- 6 months ago
River.Monsters.S07E03.Prehistoric.Terror
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00:00I'm Jeremy Wade.
00:02For more than 30 years, I've been investigating underwater mysteries.
00:07Mr. Fish?
00:09And uncovering nightmarish beasts.
00:13Ah!
00:14But if I thought I'd seen the worst, I'd be wrong.
00:21Half a billion years of evolution has seen millions of fish come and go.
00:27Among the monsters that were stranger, deadlier, and bigger than anything alive today.
00:36But with the evidence locked in stone, it's been impossible for me to pursue these prehistoric predators.
00:44Now, however, breakthroughs in technology mean I've found a way to unlock their secrets.
00:51It's amazingly clear. You've got upper jaw, lower jaw.
00:54And now that the door to the prehistoric past is open, I have to go through.
00:59This is the first time I've been so close to such a large predator.
01:03I'm going on an epic journey around the globe and back in time
01:08to hunt down the greatest river monster that ever lived.
01:23In 30 years of tracking down monsters, I've always relied on a fishing line to get results.
01:30They do exist, they do exist.
01:35But this mission is different.
01:38I need to find a way to connect with another time.
01:42Because the monsters I'm hunting now lived millions, even hundreds of millions of years ago.
01:49I'm going to hunt the special living river monsters that still carry echoes of the distant past.
01:58They're going to help me find the biggest, baddest river monster of all time.
02:04Where better to begin than with the ultimate instrument of death and destruction?
02:13This is a cast of a tooth that's around 260 million years old.
02:20It belonged to the very first river monster.
02:25One way to help me picture my prehistoric contenders is to draw them out in sand, life size.
02:34This ten foot long serpentine swamp monster was a lethal ambush predator known as the xenocanth or eel shark.
02:45These were the first prehistoric predators to take over fresh water.
02:50In Texas you still find their fossils and similar habitat today.
02:59So that's where I'm starting my investigation.
03:05These fresh water sharks were hunting.
03:07I wouldn't recognise the vegetation, it would be quite different to what we've got here.
03:10But the general feel, the general habitat would be quite similar.
03:13You'd have these channels, but then off the channels you'd have lots of trees standing very close together.
03:20Eel sharks were the top predator of warm swamps and rivers like these in the prehistoric past.
03:27And ambush hunters are defined by their habitat.
03:32If I can find the top predator here today, then maybe it can shed light on the rise of the very first river monster.
03:40Normally I tend to fish with one rod and I tend to hold that rod or have it very close to me.
03:45With more than one line I can cover a lot more water.
03:55This has taken 20 yards or so.
03:59It's still going, it's moving right to left.
04:03There.
04:04Still going, it's going across the river now.
04:06I'm.
04:07You've got to tighten up and go.
04:10OK.
04:15Yep, this is a good sized fish.
04:18There it is, there it is, there it is.
04:22There it is, there it is, there it is.
04:34Got her, guys.
04:35Fantastic.
04:37It's an alligator gar,
04:39a living fossil that's been unchanged for more than 60 million years,
04:44and is close to the size of the prehistoric eel shark.
04:49Take it to the beach here where we can actually just gently slide it up on the sand.
04:56But I'm wary of any predator that weighs in at over 120 pounds.
05:07This fish's body is packed with muscle to launch surprise attacks,
05:12just as I imagined the eel sharks was.
05:15Right, this creature is very much the top predator in the water these days.
05:18And that's a double row of teeth it's got on the upper jaw.
05:24But the eel shark took its hardware to an even more devastating level.
05:29If you can imagine something where every tooth has two prongs.
05:33Then any attempt to wriggle free would shred the prey alive.
05:38This ten foot long prehistoric predator was the largest freshwater fish of its time,
05:44and grew bigger than any fish in these waters today.
05:47The xenocamp, an eel-like shark, would have been three and a half foot longer than this.
05:54Eel sharks dominated the world's swamps and rivers for more than a hundred million years,
06:00hunting the same waters as the ancestors of the Gar.
