- 4 days ago
高棘龙是一种发现于北美洲的大型肉食性恐龙，体长可达11米，属于异特龙超科中的鲨齿龙类。其化石主要分布在美国的德克萨斯州，怀俄明州和俄克拉何马州。其牙齿化石在马里兰州也有发现，表明这种顶级捕食者曾广泛分布于北美大陆。高棘龙属下只有一种，为阿托卡高棘龙。高棘龙的生存年代为早白垩世的阿普特期至早阿尔布期。高棘龙是当时生态系统中最大的捕食者，主要捕食鸟臀类和巨型蜥脚类....
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00:03We are reconstructing a monster.
00:08It may be the greatest predator North America has ever seen.
00:13Its name is Acrocanthosaurus.
00:20If Acrocanthosaurus were to magically come back to life,
00:24it would be a truly awesome animal.
00:29It was a giant killer.
00:31It could go after prey items that were 30 tons or more.
00:38This would have been the Arnold Schwarzenegger of the dinosaurs.
00:43Now, a monster is brought back to life,
00:46and a killing machine is put to the test.
00:53Monsters resurrected.
00:56Great American Predator.
01:02The Paluxi River, one hour's drive southwest of Dallas, Texas.
01:08Embedded under this gentle stream is the tale of a desperate struggle 110 million years ago.
01:16These fossilized footprints are the Cretaceous equivalent of a crime scene.
01:23Hidden in this stone is the first-hand story of a savage past,
01:29when monsters ruled the earth.
01:33These footprints are direct evidence of an ancient combat between Acrocanthosaurus and its victim.
01:42It's the next best thing we could ever have to having a camera in the Cretaceous.
01:47By unlocking this mystery, we can resurrect the past and resurrect a killer.
01:55110 million years ago, this was the coastline of an ancient sea.
02:00Much of what is now Texas was underwater.
02:03The Gulf of Mexico basically came right up to here, and this was the coast.
02:10And the mud of this ancient coastal flat preserved the details of what looks like a hunt.
02:19Right here, we've got a real nicely preserved three-toed dinosaur foot.
02:24This cast was made from this footprint.
02:30You can see that the heel is not as well-preserved because of the angle, but the toes are beautifully
02:38preserved.
02:40These footprints were left by a vicious carnivore, Acrocanthosaurus.
02:48Acrocanthosaurus was 40 feet long and weighed more than five tons.
02:53By today's standards, it would be a terrifying monster.
02:57Imagine the panic if people saw a lion or a tiger walking free.
03:02Now blow that up ten times or more in a creature unlike anything you've seen alive today.
03:10As this footprint is examined, certain details emerge.
03:14The steep angle of the toe casts from the river showed that the Acro was running.
03:22But there is another set of footprints.
03:25And these second footprints are what make this discovery so amazing and potentially revealing.
03:33These second footprints are those of another huge dinosaur, a gigantic sauropod called Paluxisaurus.
03:41Got a fiberglass cast of a sauropod left rear foot.
03:48You've got the ground level here and you can see the claws, the heel.
03:56It just gives you a good idea of how much this thing should have weighed.
04:00And the tracks reveal that the 40-ton plant eater was also in a hurry, as if it was being
04:07chased.
04:08What we have here is a really nicely preserved set of sauropod tracks.
04:14And it goes on for about 30 feet.
04:17The trail starts here with the right rear.
04:20And it goes this direction.
04:22There's a left, right, left, right, left, and finally the last one right.
04:30But it continues underneath this limestone ledge.
04:40Did these two beasts just happen to cross each other's tracks?
04:44Or do the prints tell a more dramatic story?
04:49Professor James Farlow has no doubt.
04:51They are evidence of a dinosaur death match.
04:55Here on the left of the sauropod trackway, we see the three-toed prints of the meat-eater.
05:00And it's going in a nice left-right sequence, pretty much hugging the left side of the sauropod trail,
05:07stepping in the sauropod footprints two or three times over the length of the trackway before it ends.
