Ancient herbivore's diet weakened teeth leading to eventual starvation,
study suggests

Date:
June 9, 2023
Source:
University of Bristol
Summary:
Researchers have shed light on the life of the ancient reptile
Rhynchosaur, which walked the earth between 250-225 million years
ago, before being replaced by the dinosaurs.


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A team of researchers from the University of Bristol have shed light
on the life of the ancient reptile Rhynchosaur, which walked the earth
between 250-225 million years ago, before being replaced by the dinosaurs.

Rhynchosaurs are a little-understood group of roughly sheep-sized ancient reptiles that thrived during the Triassic Period, a time of generally
warm climates and tough vegetation.

In the new study, the researchers studied specimens found in Devon and
used CT scanning to see how the teeth wore down as they fed, and how
new teeth were added at the backs of the tooth rows as the animals grew
in size.

The findings, published today in Palaeontology, show that these early herbivores likely eventually starved to death in old age, the vegetation
taking its toll on their teeth.

"I first studied the rhynchosaurs years ago," said team-leader Professor
Mike Benton from Bristol's School of Earth Sciences, "and I was amazed
to find that in many cases they dominated their ecosystems. If you found
one fossil, you found hundreds. They were the sheep or antelopes of their
day, and yet they had specialized dental systems that were apparently
adapted for dealing with masses of tough plant food." Dr Rob Coram,
who discovered the Devon fossils, said: "The fossils are rare, but
occasionally individuals were entombed during river floods. This has
made it possible to put together a series of jaw bones of rhynchosaurs
that ranged in age from quite young, maybe even babies, through adults,
and including one particularly old animal, a Triassic old-timer whose
teeth had worn right down and probably struggled to get enough nutrition
each day." "Comparing the sequence of fossils through their lifetime,
we could see that as the animals aged, the area of the jaws under wear
at any time moved backwards relative to the front of the skull, bringing
new teeth and new bone into wear," said Thitiwoot Sethapanichsakul who
studied the jaws as part of his MSc in Palaeobiology. "They were clearly
eating really tough food such as ferns, that wore the teeth down to the
bone of the jaw, meaning that they were basically chopping their meals
by a mix of teeth and bone." "Eventually, though, after a certain age
-- we're not sure quite how many years -- their growth slowed down and
the area of wear was fixed and just got deeper and deeper," added Dr
Coram. "It's like elephants today -- they have a fixed number of teeth
that come into use from the back, and after the age of seventy or so
they're on their last tooth, and then that's that.

"We don't think the rhynchosaurs lived that long, but their plant food
was so testing that their jaws simply wore out and presumably they
eventually starved to death." The rhynchosaurs were an important part
of the ecosystems on land during the Triassic, when life was recovering
from the world's greatest mass extinction, at the end of the preceding
Permian Period. These animals were part of this recovery and setting
the scene for new types of ecologies when first dinosaurs, and later
mammals became dominant, as the modern world was being slowly constructed.

By comparing examples of earlier rhynchosaurs, such as those from Devon,
with later-occurring examples from Scotland and Argentina, the team
were also able to show how their dentitions evolved through time, and
how their unique teeth enabled them to diversify twice, in the Middle
and then in the Late Triassic.

But in the end, climate change, and especially changes of available
plants, seem to have enabled the dinosaurs to take over as the
rhynchosaurs died out.

* RELATED_TOPICS
o Plants_&_Animals
# Extinction # Endangered_Plants # Nature
o Earth_&_Climate
# Ice_Ages # Ecology # Climate
o Fossils_&_Ruins
# Dinosaurs # Fossils # Ancient_DNA
* RELATED_TERMS
o Ichthyosaur o Dinosaur o Timeline_of_evolution o
Jurassic o Mammoth o Structure_of_the_Earth o Homo_(genus)
o Feathered_dinosaurs

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


========================================================================== Journal Reference:
1. Thitiwoot Sethapanichsakul, Robert A. Coram, Michael
J. Benton. Unique
dentition of rhynchosaurs and their two‐phase success as
herbivores in the Triassic. Palaeontology, 2023; 66 (3) DOI:
10.1111/pala.12654 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230609125712.htm

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