Dinosaurs ruled the planet for over 150 million years.
They occupied almost every corner of the globe
and came in almost every shape and size imaginable.
Some were truly extraordinary.
[grunts]
We now know that T. rex was a powerful swimmer...
Velociraptors were cunning, feathered hunters,
and that some dinosaurs had the most bizarre behavior.
But new discoveries are being made almost every day
that tell us more about life on this planet 66 million years ago.
[bellowing, rumbling]
[David Attenborough] This time on Prehistoric Planet,
- we reveal new animals... - [roars]
...and new insight into their quest to find a partner...
[chirps]
...the challenges faced by raising a family...
[bellows]
...and their titanic battles.
[rumbling]
[bellows]
[roars]
- [roars] - [squawking]
Journey to a time when nature put on its greatest show.
This is Prehistoric Planet 2.
The ocean.
The largest habitat on the prehistoric planet...
and home to one of the biggest predators that has ever lived...
a giant mosasaur.
But not all mosasaurs are ferocious 50-foot-long monsters.
Taking refuge in the reef is Phosphorosaurus.
She too is a mosasaur.
One of the smallest, at less than ten feet long.
She spends the daylight hours hiding from danger.
But once or twice an hour, she has to dart to the surface to grab a breath.
Like all of her kind, she is air-breathing.
She's dwarfed by the biggest mosasaurs.
But she too is a deadly predator...
and she doesn't always hide in the shadows.
When the time is right, she becomes a hunter.
And that time is when the sun sets.
As darkness falls, her underwater world transforms.
Now, billions of creatures will begin to rise from the depths
to feed near the surface.
The largest mass migration on Earth occurs in almost total darkness
and can only be seen with special night-vision cameras.
The most spectacular of these nighttime visitors are a type of lantern fish.
Their faint, eerie light is produced by a chemical reaction inside their bodies.
A flash of this bioluminescence can be used to confuse predators.
And when seen from below, the glow enables them to blend with
and hide against the ocean's moonlit surface.
But they can't hide from Phosphorosaurus.
For her size, her eyes are the largest of any mosasaur...
allowing her to see through the illusion and pick out her prey.
[creatures bellowing]
By the time dawn arrives,
the migrating shoal has sunk once more to the depths.
And Phosphorosaurus too must return to her daytime hiding place.
The biggest mosasaurs are back on the prowl.
She will have to wait till nightfall before it's safe to hunt again.
[bird squawks]
By day, the prehistoric ocean provides opportunities
for a very different type of hunter.
[bird honking]
In the warm, shallow seas of North America,
fish numbers can almost match the nocturnal lantern fish shoal.
And they are a magnet for six-foot-long Hesperornis.
Hesperornis may be unable to fly, but it's superbly adapted for ocean life.
Large, powerful feet propel it with great agility.
There's no escape for any unfortunate fish
once it's caught by this beak full of needle-sharp teeth.
The Hesperornis don't have the shoal to themselves for long.
Xiphactinus, known as X-fish.
The feeding opportunity soon attracts them in large numbers.
At over 17-feet long, they are one of the largest and fastest fish in the ocean.
With its huge mouth, Xiphactinus can scoop up several fish at once
and has even been known to swallow prey half its size whole.
At first, there is plenty for everyone.
But as fish numbers dwindle, the X-fish turn their attention elsewhere.
Predator is about to become prey.
The Hesperornis have only one option: to swim for their lives.
Xiphactinus is faster.
Hesperornis is more agile.
But in the eyes of an X-fish, anything is on the menu...
even their own kind.
Within minutes, the banquet is all but gone...
and the predators move on.
Danger in the ocean doesn't only come from deadly hunters.
It could come from the sea itself.
Here, around the islands of prehistoric Europe,
it's the power of the tide that creates challenges for life.
Especially for the tiniest creatures.
These are ammonite eggs.
Thousands of them.
They have been swept inshore...
to rock pools.
Here, they have the chance to develop free from danger.
The eggs are tiny, only a fraction of an inch each.
Now it's time for the young within to break free.
They move by jet propulsion.
But mastering new swimming skills is not easy.
Until now, these pools have provided a nursery.
But as the tide retreats, they become isolated.
Others can make their escape.
But for the helpless ammonites,
their nursery can quickly become a deadly trap.
Under the midday sun, the water in the pool starts to evaporate.
If it dries out completely, they will all die.
But everything is not lost.
Baby ammonites can do something remarkable.
Each makes its own bid for freedom, forcing them together.
The combined effort means they effectively move as one.
Each is carried along on this tiny living tide,
pushed over the bare rock by those behind...
eventually escaping to deeper water.
Now they wait for the rising tide.
[wave crashes]
But not everyone escapes.
Countless are left stranded...
food for scavengers, like these baby Pyroraptors.
[chirps]
[chittering]
The rest are carried by powerful currents many miles from land.
Even as far as this, the very heart of the Pacific Ocean.
These enormous atolls and the lagoons at their center
provide the only shelter for thousands of miles.
[elasmosaurs calling]
In this rare place, Tuarangisaurus, a kind of elasmosaur, finds safety.
But outside these shallows, it's a different story.
Each day, the elasmosaurs must venture into deeper water.
Canyons in the atoll walls lead from the shallows to rich feeding grounds.
This deep water attracts not just the hungry elasmosaurs
but the predators that hunt them.
The biggest in the ocean.
50-foot-long Mosasaurus.
Nutrients driven up from the ocean floor ensure a plentiful supply of fish.
Streamlined bodies and four powerful flippers
give elasmosaurs great maneuverability.
