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

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