Welcome Guest [Log In] [Register]
Welcome to Carnivora. We hope you enjoy your visit.


You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are some features you can't use. If you join our community, you'll be able to access member-only sections, and use many member-only features such as customizing your profile and voting in polls. Registration is simple, fast, and completely free.


Join our community!


If you're already a member please log in to your account to access all of our features:

Username:   Password:
Add Reply
  • Pages:
  • 1
  • 2
Dinosaurs - warm or cold blooded?
Topic Started: Jan 26 2013, 11:18 PM (4,227 Views)
Varanus
Autotrophic Organism
[ *  * ]
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.
Offline Profile Quote Post Goto Top
 
Replies:
Ausar
Member Avatar
Xi-miqa-can! Xi-miqa-can! Xi-miqa-can!
[ *  *  *  *  *  *  *  * ]
Whatever floats your boat.......
Offline Profile Quote Post Goto Top
 
JD-man
Autotrophic Organism
[ *  * ]
JD-man
Jan 27 2013, 10:36 AM
There's no doubt that non-avian dinos were more endothermic (I.e. Warm-blooded) than living non-avian reptiles. The question is how endothermic were they? As indicated by the following quote, non-maniraptoran dinos were probably mesothermic & non-avian maniraptorans were apparently endothermic.


To add to the above quote from page 1, see the following quotes.

JD-man
Jun 15 2013, 03:11 AM
For more info [about mesothermy], see Chapter 11 in "Dinosaur Odyssey: Fossil Threads in the Web of Life" ( http://www.amazon.com/Dinosaur-Odyssey-Fossil-Threads-Life/dp/0520269896/ref=sr_1_1?s=books&ie=UTF8&qid=1371227367&sr=1-1 ) & Chapter 38 in "The Complete Dinosaur" ( http://www.amazon.com/Complete-Dinosaur-Life-Past/dp/0253357012/ref=sr_1_1?s=books&ie=UTF8&qid=1371227250&sr=1-1 ).


JD-man
Jun 15 2013, 08:14 AM
As far as I know, Reid's scientific paper (I.e. Chapter 38 in "The Complete Dinosaur") isn't available online. However, Sampson's semi-technical overview is (See 203-220/361: http://www.doc88.com/p-102817110518.html ) &, unlike said paper (which leaves feathered dino metabolism as an open question), explains how we know that non-avian maniraptorans were probably endothermic.
Edited by JD-man, Jul 30 2013, 02:55 PM.
Offline Profile Quote Post Goto Top
 
JD-man
Autotrophic Organism
[ *  * ]
Taipan
Jul 18 2013, 09:57 PM
New Evidence for Warm-Blooded Dinosaurs

July 17, 2013 — University of Adelaide research has shown new evidence that dinosaurs were warm-blooded like birds and mammals, not cold-blooded like reptiles as commonly believed.
In a paper published in PLoS ONE, Professor Roger Seymour of the University's School of Earth and Environmental Sciences, argues that cold-blooded dinosaurs would not have had the required muscular power to prey on other animals and dominate over mammals as they did throughout the Mesozoic period.
"Much can be learned about dinosaurs from fossils but the question of whether dinosaurs were warm-blooded or cold-blooded is still hotly debated among scientists," says Professor Seymour.
"Some point out that a large saltwater crocodile can achieve a body temperature above 30°C by basking in the sun, and it can maintain the high temperature overnight simply by being large and slow to change temperature.
"They say that large, cold-blooded dinosaurs could have done the same and enjoyed a warm body temperature without the need to generate the heat in their own cells through burning food energy like warm-blooded animals."
In his paper, Professor Seymour asks how much muscular power could be produced by a crocodile-like dinosaur compared to a mammal-like dinosaur of the same size.
Saltwater crocodiles reach over a tonne in weight and, being about 50% muscle, have a reputation for being extremely powerful animals.
But drawing from blood and muscle lactate measurements collected by his collaborators at Monash University, University of California and Wildlife Management International in the Northern Territory, Professor Seymour shows that a 200 kg crocodile can produce only about 14% of the muscular power of a mammal at peak exercise, and this fraction seems to decrease at larger body sizes.
"The results further show that cold-blooded crocodiles lack not only the absolute power for exercise, but also the endurance, that are evident in warm-blooded mammals," says Professor Seymour.
"So, despite the impression that saltwater crocodiles are extremely powerful animals, a crocodile-like dinosaur could not compete well against a mammal-like dinosaur of the same size.
"Dinosaurs dominated over mammals in terrestrial ecosystems throughout the Mesozoic. To do that they must have had more muscular power and greater endurance than a crocodile-like physiology would have allowed."
His latest evidence adds to that of earlier work he did on blood flow to leg bones which concluded that the dinosaurs were possibly even more active than mammals.

