Theropod dinosaur jaws became stronger as they evolved

Date:
December 16, 2021
Source:
University of Birmingham
Summary:
Theropod dinosaurs evolved more robust jaws through time allowing
them to consume tougher food, a new study reveals.



FULL STORY ========================================================================== Theropod dinosaurs evolved more robust jaws through time allowing them
to consume tougher food, a new study reveals.


========================================================================== Researchers used digital modelling and computer simulation to uncover a
common trend of jaw strengthening in theropods -- expanding the rear jaw portion in all groups, as well as evolving an upturned jaw in carnivores
and a downturned jaw in herbivores.

Publishing their findings today in Current Biology,scientistsrevealed that biomechanical analysis showed these form changes made jaws mechanically
more stable when biting -- minimising the chance of bone fracture.

The international team, led by scientists at the University of Birmingham, created digital models of more than 40 lower jaws from five different
theropod dinosaur groups, including typical carnivores like Tyrannosaurus
and Velociraptor, and lesser-known herbivores like ornithomimosaurs, therizinosaurs and oviraptorosaurs.

Fion Waisum Ma, PhD researcher at the University of Birmingham, who
led the study, said: "Although theropod dinosaurs are always depicted
as fearsome predators in popular culture, they are in fact very diverse
in terms of diets.

It is interesting to observe the jaws becoming structurally stronger over
time, in both carnivores and herbivores. This gives them the capacity
to exploit a wider range of food items.

"Theropod dinosaurs underwent extreme dietary changes during
their evolutionary history of 165 million years. They started off as carnivores, later on evolved into more specialised carnivores, omnivores
and herbivores. Studying how their feeding mechanics changed is key to understanding the dietary transitions in other vertebrate animals too."
For example, in carnivores like tyrannosauroids, an early form like
Guanlong had a relatively slender and straight jaw. But later forms
such as Tarbosaurus and Tyrannosaurus evolved deeper jaws with the front portion bending upward, which increase jaw strength.

Having a strengthened jaw is especially important to herbivorous
theropods, as their jaws experience considerable stress from repetitive
plant cropping.

Herbivores like Erlikosaurus and Caudipteryx have extremely
downward-bending jaws that could help dissipate such stress.

Dr Stephan Lautenschlager, Senior Lecturer at the University of
Birmingham and senior author of the study, said: "It is fascinating to
see how theropod dinosaurs had evolved different strategies to increase
jaw stability depending on their diet. This was achieved through bone remodelling -- a mechanism where bone is deposited in regions of the jaw
that experience high stresses during feeding." The researchers studied
the feeding mechanics of tyrannosaurids through growth and observed
that the deeper and more upturned jaws of adult theropods, such as Tyrannosaurus and Tarbosaurus, are structurally stronger compared to
those of their juvenile forms.

Dr Lautenschlager further explained: "The similarity between
jaw strengthening through growth and through time suggests that
developmental patterns in juvenile dinosaurs ultimately affected the
evolution of the whole group. This likely facilitated the jaw evolution of theropod dinosaurs and their overall success for over 150 million years." ========================================================================== Story Source: Materials provided by University_of_Birmingham. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Waisum Ma, Michael Pittman, Richard J. Butler, Stephan
Lautenschlager.

Macroevolutionary trends in theropod dinosaur feeding
mechanics. Current Biology, 2021; DOI: 10.1016/j.cub.2021.11.060 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211216145931.htm

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