05:14And then the meat-eater cuts across into the trackway of the sauropod.
05:21When these tracks are plotted out, a pattern develops.
05:25And this pattern can only mean one thing.
05:28The two animals are about as close together as they can be over most of the length of the trackway
05:35without physically colliding with one another.
05:40The acro is trying to take down a beast eight times its size.
05:45What kind of a monster was capable of such a massive kill?
05:50This was the top of the food chain, the king on this continent.
05:54And that's saying a lot.
05:57Still, it's hard to imagine a beast that could routinely hunt an 80-foot behemoth that weighed 40 tons.
06:04But 110 million years ago, life on Earth was anything but routine.
06:15It was one of the hottest periods of Earth's history.
06:19North America was bursting with plants.
06:21The seasons were probably split into a wet and a dry season.
06:26It was probably running in the 90s and 100s almost all the time.
06:31Vegetation exploded over the continent.
06:34Tropical weather reached as far north as Alaska.
06:37Central Texas was a lush jungle, much like the Amazon.
06:42And the giant plants supported giant sauropods, like the 40-ton paluxosaurus.
06:49Africanthosaurus seems to have been a specialist in eating sauropods.
06:54These big, long-necked, long-tailed plant eaters.
06:57They were not bright by dinosaur standards.
07:00In fact, you can think of sauropods as basically big, dumb, walking mountains of meat.
07:08An apricanthosaurus probably needed to fill its belly at least once a week.
07:13That's a big belly.
07:14That's many hundreds of pounds of meat.
07:18And for a ravenous carnivore like Acro, hunting giants now looks like a smart strategy.
07:27Aquacanthosaurus may have been the first big meat-eating dinosaur in North America that was specifically evolved just for attacking
07:33really large things.
07:35But the mystery is, how did Acro kill such mighty prey?
07:41Taking down a sauropod was an awesome challenge.
07:45And even though Acro's skeleton looks dangerous, it doesn't exactly scream giant killer.
07:52When it comes to deadly dinos, Tyrannosaurus rex is the gold standard by which all others are judged.
08:01And the one we know most about.
08:04To find clues about Acro, we must start by comparing it to T-Rex.
08:11The two awesome predators look superficially similar.
08:15But to an expert like Phil Curry, their teeth tell very different stories.
08:25This thing had an incredibly powerful bite.
08:28In fact, the most powerful bite known for any animal living or dead.
08:35It was going after animals that were about its own body weight.
08:39And because they were relatively small, there was no way that Tyrannosaurus rex could avoid hitting bone with its teeth.
08:52That's why those jaws are so powerful. Why they could bite right through flesh and bone.
08:57To understand the difference between T-Rex and Acrocanthosaurus,
09:01we have to recognize they have very different strategies against very different prey.
09:05T-Rex is up against smaller but a lot more sophisticated herbivores.
09:12And those herbivores have a lot of defenses.
09:15It's got to get past those defenses, get in there, and if possible, kill with a single wound.
09:22Crush through meat, crush through bone, kill with a single strike.
09:27So despite its massive size and monstrous reputation, T-Rex was killing tough but small prey.
09:36By comparison, Acro had narrow jaws with long narrow teeth, more like knife blades than spikes.
09:44Phil Curry believes these were specialized tools for butchering huge fleshy victims.
09:51These giant plant eaters had giant bones.
09:56And if these teeth hit those giant bones, they would just break.
10:00What Acrocanthosaurus did instead is avoided those bones by biting much more shallowly.
10:08So it would take these jaws and teeth and use them like scissors, essentially,
10:13and slice flesh off on the side of the sauropods.
10:17But it doesn't change the fact.
10:20Compared to its prey, Acro was a dwarf.
10:24Acrocanthosaurus's prey may have been big and dumb, but it certainly wasn't helpless.
10:29Because by its sheer size,
10:32Paluxosaurus and other sauropods, they were dangerous just for muscle mass.
10:38If they chose to roll over on an Acrocanthosaurus, that Acro would be an Acro pancake.
10:46It's a monstrous mystery.
