Dinosaurs v. Mammals: The Final Conflict

[jimmy olsen]

Tim, that really isn't the same thing.

However it points to how similar the animals were biologically. If many of their proteins and blood cells/vessels were similar, it's not a huge step to say their breathing system was as well, especially when the physical bone structure points in that direction.

Also, I totally fucked up the posting of those articles, it's fixed now.

[Faeelin]

I like how a thread that Quee was mocked for is actually very interesting. 

[alfred russel]

I like how a thread that Quee was mocked for is actually very interesting. 

A lot of his threads turn out that way, but without a doubt he deserved to be mocked for this opening post.

[alfred russel]

There was a much lower amount of oxygen in the mesozoic period, so a more efficient breathing mechanism was selected for.

This is a good point--there is a concept that all large animals (basically anything much larger than a foot or two long) are essentially unsustainable and doomed to die out in a future extinction event. In extinction events, all species suffer, but larger animals almost vanish. So the future belongs to organ systems that compete best within smaller animals.

The disadvantage of an avian system is its requirement for a lot of space. This is accentuated in a small animal. In a time of low oxygen levels, the better efficiency of the system seems to have overcome this problem. But when oxygen levels rose, the age of mammals began.

[jimmy olsen]

There was a much lower amount of oxygen in the mesozoic period, so a more efficient breathing mechanism was selected for.

This is a good point--there is a concept that all large animals (basically anything much larger than a foot or two long) are essentially unsustainable and doomed to die out in a future extinction event. In extinction events, all species suffer, but larger animals almost vanish. So the future belongs to organ systems that compete best within smaller animals.

The disadvantage of an avian system is its requirement for a lot of space. This is accentuated in a small animal. In a time of low oxygen levels, the better efficiency of the system seems to have overcome this problem. But when oxygen levels rose, the age of mammals began.

Well, mammals only had the opportunity for their age to begin because of a cosmological fluke.

[alfred russel]

There was a much lower amount of oxygen in the mesozoic period, so a more efficient breathing mechanism was selected for.

This is a good point--there is a concept that all large animals (basically anything much larger than a foot or two long) are essentially unsustainable and doomed to die out in a future extinction event. In extinction events, all species suffer, but larger animals almost vanish. So the future belongs to organ systems that compete best within smaller animals.

The disadvantage of an avian system is its requirement for a lot of space. This is accentuated in a small animal. In a time of low oxygen levels, the better efficiency of the system seems to have overcome this problem. But when oxygen levels rose, the age of mammals began.

Well, mammals only had the opportunity for their age to begin because of a cosmological fluke.

Arguably. I say arguably for two reasons: first, a mass extinction event at some future point was inevitable. Second, it seems as though mammal life began to explode in diversity 85 million years ago, as opposed to when the asteroid(s) hit 65 million years ago.

[HVC]

Arguably. I say arguably for two reasons: first, a mass extinction event at some future point was inevitable. Second, it seems as though mammal life began to explode in diversity 85 million years ago, as opposed to when the asteroid(s) hit 65 million years ago.

Added to that, there were plenty of small dinos that could and did compete with primitive mammals, and yet the mammals won out. It's not so much that dinos were better then mammals, it's that they got to the niches first. it's hard to break into, and specialise, in niches already occupied.

[Queequeg]

I like how a thread that Quee was mocked for is actually very interesting. 

A lot of his threads turn out that way, but without a doubt he deserved to be mocked for this opening post.

You may not believe it, but I kind of expected that. We have more than an interest in the topic, and I kind of like roleplaying here.

[Queequeg]

Arguably. I say arguably for two reasons: first, a mass extinction event at some future point was inevitable. Second, it seems as though mammal life began to explode in diversity 85 million years ago, as opposed to when the asteroid(s) hit 65 million years ago.

Added to that, there were plenty of small dinos that could and did compete with primitive mammals, and yet the mammals won out. It's not so much that dinos were better then mammals, it's that they got to the niches first. it's hard to break into, and specialise, in niches already occupied.