06:04Eel sharks were the kings of stealth.
06:06Freshwater swamp monsters that ambushed the sea.
06:07Eel sharks were the kings of stealth,
06:08freshwater swamp monsters that ambushed the sea.
06:09their victims at close range.
06:10But many factors make for a success.
06:11Eel sharks were the kings of stealth, freshwater swamp monsters that ambushed their victims at close range.
06:24But many factors make for a successful predator, like strength, size, and speed.
06:45Evidence is emerging of a fast-swimming open-water predator,
06:51which definitely ticks all these boxes.
06:56And it's being excavated from landlocked Kansas.
07:01I'm on an excavation site where this lightning-fast predator has been found,
07:06but its exact location is secret, so that the site's not looted.
07:11But I can tell you it lies in the smoky hills of Kansas,
07:15in the heart of Tornado Alley.
07:21Normally, we can't see what's beneath the surface of the earth without digging a hole.
07:27But what's happened here is that nature, in the form of wind and water,
07:31has done the excavation for us.
07:33And as I walk down into these chalk deposits, layer by layer,
07:37it's literally like travelling back in time.
07:43And just about everywhere you look, emerging into the light for the first time in 85 million years,
07:49are the remains of extinct creatures.
07:52And they're mostly things like these clams that you can see here.
07:56But there were also predators.
08:00This tooth belonged to a lightning-fast river monster called Xifactinus.
08:08Some of the bodies exhumed from this ancient seabed have reached more than 17 feet long.
08:14To get my first glimpse of this deadly speed merchant,
08:18I'm going to the Rocky Mountain Dinosaur Resource Center,
08:22where its fossils are cleaned, cast, and then reconstructed into three-dimensional skeletons.
08:28Now that I can see the whole thing in three dimensions,
08:38there are parts of it that really do remind me of fish that I've seen in the flesh.
08:43The way the jaws operate is uncannily like the goliath tigerfish.
08:50And the shape of the body is somewhat like a giant tarpon.
08:54The tarpon uses this streamlined body design to cut through the water with minimal drag.
09:00It's explosive on the line and reaches weights of 350 pounds.
09:07But Xifactinus could top a ton.
09:12This is the biggest, complete specimen of Xifactinus that's ever been found.
09:17Here's the tail.
09:20Dorsal fin.
09:21And all the way down here, giving a total length of 18 and a half foot, the head.
09:28And there are bones from other individuals that suggest they could have grown even bigger.
09:39The shape of its skeleton, especially the design of its pectoral fins and tail,
09:44is very close to another open-water predator living today.
09:50I'm heading south of the equator to the Indian Ocean to try to catch a sailfish,
09:56the fastest fish on the planet,
09:59which in terms of sheer speed could be a very close match for the torpedo-like Xifactinus.
10:04The large eye sockets on the Xifactinus skull suggest to me that it was a sight predator, just like the sailfish.
10:14We have some teasers off the back in addition to the wake of the boat,
10:19and there are baits swimming fast across the surface.
10:22I'm waiting for something to hit one of those.
10:25I'm waiting for something to hit one of those.
10:45Oh, yeah.
10:48Oh, I think it's off.
10:49No.
10:52Oh.
11:08I'm on a mission to hunt down the biggest, most terrifying river monster that ever lived.
11:15My latest contender is the Xifactinus, whose giant streamlined fossils suggest a predator engineered for speed.
11:27To help me construct a mental picture of a live Xifactinus,
11:31I'm after the fastest fish alive today, the sailfish.
11:38Oh, yes.
11:39The only problem is, I've never tried to bring in a fish that can swim this fast.
11:44That'll happen very, very quickly.
11:46It's just jumping there in the distance.
11:48I think I'm under, I'm going to come that side.
11:51Here we go.
11:53This fish can strip line in explosive bursts approaching 70 miles per hour.
11:59All right, let's get some line back in.
