Bird brains left other dinosaurs behind

Date:
July 30, 2021
Source:
University of Texas at Austin
Summary:
Research on a newly discovered bird fossil found that a unique
brain shape may be why the ancestors of living birds survived the
mass extinction that claimed all other known dinosaurs.



FULL STORY ========================================================================== Today, being "birdbrained" means forgetting where you left your keys
or wallet.

But 66 million years ago, it may have meant the difference between life
and death -- and may help explain why birds are the only dinosaurs left
on Earth.


========================================================================== Research on a newly discovered bird fossil led by The University of Texas
at Austin found that a unique brain shape may be why the ancestors of
living birds survived the mass extinction that claimed all other known dinosaurs.

"Living birds have brains more complex than any known animals except
mammals," said lead investigator Christopher Torres, who conducted
the research while earning a Ph.D. from the UT College of Natural
Sciences and is now a National Science Foundation postdoctoral fellow
at Ohio University and research associate at the UT Jackson School of Geosciences. "This new fossil finally lets us test the idea that those
brains played a major role in their survival." The fossil is about 70
million years old and has a nearly complete skull, a rare occurrence
in the fossil record that allowed the scientists to compare the ancient
bird to birds living today.

The findings were published July 30 in the journal Science Advances.

The fossil is a new specimen of a bird named Ichthyornis, which went
extinct at the same time as other nonavian dinosaurs and lived in what
is now Kansas during the late Cretaceous Period. Ichthyornis has a blend
of avian and nonavian dinosaur-like characteristics -- including jaws
full of teeth but tipped with a beak. The intact skull let Torres and
his collaborators get a closer look at the brain.

Bird skulls wrap tightly around their brains. With CT-imaging data,
the researchers used the skull of Ichthyornis like a mold to create a
3D replica of its brain called an endocast. They compared that endocast
with ones created for living birds and more distant dinosaurian relatives.

The researchers found that the brain of Ichthyornis had more in common
with nonavian dinosaurs than living birds. In particular, the cerebral hemispheres - - where higher cognitive functions such as speech, thought
and emotion occur in humans -- are much bigger in living birds than
in Ichthyornis. That pattern suggests that these functions could be
connected to surviving the mass extinction.

"If a feature of the brain affected survivorship, we would expect it to be present in the survivors but absent in the casualties, like Ichthyornis,"
said Torres. "That's exactly what we see here." The search for skulls
from early birds and closely related dinosaurs has been challenging paleontologists for centuries. Bird skeletons are notoriously brittle
and rarely survive in the fossil record intact in three dimensions.

Well-preserved skulls are particularly rare -- but that's exactly what scientists need in order to understand what their brains were like
in life.

"Ichthyornis is key to unraveling that mystery," said Julia Clarke,
a professor at the UT Jackson School of Geosciences and co-author of
the study. "This fossil helps bring us much closer to answering some
persistent questions concerning living birds and their survivorship among dinosaurs." Mark Norell, the curator and division chair of paleontology
at the American Museum of Natural History, co-authored the study. This
work was funded by the Howard Hughes Medical Institute Science Education Program, the Jackson School of Geosciences and the American Museum of
Natural History.

========================================================================== Story Source: Materials provided by University_of_Texas_at_Austin. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Christopher R. Torres, Mark A. Norell, Julia A. Clarke. Bird
neurocranial
and body mass evolution across the end-Cretaceous mass extinction:
The avian brain shape left other dinosaurs behind. Science Advances,
2021; 7 (31): eabg7099 DOI: 10.1126/sciadv.abg7099 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210730165436.htm

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