Hank gives a quick run-down of the reasons scientists think the land mammals of today are nowhere near the size of the largest sauropods. Some of them might surprise you!
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Um there are land mammals the size of dinosaurs. We call them every mammal ever. Not all dinosaurs were massive and even Triceratops and Tyrannosaurus Rex were not much bigger than elephants in height. What you mean is none the size of sauropods.
Same reason less mammals fly. Bones aren't hollow, dinosaurs (Like birds) had highly efficient respiratory systems and various other adaptations for being big, the same adaptations that allow birds to fly so well and be pretty much the dominant aerial life forms on the planet. I mean bats are unlikely to outcompete birds in niches that birds fill. They may fill similar niches. But alot of hate are nocturnal, birds don't have echo location though. Good job bats.
Another thing about metabolisms is that whatever the metabolism of Dinosaurs was like, they were probably slower than most mammals, meaning they required less nutrition than an equivalent sized mammal.
2:25 That's a pretty bad reason. Animals evolve their metabolism along with everything else, and mammals have all different metabolic demands and body temperatures depending on their size.
If selective pressures would be favorable for large mammals to exist, their metabolisms would adapt accordingly.
BLUE WHALE. Biggest mammal to ever exist.
That sentence alone destroys your whole title and thus video. All that work for nothing. All because you have made a drastic error in relation to the factual incorrectness of your statement title.
It has only been around 65 million years since dinos went extinct. In the Triassic era which lasted for 50 million years the largest land animal only weighed 3 tons. Vs the larges land mammal that weighed 18 tons.
So it isnt that surprising.
If people didn't come along and wipe out the mega fauna you'd expect that they'd slowly get bigger and bigger when conditions allowed.
So we're sorta the reason mammals wont get bigger... hurray humanity!
Well if I may interject, mmh mmh (clears throat). The moon is the reason we don't have giants anymore. Gravity. The moon is spinning away from the earth increasing the distance, scientists say one day the moon will spin so far away it'll wonder of into space. Even pangea broke up because of this spinning away of the moon. Imagine the moon a few kilometers closer to earth, this would ultimately affect the gravity on earth making it weaker. I think the low gravity made it easier for them to grow high as they were. But I don't have a degree so no one will believe me...
Not to mention that elephant cells and mitochondria are already in cell terms doing everything on slow motion to compensaste for an elephants large size, so imagine whow slow the metabolism of a mammal the size of anphicocelias would have to be.
_Amphicoelias fragillimus_ didn't had 60m in lenght, it was an over-estimated measurement based on the original 1878 description. New studies show that he could be a rebbachisaurid and not a diplodocid sauropod, so they changed his species name to _Maraapunisaurus_ and did a new measured of his lenght that turned up to be around 30m.
If we acknowledge the surviving evidence (which is very poor and could have typographical errors) and the biological plausibility of such a large land animal, I think we can agree on the point that the most recent studies are the ones we should rely on or at least we should discard the old ones.
The biggest dinosaur we know of still is _Argentinosaurus huinculensis_ that could reach 30-35m in lenght and 80-100 tons of weight.
A bigger mammal would have a higher core body temp because all of that heat generated from the mammal's center will be more difficult to dissipate, as opposed to small mammals in which the heat quickly disperses out. This is why some of the mammalian megafauna survived in the cold, it was because they were warmer and they stayed warm for longer
Well I don’t think sauropods were exactly cold blooded, personally I think all Dino’s were warm blooded. I just think the sauropods produced less heat as they got bigger, gradually re-evolving a slower metabolism, and lower natural body heat.
Saying "Erbivores" instead of "Herivores." Come on. I realise you might want to use the French pronunciation when talking about cooking, but other than that, these dinosaurs were not eating rosemary and thyme.
So there are no large land MAMMALS but why arent there giant land REPTILES in the equatorial regions of the planet where vegetation is plentiful and so is the heat? We know the catastrophe that caused the mass extinction of just about all land creatures 64 m yrs ago. but the survivors were mostly of the reptilian sort, crocks, komodos stuff like that so why didnt they re-evolve to giants?
Well one thing to know is that evolution doesn't just make and animal adapt if there are any free niches, if the animal populations are stable with the way they are they probably aren't gonna change. There's also probably too much competition if they wanna get biggger
I'm a little confused. Most of the reasons stated in this video would also have applied to the giant mammals of the past, who DIDN'T cook themselves, or crush themselves under their own weight, or die out immediately due to low birth rates. So the reasons are rather severely flawed. The only one that appears to hold up is the reduction in food supply.
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