Posted Image
T. rex (artist's rendering).
For an interesting read about the above quote, see the following quote.

Quoting John Conway ( http://log.johnconway.co/post/55787508635/stupid-ugly-dinosaur-imagery ):
Quote:
 
This is a rather strange piece, written like it’s still 1987 and people are still seriously arguing that dinosaurs were ectotherms, but that’s not the point of this rant. The point of this rant is to complain about the shitty T. rex (what else?) adorning the article.

It’s hardly the worst thing I’ve ever seen. It might even be middle-of-the-roadish as these things go, but for some reason it really got my goat. Photographs of toys do not constitute scientific illustration. Not even for popular science websites.

I know why this happens, the stock photo libraries (even the scientific ones) are chock full of this shit.

I suppose I should be glad that mainstream outlets are still so craptacular, more kudos to us more serious types, right?
Offline Profile Quote Post Goto Top
 
Taipan
Member Avatar
Administrator

Warm or Cold? Dinosaurs Had 'In-Between' Blood

By Charles Q. Choi, Live Science Contributor | June 12, 2014 02:15pm ET

Posted Image
Comparative growth rates in vertebrates. Dinosaurs grew intermediate to endothermic mammals and birds and ectothermic reptiles and fish, but closest to living mesotherms.

Dinosaurs may not have been cold-blooded like modern reptiles or warm-blooded like mammals and birds — instead, they may have dominated the planet for 135 million years with blood that ran neither hot nor cold, but was a kind of in-between that's rare nowadays, researchers say.

Modern reptiles such as lizards, snakes and turtles are cold-blooded or ectothermic, meaning their body temperatures depend on their environments. Birds and mammals, on the other hand, are warm-blooded, meaning they control their own body temperatures, attempting to keep them at a safe constant — in the case of humans, at about 98.6 degrees Fahrenheit (37 degrees Celsius).

Dinosaurs are classified as reptiles, and so for many years scientists thought the beasts were cold-blooded, with slow metabolisms that forced them to lumber across the landscape. However, birds are modern-day dinosaurs and warm-blooded, with fast metabolic rates that give them active lifestyles, raising the question of whether or not their extinct dinosaur relatives were also warm-blooded.

Animal metabolism

To help solve this decades-old mystery, researchers developed a new method for analyzing the metabolism of extinct animals. They found "dinosaurs do not fit comfortably into either the cold-blooded or warm-blooded camp — they genuinely explored a middle way," said lead study author John Grady, a theoretical ecologist at the University of New Mexico.

Scientists often seek to deduce the metabolisms of extinct animals by looking at the rates at which their bones grow. The method resembles cutting into a tree and looking at the thickness of the rings of wood within, which can reveal how well or poorly that tree grew any given year. Similarly, looking at the way bone is deposited in layers in fossils reveals how quickly or slowly that animal might have grown.

Grady and his colleagues not only looked at growth rings in fossils, but also sought to estimate their metabolic rates by looking at changes in body size as animals grew from birth to adults. The researchers looked at a broad spectrum of animals encompassing both extinct and living species, including cold- and warm-blooded creatures, as well as dinosaurs.

The scientists found growth rate to be a good indicator of metabolic rates in living animals, ranging from sharks to birds. In general, warm-blooded mammals that grow about 10 times faster than cold-blooded reptiles also metabolize about 10 times faster.

When the researchers examined how fast dinosaurs grew, they found that the animals resembled neither mammals nor modern reptiles, and were neither ectotherms nor endotherms. Instead, dinosaurs occupied a middle ground, making them so-called "mesotherms."

Modern mesotherms

Today, such energetically intermediate animals are uncommon, but they do exist. For instance, the great white shark, tuna and leatherback sea turtle are mesotherms, as is the echidna, an egg-laying mammal from Australia. Like mammals, mesotherms generate enough heat to keep their blood warmer than their environment, but like modern reptiles, they do not maintain a constant body temperature.

"For instance, tuna body temperature declines when they dive into deep, colder waters, but it always stays above the surrounding water," Grady told Live Science.

