1 00:00:15,562 --> 00:00:17,553 Patagonia, Argentina. 2 00:00:18,665 --> 00:00:20,599 This is dinosaur country, 3 00:00:20,767 --> 00:00:24,100 a land where the rocks are rich with fossils. 4 00:00:25,539 --> 00:00:29,976 For millions of years, this peaceful land has kept a terrible secret, 5 00:00:30,143 --> 00:00:34,170 and only now are paleontologists uncovering the truth. 6 00:00:35,649 --> 00:00:37,583 New finds here in South America 7 00:00:37,751 --> 00:00:41,585 are revolutionizing our picture of the prehistoric world. 8 00:00:41,755 --> 00:00:44,315 It seems that in the time of the dinosaurs 9 00:00:44,491 --> 00:00:50,225 Patagonia may have been the scene of the bloodiest battle in the history of life - 10 00:00:50,397 --> 00:00:53,992 one that matched the biggest animal ever to walk the Earth 11 00:00:54,167 --> 00:00:59,400 against a new dinosaur, the most fearsome killer that has ever evolved. 12 00:01:27,434 --> 00:01:31,268 A huge plant-eating dinosaur takes on a massive carnivore 13 00:01:31,438 --> 00:01:34,430 in an ugly pitched battle for survival. 14 00:01:37,944 --> 00:01:42,779 This idea of the two biggest creatures on the planet locked in mortal combat 15 00:01:42,949 --> 00:01:47,545 has proved irresistible to science fiction writers and movie makers. 16 00:01:50,290 --> 00:01:55,284 But for the scientists who study dinosaurs, this was pure fantasy. 17 00:01:58,165 --> 00:02:03,569 They knew that this clash of titans could never have happened in real life. 18 00:02:10,510 --> 00:02:12,307 That's because in real life 19 00:02:12,479 --> 00:02:17,576 the giant long-necked herbivores never lived alongside the mega-carnivores, 20 00:02:17,751 --> 00:02:22,916 huge dinosaurs like Tyrannosaurus rex, the king of the meat-eaters. 21 00:02:25,058 --> 00:02:30,496 The two giants never walked the Earth at the same time in the same place. 22 00:02:30,664 --> 00:02:33,758 Creatures like these could never have met. 23 00:02:36,269 --> 00:02:38,760 Or so the scientists thought. 24 00:02:48,682 --> 00:02:52,982 Plaza Huincul, a small Argentinian town in rural Patagonia, 25 00:02:53,153 --> 00:02:58,181 is famous for two things: oil and dinosaurs. 26 00:03:12,939 --> 00:03:16,670 Paleontologists come to the plains around Plaza Huincul 27 00:03:16,843 --> 00:03:20,176 searching for clues to a prehistoric world. 28 00:03:20,347 --> 00:03:25,375 This place was once home to the most extreme dinosaurs ever seen. 29 00:03:29,356 --> 00:03:33,816 Dinosaur hunter Rodolfo Coria knows he is a lucky man. 30 00:03:33,994 --> 00:03:35,791 He is chief paleontologist here 31 00:03:35,962 --> 00:03:39,898 and many of the most extraordinary finds have been his. 32 00:03:48,341 --> 00:03:53,506 Argentina is a good place for finding fossils, especially because of Patagonia. 33 00:03:53,980 --> 00:03:58,679 Patagonia is almost 50 per cent of the Argentinian surface, 34 00:03:58,852 --> 00:04:02,720 and the rocks, they are very well exposed. 35 00:04:02,889 --> 00:04:06,552 So it is very easy to find fossil evidence. 36 00:04:07,761 --> 00:04:11,857 If you are looking for dinosaurs, Patagonia is the place. 37 00:04:19,573 --> 00:04:21,598 (NARRATOR) Even Rodolfo was unprepared 38 00:04:21,942 --> 00:04:26,140 for the record-breaking monsters he was to unearth in these rocks, 39 00:04:26,313 --> 00:04:31,216 dinosaurs which would change our picture of the prehistoric world. 