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 contains a plethora of shark teeth, but fossilized shark skeletons are exceptionally rare. When they are found, though, they are always 100% sharks.^1,2