Body size may play a role in mesothermy, because larger animals can conserve heat more easily. "For instance, leatherback sea turtles are mesotherms, but smaller green sea turtles are not," Grady said. However, mesothermy does not depend just on large size. "Mako sharks are mesotherms, but whale sharks are regular ectotherms," Grady said.

Endotherms can boost their metabolisms to warm up — "for instance, we shiver when cold, which generates heat," Grady said. "Mesotherms have adaptations to conserve heat, but they do not burn fat or shiver to warm up. Unlike us, they don't boost their metabolic rate to stay warm."

Some animals are what are known as gigantotherms, meaning they are just so massive that they maintain heat even though they do not actively control their body temperature.

"Gigantotherms like crocodiles rely on basking to heat up, so they are not mesotherms," Grady said. "Gigantotherms are slower to heat up and cool down, but if they rely on external heat sources like the sun, then they are not mesotherms. In general, mesotherms produce more heat than gigantotherms and have different mechanisms for conserving it."

Advantages of being a mesotherm

Mesothermy would have permitted dinosaurs to move, grow and reproduce faster than their cold-blooded reptilian relatives, making the dinosaurs more dangerous predators and more elusive prey. This may explain why dinosaurs dominated the world until their extinction about 65 million years ago, Grady suggested.

At the same time, dinosaurs' lower metabolic rates compared to mammals allowed them to get by on less food. This may have permitted the enormous bulk that many dinosaur species attained. "For instance, it is doubtful that a lion the size of T. rex would be able to eat enough wildebeests or elephants without starving to death," Grady said. "With their lower food demands, however, a real T. rex was able to get by just fine."

All in all, Grady suspected that where direct competition occurs, warm-blooded endotherms suppress mesotherms, mesotherms suppress active but cold-blooded ectotherms, and active ectotherms suppress more lethergic sit-and-wait ectotherms

Although mesothermy appears widespread among dinosaurs, not every dinosaur was necessarily a mesotherm, Grady said. "Dinosaurs were a big and diverse bunch, and some may have been endotherms or ectotherms," he said. "In particular, feathered dinosaurs are a bit of a mystery. What do you call a metabolically intermediate animal covered in feathers? Is it like the mesothermic echidna? Or just a low-power endotherm?"

The first bird, Archaeopteryx, "was more like a regular dinosaur than any living bird," Grady said. "It grew to maturity in about two years. In contrast, a similarly sized hawk grows in about six weeks, almost 20 times faster. Despite feathers and the ability to take flight, the first birds were not the active, hot-blooded fliers their descendants came to be."

These findings could help shed light on how warm-blooded animals such as humans evolved.

"The origins of endothermy in mammals and birds are unclear," Grady said. Studying the growth rates of the ancestors of birds and mammals "will shed light on these mysterious creatures."

The scientists detailed their findings in the June 13 issue of the journal Science.

http://www.livescience.com/46293-dinosaurs-had-in-between-blood.html




Evidence for mesothermy in dinosaurs

John M. Grady, Brian J. Enquist, Eva Dettweiler-Robinson, Natalie A. Wright, Felisa A. Smith
Science 13 June 2014:
Vol. 344 no. 6189 pp. 1268-1272
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
Offline Profile Quote Post Goto Top
 
Arovinrac
Member Avatar
Herbivore
[ *  *  *  * ]
http://www.bbc.co.uk/news/science-environment-27794723

Dinosaurs not 'warm' or 'cold' blooded, are in between the two.
Posted Image
Left (Ectothermic-cold blooded) Middle (Mesothermic) Right (Endothermic-warm blooded)
Offline Profile Quote Post Goto Top
 
Spinosuchus
Member Avatar
Unicellular Organism
[ * ]
Hmm. Interesting find! I don't feel like reading the entire article right now, but maybe I will read in a bit.

I have thought that dinosaurs would be warm-blooded most likely given their body postures, which were far more reminiscent of those of modern warm-blooded animals than those of reptiles (they held their legs underneath their bodies and did not undulate like modern reptiles; instead they would have had a locomotion style more similar to birds and large mammals such as elephants and rhinos (for the large herbivorous groups of course, with theropods representing the former)
Offline Profile Quote Post Goto Top
 