40 00:04:32,452 --> 00:04:34,443 It all began nine years ago, 41 00:04:34,621 --> 00:04:41,254 when he began excavating the bones of what was obviously a very large dinosaur. 42 00:04:48,335 --> 00:04:51,202 After many days of back-breaking digging, 43 00:04:51,371 --> 00:04:55,467 they had revealed just part of an enormous skeleton. 44 00:04:56,443 --> 00:05:02,006 They hauled whole chunks of rock back to the workshop to free the bones inside. 45 00:05:04,117 --> 00:05:08,178 The amazing thing was, when they chipped away at this massive hunk, 46 00:05:08,355 --> 00:05:10,846 they found only one bone inside. 47 00:05:12,225 --> 00:05:15,524 When they calculated the size of the creature, 48 00:05:15,695 --> 00:05:20,098 they realized they had found the biggest dinosaur that ever lived, 49 00:05:20,266 --> 00:05:23,633 a completely new species, a giant plant-eater. 50 00:05:23,803 --> 00:05:27,261 They named this new creature Argentinosaurus. 51 00:05:31,778 --> 00:05:34,542 This is a human backbone. 52 00:05:36,683 --> 00:05:41,120 This is...a backbone of a whale. 53 00:05:42,322 --> 00:05:47,316 And this is an Argentinosaurus backbone. 54 00:05:48,161 --> 00:05:51,096 You can see, just from its size, 55 00:05:51,264 --> 00:05:54,631 that an Argentinosaurus was a very big animal. 56 00:05:54,801 --> 00:05:57,964 (NARRATOR) The other bones were just as massive. 57 00:05:58,138 --> 00:05:59,867 With thighs the size of a car, 58 00:06:00,040 --> 00:06:05,000 Argentinosaurus was far and away the heaviest dinosaur ever found. 59 00:06:07,180 --> 00:06:11,082 When this animal walked, the earth trembled. 60 00:06:16,690 --> 00:06:19,591 The world of paleontology was thrilled. 61 00:06:23,697 --> 00:06:28,532 (NEW SPEAKER) It's an immense plant-eater. It's perhaps 80 to 100 metric tonnes. 62 00:06:28,702 --> 00:06:31,569 It's the size of a herd of elephants. 63 00:06:31,738 --> 00:06:36,437 It may be that there are dinosaurs even bigger than Argentinosaurus. 64 00:06:36,609 --> 00:06:43,139 But at present, that's as big as we know any land-living creature has ever been. 65 00:06:56,730 --> 00:06:59,756 (NARRATOR) This replica of Argentinosaurus 66 00:06:59,933 --> 00:07:03,027 is being built for the town square in Plaza Huincul. 67 00:07:05,672 --> 00:07:10,632 When it's finished, it will stand as tall as a five-storey building. 68 00:07:15,115 --> 00:07:19,381 It wasn't just this dinosaur's size that was out of the ordinary. 69 00:07:19,552 --> 00:07:24,421 When scientists analyzed the layers of rock in which the skeleton was found, 70 00:07:24,591 --> 00:07:26,320 they discovered something. 71 00:07:26,493 --> 00:07:31,226 Argentinosaurus, along with many smaller South American long-necks, 72 00:07:31,397 --> 00:07:33,797 had been living at the wrong time. 73 00:07:37,637 --> 00:07:40,367 This fact was to prove crucial. 74 00:07:43,176 --> 00:07:45,269 Layers of fossil-bearing rock 75 00:07:45,445 --> 00:07:50,348 have shown that dinosaurs roamed the planet for 180 million years. 76 00:07:51,050 --> 00:07:52,779 Over the course of this time, 77 00:07:52,952 --> 00:07:57,184 hundreds of different species evolved and died out. 78 00:07:57,624 --> 00:08:01,492 By the middle of their time on Earth, the Jurassic Period, 79 00:08:01,661 --> 00:08:07,099 the land was dominated by massive plant-eating dinosaurs, the long-necks. 80 00:08:08,201 --> 00:08:13,503 These giant animals lumbered slowly across the landscape in large herds. 