Cloning prehistoric animals

[Dutch90]

That is pretty strange though: warm- and cold-blooded animals within the same group. Either the entire group is warm-blooded (mammals, birds) or cold-blooded (reptiles, fish, amphibians), it seems unusual for differentiation within. Then again, a couple of fish species (like the great white shark) are known to be sort of warm-blooded.

On the subject of sauropods, I've done some thinking. If they were cold-blooded they'd be immobile at night because of the cold. You'd think that this would make them vulnerable to predators, even though they'd normally be too big to be attacked (the adults anyway). However, if they were really immobile at night due to their cold-bloodedness, predators would figure that out pretty soon and a sauropod could wake up to find its left front leg gone. 

Then again, I've read that due to their large size, sauropods could store enough heat in their body to remain active at night, thus having all the benefits of cold-bloodedness (less required food intake) and none of the downsides (nocturnal sluggishness). If they were, indeed, cold-blooded.

I suppose small herbivores like hypsilophodontids would be warm-blooded as well. It's interesting how this debate always focuses on small theropods and not on other dinosaur groups.

[BishopIII]

 I find it impossible to believe that Sauropods would be cold-blooded, whilst all of their close relatives are warm-blooded. We don't find that in mammals. The theory is that this is why Sauropods had such long necks - So they could simply stand still and defoliate an entire area of forest with minimal energy. The depth of their chests show that the heart and lungs were enormous, not what you'd expect from a cold-blooded animal. The gut-space was also huge, implying a life of near constant eating. If they were mass-homeotherms (using sheer bulk to keep warm), sure it works well in a computer model, but in reality (with bad weather and winters taken into account)? Not likely, since they'd also take forever to warm up again, giving the carnivores an advantage over them, making them a nice big lump of chilled meat for the taking. Mammals would have taken over aeons before they did. Plus, since their ancestors were likely warm-bloods, such a metabolic reversal would be unprecedented in evolutionary history!

[beckmen]

Rules are meant to be broken. Look at the hive structure and near-cold-bloodedness of the Naked Mole Rat, or every fucking thing about the mighty Platypus!

[deezelboy]

Or, quite possibly, crocodiles, whose ancestors may have been endothermic.

If they were mass-homeotherms (using sheer bulk to keep warm), sure it works well in a computer model, but in reality (with bad weather and winters taken into account)? Not likely, since they'd also take forever to warm up again, giving the carnivores an advantage over them, making them a nice big lump of chilled meat for the taking.

No, they'd cool down a lot slower than they'd warm up by virtue of having a greater volume to surface area ratio.  Leatherback turtles are a great example of this.

[BishopIII]

 Okay, I'll let you have that. However, the chest structure still stands, it looks like an endothermic arrangement, with such an expanse for the heart and lungs, which were most likely avian-type lungs, as Sauropods have similar hollow bones to those of Theropods. It is possible that they kept this from their endotherm ancestors, but, if crocodilians had endotherm ancestors, why didn't they keep a large heart and lungs (I know that their hearts are four-chambered as opposed to three)? I'd expect a sauropod to have a roughly pear-shaped torso, if that was correct. Just imagine elephants had become extinct 65MYA. We'd likely have a similar debate. The limbs also, are in the fully-improved posture, whereas all mass-homeotherms have either semi-improved or sprawling limbs. Something just doesn't sit right with me about a cold-blooded Sauropod. Naked Mole Rats are NEARLY cold-blooded, but they aren't actual ectotherms, just so lazy that even their metabolisms are lethargic. Some humans suffer from the metabolic disorder Poikilothermism (Cold-bloodedness), the most famous example being a certain Howard Phillips Lovecraft.

[Neltharion]

So being a lazy bugger means I could have a disorder?

Cool!

[deezelboy]

It is possible that they kept this from their endotherm ancestors, but, if crocodilians had endotherm ancestors, why didn't they keep a large heart and lungs (I know that their hearts are four-chambered as opposed to three)?

Presumably because it was less advantageous in regards to their 'sit and wait' lifestyle. 

[Captain Crunch]

I find it impossible to believe that Sauropods would be cold-blooded, whilst all of their close relatives are warm-blooded. We don't find that in mammals. The theory is that this is why Sauropods had such long necks - So they could simply stand still and defoliate an entire area of forest with minimal energy. The depth of their chests show that the heart and lungs were enormous, not what you'd expect from a cold-blooded animal. The gut-space was also huge, implying a life of near constant eating. If they were mass-homeotherms (using sheer bulk to keep warm), sure it works well in a computer model, but in reality (with bad weather and winters taken into account)? Not likely, since they'd also take forever to warm up again, giving the carnivores an advantage over them, making them a nice big lump of chilled meat for the taking. Mammals would have taken over aeons before they did. Plus, since their ancestors were likely warm-bloods, such a metabolic reversal would be unprecedented in evolutionary history!

Sauropods probably were cold blooded, theropods though would have to be warm blooded.

[BishopIII]

 Even so, they would have had to have been endotherms for at least a portion of their lives, as the rate of growth in even sauropods was tremendous, even by mammalian standards. A low metabolism simply can't do that unless the temperature is constant and fairly hot, which wasn't so, even in the Late Jurassic/Early Cretaceous (when most of the bigger sauropods lived).