Marek
Member Avatar
Herbivore
[ *  *  *  * ]
I, firstly, did not know that this was an entirely unprecedented revelation; I thought it was an already commonplace hypothesis that dinosaurs were intermediates between endotherms and ectotherms. In any case, I do not find their potential mesothermy as being unreasonable; after all, the leatherback sea turtle evolved that very condition in what might be reduced to an attempt to economize thermoregulation, so although its descendants might bear characteristics more reminiscent of endotherms, this is absolutely unnecessary, and it would make sense for them to maintain the few additional characteristics they already bear (as they do not demand significantly improved metabolism or greater food consumption). Dinosaurs, being a superset of Aves, would be expected to have at some time evinced the transition from ectothermy to endothermy (given that other Archosaurs, including the extant Crocodilians, remain cold-blooded). This shift would not have been rapid, considering the number of factors involved, and might not have been very necessary. It is very possible that dinosaurs which tended towards flight developed better metabolic capabilities in an effort to fuel their energetically expensive endeavors, and this in turn rendered ectothermic habits obsolete.
Offline Profile Quote Post Goto Top
 
Marek
Member Avatar
Herbivore
[ *  *  *  * ]
Another interesting idea: perhaps large animals, such as dinosaurs and the leatherback sea turtle, tend towards endothermy due to its efficiency relative to ectothermy at sufficiently dilated scales. This is because basking is made extremely inefficient at these levels, owing to the square-cube law (less surface area means, obviously, less heat transfer, but greater volume means a more voluminous hemocoel, and thus more blood, which in turn requires a greater demand for heat).
Offline Profile Quote Post Goto Top
 
Vobby
Member Avatar
Omnivore
[ *  *  *  *  * ]
Marek
Jun 15 2014, 11:32 AM
Another interesting idea: perhaps large animals, such as dinosaurs and the leatherback sea turtle, tend towards endothermy due to its efficiency relative to ectothermy at sufficiently dilated scales. This is because basking is made extremely inefficient at these levels, owing to the square-cube law (less surface area means, obviously, less heat transfer, but greater volume means a more voluminous hemocoel, and thus more blood, which in turn requires a greater demand for heat).
Your idea suffers from a contraddiction: if the bigger the animal gets the more endotherm it should be, how do you explain the fact that birds are both the smallest dinosaurs and perhaps the more athletic and entothermic?

I think that the matter is particularly complicated, more than how it appears. First of all, it doesn't make much sense to talk about dinosaurs in general, both becouse they was drastically different in size, respiratory system and behaviour, and becouse they very early splitted in very different groups, ornitiscians from saurischians, prosauropods from theropods and so on.
So, to know that the study used 21 "dinosaurs" ins't really very meaningful, also becouse I don't get if they divided mesozoic dinosaurs from extant ones.

Besides all of this, grow rates as evidence can be quite problematic: are humans less endothermic than carnivorans, for example? No, but we do grow ridicoulously slower! At ten years a human is a child, a wolf or a lion is old or dead. Also, I'm quite sure to remember that grow rates varied a lot also in two clades of basal birds, but I doubt that they have very different thermoregulation and metabolism.

But I agree about the basic idea which seems to be suggested by the article, which is the existence of a spectrum of thermoregulation and metabolic rates, instead of fixed categories of endothermy and ectothermy.

Also, I think a crucial thing would be to understand how low metabolic rates can be related with efficient respiratory system: for example sauropods had an avian system, which is the only one with which is possible to achieve such absurd sizes and breath through those long necks. How athletic could have been an animal the size of a wolf, with the lungs of a bird and the metabolism of an iguana? In geral, it may be that I haven't really clear the relations between metabolism, temperature, respiration and athletic capabilities, but they are crucial here.

I think that a good start to understand metabolism and, as a consequence, athleticity in an animal is to observe its anatomy. For example, a ceratopsian may have the same weight of an elephant, while being much more anatomically build for athleticism (thanks blaze and theropod for the suggestion). Would it make sense for the ceratopsian to be metabolically speaking less athletic than the elephant, so unable to use its anatomy? Or would it make more sense being comparable in metabolism---> athleticity to animals physically similar to it, like rhinos? Note that this isn't an idea of mine, but has been used by scientists to understand the metabolism of Ichtyosaurs, comparing its anatomy to that of extant fishes and cetaceans, in order to understand how fast could them have moved and how fast its metabolism therefore was:

http://www.geotimes.org/mar02/NN_tuna.html

"But while previous models estimated the speed of aquatic reptiles based on an assumption of their metabolic rates, Motani’s model, reported in the Jan. 17 Nature, instead uses external characteristics that can be measured directly from a fossil. He calculated how the mechanical properties of its body shape helped an ichthyosaur move through the fluid medium of the ocean. To determine the predictability of his mathematical model, he compared his results to the steady swimming speeds of 12 different living species of whales, dolphins, fish and other marine cruisers.

