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Documentary, NOVA - Alaskan Dinosaurs 2022
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00:00The Arctic Circle, Northern Alaska. In one of the most inhospitable places on Earth,
00:16scientists search for clues to a mystery 70 million years in the making.
00:23They're on the hunt for a lost world of polar dinosaurs.
00:32This is not the paleontology you normally see in books. What we are learning about dinosaurs
00:37from these discoveries is just really unparalleled and unprecedented.
00:44Alaska is the last place on Earth one might expect to find large reptiles.
00:50But the discovery of fossils has revealed dinosaurs could live farther north than what
00:59was once thought possible.
01:01Oh, we got a sweet layer right here.
01:08Now, this team hopes to answer some fundamental questions.
01:16What kind of animals lived here? How did they survive the Arctic winters?
01:22How were they able to endure the cold? How were they able to endure the darkness?
01:26Where did they get their food?
01:27If they were up here year-round, were they really warm-blooded animals?
01:32Their journey will take them from the frozen wilderness of northern Alaska to the mountaintops
01:39of Denali National Park and Preserve to the south.
01:44If we can understand how they survived here, we might be able to understand why they dominated
01:49the planet for over 100 million years.
01:53A surprising story of adaptation and survival.
02:01Against the odds, Alaskan Dinosaurs, right now on NOVA.
02:23Late March, Alaska's North Slope, 28 miles south of the Arctic Ocean, a team of paleontologists
02:50is on the final leg of a 600-mile journey from Fairbanks to one of the northernmost reaches
02:59of North America.
03:02They're part of the long-term joint research project studying polar dinosaurs.
03:09Their plan is to spend the next several days searching for dino bones.
03:15What makes these dinosaurs amazing is the fact that they lived in an extreme environment.
03:20This isn't the sort of thing we typically associate with dinosaurs.
03:24So the fact that they lived at these latitudes tells us a lot about what dinosaurs were capable
03:29of doing.
03:30It shows them at their extremes.
03:33Over the past 13 years, paleontologist Pat Druckenmiller has made 11 expeditions to
03:40the north slope in search of fossils.
03:43He's joined by paleobiologist Gregory Erickson, also a veteran of this field work.
03:54Alaska is really paleontology's last front here.
03:58Dinosaurs were living in the coldest environment in the Cretaceous and it's a mystery as to
04:05how they were making it up there.
04:07How did they survive?
04:11Here, temperatures drop to 50 below at night, with wind chills plunging even lower.
04:21But despite these challenges, this is the ideal time to go fossil hunting on the north slope.
04:28The hillside we're trying to dig out likes to slump on us in the summer, but in the wintertime,
04:33it's frozen solid and we can safely excavate into the lair.
04:45Along with excavation equipment, they'll be carrying everything they need to survive, including
04:52100 gallons of gasoline to run generators, one ton of wood for fire stoves, and enough food
05:02to last for over a week.
05:04Yeah!
05:05It's been three days of travel just to reach this point and we're not over yet because we
05:13now have to travel about 30 miles by snow machine to get out to the Colville River and reach
05:18our actual dig site.
05:34The team is heading to a fossil site in the Prince Creek Formation on the north slope of
05:40Alaska.
05:43Through this remote, awe-inspiring landscape winds the Colville River, flowing north from
05:50the slopes of the Brooks Range to the Beaufort Sea.
05:57Along the bank of the frozen river, steep cliffs rise 100 feet.
06:03This is where geologist Robert Bliskom came across mysterious bones while working for an
06:10oil company in 1961.
06:14Later identified as dinosaur bones, the find was a surprise.
06:19Dinos, thought to be cold-blooded, shouldn't be able to survive in the cold and dark.
06:25Polar dinosaurs weren't really on paleontologists' radar for most of the 20th century.
06:31When you had a picture of what a dinosaur was and where they lived, it was often thought
06:34to be an equatorial sort of creature, a creature of warm environments, these swampy sort of
06:39lowland environments.
06:41Thinking of dinosaurs living in the polar north, that wasn't something that was even considered.
06:46The discovery of Alaskan dinosaurs astonishes the scientific community and puts the Prince
07:00Creek Formation on the map for paleontologists.
