4 ms·

Dinosaurs were not mammals. The jury is still out on whether they were warm blooded (but most people agree that not quite as warm-blooded as mammals). The upper

by osrec 9y ago

Dinosaurs were not mammals. The jury is still out on whether they were warm blooded (but most people agree that not quite as warm-blooded as mammals). The upper limit on size (according to the article) is defined by food availability and energy consumption, so I would guess food was simply more plentiful, or their energy demands were lower (due to lower core temperature). Thus they grew bigger.

TheOtherHobbes 9y ago
Also, average ambient temperatures in the Jurassic were significantly higher than today - up to 8C warmer according to some estimates, and even higher in the Cretaceous. Warm blood was less of a requirement for dinosaurs than it would be today. I don't understand how mammalian evolution worked through this period. Temperatures rose even further after the KT crash, so there would be no evolutionary benefit to being warm blooded. And yet - here we are.
- masklinn 9y ago
  > Also, average ambient temperatures in the Jurassic were significantly higher than today - up to 8C warmer according to some estimates, and even higher in the Cretaceous. Note that this is not necessarily an advantage for large land-bound animals, an elephant's biggest thermal issue is getting rid of heat not producing it.
- Rexxar 9y ago
  It was probably a big advantage for nocturnal animals. And lots of mammals ancestors are believed to be nocturnal during this ancient ages.
- ralusek 9y ago
  Surely there degree (no pun intended) to which a species can be"warm blooded" is a gradient. Even fractional presence of temperature regulation could have allowed for species to live in colder parts of the planet.
- grigjd3 9y ago
  A couple people have already hinted at it but self-regulating body temperature is a big benefit for crossing into non-native environments.
- stevenwoo 9y ago
  My recollection of theory is many mammals (that we know survived to evolve) at the time of the KT crash were tiny, and burrowers and able to use both of these (less exposure to damage from initial strike and need less resources to survive/procreate) to out survive the dinosaurs.

by osrec 9y ago

TheOtherHobbes 9y ago

Also, average ambient temperatures in the Jurassic were significantly higher than today - up to 8C warmer according to some estimates, and even higher in the Cretaceous. Warm blood was less of a requirement for dinosaurs than it would be today. I don't understand how mammalian evolution worked through this period. Temperatures rose even further after the KT crash, so there would be no evolutionary benefit to being warm blooded. And yet - here we are.

masklinn 9y ago
> Also, average ambient temperatures in the Jurassic were significantly higher than today - up to 8C warmer according to some estimates, and even higher in the Cretaceous. Note that this is not necessarily an advantage for large land-bound animals, an elephant's biggest thermal issue is getting rid of heat not producing it.
Rexxar 9y ago
It was probably a big advantage for nocturnal animals. And lots of mammals ancestors are believed to be nocturnal during this ancient ages.
ralusek 9y ago
Surely there degree (no pun intended) to which a species can be"warm blooded" is a gradient. Even fractional presence of temperature regulation could have allowed for species to live in colder parts of the planet.
grigjd3 9y ago
A couple people have already hinted at it but self-regulating body temperature is a big benefit for crossing into non-native environments.
stevenwoo 9y ago
My recollection of theory is many mammals (that we know survived to evolve) at the time of the KT crash were tiny, and burrowers and able to use both of these (less exposure to damage from initial strike and need less resources to survive/procreate) to out survive the dinosaurs.