[EXCITING MUSIC]
This is one of the most dramatic skulls
from our prehistoric planet.
It belonged to a plant-eating dinosaur called triceratops.
[ROAR]
This dinosaur is instantly recognizable
from the massive frill at the back of its head.
But 140 years after the first fossil was found,
scientists are still asking what was the frill for.
These are enormous structures.
So it's an enormous investment in bone and tissue
and also in the muscular effort to hold these structures up.
All of this investment must mean that these features
are very important to the animal's way of life.
But how?
Evidence of injury on triceratops fossils
suggest that the frills were important in defense
and combat.
We can see lesions on the skull, which
are areas where the skull has been damaged and healed.
We can also see where a predator has
taken a chunk out of a frill.
That might indicate that we're looking
at some sort of defensive structure.
But the story doesn't end there.
Another possibility is that the frill was used
to attract prospective mates.
We see this in living animals where structures like horns
show off how healthy they are and who's
a good prospect for producing lots of young.
For a moose, having large antlers
makes the male more attractive--
vital when it reaches sexual maturity.
Could the same apply to the triceratops' frill?
If it was only for defense, then we would expect to see them
develop to the same degree in juveniles as in adults,
but we don't.
We see them being much smaller in the juveniles
and not really developing into the very, very large structures
of the adults until much later.
This isn't the only evidence that they
were used in sexual display.
The surfaces of the frills are very heavily grooved.
These grooves probably carried nerves and blood vessels
that would have supplied the skin growing over those frills.
This may have been very brightly colored, a big surface
area for the animal to show off to potential mates.
Scientists now believe that the triceratops' best known feature
was truly multipurpose--
very useful for attack and defense but also ideal
for attracting a mate.
[ROAR]
It would have been an awe inspiring sight
to friend or foe.
[EXCITING MUSIC]