12:01Oh, no, it jumps, jump, jump, jump, jump, jump.
12:03And again.
12:04I'm going to come round to the front, round to the front, round to the front.
12:05If I can keep it on the hook, it should tire enough for me to bring it in.
12:13Slowly going.
12:14I'm fine.
12:22Sailfish have been known to impale fishermen during the struggle to bring them on board.
12:27This is a real first for me.
12:31Sailfish.
12:33That's the reason it's called that.
12:35This fish is said to be the fastest fish on the planet today.
12:40Clocked at nearly 70 miles an hour.
12:43The sail is a bit of a mystery.
12:46Some say it's used to corral smaller fish.
12:48Others, that it improves maneuverability.
12:50But when it's down, I can see how closely this fish shares a body plan with Cifactinus.
12:57It's just this streamlined, tubular shape, built for speed.
13:02Very characteristic shaped tail, like a bit of aeronautical engineering.
13:06It's almost identical to the giant fossil tail.
13:09So too are the pectoral fins.
13:14But that's where the similarities end.
13:17Cifactinus had jaws that could bite fish like this in half.
13:22Cifactinus was the biggest fish of this general body design that's ever lived.
13:26It grew up to about 20 feet long.
13:2885 million years ago, Cifactinus hunted open waters for fast swimming fish as big as I am.
13:42And those prey fish had to be fast.
13:46Because in the open ocean, there's nowhere to hide.
13:58In terms of speed, size, and hardware, Cifactinus has to be up there as one of the greatest river monsters that's ever lived.
14:11But one prehistoric leviathan grew to three times its length.
14:16And with monsters, size counts for a lot.
14:19And there's one modern day behemoth sharing these waters with the sailfish, which can give me a sense of that scale.
14:30I've never tried to go after a fish this big.
14:34And I'm starting to wonder if I should.
14:41A dark shadow betrays a giant beneath the surface.
14:49Emerging from the gloom is not a whale, but a whale shark.
14:58The largest fish on the planet today.
15:03That thing is just massive.
15:06It's a good 20-foot long.
15:11But that's a small one.
15:12They grow to about twice that length.
15:15That is the size and weight of the school bus.
15:20But compared with what came before, the whale shark is small fry.
15:25Incredible.
15:27Huge as these things are.
15:29Even a fully grown one is smaller than the biggest fish that ever lived.
15:35That was about the size of a train car.
15:38This prehistoric shadowy beast has to be a contender for the greatest river monster ever.
15:50It patrolled our planet's waters long before giants like whale sharks or whales came on the scene.
15:56The sheer scale of the biggest ever river monster is something that can only be appreciated outdoors.
16:05Normally when I go to the beach, I'm there to bring in a monster.
16:11I never get to play in the sand.
16:14Today, I'm going to create my own life-size image of this contender for the ultimate river monster.
16:20From the tip of the snout to the end of its tail, we're talking more than 50 feet.
16:27So you could line me up eight times along its length.
16:33And at up to 12 feet long, you could line up two of me along each fin.
16:42This fish was like a giant ocean glider.
16:46Then there's its enormous mouth.
16:49It had a huge gape.
16:52I could pretty much walk into its mouth.
16:55But I wouldn't find any savage fangs in there.
16:59This giant ate plankton like the largest whales do today.
17:08Long before whales came on the scene,
17:11Lidzikthis was the first plankton-eating leviathan.
17:20No bony skeleton fish has ever grown near this size again.
17:26It may have topped 20 tons,
17:29yet it flew through prehistoric oceans like a great glider.
17:36And once Lidzikthis vanished,
17:39it would be many millions of years before any other plankton feeder
17:43approached its phenomenal size.
17:45There's no denying that the Lidzikthis is an unsurpassed giant.
17:54But despite its monstrous size,
17:56I think the ultimate river monster has to be a predator.
18:00A deadly hunter.
18:04That still leaves Ziphactinus as the strongest contender so far.
