Brain feathered dinosaurs were ready to fly

The enlarged forebrain, which is typical for birds, can also be found in dinosaurs

The forebrain (green) of the dinosaur Zanabazar junior was slightly enlarged. © Amy Balanoff / AMNH
Read out

For a long time, the difference between birds and dinosaurs seemed clear: birds have feathers and can fly, dinos do not. But at least some dinosaurs not only already had feathers, they were also neurologically already prepared for flying: analyzes by US researchers show that the forebrain of these dinosaurs was enlarged and thus more similar to that of the birds than the "primeval bird" Archeopteryx.

The brain of today's birds is perfectly adapted to the complex requirements of flying: it magnifies strikingly the areas responsible for processing optical information and coordinating body movements. "The rate of this encephalization is six to eleven times higher than in other groups of animals, " explain Amy Balanoff of the American Museum of Natural History in New York and her colleagues. A similar enlargement of the brain in relation to body size otherwise exists only within the mammals.

In the case of birds, this neural growth begins very early in their evolutionary development: For example, the "primitive bird" Archeopteryx already has a brain that lies in its volume in relation to body size between that of early dinosaurs such as the Tyrannosaurus rex and today's birds, like the Researchers report. In their study, Balanoff and her colleagues wanted to explore more closely whether the Archeopteryx really is a link between birds and dinosaurs in this regard, or perhaps other, closely related dinosaurs already show the typically enlarged forehead.

Comparison of brain volume

To clarify this, the researchers studied the fossil skulls of two dozen feathered dinosaurs, including the Archeopteryx, and some modern birds using computed tomography and created 3D models of their brain shells. They then determined the total volume of the brains of these species in relation to body size, and measured the sizes of certain brain regions such as the cerebrum and the bulge of the visual and olfactory center.

Magnified brain of a modern bird for comparison, here a woodpecker. Amy Balanoff / AMNH

It showed that some of the feathered dinosaurs even had larger brains in relation to their body size than the Archeopteryx. "This species is often considered a unique link between feathered dinosaurs and birds, " says Balanoff. But this proves that he at least in terms of brain volume by no means had a special position. Instead, some Oviraptors and also the Deinonychosaur Zanabazar junior triumphed over him. The larger brain areas such as forebrain, cerebellum and optical centers are also larger in some of these dinosaurs than in Archeopteryx. display

Ready to fly in the spirit

The researchers draw two conclusions from these results: First, there is no clear, on the size or anatomy readable separation between the typical bird brain and that of its predecessor. Instead, the broadening of the brains began even before the development of the first true primitive birds - or these traits developed independently in different dinosaur groups.

On the other hand, some non-bird dinosaurs may already have possessed the neurological prerequisites for flying. "If Archeopteryx had a flying brain, which was pretty much the case, then at least some of the other closely related dinosaurs had it, " says Balanoff. This supports theories that some of the four-winged Deinonychosaurs, including Microraptor zhaoianus and Anchiornis huxleyi, may have already mastered short gliding. (

Nature, 2013; doi: 10.1038 / nature12424)

(Nature, 01.08.2013 - NPO)