81 00:08:13,706 --> 00:08:16,106 With tiny brains the size of a golf ball, 82 00:08:16,276 --> 00:08:20,736 they were neither quick-witted nor fleet-footed. They didn't need to be. 83 00:08:20,914 --> 00:08:23,041 Sheer size was their defense. 84 00:08:23,316 --> 00:08:28,583 Only the youngest or the sickest were at risk from smaller predators. 85 00:08:28,755 --> 00:08:32,418 The reign of the long-necks lasted for 60 million years, 86 00:08:32,592 --> 00:08:36,688 and then they died out; no one knows why. 87 00:08:39,532 --> 00:08:43,969 By the end of the final age of dinosaurs, the Cretaceous Period, 88 00:08:44,137 --> 00:08:47,106 things were very different. 89 00:08:49,042 --> 00:08:53,240 A new and more vicious species of dinosaur arrived on the scene, 90 00:08:53,413 --> 00:08:56,405 the massive carnivorous tyrannosaurs. 91 00:09:00,286 --> 00:09:04,450 They were enormous. They were the biggest carnivores known. 92 00:09:04,624 --> 00:09:06,990 For the next 25 million years, 93 00:09:07,160 --> 00:09:11,529 these huge meat-eaters preyed upon everything around them. 94 00:09:12,999 --> 00:09:17,527 These giant predators never met the long-necked herbivores. 95 00:09:25,378 --> 00:09:30,509 But there was a part of the world where evolution took a different path... 96 00:09:31,351 --> 00:09:33,342 South America. 97 00:09:35,255 --> 00:09:38,247 Millions of years ago, when dinosaurs first appeared, 98 00:09:38,424 --> 00:09:43,123 all the land was connected in one huge super-continent, Pangea. 99 00:09:44,731 --> 00:09:48,724 Over the ages, Pangea broke up into two giant land masses, 100 00:09:48,902 --> 00:09:51,462 one in the north and one in the south. 101 00:09:53,473 --> 00:09:59,173 (NEW SPEAKER) Probably around 100 million years ago, South America became separated. 102 00:09:59,345 --> 00:10:02,872 And then the dinosaurs, the mammals, 103 00:10:03,049 --> 00:10:08,282 the rest of the fauna and flora started to evolve in separate ways, 104 00:10:08,454 --> 00:10:10,684 in different ways. 105 00:10:11,591 --> 00:10:13,752 (NARRATOR) After the continent split, 106 00:10:13,927 --> 00:10:17,522 different dinosaurs evolved on each continent. 107 00:10:17,697 --> 00:10:22,396 While, throughout the northern continents, the giant long-necks died out, 108 00:10:22,568 --> 00:10:26,504 down south, something extraordinary was happening. 109 00:10:27,573 --> 00:10:30,906 Here, the huge long-necks not only survived, 110 00:10:31,077 --> 00:10:34,069 they just kept growing bigger and bigger. 111 00:10:36,449 --> 00:10:39,850 About 90 million years ago, 112 00:10:40,019 --> 00:10:44,979 there were not such animals this big in any other part of the world, 113 00:10:45,158 --> 00:10:46,887 but in South America. 114 00:10:47,827 --> 00:10:52,059 These four-legged plant-eaters, like Argentinosaurus, 115 00:10:52,231 --> 00:10:55,496 are a typical South American kind of dinosaur. 116 00:10:55,668 --> 00:10:57,659 In this Cretaceous Period, 117 00:10:57,837 --> 00:11:00,738 they were highly successful in the southern hemisphere. 118 00:11:02,475 --> 00:11:05,638 It wasn't just the plant-eaters that were different 119 00:11:05,812 --> 00:11:08,906 on the isolated continent of South America. 120 00:11:09,082 --> 00:11:14,486 Sealed off from the rest of the world, the tyrannosaurs never reached here. 121 00:11:15,254 --> 00:11:18,746 In the time of the long-neck Argentinosaurus, 122 00:11:18,925 --> 00:11:24,659 scientists could find no trace of any large meat-eaters stalking the continent. 