This is far more obviously the case after the KT extiction event than during the Triassic period, when therapsid/mammalform predators lost out first to general archosaurs and then to dinosaurs. It also is not so easily clear cut; huge bipedal almost entirely dromeaosaur or ornithoraptor like birds were among the top predators of the Eocene.

[Caliga]

A lot of his threads turn out that way, but without a doubt he deserved to be mocked for this opening post.

Whether he deserves it or not, he gets mocked for virtually every thread he starts here.  It's part of his schtick, really.

[Neil]

Well, mammals only had the opportunity for their age to begin because of a cosmological fluke.

Mammals were already stepping up in the late Cretaceous.  For small animals, the Age of Dinosaurs ended in the middle Cretaceous.

[Queequeg]

Well, mammals only had the opportunity for their age to begin because of a cosmological fluke.

Mammals were already stepping up in the late Cretaceous.  For small animals, the Age of Dinosaurs ended in the middle Cretaceous.

I thought this was one of the most interesting questions; why is it that we kind of took over the small terrestrial land niches in the mid-late Cretaceous, along with the birds?  Why is it that the big birds had a wonderful Eocene, but can't seem to compete with modern quadrupedal mammals in most terrestrial niches, while the birds seem to have some manner of big advantage over bats?  Why did our Therapsid ancestors loose out in the Triassic to come back stronger than ever after the Age of Dinosaurs? 

The disadvantage of an avian system is its requirement for a lot of space. This is accentuated in a small animal. In a time of low oxygen levels, the better efficiency of the system seems to have overcome this problem. But when oxygen levels rose, the age of mammals began.

This is really interesting; it would explain why even the smallest bird often appears "puffy" when compared with the smallest bat, as the bird would no doubt need room for the superior Avian-style lungs.   You'd think that the mammalian size advantage would mean quite a bit, but I suppose the birds have certain other advantages. 

Crocodilians are archosaurs, not dinosaurs.  Only dinosaurs and their close relatives seem to have that adaptation.

AR posited that the Pterosaurs had something similar to the Avian system, and I think that what we would see in the early, possibly warm blooded (there is a pretty persuasive argument that cold bloodedness was returned to in the Crocodillians, as their ancestors had the gait and build of fast animals, like some of the earlier dinosaurs and relatives of pterosaurs) crocodiles would be similar, and I'd *guess* that we would see something *descended from* and probably resembling at the early stages of fetus development to the Avian-Dinosaur-Pterosaur system.  I doubt that a completely new, more efficient respiratory system somehow sprung up anew in the relatively small time between the Crocodiles and the Pterosaurs branched off from the Dinosaurs.

[Queequeg]

An interesting question that hasn't been broached yet; do marsupials and placental mammals have a more efficient, or at least somehow better reproductive system than the "reptiles" and birds? 

[Neil]

An interesting question that hasn't been broached yet; do marsupials and placental mammals have a more efficient, or at least somehow better reproductive system than the "reptiles" and birds?

Certainly more robust.  Not tying the mother down to a single physical location is also very handy.

[alfred russel]

This is far more obviously the case after the KT extiction event than during the Triassic period, when therapsid/mammalform predators lost out first to general archosaurs and then to dinosaurs. It also is not so easily clear cut; huge bipedal almost entirely dromeaosaur or ornithoraptor like birds were among the top predators of the Eocene.

I think the theory is that during the triassic the archosaurs took over because of the generally arid conditions where reptiles have certain advantages regarding water retention (all land was in one continent at the time and temperatures were supposedly higher). Tim pointed out that dinosaurs, many if not all of which had avian respiratory systems, would be further advantaged in low oxygen environment.

We still have birds that are large and flightless--the ostrich, flamingo, and pengiuns come to mind. There was never an era of absolutes--if dinosaurs had totally dominated the mesozoic we wouldn't have modern day reptiles or mammals.