But their daily feeding forays make their movements predictable
for an intelligent and patient hunter.
[elasmosaurs calling]
Mosasaurus is an ambush predator.
This enormous animal uses its huge tail to accelerate with astonishing speed.
This time, unlucky.
In fact, most hunts fail.
But with so many elasmosaurs living here,
it's not long before there is another opportunity.
[calling]
Camouflaged against the dark canyon floor, the mosasaur can approach unseen...
waiting for a young, inexperienced individual.
The ideal victim.
Mosasaurus can strike their prey with such force
that the impact alone can kill.
It's an attack so swift, the elasmosaur almost certainly never saw it coming.
Life in the ocean can be dangerous, not only because of giants.
Of the baby ammonites that escaped the rock pools,
less than one in a hundred has survived several months at sea.
But these few have been particularly lucky.
Ocean currents have carried them to an ideal place to live:
seagrass beds off the coast of Europe.
Here, shoals of ammonites occur in a surprising variety of sizes...
and shapes.
This strange, six-foot-long giant is Baculites,
which feeds near the seafloor.
And almost matching it in size,
Diplomoceras, shaped like a giant paper clip.
They all flourish here, thanks to an abundance of food.
Plankton. Small crustaceans. Some even eat fish.
These hatchlings are beginning to acquire
the extraordinary shape they will have when they are mature.
The protruding spiral identifies them as young Nostoceras.
These are adult Nostoceras.
They favor the seafloor in deeper waters.
Ammonites have been thriving in these prehistoric oceans
for almost 400 million years.
There are thousands of species.
They are one of the most successful groups of animals to have ever lived...
flourishing in the warm, temperate seas and even the coldest waters at the poles.
Like here, in the frozen sea around the Antarctic.
After a winter of near-total darkness, the low sun is beginning to melt the ice...
making it accessible once more for a giant seasonal visitor.
[hissing, snorting]
Morturneria, a strange type of elasmosaur.
They are warm-blooded,
with a thick layer of blubber which conserves the heat in their body.
They're one of the world's most secretive and elusive animals.
[snorts]
This pod has migrated nearly 2,000 miles from South America...
[rumbles]
...to arrive here in time for spring.
It's the first time this year's calves will have encountered sea ice.
It can be dangerous for an air-breathing reptile.
They can only grab a breath of air where there are gaps in the ice.
Adults must navigate carefully to find them,
and the youngsters must stay close.
These cold waters are an excellent habitat for this giant's favorite food.
Polar mud full of small creatures.
There can be hundreds of tiny animals in every square foot of seafloor.
Separating what's edible from the sticky mud is a challenge.
[elasmosaurs calling]
But they have a neat solution.
Scooping up a mouthful, they partially close their jaws,
creating a giant sieve to filter out the food.
These are the only animals to have evolved teeth to feed in this way.
The Morturneria will feed here all summer,
until the water ices over again in the polar winter.
[bellows]
[hisses]
In warmer waters, they will face other challenges.
But the most resourceful animals will always find opportunities
in the vast oceans of the prehistoric planet.
The lands of the prehistoric planet were ruled by the dinosaurs.
But the seas were dominated by a very different group of reptiles:
the mosasaurs.
And this is the skull of one of them.
[Dr. Michael Habib] Mosasaurs were seagoing lizards.
Think of a giant, swimming, whale-sized Komodo dragon.
Tapered snout, rough skin, four fins instead of normal limbs
and a long tail that would look a lot like a shark tail but upside down.
That's basically a mosasaur.
[Attenborough] The largest was Mosasaurus hoffmanni.
It was an ambush predator.
But what was the secret of its success?
They can move from just still, not moving at all
to incredible speeds right before your eyes.
[Attenborough] In the modern world, we see this ability in reptiles like crocodiles.
Their muscles can deliver short bursts of tremendous power.
[wildebeest bleating]
Mosasaurus, given that they're reptiles, given that they're lizards,
probably had similar capabilities in their muscles.
[Attenborough] They also had another adaptation
that could increase the element of surprise.
[Habib] One of the tricky things about swimming is
you need a special kind of dynamic to get out of the gate quickly,
to do the equivalent of a sprinter's start from the blocks.
And one of the best ways of doing that is to bend yourself into a C-shape
and then push off of the water with the side of your body.
[Attenborough] Fish today use this technique.
Known as a C-start,
it allows them to accelerate from a standstill to full speed in an instant.
[Habib] Mosasaurs likely were able to do something very similar,
but of course at a much grander scale.
[Attenborough] So, exactly how fast could a giant like Mosasaurus hoffmanni swim?
To find out, the Prehistoric Planet team commissioned a unique scientific study.
[Habib] Until recently, no one had really attempted to estimate
these kinds of performance values in detail.
Our work is one of the first attempts
to really put numbers to the abilities of these animals.
And the results we got from that are really pretty stunning.
[Attenborough] The team ran the calculations four times
to ensure they were correct.
[Habib] All four of the different trials came to the same overall conclusion.
These animals were able to generate massive accelerations.
[Formoso] This mosasaur, it could probably clear 75% of its body length
in one single second.
That means, if that mosasaur is 17 meters away from you,
in one second, it will be 75% closer.
And in the second second, it would have surpassed you
and probably eaten you along the way.
[Habib] Being hit by a Mosasaurus would be
a bit like being hit by a full-size semitruck.
Just the impact of the animal alone, much less the bite that would follow,
would kill a lot of its prey instantly.
[Attenborough] Mosasaurs could reach 30 miles an hour
in as little as one second.
This is what makes them, arguably, the ultimate marine predator of all time.