123 00:11:25,765 --> 00:11:28,393 But all that was about to change. 124 00:11:30,937 --> 00:11:34,134 A few years after the discovery of Argentinosaurus, 125 00:11:34,307 --> 00:11:39,370 Rodolfo started exploring a new fossil location near Plaza Huincul. 126 00:11:40,813 --> 00:11:45,876 Little did they realize what a fearsome creature they would uncover. 127 00:11:51,924 --> 00:11:54,791 Buried for 95 million years, 128 00:11:54,961 --> 00:11:58,658 a new monster began to emerge from its rocky grave. 129 00:12:05,171 --> 00:12:07,537 When they put the bones together, 130 00:12:07,707 --> 00:12:11,006 they had uncovered their second record breaker. 131 00:12:11,177 --> 00:12:13,668 This was a truly astonishing find. 132 00:12:14,614 --> 00:12:18,607 But this wasn't a long-necked plant-eater. 133 00:12:18,785 --> 00:12:23,552 It was the skeleton of the biggest meat-eating dinosaur that ever lived. 134 00:12:25,858 --> 00:12:30,227 It was a new species of animal, unrelated to the tyrannosaurs. 135 00:12:30,396 --> 00:12:31,954 And it was huge, 136 00:12:32,131 --> 00:12:36,261 the first giant carnivore ever discovered in South America. 137 00:12:36,436 --> 00:12:39,098 They called it Giganotosaurus. 138 00:12:43,743 --> 00:12:48,771 Giganotosaurus is 10-15 per cent more massive than Tyrannosaurus rex, 139 00:12:48,948 --> 00:12:50,882 which was the record holder. 140 00:12:51,050 --> 00:12:57,785 Giganotosaurus was an incredible animal, around 13 meters in length. 141 00:12:59,058 --> 00:13:05,258 The head was huge, around one meter and 80 centimeters. 142 00:13:06,099 --> 00:13:09,535 (NARRATOR) Giganotosaurus had a skull the length of a man. 143 00:13:11,571 --> 00:13:14,904 But this giant predator had one more thing to reveal. 144 00:13:15,074 --> 00:13:20,444 When the team dated the bones, they found Giganotosaurus lived in the Cretaceous, 145 00:13:20,613 --> 00:13:23,104 the time of the long-neck Argentinosaurus. 146 00:13:23,282 --> 00:13:27,480 The two dinosaurs were found only 80 kilometers apart. 147 00:13:30,890 --> 00:13:33,017 For the first time anywhere, 148 00:13:33,192 --> 00:13:37,094 scientists had discovered mega-carnivores and huge plant-eaters 149 00:13:37,263 --> 00:13:41,359 living during the same time period and in the same place. 150 00:13:41,734 --> 00:13:45,500 This is a peculiar ecological relationship 151 00:13:45,671 --> 00:13:49,266 that we found in Patagonia. 152 00:13:49,442 --> 00:13:52,104 Big preys and big predators. 153 00:13:52,311 --> 00:13:55,838 If we look at South America in the age of Giganotosaurus, 154 00:13:56,015 --> 00:13:58,950 the main potential prey for this immense meat-eater 155 00:13:59,118 --> 00:14:03,145 is an even more immense plant-eater, Argentinosaurus. 156 00:14:04,657 --> 00:14:09,287 (NARRATOR) Could it be that in Patagonia something unique happened? 157 00:14:12,498 --> 00:14:14,966 That the largest-ever plant-eater 158 00:14:15,134 --> 00:14:18,194 came face-to-face with the largest meat-eater 159 00:14:18,371 --> 00:14:21,568 in an extraordinary clash of the titans? 160 00:14:25,444 --> 00:14:27,105 (ROARING) 161 00:14:30,449 --> 00:14:33,179 Could this really ever have happened? 162 00:14:33,352 --> 00:14:38,949 As paleontologists considered the idea, they immediately saw a problem. 163 00:14:43,462 --> 00:14:47,193 The giant meat-eater, Giganotosaurus, may have been large, 164 00:14:47,366 --> 00:14:50,802 but he was still no match for Argentinosaurus. 