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The earth was much warmer during the era of dinosaurs, and yet they still grew to such sizes. I'm not sure that body heat retention is a great explanation, espe

The earth was much warmer during the era of dinosaurs, and yet they still grew to such sizes. I'm not sure that body heat retention is a great explanation, especially given the thick fur coats of most modern mammals that were evolved for the cold. I'm mostly curious how the ecosystem was able to support so many large animals, from the base layer of the food chain up. If there was an ice sheet a mile thick covering all of Canada down to Wisconsin, then most of north America must have been tundra. Were there less trees? Did grasslands thrive across the continent which supported ruminants more, which in turn provided more food for large predators?

EdwardDiego 4y ago
Fair comment. :) I was referencing Bergmann's Rule [0], which really only applies to warm blooded animals but there's also a theory that evolving a larger size helps ectotherms maintain a stable temperature also. [1], and relating to your question on carrying capacity of the food available - the Jarman-Bell Principle [2] that larger herbivores can subsist better on low quality food than smaller herbivores. And, for interest, Allen's Rule on body appendages for temperature regulation. [3] There's also Cope's Rule - that animals just tend to evolve to get larger, until that's no longer viable. [4] I can't comment on how valid any of them are, as I'm just an armchair biologist :D [0]: https://en.wikipedia.org/wiki/Bergmann%27s_rule https://en.wikipedia.org/wiki/Bergmann%27s_rule [1]: https://en.wikipedia.org/wiki/Gigantothermy https://en.wikipedia.org/wiki/Gigantothermy [2]: https://en.wikipedia.org/wiki/Jarman-Bell_principle https://en.wikipedia.org/wiki/Jarman-Bell_principle [3]: https://en.wikipedia.org/wiki/Allen%27s_rule https://en.wikipedia.org/wiki/Allen%27s_rule [4]: https://en.wikipedia.org/wiki/Cope%27s_rule https://en.wikipedia.org/wiki/Cope%27s_rule

EdwardDiego 4y ago

Fair comment. :) I was referencing Bergmann's Rule [0], which really only applies to warm blooded animals but there's also a theory that evolving a larger size helps ectotherms maintain a stable temperature also. [1], and relating to your question on carrying capacity of the food available - the Jarman-Bell Principle [2] that larger herbivores can subsist better on low quality food than smaller herbivores. And, for interest, Allen's Rule on body appendages for temperature regulation. [3] There's also Cope's Rule - that animals just tend to evolve to get larger, until that's no longer viable. [4] I can't comment on how valid any of them are, as I'm just an armchair biologist :D [0]: https://en.wikipedia.org/wiki/Bergmann%27s_rule https://en.wikipedia.org/wiki/Bergmann%27s_rule [1]: https://en.wikipedia.org/wiki/Gigantothermy https://en.wikipedia.org/wiki/Gigantothermy [2]: https://en.wikipedia.org/wiki/Jarman-Bell_principle https://en.wikipedia.org/wiki/Jarman-Bell_principle [3]: https://en.wikipedia.org/wiki/Allen%27s_rule https://en.wikipedia.org/wiki/Allen%27s_rule [4]: https://en.wikipedia.org/wiki/Cope%27s_rule https://en.wikipedia.org/wiki/Cope%27s_rule