Dinosaur intelligence

Dinosaur intelligence has been a point of contention for paleontologists. Non-avian dinosaurs were once regarded as being unintelligent animals but have largely been appraised more generously since the dinosaur renaissance. This new found optimism for dinosaur intelligence has led to highly exaggerated portrayals in pop-cultural works like Jurassic Park. Paleontologists now regard dinosaurs as being very intelligent for reptiles, but generally not as smart as their avian descendants. Some have speculated that if the Cretaceous–Paleogene extinction event had not occurred, the more intelligent forms of small theropods might have eventually evolved human-like levels of intelligence. Popular misconceptions of dinosaur neurology include the concept of a second brain in the pelvis of stegosaurs and sauropods.

Traditional comparisons of brain volume to body mass in dinosaurs use the endocast as a proxy for brain volume. However, the brain of the modern reptile genus Sphenodon fills only about half of its endocranial volume. Some paleontologists used this fifty percent estimate in their estimates of dinosaur brain volume. Other workers have observed that details on the endocranial surface indicates that some fossil reptiles had brains that occupied a much larger portion of the endocranium. Hans Larsson notes that the transition from reptiles to birds prevents using a set ratio from being a valid approach to estimating the volume of the endocranium occupied by a dinosaur's brain.

In a 2001 study of a Carcharodontosaurus saharicus endocast, Hans C. E. Larsson found that both C. saharicus and Allosaurus had a ratio of cerebrum to brain volume that lay within the 95% confidence limits of non-avian reptiles. By contrast, Tyrannosaurus lies just outside it in the direction of a more avian proportion. Since tyrannosaurs are relatively basal coelurosaurs, this is evidence that the advent of the Coelurosauria marks the beginning of trend in theropod brain enlargement.

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