165 00:14:50,970 --> 00:14:56,465 There was no way even this big meat-eater could have killed such a huge animal. 166 00:14:57,343 --> 00:15:02,576 No way, that is, unless Giganotosaurus did what many other predators do 167 00:15:02,748 --> 00:15:04,682 when faced with a bigger prey. 168 00:15:10,723 --> 00:15:16,821 For these hyenas, hunting together is the only way to bring down this wildebeest. 169 00:15:16,996 --> 00:15:20,159 Could this have been what the clash of titans was like? 170 00:15:20,333 --> 00:15:24,326 Not two solitary dinosaurs battling it out by themselves, 171 00:15:24,503 --> 00:15:27,097 but a pack of marauding Giganotosaurus 172 00:15:27,273 --> 00:15:30,174 hunting one enormous Argentinosaurus? 173 00:15:36,549 --> 00:15:41,248 Unfortunately, there was a fundamental problem with this idea. 174 00:15:42,588 --> 00:15:45,352 Paleontologists have traditionally believed 175 00:15:45,524 --> 00:15:49,654 that large carnivorous dinosaurs lived and hunted alone. 176 00:15:49,829 --> 00:15:53,731 There was no evidence to support the idea of them as pack hunters. 177 00:15:53,899 --> 00:15:58,996 If they weren't pack hunters, they could never have attacked Argentinosaurus. 178 00:16:03,376 --> 00:16:06,106 Angela Milner, like many paleontologists, 179 00:16:06,279 --> 00:16:10,477 believes the mega-carnivores were solitary creatures. 180 00:16:11,017 --> 00:16:14,350 (MILNER) The traditional view of large meat-eaters 181 00:16:14,520 --> 00:16:19,822 was that they were large, ferocious animals, perhaps rabid predators, 182 00:16:19,992 --> 00:16:21,960 but probably living singly. 183 00:16:27,066 --> 00:16:31,025 There's no real evidence at all that they worked together in big groups. 184 00:16:31,203 --> 00:16:33,933 Pack hunting is really hard to evolve. 185 00:16:34,140 --> 00:16:37,041 Unless there's a reason for it to be there, 186 00:16:37,209 --> 00:16:39,507 my default would be to say it's not there. 187 00:16:41,781 --> 00:16:47,617 (NARRATOR) For the skeptics, evidence supports their view of solitary predators. 188 00:16:53,326 --> 00:16:56,227 These are footprints made by dinosaurs. 189 00:16:59,799 --> 00:17:04,099 They've been preserved in rock for over 150 million years. 190 00:17:11,310 --> 00:17:17,442 Mark Norell believes such footprints show which dinosaurs lived in groups. 191 00:17:19,719 --> 00:17:25,521 The biggest plant-eating dinosaurs left track-ways, fossilized footprints, 192 00:17:25,691 --> 00:17:30,094 which really show that they lived in groups or herds, 193 00:17:30,262 --> 00:17:32,492 whatever you want to call them. 194 00:17:32,665 --> 00:17:37,967 These footprints are not arranged randomly, they're arranged in groups. 195 00:17:38,137 --> 00:17:40,537 Large ones walked in front of the packs, 196 00:17:40,706 --> 00:17:46,042 and these groups had a structure and they're all going in the same direction. 197 00:17:46,212 --> 00:17:52,481 You can follow them for long stretches, hundreds and thousands of meters. 198 00:17:52,651 --> 00:17:58,419 And you can see that they all move, they all turn, they're moving together. 199 00:17:58,591 --> 00:18:01,287 It's not just a coincidence. 200 00:18:01,460 --> 00:18:06,989 This is really powerful evidence, suggestive of this sort of behavior. 201 00:18:07,166 --> 00:18:11,967 The evidence for giant carnivorous dinosaurs isn't as good. 202 00:18:14,940 --> 00:18:19,468 (CARRANO ) We have meat-eating dinosaur footprints, but they all seem solitary. 