Odd saber-toothed beast discovered
Preyed on ...plants:
Brian HANDWERK
“It takes some time to believe it when you see
this animal,” researcher says.
Thriving long before the dinosaur age, Tiarajudens eccentricus was
armed with an incredible arsenal of teeth for grinding, tearing and even
scaring. But the newly discovered saber-toothed mammal ancestor was a
vegetarian, a new study says.
Shown in a paleontologist’s illustration, Tiarajudens
eccentricus bears its unexpected saber teeth. Illustration
courtesy Juan Cisneros, Science/AAAS |
Not only did the big-dog-size animal have huge canines - each as
large as a crayon - but the roof of the animal’s mouth appears to have
been studded with teeth, which allowed for rapid replacement of lost
teeth, as in sharks, researchers say.
Part of the Anomodontia suborder within the Therapsida order - often
called mammal-like reptiles - the 260-million-year-old fossil vegetarian
“looks like a combination of different animals, and it takes some time
to believe it when you see this animal in front of you,” said
paleontologist Juan Carlos Cisneros, who discovered the fossil in
Brazil.
“It has the incisors of a horse, which are very good for cutting and
pulling plants; the big molars of a capybara (picture), for grinding;
and the canines of a saber-toothed cat.”
Paleontologist Jörg Fröbisch said the saber teeth are a particular
surprise, considering the animal’s diet of fibrous plants.
“You would usually expect saber teeth in a carnivore,” said Fröbisch,
of the Humboldt University of Berlin.
“The best known animals are obviously saber-toothed cats or tigers,
but there are also some (extinct) forms known among the marsupials,
relatives of kangaroos and wombats,” added Fröbisch, who wasn’t involved
in the Tiarajudens eccentricus study, to be published tomorrow in the
journal Science.
T. eccentricus saber teeth might have deterred predators or
intimidated or wounded rivals of the same species, the study authors
speculate.
“Saber teeth used for display or fighting between members of the same
species is something that we thought appeared in herbivores less than 60
million years ago,” said study leader Cisneros, of Brazil’s Federal
University of Piau”.
“If Tiarajudens eccentricus (used them this way), then it appeared
much earlier, when terrestrial communities were...dominated by
herbivores.”
Tooth trials: secret of evolutionary success
Why did plant-eating Tiarajudens eccentricus - “the eccentric tooth
of the Tiarajú region” - have idiosyncratic dentition? The answer may
lie in evolutionary experimentation.
No matter how unusual, Tiarajudens eccentricus wildly differing teeth
fit closely together during a bite - the better to grind up and process
fibrous leaves and stems. This early example of a tight tooth fit in a
therapsid may offer insights into why humans and other mammals are so
equipped today, since mammals evolved from therapsids.
“This animal was already capable of eating like a modern ruminant,
and that’s very interesting,” Cisneros said. Ruminants are animals such
as cows and goats, which chew their cud and have complex,
multi-chambered stomachs.
These unique dental adaptations may also offer some clues to the
striking success of the anomodonts during the middle Permian era, before
dinosaurs dominated Earth.
“Anomodonts were the most successful group of terrestrial
vertebrates, with the most species, most diverse morphologies, and most
ecological adaptations during this time,” the University of Humboldt’s
Fröbisch said.
“There were burrowing forms, climbing forms, semiaquatic forms, small
rat-sized animals, and large cow-sized animals in this same group, and
this is unique in the ancestral lineage of mammals,” he said.
“This early experimentation in different teeth, I’m sure, is part of
why this group became so successful.”
National Geographic News
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