07:05To find them in a place like this, where the environment is so dramatically different,
07:15it really does challenge what we thought about these animals.
07:19So far, scientists have identified over a dozen species, both large and small.
07:26Herbivorous beasts such as Pachyrhinosaurus, a formidable horn ceratopsid,
07:34Anugrunaluk, a duck-billed dinosaur over 25 feet long.
07:41As well as predators like Nanuxaurus, a fearsome tyrannosaur and close cousin to T. rex.
07:49And a Troodontid, a lightly-built, horse-sized dinosaur with deadly slasher claws.
07:57The team finally arrives at base camp, half a mile from the dig site.
08:09It's getting dark and the temperature is dropping, now down to minus 4 degrees Fahrenheit.
08:16The site that we're interested in is going over there.
08:21Some of our crew is getting cold, and so it's important to get our tents up and, you know, get our stoves going.
08:26Working on the North Slope in the late winter means the days are still short and cold.
08:35Scientists agree, 70 million years ago, the Earth was generally much warmer.
08:45The dinosaurs living here, however, would have faced the same inescapable reality.
08:53As the Earth orbits the Sun, it rotates on a tilted axis.
08:58During summer in the Northern Hemisphere, the North Pole is angled toward the Sun.
09:04Areas above the Arctic Circle receive 24 hours of sunlight.
09:09But when Earth arrives at the opposite side of its orbit, the pattern reverses and the North is tilted away from the Sun.
09:19Because during the Cretaceous, Alaska was even farther north than today.
09:25Even today, the North Slope experienced four months of total darkness.
09:32The best indications from all of the geological and fossil evidence is that during the darkest, coldest winter months,
09:39it would have gotten below freezing.
09:43It would have been much colder than almost anywhere else dinosaurs would have been living.
09:55Early the next morning, Pat and Greg visit the site where the first Alaskan dinosaurs were discovered.
10:13The Liscum Bonebed.
10:16We have somewhere around 6,000 catalogue bones in our collection from this one layer alone.
10:27And it's also the same layer that provided most of the material from which we named a new species of duck-billed dinosaur,
10:35called Agrunalik kukpikensis.
10:37The areas that we work in have been long occupied by indigenous peoples.
10:42And we think it's only fitting that when we construct a new scientific name,
10:47that we incorporate words from those languages, from the areas in which we work.
10:52The Grunalik kukpikensis has its origin in Inupiaq words that mean roughly ancient tour of the Colville River.
11:04Close cousin to Edmontosaurus, found to the south, Agrunalik kukpikensis is a four-ton herbivore.
11:15Its discovery in Alaska's north slope created a puzzle for scientists.
11:21How did these large animals manage to survive so far north?
11:27Did they migrate to and from lower latitudes each year?
11:34Like caribou do today.
11:38If they weren't migrating, how did they make a living up here?
11:44You can't imagine there was enough to eat, so it's just, you know, a bit of a mystery.
11:50To find clues, the scientists hope to recover more bone material.
12:01During the Cretaceous, some 145 to 66 million years ago, the section they're planning to dig was a river floodplain.
12:11Over millennia, some remains of dinosaurs find their way into rivers.
12:19Bones and other material from different species pile up at the bottom of the river channel.
12:26Layers of sediment bury the remains.
12:30Millions of years later, a new river, the Colville, carves through these layers,
12:36exposing the edge of the fossil bone bed, along these cliffs.
12:46Pat examines a spot where they've found bones before.
12:53They've come back to continue the work.
12:56But the familiar landscape has changed.
13:01Huh.
13:02That's kind of scary.
13:05It might have gone bye-bye.
13:08On first inspection, things don't look promising.
13:12It's all slump.
13:17Yeah.
13:18The layer's gone.
13:24In the summer, the faces of these cliffs regularly slump or slide down into the river,
13:30making it dangerous to work here.
13:35That process can expose fossils that had been hidden.
13:40But it can also bury the bone layer and paleontologists under tons of rock and mud.
13:49The team fears its bone bed may have been washed away.
13:53The hills are ungluing themselves.
13:56Rack it up to climate change or whatever.
13:58But you never know.
14:00The slumps can randomly just take out your favorite dinosaur sight.
14:04Yeah.
14:05That's not good.
