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Dinosaurs May Have Been Neither Warm-blooded Nor Cold-Blooded
An anonymous reader writes An article published in Science (abstract) points to the possibility that dinosaurs were mesotherms more akin to modern Tuna. Their internal temperature would have been warmer than their surrounding environment, conferring on them the ability to move more quickly than any ectotherm ("cold blooded" animal), but wouldn't have been constant or as warm as any endoderm ("warm blooded" animal). Their energy use and thus their necessary food intake would have been greater than an ectotherm, but much less than an endotherm. In order to arrive at this possibility, bone growth rings in fossilized bone were used to establish growth rates and then compared to modern ectotherms and endotherms.
Scientists have deemed it "just right".
So did the dinosaurs become birds or were they parallel evolved species after some earlier branching point?
Sounds likely, if birds are their warm-blooded descendants.
TFA makes this sound like a new theory, but the first time I read an article proposing this (with supporting evidence) was at least 20 years ago, and may well have been longer ago than that.
It's nice that they've come up with more evidence for it, but it would also be nice if every time someone tested an idea out they didn't feel compelled to pretend they were the first to have it.
Now that the false dichotomy between cold-blooded and hot-blooded has been debunked, let's work on that pesky false dichotomy between animals and plants.
You see, son, this kind of thing is what makes you a moron in everyone's eyes.
As a side note, republicans have quietly cut funding over the years for dinosaur research to support their creationism agenda. We will see less and less of this type of great paleontology research largely due to the United States.
Are these classifications entirely distinct? Or do we see animals existing along a range from one end to another?
Have gnu, will travel.
...juuust right!
They're Kombat Blooded.
I first posed the question to my elementary school science teacher circa 1973 whether the dinosaurs weren't in some way usefully self-warming. I didn't have the vocabulary about homeostasis or mesotherms at that age.
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So, young man, you're suggesting that the dinosaurs might have been mesotherms?
"Meso", everyone, means "in between" or "intermediate". So the idea here is that dinosaurs would be warmer than modern reptiles but not as warm as modern mammals—whales and cats and dogs and humans and horses—who maintain a fixed body temperature. By "fixed" temperature we mean within a narrow range, subject to regulation, or control. Among the regulatory abilities in humans are sweating when we get too hot, and shivering when we get too cold. (Does anyone know if whales shiver? Someone try to find that out for class tomorrow.) When our body temperature regulation fails we experience fever or chills. Chills are known to doctors as hypothermia, "hypo" meaning reduced and "thermia" meaning temperature; hypothermia means "reduced temperature". Fever and hypothermia are dangerous conditions that require prompt medical attention.
It's different when a lizard gets cold. For the lizard it's not an immediately dangerous condition; it just becomes sluggish until its environment warms up again. Now our lizard might be subject to predation—being eaten by a predator like an eagle or a snake—if it becomes sluggish at the wrong time or in the wrong place.
Mammals are the opposite in both ways: our temperature remains fairly constant regardless of our environment, and when our body temperature—not in our arms and legs and hands and feet, but inside our skull, our chest, or our belly—when this internal temperature changes, that's a big thing to worry about.
A mesotherm would be an intermediate creature, one who is able to generate enough body heat to remain active in a cold environment, which helps to avoid predation (remember that means being eaten), but isn't directly threatened by having a cold body temperature, if the food supply does not support maintaining a high activity level.
Something science has learned is that any organism that goes too long without food ceases to generate warmth internally. Now a large pile of dead plant matter—yard waste—can become much warmer than the surrounding environment, but this is due to smaller organisms with the plant matter which are busy eating the plant matter. It is also true that rotting meat will generate warmth from the small organisms inside the meat causing the meat to rot. Whatever the situation, if heat is being generated in a biological system, somewhere in that system there is some form of digestion taking place.
Now let's go back to the excellent question about dinosaurs could have been mesotherms. As young scientists, you are probably all wondering what is the evidence that dinosaurs were cold blooded or not. That's a very good question, everyone.
As a scientist, I wondered this myself. As a scientist we are trained to ask these questions whenever possible and seek as hard as we can to obtain the answers. Over my summer holidays—can you believe that?—I scoured all the science textbooks available to this school district, and I can't find a single sentence in any book explaining why dinosaurs are believed to be cold blooded, apart from their having a distant kinship with modern reptiles.
But then, think about this yourself. We know modern reptiles are much smaller than dinosaurs, who were waaaaay bigger than elephants. Large creatures often generate more heat than they want to have, which is why elephants have those giant, thin ears. All that extra skin helps them to transfer unwanted heat into their environment.
We'll be talking more about the relationship between heat and temperature in future classes. This is an important concept which is central to life as well as to modern machinery, which is why we eat regular meals and our c
I'm not sure how, in your world, "points to the theory" becomes "holy fucking shit, this is totally new shit". If I pointed to a Starbucks, would you take that as a claim that I "discovered" Starbucks?
To paraphrase what I've said elsewhere in this thread. These are distinct, meaningful, well defined terms.
Endotherms maintain an internal temperature within a narrow range effectively regardless of the external temperature.
Ectotherms have their internal temperature almost entirely governed by their external temperature.
Mesotherms maintain a consistently higher temperature than ectotherms in cooler environments, but do not maintain a temperature in a narrow range.
You are an endotherm not because you're always 37 C, but because you're never 31 C or 43 C and alive.
A lizard is an ectotherm because if it's 20 C out, he'll be close to that.
A dinosaur could be classified a mesotherm if it were 20 C and he was 26 C, or if it was 15 C out and he was 21 C or if it was 24 C out and he was 30 C. The warmer temperature allows him to outrun his crocodile lunch.
The value to these classifications is that they allow you to understand important aspects of a new species almost instantly.
To go your way, to say any temperature modification regardless of source means "warm blooded" would to be classify everything thusly and render the whole deal meaningless.
This is why you ought to be ignored.
I think that Dinosaurs were magical trees, fueled by the energy of the stars and filled with aetheric pitch or sap, that responded to the vibratory symphonies described by the planetary epicycles.
It is said that the largest dinosaurs had two brains - one in the head and another near the tail, like a fireman driving a ladder truck. This is nonsense. Dinosaurs know nothing of firemen, even if one factors their trans-dimensional aspect into consideration. This is because the creatures never had two brains, or even one brain to speak of. The cranium of a dinosaur contains only timecube, all the way down.
"Flyin' in just a sweet place,
Never been known to fail..."
Seems that "endoderm" is wrongly spelled.