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Prehistoric Planet — Uncovered: Armed for Seduction? | Apple TV+ - YouTube
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♪♪
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This is the enormous skull of
Tyrannosaurus rex.
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Many, many times bigger than
mine.
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And these are the bones of its
forelimbs...
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...relatively tiny.
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And there are other dinosaurs in
which the difference in size is
even more marked.
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Why should we think that these
tiny limbs got anything to do
with display?
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(Roaring)
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Dr. Darren Haish:
Everyone knows that T-rex had
small arms.
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Dr. Darren Haish:
But dozens of other predatory
dinosaurs
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from all around the world had
small arms too.
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Dr. Darren Haish:
They all evolved from earlier
dinosaurs that had much longer arms.
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Dr. Darren Haish:
But over millions of years
these dinosaurs
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Dr. Darren Haish:
came to rely more on their
mouths for holding and killing prey.
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Dr. Darren Haish:
So their heads became more
powerful and their arms became smaller.
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♪♪
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David Attenborough:
Some of the smallest
arms relative to body size
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David Attenborough:
belong to the South American
dinosaur Carnotaurus.
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David Attenborough:
When the bones of these arms
were first discovered
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David Attenborough:
it was assumed that they would
be of little use
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David Attenborough:
and were evolutionarily
leftovers,
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David Attenborough:
much like a human's tiny tail
bone.
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David Attenborough:
The closer look at the bones
revealed
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David Attenborough:
that these tiny arms also
probably lacked any claws.
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Carnotaurus's upper arm bone,
the humerus,
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up here, has this weird ball and
socket joint.
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Prof. John Hutchinson:
It's very round at the upper
end.
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And that suggests that its
shoulder joint had quite a bit
of mobility.
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David Attenborough:
And they were attached to the
shoulder with lots of powerful muscles.
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David Attenborough:
Evidence that they were used for
something.
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David Attenborough:
But could they have been used
during courtship?
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♪♪
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Carnotaurus's tiny arms were too
small for anything like digging
or fighting opponents.
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Dr. Darren Haish:
The most likely explanation for
such small yet mobile arms
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Dr. Darren Haish:
is that they were used in
display.
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In the natural world today,
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highly specialized body parts
that appear to have no other
function
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often turn out to be used for
display and to attract mates.
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David Attenborough:
These range from colorful
feather plumes...
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David Attenborough:
to long cumbersome horns and
antlers.
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David Attenborough:
In many cases, the owner of such
appendages puts up with the cost of having them
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David Attenborough:
because they're so attractive
to potential mates.
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♪♪
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David Attenborough:
In modern day birds and
reptiles
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David Attenborough:
iridescent colors also help
physical displays to stand out.
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David Attenborough:
And the same could be true for
Carnotaurus's arms.
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♪♪
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David Attenborough:
A wide range of arm movement and
a show of bright colors
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David Attenborough:
is certainly eye catching.
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David Attenborough:
But in the end...
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David Attenborough:
...potential mates can still be
very choosy.
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♪♪
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