Why the bird brain is actually a dinosaur brain
A team of scientists has found that the enlarged brain once believed unique to birds actually predates the bird, complicating the bird's already murky evolutionary trajectory.
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But a team of scientists has now found that the Archaeopteryx’s flight-ready skull size is not unique among its relatives. CT scan data comparing Archaeopteryx’s brain size to those of about 20 living birds and 10 non-avian dinosaurs show that Archaeopteryx’s skull size is actually smaller than some of the closely related dinosaur skulls to which it was compared.Skip to next paragraph
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That means that an enlarged braincase, once considered a bird trademark, is not actually unique to birds: some non-avian dinosaurs also had big brain cases, a find similar to previous research showing that feathers and long hands pronged like a fork – once fingered as specifically avian attributes – were also present in non-avian dinosaurs, the authors said.
“It’s hard to say what a bird is, because all these characteristics we’ve traditionally associated with birds keep getting moved down and down the evolutionary tree,” said Amy Balanoff, a researcher at the American Museum of Natural History in New York.
Still, most evidence suggests that Archaeopteryx was anatomically capable of flight. In 2004, a team of scientists from the Natural History Museum in London reported in Nature that the animal’s neurological system was sophisticated enough to allow flight. And in 2011, scientists from German and American universities found that the animal’s wings were likely underpinned with a layer of strong, black feathers that could have born the animal aloft.
So if Archaeopteryx had the capacity to fly, and if other feathered dinosaurs had bigger brain cases than did Archaeopteryx, its possible that those dinosaurs also had the capacity to take flight – though whether or not those animals did in fact fly is still unknown, said Balanoff.
The research, published in Nature, does not address the question of whether or not Archaeopteryx was the first bird. Instead, it suggests that Archaeopteryx was one among several lookalike animals with flight-supporting brains.
“Archaeopteryx is in the evolutionary middle – but it’s not uniquely in the middle,” said Dr. Balanoff.
One of those animals would continue on to give us modern birds, and maybe that animal was Archaeopteryx. But pinpointing where exactly modern birds came from is now largely a matter of splitting evolutionary hairs, said Bhart-Anjan Bhullar, a postdoctoral researcher at Harvard University who was not involved in the research.
“This paper represents a fundamental evolutionary insight,” said Dr. Bhullar.
“What this essentially means is that there were a whole bunch of things running around that looked like Archaeopteryx,” he said. “It was an Archaeopteryx world.”
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