[Animal] Oddly modern skull raises new questions about the early evolution of birds

[BirSaNN]

A fossil skull from a toothy early relative of today's birds shows a weirdly modern skull configuration, raising new questions about the early evolution of birds.

The earliest birds on Earth may have been more modern-looking than scientists expected — a discovery that raises new questions about a murky period in evolutionary history. 

The first birds diverged from two-legged theropod dinosaurs around 165 million to 150 million years ago, during the Jurassic period, according to a 2015 paper in the journal Current Biology(opens in new tab). They coexisted with dinosaurs during the Cretaceous. After the mass extinction that wiped out the nonavian dinosaurs about 66 million years ago, birds took off, evolutionarily speaking (they were already adept at flight). 

But a more detailed understanding of this process is elusive, in part because there are barely any bird fossils from the Cretaceous. This was a crucial period of bird history, because the dino-killing asteroid also wiped out many ancient lineages of birds, leaving only the survivors to give rise to modern birds. That leaves a lot of questions about what the first birds looked like before this great winnowing. 

"This event was really pivotal in terms of bird evolutionary history, because it dictated which lineages of bird-like animals were winners and losers," Daniel Field(opens in new tab), a vertebrate paleontologist at the University of Cambridge in the U.K., told Live Science. 

Enter a new discovery by Field and his colleagues: Janavis finalidens, a vulture-size, toothed bird that isn't directly related to any modern birds but was a close relative of modern bird ancestors in the final days of the dinosaurs. This newly described species surprised Field and his team because of a quirk of its skull: The bird's palate (what would be the roof of the mouth in humans) is unfused, giving the animal a mobile upper beak, like that of a modern duck. This was surprising, because scientists had thought the most primitive birds had fused palates and rigid upper beaks, much like today's emus and ostriches. 

Related: How did birds survive the dinosaur-killing asteroid?

The new finding, published Nov. 30 in the journal Nature(opens in new tab), suggests an alternative hypothesis: that the earliest birds looked "modern" and the "primitive" beak of emus and ostriches may have evolved later.

"It's an interesting new piece of info

rmation that definitely complicates the picture," said Jingmai O'Connor(opens in new tab), associate curator of fossil reptiles at Chicago's Field Museum. "But what it says, we really can't yet say," said O'Connor, who studies the dinosaur-bird transition but was not involved in the new research.

A single bone 
To understand why the bird that Field refers to as Janavis is weird, you have to know a little about bird-science history. Back in the mid-1800s, British biologist Thomas Huxley (famous for being "Darwin's bulldog" due to his advocacy of evolutionary theory), working with what he had, split all birds into two ancestral groups: the "ancient jaws," or paleognaths, which had rigid, ostrich-like palates; and the "modern jaws," or neognaths, which had mobile, duck-like palates. 

A mobile palate gives rise to a mobile beak, so scientists assumed that the unfused "modern jawed" birds were an evolutionary advance over their more primitive "ancient jawed" ancestors. With a mobile beak, birds are better at grooming, feeding, nest building and other tasks requiring dexterity. 

link: https://www.livescience.com/early-bird-evolution-skulls