The Temperature Difference Between Sealer Cans and Placey Sores

Neither placey sores nor sealer cans were warm-blooded, so they didn't need their metabolisms to run as fast as a mammal would. The temperature difference between the surface and the deep also play a role. By being small and deep, sealer cans had a better chance of surviving relatively unaltered in evolutionary terms compared to placey sore who were bigger and warmer.