10:49How did Acro kill giants?
10:52Like Paluxosaurus.
11:04We are resurrecting a walking nightmare.
11:12A 40-foot hypercarnivore.
11:41Fortunately for us, it's extinct.
11:48it. But it once terrorized the North American continent. 110 million years ago, this riverbed
11:59in central Texas was the scene of a fight to the death between two behemoths, Paluxosaurus,
12:06a 40-ton herbivore, and Acrocanthosaurus, a 5-ton predator. How could Acro take down a beast
12:17eight times its weight? To answer this question, we must reconstruct both the victim and the
12:25killer. Welcome to CSI Dinosaur. Acrocanthosaurus was armed with blade-like teeth and massive
12:36arms, tipped with eight-inch claws. They are the key to understanding how this monster
12:43killed. Once again, a comparison to the most famous dinosaur predator tells us a lot about
12:51Acro's weapons. Even though T-Rex was much larger, it was a weakling compared to Acro.
13:02These are the arms of Acrocanthosaurus and Tyrannosaurus rex. The big surprise on this, I guess, is
13:09that when you look at these arms, you would suspect this is from the bigger animal, this
13:14is from the smaller animal, but it's exactly the opposite. And this is the arm of a Tyrannosaurus
13:19rex. And a Tyrannosaurus rex was probably two meters or almost six feet bigger than this Acrocanthosaurus.
13:25So it's clearly using its arm for something in a different way than Tyrannosaurus rex.
13:32But the bones only tell half the story. Acro's arms were layered with muscle.
13:39Based on the shape of this arm, I estimate the muscle is going to be roughly like that. It's
13:45almost a foot in diameter. This arm here could easily hold a ton.
13:51Unlike T-Rex, whose arms were practically useless, Acro's arms were lethal weapons.
14:00Those arms are incredibly powerful and very, very heavily muscled. This would have been the
14:06Arnold Schwarzenegger of the dinosaurs.
14:10Strength alone isn't what made these arms so deadly. They powered a set of giant meat hooks,
14:17two three-fingered claws tipped with sharp talons.
14:22The claws of Acrocanthosaurus are clearly a major killing weapon. They're tremendously large.
14:29They're very well adapted to piercing into meat and causing serious wounds.
14:37If Acrocanthosaurus were to reach down and grab a human with its claws, those talons would go right
14:43through the torso. In fact, you probably would have one of those claws going in one side of the back
14:48and
14:49popping out the front.
14:51With most meat-eating dinosaurs, the mouth and the teeth are kind of the business end of the animal,
14:56if you will. In many ways, the hand of Acrocanthosaurus is the business end of the animal.
15:03But short of going back in time, how can we determine how Acro used these lethal weapons?
15:11Using castings from actual finger bones, animatronics fabricator Elvis Jones and paleontologist Dr.
15:20James Lamb have built a mechanical Acro claw. Ballistic gelatin will act as a stand-in for the flesh of
15:28the prey animal.
15:29This material is formulated to simulate the density of muscle tissue.
15:35We have the ability to slide forward and back to emulate not only his arms movement, which is limited,
15:42but also the momentum of his entire body running towards something.
15:45And so what's going to happen is this guy will slide in, slam down onto the jelly, and then we'll
15:49pull back.
15:54Oh, good one.
15:58It's really interesting. These two outside fingers have completely dug in all the way down to the bone itself.
16:05Now Acrocanthosaurus has sort of a grappling hook in its prey and can bring its mouth in to start doing
16:12some real damage.
16:17And when Acro pulls those powerful arms back, the damage is devastating.
16:25Oh, there we go.
16:27I don't know. I think that tells the story right there, don't you?
16:29Yeah, that's a big chunk.
16:31That's... I can't even get hold of it. Look at that.
16:34That's multiple pieces from our three rakes.
16:37That's all one grab.
16:42Clearly, these claws were deadly weapons when used against smaller prey.
16:50But would they be able to take down a 40-ton opponent?
16:55The answer to this question may lie beneath this quiet stream.
