A recent study of dinosaur sizes claims to break Bergmann’s rule.¹ Bergmann’s rule was named after biologist Carl Bergmann, who in 1847 noticed that warm-blooded animals tended to be larger in cold climates compared to the same animal in a warm climate. Larger body mass tends to help an animal retain more heat, helping animals survive in the cold. “The fossil record provides a window into completely different ecosystems and climate conditions, allowing us to assess the applicability of these ecological rules in a whole new way,” said Jacob Gardner, a co-author...