Raz Science question: Why no tiny Dinosaurs?

[Neil]

That's not a dinosaur.

I disagree.

Hemidactylus turcicus isn't even an archosaur.

[MadBurgerMaker]

Your science-speak doesn't phase me!  I can see through your lies!

[Viking]

Your science-speak doesn't phase me!  I can see through your lies!

Words have meaning duude.

[MadBurgerMaker]

Words have meaning duude.

Well I was going to say something about pictures being more meaningful and finding another photo of geckos and something some such, but ugh

[Razgovory]

One theory for why dinosaurs tended to be excluded from small sizes is that they had avian-style respiratory systems. These are more efficient than those of mammals, but they also take up more space (with air sacs). Space is at a premium at smaller sizes, so this could have been a disadvantage for them. But there isn't evidence that all dinosaurs had that style of respiratory system.

It does seem that land mammals are excluded from the general design of some of the largest dinosaurs, because of limitations of the respiratory systems.

Interesting, but birds can get pretty small.  Like Humming birds. 

[Viking]

Words have meaning duude.

Well I was going to say something about pictures being more meaningful and finding another photo of geckos and something some such, but ugh

The thing is we have dinosaurs living today, they are called birds. So if you had used this picture



then you would have a point.

[MadBurgerMaker]

The thing is we have dinosaurs living today, they are called birds. So if you had used this picture

a fucking picture of penguins for gods sake

then you would have a point.

e: oh I hope that Fry gif works now. 

[alfred russel]

Interesting, but birds can get pretty small.  Like Humming birds.

Birds are a special case, because flying requires high oxygen useage and is benefited by low body weight and a lack of side to side movement in flight. I think they are strong evidence of the theory, actually. Dinosaur descendants exist, but in the smaller variety are relegated to a specialized niche that the respiration system seems tailored for (the flightless birds tend to be large).

The theory is the respiration system evolved when oxygen levels were much lower than today.

[Razgovory]

When was the oxygen levels lower?

[FunkMonk]

That one... when she looks at you, you can see she's working things out.

[Darth Wagtaros]

I believe it was much,much higher during the Permian and Cretaceous.

[alfred russel]

When was the oxygen levels lower?

Right after the PT extinction event about 250 million years ago (the beginning of the triassic). Initially mammal like animals were more prevelant, but these were replaced by antecedents of dinosaurs.

[alfred russel]

I should emphasize that I'm not a scientist and I'm probably full of crap--this is just my lay understanding.

[The Brain]

Why aren't you a scientist?

[alfred russel]

Why aren't you a scientist?

When I was in school the scientist path promised harder classes, many more years in school, and then crappy pay. On the plus side I could look smart whenever topics regarding dinosaur physiology came up, but at the time I didn't think that outweighed the horrors of a biochemistry class.