall into this category.

Cold-blooded animals, or ectotherms, including alligators, crocodiles and lizards, rely on external environmental heat sources to regulate their body temperature. Lizards, for example, often sit on rocks in the sun to absorb heat, which enables them to be more active.

Scientists have debated since the 19th century whether dinosaurs were endotherms or ectotherms. The UCLA research indicates that the answer could lie somewhere in between. The dinosaurs, at least the oviraptorid theropods, had the ability to elevate their body temperature above the environmental temperature.

"The temperatures we measured suggest that at least some dinosaurs were not fully endotherms like modern birds," Eagle said. "They may have been intermediate -- somewhere between modern alligators and crocodiles and modern birds; certainly that's the implication for the oviraptorid theropods."

"This could mean that they produced some heat internally and elevated their body temperatures above that of the environment but didn't maintain as high temperatures or as controlled temperatures as modern birds," he added. "If dinosaurs were at least endothermic to a degree, they had more capacity to run around searching for food than an alligator would."

The study was the first direct measurement of body temperatures in two types of dinosaurs. Tripati said it shows clearly that they are different from each other.

The researchers also analyzed fossil soils, including minerals that formed in the upper layer of the soil on which the oviraptorid theropods' nests were built. This enabled them to estimate that the environmental temperature in Mongolia shortly before the dinosaurs went extinct was approximately 79 degrees Fahrenheit.

"The oviraptorid dinosaur body temperatures were higher than the environmental temperatures -- suggesting they were not truly cold-blooded, but intermediate," Tripati said.

Eagle, Tripati and their colleagues initially measured modern eggshells from 13 bird species and nine reptiles to establish their ability to measure body temperature from the chemistry of eggshells.

The researchers measured, in calcium carbonate minerals, the subtle differences in the abundance of chemical bonding between two rare, heavy isotopes: carbon-13 and oxygen-18. They studied the extent to which these heavy isotopes clustered together using a mass spectrometer -- a technique that enabled them to determine mineral formation temperatures. Mineral forming inside colder bodies has more clustering of isotopes.

The scientists analyzed six fossilized eggshells from Argentina, three of which were well-preserved, and 13 eggshells from Mongolia's Gobi desert, again selecting three that are well-preserved. They determined whether the fossilized eggshells maintain their original chemistry or were altered over tens of millions of years. They also analyzed fossilized dinosaur eggshells from France, but found these were not well-preserved, and excluded them.

The researchers acquired the Argentine eggshells from the Los Angeles County Natural History Museum, and the eggshells from Mongolia's Gobi desert from New York's American Natural History Museum.

Eagle, Tripati and colleagues published the first analysis of fossilized dinosaur teeth in the journal Science in 2011. They studied the chemistry of fossil teeth to measure the body temperature of titanosaur sauropods, and determined their body temperature was between approximately 95 and 100.5 degrees Fahrenheit. The new research on eggshells is consistent with the 2011 findings, and adds new body temperature data on oviraptorid theropods.

Story Source: University of California - Los Angeles. "Sun-warmed dinosaurs may have been surprisingly good sprinters: Some had the ability to warm themselves by drawing heat from the sun." ScienceDaily. www.sciencedaily.com/releases/2015/10/151013135543.htm (accessed October 14, 2015).




Journal Reference:
Robert A. Eagle, Marcus Enriquez, Gerald Grellet-Tinner, Alberto Pérez-Huerta, David Hu, Thomas Tütken, Shaena Montanari, Sean J. Loyd, Pedro Ramirez, Aradhna K. Tripati, Matthew J. Kohn, Thure E. Cerling, Luis M. Chiappe, John M. Eiler. Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs. Nature Communications, 2015; 6: 8296 DOI: 10.1038/ncomms9296

Abstract
Our understanding of the evolutionary transitions leading to the modern endothermic state of birds and mammals is incomplete, partly because tools available to study the thermophysiology of extinct vertebrates are limited. Here we show that clumped isotope analysis of eggshells can be used to determine body temperatures of females during periods of ovulation. Late Cretaceous titanosaurid eggshells yield temperatures similar to large modern endotherms. In contrast, oviraptorid eggshells yield temperatures lower than most modern endotherms but ~6 °C higher than co-occurring abiogenic carbonates, implying that this taxon did not have thermoregulation comparable to modern birds, but was able to elevate its body temperature above environmental temperatures. Therefore, we observe no strong evidence for end-member ectothermy or endothermy in the species examined. Body temperatures for these two species indicate that variable thermoregulation likely existed among the non-avian dinosaurs and that not all dinosaurs had body temperatures in the range of that seen in modern birds.

http://www.nature.com/ncomms/2015/151013/ncomms9296/full/ncomms9296.html
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