17:00We decode the fossil record when Monsters Resurrected returns.
17:12The answer to this question may be, well, when you have to pack a tank that hardships a lot of
17:22people,
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17:23You can keep some thunder and 5-9 leave.
17:35Arntzen using theけて to the utility that Fabric might provide you with ponieważ
17:36We are lucky, 110 million years separates us from a giant killer, but that killer left
17:43his mark on our modern world.
17:49110 million years ago, a savage fight to the death took place between two monsters, Paluxosaurus,
17:59one of the largest plant-eating dinosaurs of the era, and Acrocanthosaurus, a fierce hypercarnivore
18:08that ruled North America.
18:16The evidence of this titanic struggle is preserved in footprints in the rocks, but the footprints
18:23only tell half the story.
18:26Just how could a five-ton acro kill a 40-ton sauropod?
18:32We know the acro was equipped with massive arms and horrific meat-hook claws, but were
18:40these the killer app that helped it take down titanic prey?
18:48For a predator like Acrocanthosaurus, the Mid-Cretaceous was a brutal and dangerous world.
18:54A constant battle for survival.
18:58These huge creatures competed with each other for mates and territory.
19:04Even small prey like this herbivore called Tenontosaurus could put up a big fight.
19:13This is Tenontosaurus.
19:15This guy is half grown in terms of mass.
19:19Its hip height of an adult would be up to about here.
19:24So in some ways, Tenontosaurus was sort of the cow of the Mid-Cretaceous.
19:30A fully grown Tenontosaurus could weigh in at two tons and stretch out over 20 feet long.
19:38And even a lone Tenontosaurus was anything but a soft target.
19:43It doesn't have armor and it doesn't have horns, so it can't fight back that way.
19:48But it will have its one major weapon, if you will, that's the tail.
19:59The tail of Tenontosaurus is actually one of the biggest and broadest tails among the dinosaurs.
20:07And a swamp from that tail could certainly discourage, at least in the short term, an Acrocanthosaurus
20:13coming in trying to fight it.
20:15Its tail versus eight-inch claws.
20:20But as we have seen from our mechanical reconstruction, these deadly claws ultimately give Acro the advantage.
20:32But exactly how would Acro's claws work against a beast 20 times the size of Tenontosaurus?
20:42Here at the North Carolina Museum of Natural Science, an examination of the Acro's biomechanics
20:50reveals a fatal flaw.
20:52When trying to figure out the range of motion in an extinct animal, what you do is look at
20:56the shape of the joint surfaces.
20:58Notice we have a nice concave surface here and a convex surface here that fits into it.
21:04And so we can take this arm back about this far before dislocation.
21:10And we can take it in front about that far before dislocation.
21:14Not an impressive range of motion there.
21:18Acro's arms, while powerful, were limited.
21:22They could only move up or down about 25 degrees.
21:25And this would be a big problem when trying to take down really big prey.
21:35Phil Center and curator Vincent Schneider have assembled a cast of the arm bones and mounted
21:41them to a frame to approximate their height as the predator reaches the mammoth prey.
21:49Seeing these arms next to the sauropod model makes Acro's task look impossible.
21:57Notice that as we move this into position and swing the arm as far forward as it can go,
22:03which is no further forward than this, the animal is not really in the best position to
22:09grab the prey.
22:10Notice how the hands don't even come up to the elbows of the prey.
22:15And the same would work on the hind limb.
22:18The hands don't even come up to the knees.
22:20So, if you're an Acrocanthosaurus, grabbing your prey with your hands first, not such a
22:26good idea.
22:27You're going to get dragged.
22:31Acro couldn't get its claws in close enough to fatally wound the Paluxosaurus.
22:38These massive arms and talon-like claws would be useless against the giant herbivore.
22:44They clearly weren't the murder weapon.
22:48So what did Acro use to take down this huge beast?
22:52There was only one weapon left in its arsenal, a very deadly one, when Monsters Resurrected returns.
