- [Narrator] Have you ever wondered about what lies in the dark depths of the ocean? Most specifically, the deepest known point of the world's ocean known
as the Mariana Trench. What creatures are able to live there and more importantly, are
they any more frightening than the scariest creature
that ever lived in the ocean? Let me show you the
bizarre array of creatures that call the Mariana Trench home. And I bet you'll find them
scarier than a megalodon. (bright chimes) The Mariana Trench is found
in the western Pacific Ocean, 124 miles away from the
crescent-shaped archipelago, known as the Mariana Islands. It's a whopping 2550 kilometers
long and 69 kilometers wide. So, how deep is it? The Mariana Trench starts
at a depth of 5000 meters but its deepest point is
called the Challenger Deep and measures 10994 meters. The 8848 meter high Mount Everest can be placed in the Mariana Trench and there'd still be
over 2000 meters to fill. Given its unique geographic features, the Mariana Trench
presents several factors that makes it hard for life to exist. For one, sunlight cannot
reach these depths. The area is shrouded in complete darkness, making it difficult for all
animals to traverse the trough. Second, there's no algae
or plants to eat down there because there's no sunlight to feed them. Third, given its lack of sunlight, it's very cold down there. With a temperature
range of four degrees to negative one degrees Celsius and finally, the pressure in the Mariana Trench is at 8000 tons per square inch,
which is nearly 1200 times more than the average atmosphere
pressure at sea level. That's like bearing the
weight of a fully loaded truck on your head while stuck
inside a refrigerator. As you're about to see, to survive, given these extreme factors,
the creatures in those depths have evolved in some bizarre ways. First up, this creepy fish
dwelling in the Mariana Trench, known as the fangtooth. It's a beryciform fish,
which means it's carnivorous and lives in deep nocturnal habitats. It got its name for how big
its fang-like teeth are, which are the largest teeth of any fish, relative to their body size. Two of its fangs are so long that the fangtooth evolved two sockets beside its brain to contain
them when the mouth is closed. Even so, its teeth are so large, it can't fully close its mouth. It's large teeth are thought to be an advantage in the dark isolated depths where anything encountered
must be preyed upon. Even if its prey turns out to
be much larger than itself, its disproportionately
large teeth and mouth will prove useful. Basically, it moves around and hopes what it bumps into is food. It's terrifying for sure, but at an average length
of 16 centimeters, it's actually too small to
severely harm a human being. Juvenile fangtooth stay at a depth ranging between 200 and 2000 meters
but adults can go much deeper, reaching as far as 5000 meters. Without light to locate its prey, it uses contact chemoreception. It has receptors that respond
to chemical substances given off by potential
prey upon physical contact. Now, that's disturbing. Apart from the small but freaky fangtooth, there are other creatures, such as the Mariana snailfish
and the benthic comb jelly that are known to survive in waters as extreme as the Mariana Trench. But none of them are as terrifying or bizarre as the megalodon,
an extinct shark species that averaged a frightening
length of 10 meters, about the same as a T. rex. So, to find creatures as
scary as the megalodon that could live in the Mariana Trench, we have to go back in time
to the prehistoric period when sea levels and the
geography of the world were vastly different. After all, only four brief
descents have ever been made to discover what lives
in the Mariana Trench, which means all we can do is guess about what lives down there. We've still got 95% of the
ocean to explore and since the Mariana Trench is over
95000 square miles, who knows? We might even find some deep sea creatures we previously thought were extinct. Let's explore the possibilities now. First up is a carnivorous
marine reptile that is probably the most frightening creature
that ever roamed the seas. At over six meters in
length, creatures of the Liopleurodon genus were apex
predators that ruled the waters during the middle and late
periods of the Jurassic era. So, could Liopleurodon have
lived in the Mariana Trench millions of years ago? Its physical features suggests so. First of all, it was strong
enough to swim long distances. It had four mighty limbs that worked like paddles to move its body. Researchers noted that
reptile's repulsion method wasn't exactly the most efficient but it allowed the carnivore to accelerate and successfully ambush its prey. Plus, studies about the
Liopleurodon's skull suggests that it might have used
its nostrils to identify distinct smells and locate their source. This suggests it lived in deeper waters like the Mariana Trench,
where lack of visibility didn't affect its ability to hunt prey. In addition, Liopleurodon
had eyes designed to ambush its prey from below. Their eyes were pointed upwards to see the silhouette of their prey. It's true that sunlight no
longer reaches the Mariana Trench but some deep creatures have
developed bioluminescence, allowing them to emit light
to lure prey, attract a mate, or deter other creatures. So, apart from locating its
prey in the dark by scent, the Liopleurodon also
likely hid in the depths below its bioluminescent prey
and waited for an ambush. A second prehistoric monster that may have well lived
in the Mariana Trench is this giant marine mosasaur,
