Bird skull evolution slowed after the extinction of the dinosaurs
A detailed analysis of skull morphology shows non-avian dinosaurs evolved
more rapidly than birds

Date:
August 18, 2020
Source:
PLOS
Summary:
From emus to woodpeckers, modern birds show remarkable diversity
in skull shape and size, often hypothesized to be the result of
a sudden hastening of evolution following the mass extinction
that killed their non-avian dinosaur cousins at the end of the
Cretaceous 66 million years ago. But this is not the case according
to a new study.



FULL STORY ==========================================================================
From emus to woodpeckers, modern birds show remarkable diversity in
skull shape and size, often hypothesized to be the result of a sudden
hastening of evolution following the mass extinction that killed their non-avian dinosaur cousins at the end of the Cretaceous 66 million years
ago. But this is not the case according to a study by Ryan Nicholas
Felice at University College London, publishing August 18, 2020 in the open-access journal PLOS Biology. In the most detailed study yet of
bird skull morphology, Felice and an international team of researchers
show that the rate of evolution actually slowed in birds compared to
non-avian dinosaurs.


==========================================================================
The researchers used high-dimensional 3D geometric morphometrics to map
the shape of 354 living and 37 extinct avian and non-avian dinosaurs
in unprecedented detail and performed phylogenetic analyses to test for
a shift in the pace of evolution after the origin of birds. They found
that all regions of the skull evolved more rapidly in non-avian dinosaurs
than in birds, but certain regions showed rapid pulses of evolution in particular lineages.

For example, in non-avian dinosaurs, rapid evolutionary changes in the jaw joint were associated with changes in diet, while accelerated evolution
of the roof of the skull occurred in lineages that sported bony ornaments
such as horns or crests. In birds, the most rapidly evolving part of
the skull was the beak, which the authors attribute to adaptation to
different food sources and feeding strategies.

The authors say that overall slower pace of evolution in birds compared to
non- avian dinosaurs calls into question a long-standing hypothesis that
the diversity seen in modern birds resulted from rapid evolution as part
of an adaptive radiation following the end-Cretaceous extinction event.


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


========================================================================== Journal Reference:
1. Ryan N. Felice, Akinobu Watanabe, Andrew R. Cuff, Michael Hanson,
Bhart-
Anjan S. Bhullar, Emily R. Rayfield, Lawrence M. Witmer, Mark
A. Norell, Anjali Goswami. Decelerated dinosaur skull evolution
with the origin of birds. PLOS Biology, 2020; 18 (8): e3000801 DOI:
10.1371/ journal.pbio.3000801 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200818142141.htm

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