18:08But I've just found out that one of the most feared freshwater fish alive today,
18:15the piranha,
18:17had a giant, even more horrific, prehistoric relative.
18:23Enter Mega Piranha.
18:25My hunt for the greatest river monster that ever lived has unearthed a sinister ambush predator,
18:32an aquatic leviathan, and a fanged torpedo.
18:35Now I've discovered evidence for what might be my most bloodthirsty contender so far.
18:42These photographs show a unique and very disturbing fossil from the banks of the Rio Paraná in Argentina.
18:48It's part of a fish's jaw with three teeth.
18:49Based on the size and curvature of this jaw fragment, its owner was a giant piranha three feet long.
18:54If it was swimming alongside me,
18:55it would extend from my head to my waist.
18:58It's a giant piranha.
19:00It's from my head to my waist.
19:01My most bloodthirsty contender so far.
19:04These photographs show a unique and very disturbing fossil from the banks of the Rio Paraná in Argentina.
19:09It's part of a fish's jaw with three teeth.
19:11Based on the size and curvature of this jaw fragment, its owner was a giant piranha three feet long.
19:18If it was swimming alongside me, it would extend from my head to my waist.
19:25And if the Mega Piranha shared the aggressive pack hunting behavior of these guys,
19:30then the Mega Piranha is a truly terrifying candidate for the baddest river monster of all time.
19:39But with nothing else to go on, how can I bring this beast to life?
19:44I'm going to scale up the piranha's body to match scientists' estimates of Mega Piranha.
19:56I've also had the piranha's skull laser scanned, then scaled up and 3D printed.
20:08The biggest piranha that's ever lived, with the deadliest smile,
20:14I've ever seen.
20:17This could take a handoff, and that's just for starters.
20:21I can scarcely begin to imagine what a pack of hungry Mega Piranhas might be capable of.
20:27Even a school of red-bellied piranhas, the most feared fish in the Amazon today,
20:40wouldn't stand a chance against Mega Piranha.
20:43But we only have a single solitary fossil for this entire species.
21:06We don't really know anything about its behavior.
21:09If it was a pack hunter, then I pity anything else in the water.
21:15But not all piranhas hunt in packs.
21:19So despite its horrific teeth, I'm going to park this one until more evidence turns up.
21:24Which is exactly what has happened with another fiercely armed prehistoric predator.
21:32I've heard from a scientist who's just solved a fiendish century-old puzzle
21:38about a much bigger, stranger, and possibly more deadly contender.
21:42This is an announcement from more than 100 years ago of a great discovery by a Russian scientist,
21:51Alexander Karpinski.
21:53And this is the strange fossil at the heart of the puzzle.
21:58At first sight, this fossil looks like the familiar ammonite.
22:02But in Karpinski's fossil, these are teeth.
22:09Karpinski named the mystery fish Helicoprion, which means spiral saw.
22:17To put that into more modern language, let's call it the buzzsaw killer.
22:21To build a better picture of this killer contender, I'm heading to Idaho,
22:28where these weird weapons keep turning up.
22:31The site of this phosphate mine is now more than 600 miles from the coast.
22:37But once, it was at the bottom of the Sea of Phosphoria,
22:40a shallow, virtually landlocked sea, which was home to a population of Helicoprion.
22:45And last year, Dr. Leif Tapanila from Idaho State University
22:52solved the century-old mystery of how these lethal blade spirals were used
22:58by analysing a unique and now priceless specimen.
23:05So that is it.
23:06That is the fossil.
23:09Looking at this, the first thing I think you think of is,
23:12it looks like a saw blade.
23:14But this fossil isn't unique for what's on the surface,
23:19but for what lies beneath.
23:22Dr. Tapanila used CT x-rays to scan the fossil
23:26and revealed, for the very first time,
23:29the cartilage jaws that held the bizarre tooth world.
23:34The next step was to bring these jaws to life with 3D printing.
23:38And this is the result.
23:40This is an exact one-to-one replication of what's in the rock to scale.
