Dinosaurs v. Mammals: The Final Conflict

[grumbler]

Archosaurs-Advantages:
Much more efficient breathing

This is precisely the opposite of what I recall from my bio classes.  Mammals, as I recall, are something like 10 times as efficient at breathing as reptiles.

Edit: http://books.google.com/books?id=p7rRLryz2cgC&pg=PA145&lpg=PA145&dq=reptile+%22breathing+efficiency%22&source=bl&ots=_Wa8_ubCon&sig=FCRE6JGRsljAOMW0PLkkuSbxJGk&hl=en&ei=4qpAS-mxHsfRlAfU6eCjBw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBIQ6AEwAg#v=onepage&q=&f=false
seems to bear this out: "...the relative cost of ventilation for all three classes of lower vertebrates is an order of magnitude greater for all three species of lower vertebrate compared to the mammals."

[The Brain]

You're biased.

[Neil]

I would imagine that deer would get eaten in relatively short order, although that would depend on their ability to maintain their high activity levels.  The other, smaller animals would essentially be occupying the sort of niches that mammals were already in around that time.  By the late Cretaceous, the changes in the biosphere had forced the dinosaurs out of the small end of the scale.  They'd be competing with their own ancestors, not with dinosaurs.

[Ed Anger]

Then the Count Belisarius comes through a rip in the space time continuum, kills all the dinosaurs, forms an alliance with Neanderthals and conquers the world with his Neo-roman greek speaking empire.

bork! bork! bork!

[Neil]

Archosaurs-Advantages:
Much more efficient breathing

This is precisely the opposite of what I recall from my bio classes.  Mammals, as I recall, are something like 10 times as efficient at breathing as reptiles.

Edit: http://books.google.com/books?id=p7rRLryz2cgC&pg=PA145&lpg=PA145&dq=reptile+%22breathing+efficiency%22&source=bl&ots=_Wa8_ubCon&sig=FCRE6JGRsljAOMW0PLkkuSbxJGk&hl=en&ei=4qpAS-mxHsfRlAfU6eCjBw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBIQ6AEwAg#v=onepage&q=&f=false
seems to bear this out: "...the relative cost of ventilation for all three classes of lower vertebrates is an order of magnitude greater for all three species of lower vertebrate compared to the mammals."

There's something of a debate on that.  Older sources take it for granted that dinosaurs are essentially scaled up lizards, whereas these days it's popular to assign them features more similar to birds.  Clearly, the dinosaurs could not have been the same as reptiles, because otherwise the Jurassic atmosphere would have required oxygen levels of around 40% to support observed activity levels on large sauropods.  At levels like that, the biosphere would spontaneously combust.  The question is, how bird-or-mammal-like were they?

[Tamas]

Actually, I own a boardgame about this, which no one wants to play.

[Ed Anger]

Actually, I own a boardgame about this, which no one wants to play.

You smell like cabbage.

[jimmy olsen]

Archosaurs-Advantages:
Much more efficient breathing

This is precisely the opposite of what I recall from my bio classes.  Mammals, as I recall, are something like 10 times as efficient at breathing as reptiles.

Edit: http://books.google.com/books?id=p7rRLryz2cgC&pg=PA145&lpg=PA145&dq=reptile+%22breathing+efficiency%22&source=bl&ots=_Wa8_ubCon&sig=FCRE6JGRsljAOMW0PLkkuSbxJGk&hl=en&ei=4qpAS-mxHsfRlAfU6eCjBw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CBIQ6AEwAg#v=onepage&q=&f=false
seems to bear this out: "...the relative cost of ventilation for all three classes of lower vertebrates is an order of magnitude greater for all three species of lower vertebrate compared to the mammals."

I could be mistaken, but if I recall correctly, dinosaur's breathing was as efficient as birds, which is more efficent than mammals.

[Viking]

Mammals vs Dinosaurs

[grumbler]

I could be mistaken, but if I recall correctly, dinosaur's breathing was as efficient as birds, which is more efficent than mammals.

The flying dinosaurs had air sacs in their bones, which gave them great efficiency at the cost of great fragility.  I doubt that this was true of the larger saurians.

In any case, we are talking archosaurs here, and only aviary species appear to have evolved the efficient-but-fragile breathing system.  Crocodiles certainly don't have it, and they are archosaurs as well. 

[jimmy olsen]

I could be mistaken, but if I recall correctly, dinosaur's breathing was as efficient as birds, which is more efficent than mammals.

The flying dinosaurs had air sacs in their bones, which gave them great efficiency at the cost of great fragility.  I doubt that this was true of the larger saurians.

In any case, we are talking archosaurs here, and only aviary species appear to have evolved the efficient-but-fragile breathing system.  Crocodiles certainly don't have it, and they are archosaurs as well.

