why did dinosaurs get bigger? was gravity lower 100 million years ago?

[Caliban]

It fits comfortably in my mind and spirit.

No, that's not what I am talking about. How could you show me this is true?

 

[OldWiseGuy]

No, that's not what I am talking about. How could you show me this is true?

I can't show you why I believe as I do any more than I can show you why I like to hunt coyotes. I just do.

 

[Warden_of_the_Storm]

Part of why dinosaurs grew so big (sauropods in particular) is suggested to have been through evolution of long necks which allowed them access to greater amounts of food. But with that, atmospheric changes are considered to have played a role as well. Significant amounts of CO2 and vegetation may have offered a surplus of food.

Also, much like the increased size of blue whales versus their tiny ancestors, size can also provide a means of self defense for plant eaters. I've read suggestions that whale size growth might have provided defense against large sharks like megalodon. Much the same a large sauropod could fight against meat eaters like T-Rex.

So a combination of atmospheric changes and an evolutionary arms race could be the explanation, which is similar to explanations of other radiations of life throughout time.

The arms race idea has a lot of merit to it.
I mean... large carnivorous dinosaurs (therapods like the Allosaurus, Carnotaurus, Tyrannosaurids, etc) most likely could go for relatively long periods without food, maybe a few weeks up to a month (if we use lions as the closest analogue for terrestrial predators) but when they need to eat, they would need to EAT. A body of that size and mass needs a lot of energy to hunt and feed for itself, and that's not including females that are pregnant or have given birth.

So what would be the best source of food, fat and protein? Not the scrawny little lesothosaurus. No, that's just a snack. The BIG meals are the sauropods. Huge brutes, lots of meat, lots of fat and protein for top predators. And most of all important for therapods; slow.

I'm going to stop myself there since I'd basically end up over-extending your point about size as a defence mechanism.

 

[Job 33:6]

The arms race idea has a lot of merit to it.
I mean... large carnivorous dinosaurs (therapods like the Allosaurus, Carnotaurus, Tyrannosaurids, etc) most likely could go for relatively long periods without food, maybe a few weeks up to a month (if we use lions as the closest analogue for terrestrial predators) but when they need to eat, they would need to EAT. A body of that size and mass needs a lot of energy to hunt and feed for itself, and that's not including females that are pregnant or have given birth.

So what would be the best source of food, fat and protein? Not the scrawny little lesothosaurus. No, that's just a snack. The BIG meals are the sauropods. Huge brutes, lots of meat, lots of fat and protein for top predators. And most of all important for therapods; slow.

I'm going to stop myself there since I'd basically end up over-extending your point about size as a defence mechanism.

We may need computer simulations of dinosaur combat to settle these questions. One of my favorite past time activities...

 

[Shemjaza]

The arms race idea has a lot of merit to it.
I mean... large carnivorous dinosaurs (therapods like the Allosaurus, Carnotaurus, Tyrannosaurids, etc) most likely could go for relatively long periods without food, maybe a few weeks up to a month (if we use lions as the closest analogue for terrestrial predators) but when they need to eat, they would need to EAT. A body of that size and mass needs a lot of energy to hunt and feed for itself, and that's not including females that are pregnant or have given birth.

So what would be the best source of food, fat and protein? Not the scrawny little lesothosaurus. No, that's just a snack. The BIG meals are the sauropods. Huge brutes, lots of meat, lots of fat and protein for top predators. And most of all important for therapods; slow.

I'm going to stop myself there since I'd basically end up over-extending your point about size as a defence mechanism.

There's some evidence that even some of the larger predators hunted in packs (or family groups). So size is an even better advantage for a herbivore.

 

[Warden_of_the_Storm]

We may need computer simulations of dinosaur combat to settle these questions. One of my favorite past time activities...

There's some evidence that even some of the larger predators hunted in packs (or family groups). So size is an even better advantage for a herbivore.

Funny you both mention that, because it reminded me of this:

From the BBC's Planet Dinosaur series, the video shows a pack of large therapod dinosaurs, Mapusaurus', hunting a herd of Argentinosaurus', and showing how both groups would end up dealing with the other.
Spoiler warning for the end: we see what happens a nearly 100 tonne saurapod lands on a therapod.

 

[FrumiousBandersnatch]

We may need computer simulations of dinosaur combat to settle these questions. One of my favorite past time activities...

You could start a dinosaur combat re-enactment group