23:47Life size.
23:48Life size.
23:49You're holding a Helicoprion that no one ever has touched.
23:53The only thing that's missing from this now is the tooth world.
23:56This animal is meant to eat meat, but not a bone.
24:06Very little wear has been found on any teeth,
24:09suggesting these tooth worlds were designed to eat boneless prey,
24:13like squid or sharks.
24:14This world belonged to a buzzsaw killer the size of a great white,
24:19but they got a lot bigger than that.
24:22We have spirals that go up over two and a half feet in diameter,
24:26which means the skull is now pushing us up to four feet
24:29and gives us an animal that reaches well past 20, 25,
24:33maybe even up to 30 feet for the largest Helicoprions.
24:40With this knowledge, I'm able to imagine such a beast in action.
24:45Perhaps on a moonlit night,
24:47when ancient squid called Bellum Knights gather near the seabed to mate.
24:52Any fish armed with a weapon like this
25:22has to rank very highly on the list of the deadliest river monsters ever.
25:28For me, sheer size and incredible weaponry
25:33push the buzzsaw killer way ahead of the Zephytonus.
25:41But now my challenge is to find out if there's anything bigger,
25:46badder, or even more terrifying
25:50that can possibly rival it.
26:04I'm on an epic mission around the world
26:07to hunt down the greatest river monster that ever lived.
26:11Let me take you on a journey back through time.
26:16If this line here represents today,
26:23and this line here represents 400 million years ago,
26:30then all of the monsters that I'm hunting are somewhere in this space.
26:34Now, the vast majority of fish alive today are the so-called ray-finned fish.
26:40They've got very obvious bony rays in their fins.
26:44There are tens of thousands of these species,
26:48including piranhas, tigerfish, and catfish.
26:51This group is also home to Zephytonus, the Leedsichthyus, and Megapurana.
27:00But when you dig back into the fossil record,
27:04the number of ray-finned fish steadily diminishes
27:07until there are none around.
27:09The other significant group of fish around today
27:12are the sharks and their relatives.
27:15Sharks originated significantly further back than the ray-finned fish.
27:23This was the era of the eel shark and the buzzsaw killer.
27:28But there was another group of fish.
27:32They were on the scene for more than 50 million years.
27:36But then they all became extinct.
27:38There are no descendants alive today.
27:41These were the placoderms, or plate skins.
27:47Ancient armoured fish that started a monumental arms race.
27:52Not only were their heads encased in bony armour,
27:55but these were also the prehistoric fish
27:57that pioneered and perfected biting jaws.
28:02And one armoured fish grew into a gargantuan bone-crunching giant,
28:08the Duncalosteus.
28:09And this is how big its head armour was.
28:14Somehow I have to figure out
28:16whether this long-extinct beast
28:18is the greatest river monster that ever lived.
28:29There's only one living fish I know
28:31that even approaches the ancient ancestry,
28:34giant size, and armour plating of the Duncalosteus.
28:37It lurks in the dramatic landscape
28:41of Canada's Fraser Canyon
28:43in the wilds of British Columbia.
28:46But fishing here is extremely challenging.
28:49This is tremendously deep, powerful, turbulent water.
28:53And even though I've been fishing a long time,
28:55I have to remind myself that it's possible
28:57for creatures to live and hunt in water like this.
29:00Who knows what could be down at the bottom of this water?
29:08Yeah, so we're all set.
29:09Baits are down.
29:11Just waiting there.
29:12Below me, these churning waters plunge
29:18into more than 150 foot of darkness.
29:23Because of the current,
29:24there's a certain amount of line movement
29:26and rod movement.
29:28But when a fish takes one of those baits,
29:30it should be fairly unmistakable.
29:32That's a good size, I think.
29:50Let's do that.
29:53I'm going back millions of years
30:05to unearth the greatest river monster of all time.
30:10In Canada's Fraser Canyon,
30:12I'm searching for the only armoured giant alive today
30:15that can shed light on what could be
30:17my strongest contender so far.