14:08Then, after further exploration, they find a newly exposed outcrop.
14:15Oh, it's kind of got some slump on it.
14:18All right.
14:19I'll go up and have a look.
14:22Just when it looks like the trip may have been for nothing, the team has a stroke of luck.
14:30And look at that.
14:32Right there.
14:33Woo-hoo!
14:34Throwing the first bone!
14:38Oh, we got a sweet layer right here.
14:43Feels good.
14:45Pieces of bone are clearly visible, sticking out of the frozen rock.
14:51I whacked right through one here.
14:54It's a classic bone texture.
14:57For Pat, this layer is a paleontological gold mine.
15:02And that's what this bone layer is all about.
15:05It's just dripping with bones.
15:10The challenge now is to safely extract the samples.
15:16No one's ever tried this up here before.
15:19Digging these animals up here, basically at the end of wintertime,
15:22we're going to take the whole layer, the rock and the bones, and try to extract it.
15:27Got to find the sweet spot.
15:28Yep.
15:29There it is.
15:32They have just six days left to collect specimens before they need to return.
15:39The next steps are to break up the frozen mud and rock below the bone layer with jackhammers
15:46to create a working platform.
15:49Then carve out several blocks with chainsaws.
15:53Each chunk will be about three feet across and weigh up to 200 pounds.
16:00It's five days into a ten-day expedition.
16:07They still haven't extracted a single block.
16:12And then they suffer another setback.
16:15The chainsaws break down.
16:19It's up to head of operations, Kevin May, to fix the equipment.
16:26It is.
16:28We have been presented with some significant challenges here with the temperatures.
16:34If he can't get the chainsaws back up and running, the expedition could be over.
16:41Here's the other bread.
16:42Here's the other bread.
16:43Well, you're too soon.
16:44How long did you do?
16:48I was really hoping to get over here and work on the chainsaws by myself, so...
16:54You had too many PhDs in a small area, and nothing gets done.
17:02Kevin soon discovers a possible solution.
17:05Yep, that's what shut us down last night.
17:08Look at that.
17:09Can you thaw that, please?
17:11The friction from the chainsaws melts the permafrost, which seeps into the mechanics and
17:21immediately refreezes.
17:23Turns out that because of these temperatures, we're going to have to repeatedly warm our chainsaws
17:33and get the chains thawed out a bit.
17:43After a thorough cleaning, the team tries again.
17:46Four more days in the biting cold.
17:54Digging.
17:55Sawing.
17:56Sleeping.
17:57And more sawing.
18:00Before the first block is finally freed.
18:06It's coming.
18:07It's coming.
18:08Well done, Pat.
18:17They have success.
18:18Yeah, that's a really nice big chunk.
18:21There's a big one right there.
18:24Big, very dark.
18:25There's one right here.
18:27There's one there.
18:29There's one there.
18:31Let's fold on.
18:35After all that time, we've got it.
18:40We're hitting a jackpot right now.
18:43This is going to pay off.
18:45Let's bring it in for a landing.
18:48In total, the paleontologist managed to extract eight frozen blocks, a thousand pounds to haul home.
18:56And now it's just a matter of bringing home a bunch of rock.
18:59We'll get that stuff back in the lab, and we can prepare it out, and we'll see what we find.
19:08They hope the samples will contain fossils that can fill out their understanding of the animals that lived here.
19:16And help answer the question at the heart of the Alaskan dinosaur mystery.
19:22How did they survive the dark polar winter?
19:25That's a tough place to make a living.
19:29How were dinosaurs able to do that?
19:31Did they have to leave, maybe migrate south?
19:35Or were they able to park themselves in the poles year round?
19:40If we have evidence that they were staying year round, it really has a powerful impact on what we expect of dinosaur physiology.
19:50Early July.
19:55At the University of Alaska Museum of the North in Fairbanks, the blocks from the Prince Creek Formation are in the prep lab.
20:05It's not just the big bones the scientists are after.
20:12Even the tiniest, unassuming crumbs could hold vital pieces of the Alaskan dinosaur puzzle.
20:24To ensure the tiniest fragment isn't overlooked, the scientists scrutinize buckets of material grain by grain.