It seems that Theropods at least breathed like birds.

Not a great article, though, I'll look for a better one.

http://www.livescience.com/animals/050713_dino_bird.html

Dinosaurs Breathed Like Birds

By Robert Roy Britt, LiveScience Senior Writer

posted: 13 July 2005 01:04 pm ET

Birds evolved from dinosaurs, most paleontologists agree. But there are big questions about just how similar the large dinosaurs really were to today's eagles and hawks.

Experts still argue whether dinosaurs were hot-blooded, agile and active like the cunning predators in "Jurassic Park" or, as scientists at U.C. Berkeley phrase the old conventional view, "sluggish and stupid."

A new study finds an important bird trait embedded in dinosaur bones that argues for the more nimble view.

Big meat-eating dinosaurs had a complex system of air sacs similar to the setup in today's birds, according to an investigation led by Patrick O'Connor of Ohio University. The lungs of theropod dinosaurs -- carnivores that walked on two legs and had bird-like feet -- likely pumped air into hollow sacs in their skeletons, as is the case in birds.

"What was once formally considered unique to birds was present in some form in the ancestors of birds," O'Connor said.

The study, funded in part by the National Science Foundation, is detailed in the July 14 issue of the journal Nature.

Theory takes flight

For more than three decades, scientists have seriously pondered the idea that birds are today's dinosaurs. The theory was put on solid footing in 1996 with the discovery of a well preserved, small and feathered dinosaur named sinosauropterx.

Other studies have since suggested that while an adult T. rex likely had scales, its young may have been covered in downy feathers.

Yet paleontologists had long thought that dinosaurs were cold-blooded, like reptiles. A reptile's simple heart puts only low amounts of oxygen in its blood -- not the right mix in the recipe of flight.

Modern computerized tomography (CT) scans of dinosaur chest cavities five years ago found the apparent remnants of complex, four-chambered hearts more like mammals and birds.

Earlier this year, rare soft tissue of a T. rex showed its blood vessels were similar to those of an ostrich.

Meanwhile, sketchy evidence in recent years had suggested dinosaur bones might contain air cavities. Still, some experts contended dinosaurs breathed more like crocodiles.

In the new study, O'Connor and his colleague, Leon Claessens of Harvard University, examined Majungatholus atopus, a recently discovered primitive theropod that is several yards long. They found cavities in its vertebral bones similar to those found in birds.

They found that "the pulmonary system of meat-eating dinosaurs such as T. rex in fact shares many structural similarities with that of modern birds," Claessens said.

Warm or cold?

A bird's air sacs are distributed throughout its body. The lungs never change shape, Claessens explained. Instead, fresh air is constantly being drawn from the air sacs through the lungs, in both directions, creating a very efficient respiration system.

There is also evidence that the dinosaur's rib cage was adapted for this type of system, Claessens told LiveScience.

The superior breathing apparatus, along with their complex hearts, increases bird metabolism and makes them warm-blooded, meaning they generate internal heat that controls their body temperature.

Reptiles are cold-blooded, relying on the environment and their behavior to regulate body temperature.

Though the dinosaur breathing system was not likely identical to living birds, "it's nothing like the crocodile system as we know it," O'Connor said.

The newfound similarities do not necessarily mean dinosaurs were warm-blooded, however. While that debate continues, O'Connor speculates that the blood of the long-gone beasts was probably somewhere between warm and cold.

   

[jimmy olsen]

These articles seem better.

http://www.bioedonline.org/news/news.cfm?art=680

http://www.ns.umich.edu/htdocs/releases/story.php?id=6758

[grumbler]

Interesting.  I would have thought these kinds of dinosaurs would have suffered more from the fragility/brittleness of the bones than gained from the forced-pump breathing system, but obviously not.

However, this doesn't say that all dinos had this system.  OTOH, every one whose heart shapes have been fossilized appear to have had four-chamber hearts, so maybe they all had the breathing system as well.

In any case, i withdraw my objection; my info was out of date, it seems.

[Razgovory]

Didn't mammals survive in real history at the time of the dinosaurs by being little rodent/rabbity things?
I'd think our modern swarm creatures would do very well assuming they can eat the food and breath the air (handwavium ftw).
In the colder regions I'd imagine mammals do a lot better too....not that there was much in the way of 'cold' regions back then.

Don't forget that the mammal like reptiles dominated the world before the Jurassic.

I'm not old enough to remember that.

[Darth Wagtaros]

Then the Count Belisarius comes through a rip in the space time continuum, kills all the dinosaurs, forms an alliance with Neanderthals and conquers the world with his Neo-roman greek speaking empire.

bork! bork! bork!

OH FUCKYEAH!!!! KEEEP GOIN!