30:22The dunkelosteus, or bone crusher.
30:34Here we go, chance to get a little bit of line back.
30:39Yeah.
30:43I think it might be approaching the surface.
30:47Up, here we go, here we go, here we go, here we go.
30:50Yep, here we go.
30:56There it is, there it is.
30:57It's a 140-pound white sturgeon,
31:01the largest fish in North American rivers.
31:04Sturgeon belong to the most ancient group
31:06of ray-finned fish around today,
31:08and they're incredibly long-lived.
31:10184 and a half.
31:12That's just over six foot, isn't it?
31:14Heavy fish.
31:15Two of us struggling to hold this up briefly.
31:17But by sturgeon standards, this isn't big.
31:19They grow up to three times the length of this.
31:23Hard to believe.
31:26That's around the same size range as the bone crusher.
31:30The sturgeon's bony plates are unusual in living fish.
31:35And its body helps me imagine the strength and power
31:38of the bone crusher's body.
31:39It really is a strange-looking beast,
31:41but back when these started to emerge,
31:46this look was actually very common, armor plating.
31:48And this is one of the few remnants of that age
31:51that survives to this day.
31:53This sturgeon has given me living clues
31:57to a lost armored predator.
32:01It's going.
32:03It's going.
32:04But to find the last piece of the puzzle,
32:07I'm heading back to the U.S.,
32:09to the Cleveland Museum of Natural History,
32:12to come face-to-face with the very first
32:16ocean-going apex predator,
32:19the Dunkleosteus.
32:20And this is it.
32:37This is Dunkleosteus.
32:40And I have to say,
32:41I'm having a bit of trouble believing
32:43that this was actually a fish.
32:44It's unlike anything I've caught or seen
32:47or anything that's alive on the planet today.
32:51Based on the remains of close relatives,
32:54experts here think the bone crusher
32:56reached lengths of around 20 feet.
33:01And you just can't fail
33:03to notice these huge fangs.
33:06They're not actually teeth,
33:08but sharpened bare jaw bones.
33:11It's estimated that the bone crusher
33:13could slam its jaws shut
33:15with a force of around 8,000 pounds per square inch
33:19inside five hundredths of a second.
33:22Possibly the strongest fish bite ever
33:24and horrifically more powerful
33:26than any creature alive today.
33:29And what all of this tells us
33:31is that this wasn't a fish
33:32that merely grabbed prey,
33:34which had to be small enough to swallow whole.
33:36This could slice through flesh and bone,
33:40which meant it could go after much larger prey
33:42and bite clean mouthfuls out of them.
33:45And this took predation to a whole new level.
33:49That's amazing.
33:50That's just an opportunity for you.
33:51That's a very good one.
33:52That's the way it was going to be small enough.
33:52That's what you can do.
33:53That's just an opportunity for you.
33:54That's what we thought about here.
33:55That's what we thought about here.
33:56If that's something for you.
33:57That's what you thought about here.
33:59You die.
33:59How about you to end up in a movie?
34:00Here's the one.
34:02That's what we thought about here.
34:02You get it.
34:05You get it.
34:05You get it.
34:08I get it.
34:11Yeah.
34:12You get it.
34:13That's what you think,
34:14you get it.
34:14All right.
34:15Well,
34:15it's not a big one.
34:16As a contender for the ultimate prehistoric river monster,
34:28the bone crusher is hitting hard.
34:32But there's one more group of fish with even more formidable roots.
34:38The armored fish weren't the only other group of ancient fish
34:42thriving back here in prehistory.
34:47There were also the lobe fins.
34:51They are still hanging on by a thread.
34:56There's only a handful left, and the most famous is the coelacanth.
35:02It was thought to be extinct until one was found in the Indian Ocean in the 1930s.
35:07When it was first found, the coelacanth was nicknamed old forelegs
35:14because of its strange, fleshy paired fins, which looked like simple limbs.