20:40It's a process of finding a needle in a haystack, or I liken it more to a panning for gold.
20:47Three years earlier, on their previous expedition to the Prince Creek Formation, Pat and Greg find something exceedingly rare,
21:01and a potential clue to the mystery of the lifestyle of polar dinosaurs.
21:06Very small bones, they suspect, are from a very young dinosaur.
21:13Some are no larger than the head of a pin.
21:17Small size alone doesn't necessarily mean that this is from a very young individual dinosaur.
21:27For that information, I look at other clues, and one of the best clues can be seen in the surface texture.
21:37What I'm seeing is a surface that's highly porous, as if somebody took a little pin and pricked the surface over and over and over again.
21:46And each of those holes represents places for little vascular canals, where nutrients were flowing into a bone at a stage of rapid growth.
21:56That sort of surface texture is highly indicative of animals in very early stages of development.
22:03And by that we mean days, weeks, maybe as much as a couple of months.
22:07Meaning that this is a great clue to help identify baby bones.
22:19It's an unprecedented find.
22:21Baby dinosaurs have never been found this far north before.
22:28This was a totally unexpected discovery.
22:33When we first started to see these small teeth and bones, it was really a jaw-dropping experience.
22:40Further investigation reveals remains of the teeth and bones of seven different species of dinosaur.
22:49All in their very earliest stages of development.
22:53It's evidence that 70 million years ago, several species of dinosaurs nested in the Arctic.
23:02Not only living in Alaska during the mild summer, but breeding here as well.
23:13It raises a whole bunch of really interesting questions.
23:18One of the most important is, if they reproduced in the Arctic, is it actually possible for them to have also had time to migrate to lower latitudes?
23:27If migratory, dinosaurs would have to move north, incubate, and hatch their eggs.
23:35And then return to the south, 2,000 miles away, with baby dinosaurs in tow.
23:42In order to escape the depth of the polar winter shadow.
23:46And all between spring and early fall.
23:49Could the hatchlings have managed it?
23:52One important clue can be found inside specimens like this.
24:01Less than an eighth of an inch long.
24:05It looks like a drill bit, but it's actually a tooth from a baby dinosaur.
24:13When teeth form, daily growth lines are laid down.
24:16And by counting those up, one could figure out how long it took dinosaurs to incubate their eggs.
24:23So we looked at really small embryos.
24:25Animals were just about to hatch out.
24:27And we were able to figure out really large dinosaur.
24:30Eggs took six months to incubate.
24:32If it took large animals, such as Ugrunoluk, six months to hatch.
24:42And eggs were laid during the spring.
24:45The dinosaurs would have only one month to move south before the onset of polar winter.
24:51There's no way that those dinosaurs could have hatched out and made a 2,000 mile trek all the way down to Alberta to warmer climatic conditions.
25:03It just wasn't possible.
25:05It's just unavoidable.
25:06They were up there year round.
25:08The idea that dinosaurs lived in cold darkness challenges previous assumptions about dinosaur biology.
25:16And the traditional view that they were giant, cold blooded animals, like today's reptiles, relying on ambient temperature to warm their bodies.
25:28What we don't find in the Prince Creek Formation is evidence for cold blooded animals such as crocodiles and turtles, lizards, amphibians.
25:38It's almost like they were physiologically mooted.
25:43What we do find up there are birds and mammals and dinosaurs.
25:50That alone suggested that they were warm blooded.
25:57Even if they weren't cold blooded, how did herbivores like Ugrunola find enough food?
26:05Without sunlight, many trees shed their leaves.
26:11During these winter months, food for the plant eaters would have withered or died.
26:17If we think about those Alaskan ecosystems, we have to address the fact, where do they get their food?
26:34Karen Chin is one of the world's leading experts in dinosaur dung.
26:41She's been investigating hadrosaur diet by studying the fossilized remains of their feces, known as coprolites.
26:51At 100 times magnification, even the individual fossilized cells of the dinosaur's last meal are visible.
27:08Investigating coprolites from nonpolar dinosaurs living in southern Utah and Montana, Karen finds something intriguing.
27:16We can see chunks of intact wood, and that's where you see all of the cells are almost glued together.
27:24They're glued together with lignin.
