Did Dinosaurs Really Have Brains in Their Tails?

Many people have wondered about the intelligence of dinosaurs, especially the large and carnivorous ones. Were they smart and if so, just how smart? It appears that most large dinosaurs would probably have been sitting at the back of the class wearing the classic dunce cap, which may make them look a bit less ferocious. Smaller dinosaurs, especially the raptor group, tended to have the largest brains, suggesting greater intelligence. Larger dinosaurs on the other hand, were, to put it nicely, a bit dim, though their brains certainly functioned well enough for years of survival.

In the early 20th century, while studying the anatomy of the stegosaurus, some scientists advanced the theory that at least some dinosaurs had brains in their tails. From stegosaurus, this theory was applied to other large dinosaurs, like the nonexistent brontosaurus (really apatosaurs or brachiosaurs). Scientists found evidence that stegosaurus had a cavity near the base of the tail that could have held a brain even larger than the one in a stegosaurus’ head.

Just as the name brontosaurus has stuck, the idea that some dinosaurs have brains in their tails has remained a persistent belief, especially by those who don’t keep current on dino research. The fact is, dinosaurs's brains weren't located in their tails. What was previously thought a second brain center, likely represented an accumulation of fat cells, and a large number of nerve cells that could help control lower body and tail movement. In a sense you could almost say dinosaurs had brains in their tails because of the high number of nerve cells. In reality, though, these don’t function as a second brain.

Further, the urban legend about brains only applied to a very small group of dinosaurs. Most dinosaurs didn’t have this lump of tissues and the nerve/tissue space is only present in a few of the larger dinosaurs, primarily stegosaurus, brachiosaurus, and apatosaurus. The theory is that large heavy tails needed a lot of nerve receptors and independent control so as not to throw the dinosaur off balance. If you’ve ever looked at the twitching of a cat’s tail, it does appear to have a mind of its own, and thus though the idea that dinosaurs have brains in their tails is not true, their tails may have had that same kind of seemingly independent movement associated with modern animals.

For lovers of dinosaurs, who grew up studying them one way, we’re in for big revelations as DNA research becomes more refined. Recently, scientists found matter on a raptor that may confirm these dinosaurs really did have feathers, leading credence to the “birds are dinosaurs” theory. Ostriches have the same type of nerve structure at the base of their tails, but then, so do several lizards. It’s interesting to speculate how dinosaur books and illustrations may look in another twenty years or so. Perhaps instead of seeing the lizard-like beasts with which we’re so familiar, we may actually be looking at a lot of Big Bird’s ancestors in years to come.

No, dinosaurs did not have a second brain in their tails. This misconception arises from the discovery of a large nerve cavity in the hips of some dinosaur species, such as Stegosaurus, which scientists once thought might house additional neural tissue. However, this space was likely filled with glycogen bodies, which are energy reserves, not a secondary brain.

The enlarged nerve cavity, or the 'sacral brain' as it was once mistakenly called, likely served as a storage site for glycogen, a complex carbohydrate that provides energy. According to research, this cavity contained glycogen bodies, similar to what is found in modern birds, and helped support the heavy tail and control its movements.

The myth originated in the late 19th century when scientists discovered a large cavity in the hip region of some dinosaur fossils. Given the limited understanding of dinosaur anatomy at the time, some paleontologists speculated that this space might have contained neural tissue to help control the animal's hindquarters and tail, leading to the 'second brain' theory.

Stegosaurus is the most famous example of a dinosaur that was once thought to have a 'second brain.' This belief was due to its relatively small head brain and the large canal in the hip area. Other large sauropod dinosaurs with substantial body mass and long tails were also subjects of this speculation.

Advancements in paleontology and better imaging techniques have allowed scientists to study fossilized remains in more detail. Comparative anatomy with modern descendants of dinosaurs, such as birds and reptiles, has shown that these cavities are more consistent with areas that store glycogen bodies, not additional brain matter.

Glycogen bodies serve as an energy reserve, which would have been crucial for large dinosaurs that needed a lot of power to move their massive tails. This adaptation could have been particularly important for maintaining balance, supporting locomotion, and enabling complex movements of the tail without the need for direct control by the main brain.