23:07It may look like something out of a science fiction movie, but 110 million years ago, this
23:15dinosaur rampaged throughout North America.
23:21It's name is Acrocanthosaurus.
23:26And these fossilized footprints are mute evidence of a titanic fight to the death between this
23:34prehistoric predator and a giant Paluxosaurus.
23:40How did the Acro take down this 40-ton Goliath?
23:45We've seen that the claws would be useless against an animal this size.
23:52So if Acro can't grab it with its arms, how could it overpower a creature eight times its
23:58size?
23:59Could it do it with its teeth?
24:01It'd be like one of us, an adult human being, trying to take down a full-sized rhino with just
24:08our hands and teeth.
24:16Paleontologist Jerry Harris has found in some fossil fragments a critical clue to why Acro
24:22was such a deadly killer.
24:25Acro's skeleton made it a fast and lethal weapon.
24:30These are a couple of the skull bones from Acrocanthosaurus.
24:33And you can see that they have these very large openings here, smaller openings that are tunneling
24:37into these various prongs, sticking out in every direction.
24:39So most of the skull bones, at least on the palate and on the back end of Acrocanthosaurus'
24:44skull, had a lot of these big air openings.
24:46These bones actually are not big, solid pieces of bone.
24:49The interiors of most of these, especially up in the head and the neck and going into the
24:52part of the back, were very spongy and full of these air holes.
24:55And the lighter bones are found not just in the skull.
25:00More hollowed out bones are found throughout the Acrocanthosaurus skeleton, making it light
25:05and agile.
25:07So it looks like it would be very, very solid and as bone would actually be heavy, but the
25:11interior of the vertebra itself is actually very hollow.
25:17Being lighter means you're going to have less food and still move very efficiently and
25:20also move very quickly.
25:22The hollow bones also served as air channels, allowing Acro to pump oxygen throughout its
25:28entire body more efficiently.
25:31Not only would it be lighter than you would expect, it would be turbocharged by this extra
25:36oxygen coming through the body continuously, making this one very impressive hunter.
25:42Acro was strong, maneuverable, deadly.
25:47A perfectly engineered killing machine with parts that fit together like a brilliantly
25:52designed weapon.
25:54What we're looking at here is the second, third, fourth and fifth neck vertebrae of Acrocanthosaurus.
25:59So the head would be fitting on right about here and then the rest of the body would go
26:03off in this direction.
26:05What's very unusual about these particular vertebrae is that they have these big hollows on the backside
26:10and then these big processes that stick off the front.
26:13And what happens when they fit together is that these processes that stick off the front
26:19actually nest inside those hollows on the back of the next vertebra in front of them, the
26:24next backbone.
26:24This helps lock the whole neck very tightly together.
26:27This is not anything like I've seen in any other animal.
26:29It may be that Acrocanthosaurus evolved these features specifically to help it attack large
26:35animals like sauropods, like Paluxosaurus.
26:38This mechanical support system allowed Acro to lock onto its prey like a pair of vice clamps.
26:46With its neck locked and protected, Acro could use its powerful jaws to tear hunks of flesh
26:51from its victims.
26:54Now one of the most magnificent features of Acrocanthosaurus is its skull.
26:59That whole lower jaw can fit within the entire tooth row of the upper jaw.
27:05And that gives the dinosaur a very scissor-like action as it bites.
27:11At first look, these jaws may seem dangerous enough, but science can now reveal just how deadly
27:19they were.
27:22Acro's teeth were perfectly designed killing machines, even on the microscopic level.
27:28What you see on the screen is the rear edge of the tooth.
27:34And you can kind of make out the serrations that we see on the tooth.
27:38Now these serrations act as kind of grip and rip structures.
27:42As the tooth is penetrating the victim, those serrations catch on to the muscle fibers and help to tear them,
27:50and thus increase the severity of the wound.
27:54The teeth of Acrocanthosaurus are well constructed for cutting, for slashing, and thus ripping out big chunks of meat.
28:03But to bring down a giant herbivore like Paluxosaurus, this walking weapon had to first get close enough to strike.