27:26But then you can also see all of these loose cells all over the place in no particular order scattered all around.
27:36And that indicates rotting wood.
27:46To break down lignin, it requires oxygen.
27:51So that can't happen in an animal's gut.
27:54It has to happen outside where there is access to oxygen.
27:58So we know that the wood was degraded, decomposed, before it was ingested by the dinosaur.
28:06I was quite surprised.
28:09Why were they eating so much wood?
28:13The incredible new evidence suggests the southern hadrosaurs could diversify their diets,
28:19feeding on rotting wood to survive.
28:24Where are you going to get protein if you're an herbivore?
28:27Or you can go to a rotting log where there's lots of creepy crawlers like beetles and millipedes and pill bugs.
28:38It raises the tantalizing possibility that this could have been a winter food source for Alaskan dinosaurs as well.
28:48Herbivorous dinosaurs, like a Gruneluk, might also have been feeding on rotting wood during the four months of the year or so when they had the polar winter.
29:02With the arrival of winter, darkness is one problem for the Alaskan dinosaurs.
29:09They also face much colder temperatures.
29:12What in their physiology allowed them to remain in Alaska, shielding them from the elements?
29:25So for a long time the image of a traditional classic dinosaur was of a very scaly, very reptilian, almost a monstrous sort of creature.
29:34But lately dinosaurs have been getting softer, they're getting fuzzier, like dare I say it, they're getting cute.
29:40There was an early tyrannosaur that lived about 125 million years ago, named Euteranus, covered almost head to tail in fluffy feathers.
29:49And this was not a small animal, this animal was about 30 feet long.
29:53Intriguingly, Euteranus lived in a part of China during the early Cretaceous that had a cool climate similar to Alaska 70 million years ago.
30:05Most dinosaurs had simple feathers that looked like hair.
30:11Our hair keeps us warm, that's what hair does in mammals.
30:14And for many dinosaurs, they had these simple feathers probably to keep their bodies warm.
30:19If dinosaurs that were living in an area of similar temperatures earlier in the Cretaceous had all of these thick coats of feathers, that probably a lot of the Alaskan dinosaurs did too.
30:36In addition to feathers, Alaskan dinosaurs may have had other adaptations for surviving colder temperatures.
30:43One of the interesting groups of dinosaurs that we have represented in our fauna in the Prince Creek Formation are Thescalosaurids.
30:53Thescalosaurids are dwarves in a land of Alaskan giants.
30:58The smaller of two Arctic species is just 18 inches tall at the hip.
31:06Small creatures lose heat more rapidly, and they freeze a lot faster.
31:13So how did these small dynoms survive the cold?
31:21A clue can be found in their Montana cousins.
31:24Some species of Thescalosaurs were found actually preserved in a burrow.
31:35Up until about 20 years ago, that's not something that we thought dinosaurs did.
31:40That raises the exciting possibility that perhaps the species of Thescalosaurid in Alaska might also have been capable of burrowing and potentially overwintering by hibernating.
31:57Feathers and the ability to burrow aren't the only adaptations that may have helped polar dinosaurs survive the cold temperatures.
32:04We're finding a very exciting number of bones from Troodontids in the bone bed layer we excavated this winter.
32:16And because they're so rare, every single bone that we find is providing another new piece of the puzzle and understanding what this animal was.
32:25Troodontids were lightweight, fast-moving and agile predators.
32:32With eyes set towards the front.
32:37A common adaptation in predators giving them binocular vision to triangulate small, scurrying prey.
32:47They were raptors, so to speak.
32:50They had giant sickle claws on their second toe and clawed hands and menacing teeth.
32:58In many ways, this was a roadrunner from hell.
33:06But the Alaskan Troodontid has one noticeable aspect that sets it apart.
33:14So I'm looking at an adult Troodont tooth from the Prince Creek Formation.
33:18And this is a monster. It's a big one.
33:26This tooth is probably 50% longer than we see in Troodont furmosis, which is a species found down in Montana.
33:35That suggests that this is a different species or the same species got larger up here.
33:46Troodontids that lived elsewhere stood three feet at the hip.
33:51But the Alaskan Troodontid was twice as tall.
33:54Why would living in a harsher environment lead to a larger size?
