Australia: The Land Where Time Began

A biography of the Australian continent 

Dinosaur Behaviour - Brain, Nerves and Intelligence1

The great majority of dinosaurs had brains that in size relative to the body and structure were similar to those of reptiles, though with some variation of the size to body mass ratio. The brains of the very large tyrannosaurids were unusually large for dinosaurs of their size. The same applied to the hadrosaurs that they hunted. The brains of stegosaurs and sauropods, though small, were in the size range of reptiles for animals of their very large mass.

According to the author1 because of the small, fairly simple brains of most dinosaurs they probably had a limited repertoire of behaviour compared to that of birds and mammals, most likely being more programmed genetically and stereotypical, though remarkable levels of mental ability can be achieved by small-brained animals. Examples of this are found among lizards and fish that can retain new information and learn new tasks, such as many fish that live in organised groups, and crocodilians care for their nests and young. Though being driven by neural systems that are tiny social insects live in organised collections that carry out a number of tasks such as rearing the young, build large complex architectural structures, as well as enslaving other insects such as aphids, and farm fungi on plant material they bring back to the nest specifically for that purpose - leaf-cutter ants.

The avepectoran theropods, that were bird-like, were a major exception to the reptile-like brains. The size range and complexity of their brains were both within the lower portion of the range of the birds, their brains being proportionally larger than those of other dinosaur groups. He suggests the expansion and upgrading of dinosaur brains among the avepectorans probably evolved in the context of the initial stages of dinosaurian flight, the assumption being that the dinosaurs with bigger brains also had a level of behaviour that was more sophisticated than in other dinosaurs with the more reptilian-style brains.

In many small-brained dinosaurs there was an enlarged spinal cavity in the pelvic region that was an adaptation to assist with the coordination of the function of the hindlimbs, a structure that is paralleled in big ground birds. Among the longer dinosaurs there was a problem with the distance of the brain from the rear portions of the body and tail, as nerve impulses took longer to travel to the greater distances. The distance the nerve signals needed to travel to the tip of the tail and back to the brain was about 75 m (250 ft) or possibly more. As the speed of the nerve impulses is reduced by the presence of synaptic gaps there is a speed advantage in growing individual nerve cords as long as possible.

Sources & Further reading

  1. Paul, Gregory S., 2010, The Princeton Field guide to Dinosaurs, Princeton University Press.


Author: M. H. Monroe
Last updated 28/01/2012 






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