[Dutch90]

BishopIII, your arguments are sound, but I do wonder what you think of the counter suggestion that warm-blooded sauropods would have to consume a lot more food than cold-blooded sauropods to keep going. Multiple genera of sauropods of significant size coexisted in various regions, especially Africa and North America in the Late Jurassic, and I think they'd already have a dramatic impact on their environment with a cold-blooded food intake. If they were warm-bloosed, they'd require even more food. Also, since their manner of food processing was quite inefficient - they didn't chew, instead relying on ingested stones (gastroliths) to grind the food in their stomach - they'd need to consume more plant material than a more efficiently processing animal (like ornithopods, which chewed their food) to acquire the same amount of nutrients. With no predators large enough to prey on adult sauropods, there'd be little to keep them in check as well. One can imagine a large sauropod population causing something of an ecological disaster.

Of course, maybe this is why sauropods didn't do so well after the Jurassic (except in South America).

[BishopIII]

 On the subject of Gastroliths; they are a constant grinding 'mechanism', allowing for far more food to be swallowed than would be possible for a chewing herbivore, making them far more efficient. The animal could just keep cropping off vegetation, then swallowing, and search for more food whilst the gizzard does all the chewing. That is one theory why Sauropods have such long necks, not because they reached up into high tree branches, but because they used them to sweep their heads back and forth over a wide arc, stripping vegetation and allowing tons of food to be consumed with minimal effort, in one day alone.
  Elephants cause huge impacts on the flora in their habitats, pushing over trees to get to the leaves, then taking advantage of the fast growing, low growing plants that come up after such destruction. There are theories that such Dinosaurs are ultimately responsible for the fisrt evolution of primitive flowering plants, both fast-growing, and fast-reproducing. This would be a logical evolutionary response to overpredation by huge herbivores.

 And yes, the bigger, high-metabolism-endowed animals are always the worst hit in any extinction event, possibler evidence that Sauropods were endotherms - they were among the most fragile of all Dinosaur groups, being huge, with high metabolisms and an inefficient lifestyle.

[CanadianHero67]

Things to think about is the fact that back in prehistoric times seasons were very different, infact I think I heard at some points there weren't any seasons. Also oxygen levels were very different back then. I could see genetically making new dinosaurs species but cloning a species from the past would probably just result in a dead dino because their bodies are not meant to survive in today's global environment.

[Dutch90]

Things to think about is the fact that back in prehistoric times seasons were very different, infact I think I heard at some points there weren't any seasons.

I'm pretty sure there were seasons, but not summer/fall/winter/spring. Instead, there was only a wet season and a dry season. It should be noted that Cretaceous Antarctica, which was located much more to the north than today, probably did have the quadrupal seasons we have today (or at least winter and summer). Dinosaurs have been found in Australia, which was attached to Antarctica at the time and probably had a similar (though warmer) climate. It's entirely possible these dinosaurs also existed on Antarctica, where they coped with freezing winters (which also means they'd have to be cold blooded). In 1990 a medium-sized (in dinosaur terms that means it was about 8 m long) carnivore from the Early Jurassic (c. 185 million years ago) was found on Antarctica itself, dubbed Cryolophosaurus. The presence of such a large predator indicates there must have been various large and smaller herbivores as well. All these dinosaurs would have to be able to survive the cold, dark winter, which I think means they'd also be able to survive today.

 

Also oxygen levels were very different back then. I could see genetically making new dinosaurs species but cloning a species from the past would probably just result in a dead dino because their bodies are not meant to survive in today's global environment.

Would it be possible to genetically engineer the creatures so they could survive in our current environment? Granted, that would mean changing their nature, but if only these characteristics were altered it wouldn't really be a "new" dinosaur - just an "old" one with a few tweaks so it doesn't keel over.

I'm not entirely sure oxygen levels were that different in the Mesozoic, although I do know they were much higher than today in the Carboniferous (c. 350-290 million years ago, before the Age of Dinosaurs), and in preceding periods (the Silurian (450+ mya) and everything before that) they were much lower due to the lack of terrestrial plant life. Still, I was under the impression that post-Carboniferous O2 levels were more or less in line with today's figures.

As for temperature, I remember reading that on average, the Cretaceous was the warmest period in our planet's history. Which rather surprised me, since I expected the Permian or Eocene to be warmer.

On a side note, it does seem this discussion has become a bit biased towards dinosaurs.

[BishopIII]

Dinosaurs have been found in Australia, which was attached to Antarctica at the time and probably had a similar (though warmer) climate. It's entirely possible these dinosaurs also existed on Antarctica, where they coped with freezing winters (which also means they'd have to be cold blooded).

 They have to be insulated endotherms, due to Leallynasaura having not only a large brain (for a herbivore), but huge optic lobes, enabling it to see in the dark. This would indicate that it was active during the winter 'night'. If it was that cold, and such an animal was active, it would mean that it had to be warm-blooded, and insulated to boot!! Also, no land-living cold-bloods larger than a cat (amphibians notwithstanding) are found in cold climates, something that hasn't changed since the Mesozoic era. The fossil record clearly shows large lizards, turtles and crocodiles living within and below below the modern temperate zones, but never near the poles. Dinosaurs, on the other hand, are found in large numbers around the poles, indicating a definite difference of metabolism to that of crocodiles and other reptiles.

[Dutch90]

I'm a moron. I posted "cold-blooded" when I meant "warm-blooded"