34:01It's been shown with some mammals and a few other birds and a few other creatures that they get larger when they live closer to the poles.
34:10It's a thermal advantage to be bigger in a cold environment.
34:13You're less likely to cool down, so to speak.
34:16So far, from the Prince Creek Formation alone, scientists have identified at least 13 unique species of dinosaurs, specially adapted to life in the Arctic.
34:29But among all the species found there, one is of particular interest to the team.
34:36It's an animal that was originally thought to have evolved to be smaller, not larger, like the Troodontid.
34:42That animal came to light in 2014, when another team of scientists working at the Prince Creek Formation announced the discovery of Nanuxaurus, the Arctic's apex predator.
34:57Ultimately, what this comes down to is this.
35:00T-Rex, the most iconic dinosaur of all.
35:03How do you take that type of animal and move it into the Arctic?
35:08What does it become?
35:09Estimated to be half the size of an adult T-Rex, it's labeled a dwarf species.
35:17Mysteriously, it comes from a lineage of giants.
35:22But when first discovered, it was thought to have bucked the evolutionary trend that suggested Tyrannosaurus evolved to become larger over millions of years.
35:32If it's tough to survive there, animals often get smaller. It's easier to cope with limited resources if you're getting smaller.
35:40So maybe because the Arctic was a tough place to live, it was cold, it was dark, the Tyrannosaurus could not get as big there.
35:46But these initial findings are made on just a handful of bone fragments.
35:54Leading them to wonder, was it really as small as it looked?
36:00Pat and the team haven't identified any new Nannosaurus bones from the Colville this time.
36:14But there is another place they hope to find evidence.
36:22Not with bones, teeth or dinosaur droppings however, but thanks to a different record of the past.
36:29Preserved in the very ground they walked on.
36:36Their footprints.
36:38It's not just finding new species.
36:41It's not just tracking these animals.
36:43It's really revealing a world that we know very little about.
36:46It's a unique ecosystem that really doesn't have an equivalent on our modern planet.
36:52Using geological maps, Pat identifies several new sites in Denali National Park
36:58where Dino Prince might be preserved in its Cretaceous Rock.
37:04Dinosaur tracks were first cataloged here in 2005.
37:09But they've never been fully surveyed.
37:13Pat and his team will systematically explore these sites deep into the backcountry.
37:20One of the things we're interested in investigating is
37:23are dinosaurs that lived in the polar regions slightly larger than their close relatives at lower latitudes or even smaller?
37:36450 miles south of the Prince Creek Formation, in the Alaska Range, is Denali National Park and Preserve.
37:45It's six million acres of tundra.
37:48Boreal forest and ice cap mountains cover an area equivalent in size to the state of Vermont.
37:59To get to the suspected track sites, it's a six-mile hike through unforgiving terrain.
38:06The only way in is by foot.
38:10There are so many things that can go wrong.
38:13You've just got to be really on top of it.
38:17This wilderness is beautiful, but it's beautiful because it's a very raw place.
38:27During the late Cretaceous, Denali looked completely different.
38:31Millions of years of uplift and faulting have created the stunning landscape seen today.
38:47On Pat's last expedition to Denali, they located a huge vertical wall riddled with thousands of tracks.
38:56Preserved for millions of years.
38:58It's multiple layers of rock and there's over a hundred feet of vertical rock section exposed here, now tilted up on end.
39:09So we're seeing a story told at different levels and through time.
39:15Each depression on what was once flat ground represents a footprint.
39:20Occupying an area over a football field in size, it's the largest dinosaur track site in Alaska.
39:33Most prints come from one species, a duck-billed dinosaur, like Ugruniluk.
39:39Graduate student, Evan Johnson Ransom, examines a trackway.
39:49One of the most fun things about the duck-billed dinosaurs is that they may have had different forms of locomotion.
39:55Some think that bipeds may have been for the juveniles, but for the larger adults it would have been like quadrupedal, however.
40:01But the jury's still out, though. It's really cool to pull CDs all in person, though.
40:07As well as providing clues to the animal's locomotion, for science writer Riley Black, trackways also provide a fascinating glimpse into their behavior and world.
40:19These tracks themselves are fascinating because of their fossilized behavior.
