SCIENCE & SOCIETY - #dinosaurs #Trex

Study: Dinosaurs Lost Teeth,

Grew Bird-Like Beaks

Fossil analysis suggests members of at least one dinosaur species started out with full sets of teeth, only to lose them in adulthood and develop beaks instead.

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Issue 14

28 August

Lower Secondary

At the height of the Jurassic Period, 19 dog-size

dinosaurs drowned in a mud pit in what is now

northwestern China. But 160 million years later,

these Limusaurus inextricabilis specimens—aptly

named “inextricable mud lizards”—would be

declared the only known reptiles to lose their teeth

after birth and develop bird-like beaks as they

matured. This odd phenomenon, described in a

study published in Current Biology last week

(December 22), may shed light on the mechanism of

beak evolution.

The discovery came after a team of biologists and

paleontologists re-examined the 19 specimens and

noticed marked differences in the fossilized facial

features. “At first we thought they were different

dinosaurs—one with teeth and one without,”

coauthor Wang Shuo, an evolutionary biologist at

Capital Normal University in Beijing, told CNN.

“But they were largely identical and we found solid

evidence that teeth were lost. There were empty

tooth sockets in their jaw bones.”

While the younger specimens had all of the usual

trappings of carnivorous, reptilian dinosaurs, the

adults seemed to have lost their teeth entirely,

while the most mature specimens had developed

bird-like beaks. Some of the adult specimens even

had rocks in their gullet, one of the telltale signs of

modern bird digestion.

Artist’s rendering of limusaurus.

"Who would have thought that a dinosaur would

start off with teeth and then replace them with a

beak when it became an adult?” Stephen Brusatte, a

paleontologist at the University of Edinburgh, U.K.,

who was not involved in the study, told The

Christian Science Monitor. These different diets

may have allowed adult and juvenile dinosaurs to

live together without competing for food, Brusatte

added.

While the findings may provide some information

about how beaks could theoretically evolve, the

authors stressed that further investigations are

needed. Limusaurus is part of the vast group of

theropod dinosaurs (which includes birds) but part

of a distant lineage. “This is definitely not on the

way to bird beaks,” coauthor James Clark of George

Washington University told The Christian Science

Monitor. Still, he added, “this is the first time it has

been found in the fossil record.”

A study of 19 fossilized

dinosaurs have found that one species had teeth when young, but

lost them in adulthood. The species involved was related to modern birds,

and may help unravel the origins of the beak.

Adapted from: http://www.the-scientist.com/?articles.view/articleNo/47870/title/Study-Dinosaurs-Lost-Teeth--Grew-Bird-Like-Beaks/

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