35:20It's a nickname that's very apt because way back in prehistory,
35:25some lobe fins branched off to eventually become all modern-day four-limbed vertebrates,
35:32including us.
35:35And one prehistoric lobe fin cousin was a gargantuan heavyweight,
35:42a 23-foot, four-ton river monster.
35:46The rhizodont.
35:48A predatory freshwater fish.
35:52The size and weight of a killer whale.
35:54330 million years ago, they hunted lakes and rivers in Scotland.
36:07The first time I came to the Hunterian Museum in Glasgow,
36:11it was to see the plesiosaur,
36:13the reptile some believe is behind the biggest aquatic monster myth of all time,
36:19Loch Ness.
36:20But I've heard that massive rhizodont teeth found near here
36:25leave the plesiosaurs' deadly hardware in the dust.
36:32Rhizodont means rooted tooth,
36:35and you can clearly see from where the enamel ends
36:39that fully half of this weapon was buried in the jawbone.
36:44This tusk was clearly designed to drive into flesh and bone and rip prey apart.
36:51Now, the size of the teeth suggests large prey.
36:57And at 23 feet long,
36:59this fish had more than enough muscle to take on anything else in the water.
37:03But apart from its huge tusks and fangs,
37:07most of its remains are the bony scales that made up a suit of full-body armor.
37:15There's no fish alive today that comes anywhere near the rhizodont's size,
37:20appearance, and aggression.
37:23But in Australia, there is a river monster that does.
37:28The estuarine crocodile.
37:30To complete this nightmarish picture,
37:34I'll stare into the jaws of death
37:36to bring the gargantuan rhizodont to life.
37:49My worldwide hunt for the biggest, baddest river monster of all time
37:55has finally brought me to the rhizodont.
37:58The size of a killer whale and armed with 10-inch tusks,
38:03no freshwater fish comes close to the rhizodont's scale and power.
38:09But the world's largest reptile does.
38:21His missing limbs are the price a top predator pays to stay at the top.
38:26At 18 feet long, chopper is three times my length.
38:33But the giant rhizodont could have been another five feet longer.
38:41I'm just trying to sort of calm myself down a little bit
38:43and get into proper observation mode.
38:45This giant aquatic predator deploys the same ambush strategy as the rhizodont.
38:56And the power of that strike is rooted in the tail.
38:59It's half the body length, so on an 18-foot animal like this,
39:06you've got a nine-foot tail, and that's a solid muscle.
39:09It works in the same way as a fish's tail, and it's all about propulsion.
39:14Judging by size alone,
39:16the rhizodont's massive tail
39:18must have packed more than twice the croc's muscle power.
39:21It's an uncomfortably close view I'm getting of the teeth and jaw of this animal.
39:29These crocs have the strongest recorded bite of any animal alive today,
39:34close to 4,000 pounds per square inch for a beast this size.
39:38A 23-foot, 4-tonne rhizodont might pack more than double that.
39:49Chopper has given me a visceral insight
39:51into the awesome killer potential of this prehistoric fish.
39:57I'm starting to think the rhizodont could even out-bite the bone crusher.
40:02It's time to put this gargantuan fish in context in Scotland,
40:10where it terrorized lakes and rivers 330 million years ago.
40:17My journey halfway around the world
40:19has given me the final information I needed
40:21to picture this river monster's general body plan and size.
40:27Now, I'm trying to imagine the world that that beast lived in.
40:32It's time to ask for this project.
40:34Millions of years before solid ice carved out the locks,
40:39rhizodont stalked prey as big as a man
40:42in murky, slow-flowing waters.
40:52Rhizodont storing prey as big as a man in murky, slow-flowing waters.
40:56At the end of my search for the greatest river monster of all time,
41:21it's a very close contest between the Bone Crusher
41:25and the Rhizodont.
41:27But I now know where I'd place my bet.
41:31So for me, there's no question.
41:34The Rhizodont is the ultimate prehistoric river monster.