40:24In places like this where we have multiple tracks on any given slab, you start to ask yourself,
40:30OK, well, why is that?
40:32Oftentimes you'll have something like a sandbar or the edge of a lake that's the best place to sort of skirt around it,
40:38and you'll have animals going back and forth over time making these dinosaur dance floors.
40:42Over the next several days, the scientists continue to probe the surrounding area.
40:55Because not all tracks are easy to identify with the human eye,
41:00the paleontologists use a tablet equipped with the latest LiDAR technology to document each track they find.
41:07Scanning the surface of the print produces a 3D model the scientists can analyze further.
41:18As well as prints that preserve the impression of the foot,
41:22tracks can also survive as natural casts,
41:25made by the material that filled the original imprint,
41:29like this outcropping that once filled a footprint.
41:33These are classic ceratopsid or horned dinosaur footprints.
41:43The only kind of ceratopsid dinosaur that we know of in Alaska is a Pachyrhinosaurus from northern Alaska.
41:50Ceratopsids are large plant-eating dinosaurs that stand on four sturdy legs.
41:58Pachyrhinosaurus paraorum is a unique species to Alaska,
42:05lacking the large horns typical of this group.
42:09At 7 feet high and 18 feet long, it could weigh up to 4 tons.
42:15It's bulky and muscular, like a modern rhinoceros.
42:19So far the scientists have found numerous footprints, not just from dinos, but also of flying reptiles and birds.
42:40And they've discovered an abundance of tracks from plant-eaters, sharing the land and the food it has to offer.
42:49Where there are herbivores, there are usually predators.
42:54But where are they?
43:03The team ascends the mountains of Denali,
43:07looking for evidence of Alaska's Cretaceous carnivores.
43:11The more different track types that you can record, the more likely you are to figure out at least some broad sense of diversity of the dinosaurs and of other creatures like birds and possibly flying reptiles.
43:27And that's one of our big questions at this site, is who is here?
43:30In Denali, the team identifies a promising site.
43:39The surface appears to have been trampled on by a large creature.
43:44To get a closer look, Pat and Greg decide to descend the cliff face.
43:50They scan the trackway.
44:08Look at that.
44:11It's almost like we use our eyes to find them in that to actually see them better.
44:16Back at the top, Pat measures the dimensions of the prints.
44:27At 59 centimeters.
44:29So that's a big footprint.
44:32If I measure the width, we'll see what we get.
44:3533 centimeters.
44:37So the footprint is longer than it is wide.
44:40And each foot was laid down.
44:41They're almost purely in a straight line.
44:43All the evidence appears to point to one creature.
44:48This could very well be from a Tyrannosaur.
44:53Which is pretty exciting, because if that's the case, this is the longest Tyrannosaur track site now we've found in the park.
45:03But the findings are inconclusive.
45:05The prints lack detail to positively identify the track maker.
45:16For a better indication of a large predator, the scientists need to find a track that has preserved the original features of the dinosaur's foot.
45:25We got a good one.
45:27Exploring the summit of an outcrop, graduate student Tyler Hunt makes a surprising discovery.
45:38So we have one toe here, one toe here, and one toe here.
45:43There's a pretty prominent claw impression here, and then I'm seeing some pads with a raised area in between.
45:50So this count of pads is pretty indicative of a theropod, along with the shape of the toes.
45:58Its three skinny toes with claws at their tips points to a carnivore.
46:03But which meat-eater is it?
46:08The middle toe right here is really long.
46:11Along with this asymmetry is pretty indicative of a Tyrannosaur.
46:18Would have been a very big Tyrannosaur as well.
46:21It's an extremely rare find.
46:24A detailed footprint of a Tyrannosaur.
46:27At least we got the one.
46:30Now we know they're here.
46:33Absolutely.
46:34Got really lucky there.
46:35Why couldn't you find it in a more accessible place?
46:37I know, right?
46:43Back at base camp, Pat and theropod specialist Evan Johnson-Ransom analyze the track.
46:51Measuring the print reveals the size of the creature.
46:5450 centimeters, so that is a very big theropod, eh?
46:59That's a big theropod.
47:01Doing the standard method of four times the foot length would put us at at least a two-meter hip height.
47:08In that other track site, you found footprints of a large duckled dinosaurs.