known as a hainosaur, which scientists think
grew up to 12 meters long, about the same length
as an average megalodon. And with teeth like that, it would have even scared a megalodon. Scientists say that it lived predominantly in the shallow waters of
Europe and North America but there's also some evidence that it may have roamed the
depths of the Mariana Trench because of how it had
a wide variety of prey. Though we're unaware of
most creatures that roamed or are roaming the Mariana Trench, certain sharks and cephalopods have been identified to live
in similar deep water habitats. At present, goblin sharks can
live up to 1300 meters below while frilled sharks can
reach depths of 1500 meters. The giant squid, a
cephalopod, has been found at a depth of over 1000 meters. The leatherback sea
turtle, on the other hand, has been found at a depth of 1200 meters. And a Hainosaurus specimen was found to have eaten a giant turtle in Belgium. These depths are approximately the same as the starting depth
of the Mariana Trench but it's possible that prehistoric sharks and cephalopods traveled
down much further. And if they did, the
Hainosaurus may have adapted to the conditions of the
habitat of their prey. It even had large nostrils, which means it must have lived in an area where having a better sense
of smell was beneficial. Its big nostrils would
have helped it locate food in deep waters such as
those of the Mariana Trench. Up next, here's a shark-like fish that lived 290 million years ago and measured about 6 meters long. Helicoprion could have
lived in the Mariana Trench for several reasons. First, its closest living
relatives are the chimaeras. With most species in this
order living in depths of up to 2600 meters, since chimaeras
thrive in these depths, perhaps the Helicoprion lived even deeper. It's a particularly mysterious creature with scientists still
researching how it behaved and what its anatomy was like since we haven't discovered
a complete fossil of it. Still, it's thought to have lived around the location of the trench so there's a good chance the
seabed around that location is the only place we'll find
a complete fossil of it. Furthermore, its diet is
similar to the Hainosaurus' since it also ate fish and cephalopods. You see, researchers
always wondered what its spiraled-shaped teeth were used
for and where it developed. It wasn't until 2013 that a skull of the prehistoric creature was
scanned to reveal the truth. The Helicoprion's tooth whorl was located inside its lower jaw. If it hunted down a deep-sea fish or squid that lived in the Mariana
Trench 290 million years ago, it would have likely sliced
into its prey's body, using its serrated saw-like teeth. When the Helicoprion then
closed its lower jaw, the teeth whorl inside
would have moved backwards, not only to slice its prey
but also to move it to the back of its oral cavity
to begin digestion. The fact that a complete
fossil of the Helicoprion is yet to be discovered means the mystery of this creature is yet
to be fully resolved. But I, for one, can't
wait to find out more. Another frightening deep
sea creature worth noting is the Odobenocetops, a
whale that became extinct before the Pliocene Epoch began
about 5.3 million years ago. It measured about four meters long and weighed up to 650 kilograms. It's not the biggest marine
mammal but it's hefty enough to be feared by the many
small creatures in the deep. There's a lot to suggest that it may have lived
in the Mariana Trench. The first clue is how
whale species alive today are capable of venturing into the deep. The sperm whale, for example, is known for diving over 2200 meters down. Likewise, Cuvier's beaked
whales have traveled nearly 3000 meters down, the deepest
recorded dive by any mammal. The pressure is already
so great in these depths that a creature's lungs could collapse and they could suffer from convulsions. Yet, whales are willing
to go there to find food such as the deep-sea squid. The secret here is that marine
mammals, such as whales, have flexible, foldable rib
cages that keep air pockets, like the lungs, protected. The mystery remains,
however, of how these whales prevent convulsions caused by a disorder, known as high-pressure nervous syndrome. If whales today have a physical feature that counter the risk of
highly pressured deep waters, the same could have been
true for the Odobenocetops. Another clue as to whether
the Odobenocetops went down as deep as the Mariana Trench is how its snout and neck evolved. The whale's snout
resembles that of a walrus, which indicates it was
probably a bottom feeder that ate mollusks by sucking
them out of their shells. That bodes well for
our thought experiment, as scientists have observed
mollusks in the Challenger Deep, the deepest point of the Mariana Trench, at a depth of 11000 meters. Also, its neck is flexible,
allowing it to move its head about 90 degrees to have a
better view of its food below. Apart from that, we don't know much more
about the Odobenocetops but scientists think that
it may have used its tusks, not only to find any nearby
prey, but also to stun them, similar to narwhal stag use
their tusks to stun Arctic cod. All in all, the Mariana Trench remains a mysterious elusive habitat that we may never get to fully explore. So the possibilities of strange
life down there are endless. What do you think we'll find down there? Also, my forensic question
king made a video about what happens if megalodon
sharks were still alive. It's very interesting,
so have a watch of it by clicking the video on the screen now. Thanks for watching. (eerie orchestral music)