When he saw his model fit tightly with the empirical data, he turned to study several specimens of the Early Jurassic ichthyosaur called Stenopterygius."


"The tail of a large fish determines the size of its wake and consequently the amount of thrust it can produce. The tips of the tail flukes act as oscillating foils producing an expected power output. Motani developed a few equations to quantify the constraints of swimming for animals with tuna-like tails, tunas being the common reference fish for the design even through they weren’t around until the Pliocene. Ichthyosaurs, he discovered, with lengths ranging from 0.45 meters to 2.4 meters, swam most efficiently at speeds between 1.3 and 1.6 meters per second, slightly slower than whales and dolphins of the same size and more like tunas. "

" here Motani took physical measurements, compared them with modern taxa, like tuna and lamnid shark, and demonstrated using his model that yes, they had a similar cruising speed and, ultimately, raised basal metabolic rates — just like tuna.”
Edited by Vobby, Jun 17 2014, 12:18 AM.
Offline Profile Quote Post Goto Top
 
theropod
Member Avatar
palaeontology, open source and survival enthusiast
[ *  *  *  *  *  *  *  * ]
I’m generally agreed with vobby.

One thing: The tracheae of sperm whales are comparable in lenght to those of many sauropods, so their breathing system apparently works too. And the reason for bird athleticism is actually their size, it enables them to perform feats that a larger animal could not do, no matter how high its metabolic rate.

@marek: You are certainly right in terms of size being an advantage for insulation. It is for this very reason that the metabolic rates of large animals don’t have to be as high as those of small ones. Larger animals loose less heat in relation to their body weight, so they also have to produce less.

Offline Profile Quote Post Goto Top
 
Black Ice
Member Avatar
Drom King
[ *  *  *  *  *  *  *  * ]
The new argument we will here from everyone

"It may be better than a crocodile but it's still worse than a mammals."
Online Profile Quote Post Goto Top
 
Vobby
Member Avatar
Omnivore
[ *  *  *  *  * ]
theropod
Jun 17 2014, 02:10 AM
I’m generally agreed with vobby.

One thing: The tracheae of sperm whales are comparable in lenght to those of many sauropods, so their breathing system apparently works too. And the reason for bird athleticism is actually their size, it enables them to perform feats that a larger animal could not do, no matter how high its metabolic rate.

Didn't know about sperm whales, cool, but isn't cetaceans respiratory system a little different and particularly specialized amongst Mammalia? I don't really know how, but they just must breath "better", and hold on more, than every other mammal but seals.

About birds, note that they can be far more athletic than similar sized mammals and other reptiles. Flight is the most fatigous way of moving, and migratory birds can still do this with great proficiency even at the highest altitudes, while no bat, for example, could achieve similar feats.
Offline Profile Quote Post Goto Top
 
theropod
Member Avatar
palaeontology, open source and survival enthusiast
[ *  *  *  *  *  *  *  * ]
Afaik cetaceans, at least when diving deep, don’t actually keep any air in their lungs, they store the entire oxygen in their bloodstream. But I’m not very knowledgeable on that part of their physiology.
In any case their respiratory system isn’t the same as birds’, so at least there are other systems that allow breathing through long tracheae.

There are certainly numerous reasons why birds have such great stamina when flying.
Offline Profile Quote Post Goto Top
 
Sam1
Herbivore
[ *  *  *  * ]
I have no doubt in my mind that all big theropod and sauropod dinosaurs were endothermic just like mammals and birds.

All logic points towards that assumption
Offline Profile Quote Post Goto Top
 
Jinfengopteryx
Member Avatar
Aspiring paleontologist, science enthusiast and armchair speculative fiction/evolution writer
[ *  *  *  *  *  *  *  * ]
OK theropod, you were right with the gigantothermy theory you told me in 2012. Even though this doesn't surprise me at all, since I remember the study on theropod energy efficiency (I can post it if you want).
theropod
Jun 17 2014, 03:12 AM
There are certainly numerous reasons why birds have such great stamina when flying.
Hasn't Ursus shown that the greater stamina in birds is a common fallacy?
Offline Profile Quote Post Goto Top
 
1 user reading this topic (1 Guest and 0 Anonymous)
DealsFor.me - The best sales, coupons, and discounts for you
Go to Next Page
« Previous Topic · Debate & discussion of dinosaur related topics. · Next Topic »
Add Reply
  • Pages:
  • 1
  • 2

Find this theme on Forum2Forum.net & ZNR exclusively.