47:13And so those duckled dinosaurs were probably prey to this large Tyrannosaur.
47:17They were a top dog, right?
47:18Oh, definitely.
47:19Yeah, that was no small predator.
47:21Yeah, there's no way this is a pygmy tyrant.
47:25Cretaceous Alaska's apex arctic predator is the so-called dwarf Tyrannosaur, Nanoxaurus.
47:36Over the last several years, researchers at the Museum of the North have collected and catalogued dozens of its bones from the Prince Creek Formation.
47:45Their new investigations in the North Slope shed light on the true size of this mysterious carnivore.
47:55In the imaging lab, researcher Zach Perry scans a vertebra by laser, then digitally enlarges it.
48:06What we've noticed is that these are much larger bones than we initially thought. These would not fit a dwarf Tyrannosaur model.
48:16So just how big is Nanoxaurus?
48:19Zach examines a tooth, also recovered from the Prince Creek Formation.
48:27This is about a three inch long tooth. This is a massive tooth. It is more the size of an Albertosaurus or a Gorgosaurus tooth, which are definitely not dwarf Tyrannosaurus.
48:36From this, we can infer a similar size to those species, which are about 30 feet long, maybe about a two meter hip height.
48:45So much, much larger than the initially described size of Nanoxaurus.
48:51This is a Tyrannosaur to rival the biggest carnivores.
48:56Nanoxaurus would have had a mouth full of these teeth. They're very large and they have these serrations for tearing flesh off of its prey.
49:04With an estimated bite force of 4,000 pounds, Nanoxaurus is the top predator in the Arctic.
49:21To catch its food, it could use its serrated teeth to tear flesh off its prey, likely causing it to bleed to death.
49:32For the dino hunters, the new finds help illuminate this lost world and paint a picture of its wider ecosystem.
49:46To support such a big apex predator, the environment must have had more food, more flora and fauna, than thought possible at such an extreme latitude.
50:09Pretty much everything we found bones of in northern Alaska, we're finding footprints of very similar looking creatures here.
50:19We see things like duck-billed dinosaurs, horned dinosaurs, small and large meat-eating dinosaurs, and even things like birds.
50:29This must have been a very productive landscape, home to a really interesting and diverse set of organisms that called Denali home 70 million years ago.
50:39The fossils recovered from the Prince Creek formation, along with the Prince Creek formation, along with the Denali tracks, give us a compelling glimpse of a rich ecosystem and the incredible adaptability of these Arctic dinosaurs.
50:58Here, during the warmer months, the landscape is a spectacular sight, covered in hundreds of dino nests, with thousands of dinosaurs of different species, feasting on an abundance of plants and animals.
51:21With extraordinary adaptations to survive and thrive, in this lost world of Alaskan dinosaurs.
51:36Evolution is always operating to fine-tune organisms to their environment.
51:43The finds here are going to help us zero in on what made these animals so flexible.
51:49They weren't really constrained by the temperatures on the planet to a particular zone or a particular range.
51:55They lived in almost every conceivable environment on land. That was one of the keys to their success.
52:01So, these Alaskan dinosaurs are a prime example of life finding a way.
52:07A lot of times, they are known and they are pale.
52:09They were picked up in on the planet to a particular area, with a particular place where they are so long.
52:10They are a large-scale family, who are also used to the planet to a particular distance in the world.
52:11They are so strong and strong and powerful and powerful.
52:13And, in fact, the planet in the world the world will seem to be a unique concept.
52:14And, in fact, the planet in the world ofアーチ, the planet's perspective, can't live just to the planet.
52:16And, in fact, the planet in the world of the planet.
52:19And, when you do this, there's a planet of a planet in the world of Earth.
52:21And of the planet is now growing up, you can see how many of the planet across the planet could have finished there,
52:22and are protected from a planet, you can live in the world of it...
52:24Discover the science behind the news with the Nova Now podcast.
52:41Listen at pbs.org slash nova now podcast or wherever you find your favorite podcasts.
52:47To order this program on DVD, visit shoppbs or call 1-800-PLAY-PBS.
52:55Episodes of Nova are available with Passport. Nova is also available on Amazon Prime Video.
53:17We'll see you next time.
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