28:13Easier said than done.
28:14In order for Acrocanthosaurus to kill a giant herbivore, it's got to go after some vulnerable spot.
28:23It's got to come up alongside the herbivore.
28:26It's got to seize it with its jaws, grapple with its claws, get in there and seriously wound that big
28:34herbivore.
28:35It can't hang on for too long because if the herbivore rolls over it, that's one dead Acro.
28:42So how does the hunter get in close enough to kill without getting killed itself?
28:49The fossilized footprints tell the story when Monsters Resurrected returns.
29:15Once it ruled this land.
29:22Acrocanthosaurus may be North America's greatest ever predator.
29:27This mega carnivore lived by killing giant sauropods, the biggest creatures to walk the Earth.
29:35It was high risk hunting on a giant scale.
29:40Here in Texas, a trail of 110 million year old footprints spells out the secrets of Acro's hunting technique.
29:50The huge Paluxosaur is slow, but not defenseless.
29:59Going after a giant prey item is dangerous.
30:04So Acrocanthosaurus had to be pretty sophisticated in order to take one of these giants down.
30:13The Acro has huge sharp talons, but we have seen that against a behemoth like this, they are useless.
30:23The Acro is much faster, but its lightweight skeleton is also a handicap.
30:31The Paluxosaurus swinging its tail around would have been like swinging a giant 2x4 around with a lot of muscle
30:38power behind it.
30:39One blow from this mega beast could lay out an Acro.
30:44The skull, as you can see, is made up of a lot of very thin, narrow bones.
30:49If I have a ton of tail hitting this skull, it basically would literally break the face.
30:54With the face skewed to the side, this poor animal couldn't feed and it would end up starving to death.
31:02But the hunt is still on.
31:08As with many crime scenes, the footprints tell the story.
31:14Now, 110 million years after a killing, the mystery is revealed.
31:20So, if we follow the trackway of the meat-eater, the theropod, we have pretty good left-right sequencing of
31:27the feet.
31:28We go left, right, left, right, left, right, left, right.
31:35And then something odd happens, because here this right footprint is followed by another right footprint,
31:43after which we go back into good left-right sequencing again.
31:48So, there is a missing left footprint right about here.
31:55The fossilized footprint show the Acro had to begin its attack from close behind its prey.
32:03What had happened was that the meat-eater, somewhere about here, had actually latched on to the plant-eater,
32:10that it was attacking it and trying to slow it down.
32:13But it was being dragged forward by the greater weight and the greater strength of the larger animal.
32:20The sauropod tries to wrench itself away, but the Acro refuses to release its prize.
32:27The Acro is clinging for life, hanging only by the grip of its jaws.
32:33This might snap the neck of a lesser predator, but not the Acro.
32:39This was an animal built for battle.
32:44Wounded, the Paluxosaurus weakens.
32:50The Acro now has the upper hand.
32:54It's going to want to go for the soft portions of the neck.
32:57It would have enough power that it could, with its massive arms and its strong back and its great teeth,
33:03could probably crush the neck and drag an animal like that down.
33:07If it could slice through the jugular, if it could take out the trachea, that big herbivore is going down.
33:14And it doesn't matter how big it is, it's going to be meat.
33:17We have examined the weapons.
33:22We've deconstructed the chase.
33:26Now, we must go back in time to the scene of the crime and witness a prehistoric murder
33:34when Monsters Resurrected returns.
33:41The Stones have spoken.
33:44A 110 million year old murder mystery has been solved.
33:51We can now finally see how a mega predator took down a dinosaur eight times its size
33:59and recreate the entire life and death struggle from beginning to end.
34:04We've 완벽ated.開心
34:11The
34:13Avengers Theapple
34:25The Applicant
34:35Let's go.
35:03Let's go.
35:33Here, the fossil record ends.
35:36The tracks run out, but we know that the acrocanthosaur would not have given up, and the killing odds were
35:44in its favor.
35:45Let's go.
35:56Let's go.
36:23Let's go.
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44:02You