203 00:18:19,645 --> 00:18:22,478 Even with a track-way of footprints in a row, 204 00:18:22,648 --> 00:18:27,449 we never seem to have a track-way that show a group moving together. 205 00:18:27,620 --> 00:18:31,716 Whereas that is common for the plant-eating dinosaur footprints, 206 00:18:31,891 --> 00:18:34,985 it's absent for the meat-eating dinosaurs. 207 00:18:38,864 --> 00:18:41,355 (NARRATOR) Another key piece of evidence 208 00:18:41,534 --> 00:18:46,267 supports the view that plant-eating dinosaurs were group animals. 209 00:18:56,081 --> 00:18:59,744 This desolate landscape contains a bone bed, 210 00:18:59,919 --> 00:19:03,514 a collection of dinosaur bones buried together. 211 00:19:06,492 --> 00:19:11,953 The fossilized remains of plant-eating dinosaurs, all of the same species, 212 00:19:12,131 --> 00:19:15,294 carpet an area the size of a football pitch. 213 00:19:18,170 --> 00:19:22,698 (MILNER) This bone bed is full of horned dinosaurs of different ages - 214 00:19:22,875 --> 00:19:26,072 little babies, large full-grown ones. 215 00:19:26,245 --> 00:19:29,476 They were probably crossing a swollen river 216 00:19:29,648 --> 00:19:32,242 and got drowned trying to cross. 217 00:19:50,870 --> 00:19:55,637 Sites where many plant-eating dinosaurs have been killed in an accident 218 00:19:55,808 --> 00:20:01,110 lead paleontologists to believe these herbivores were living in herds 219 00:20:01,280 --> 00:20:03,271 when they died together. 220 00:20:04,283 --> 00:20:06,410 (MILNER) With plant-eating dinosaurs, 221 00:20:06,585 --> 00:20:12,080 it's very frequent to find groups of animals preserved together in the rocks. 222 00:20:12,258 --> 00:20:16,217 Because they're all associated, and they're mixed ages, 223 00:20:16,395 --> 00:20:19,296 that's good evidence they were living as a herd. 224 00:20:20,599 --> 00:20:24,695 (NARRATOR) Bone beds of herds of plant-eating dinosaurs are common. 225 00:20:24,870 --> 00:20:30,399 But there was no such evidence that meat-eating dinosaurs lived in groups. 226 00:20:30,576 --> 00:20:34,569 In the case of the early fossil finds of meat-eating dinosaurs, 227 00:20:34,747 --> 00:20:38,979 they reinforce this idea of meat-eaters as solitary hunters. 228 00:20:41,120 --> 00:20:44,988 People had only found individual specimens of each of the species. 229 00:20:45,157 --> 00:20:48,854 They never found a bunch of individuals together. 230 00:20:52,264 --> 00:20:57,998 (NARRATOR) The evidence indicated these predators lived as solitary hunters. 231 00:21:01,907 --> 00:21:04,034 And if they were solitary hunters, 232 00:21:04,209 --> 00:21:06,643 no single carnivore, however big, 233 00:21:06,812 --> 00:21:12,307 would have gone for a prey as huge as the giant herbivore, Argentinosaurus. 234 00:21:13,719 --> 00:21:19,123 The tantalizing idea of a clash of the titans down in Patagonia was doomed. 235 00:21:23,495 --> 00:21:26,555 Or so most paleontologists thought. 236 00:21:34,840 --> 00:21:37,934 But one man was going to change all that. 237 00:21:42,615 --> 00:21:47,416 Phil Currie is one of the world's most accomplished paleontologists. 238 00:21:47,586 --> 00:21:53,218 He can identify any meat-eating dinosaur from a single tooth. 239 00:21:56,895 --> 00:22:02,026 Currie's passion for predatory dinosaurs led him to work with Coria 240 00:22:02,201 --> 00:22:04,169 on the plains of Patagonia. 241 00:22:05,671 --> 00:22:09,198 When an opportunity came up in 1995 to go to Argentina 242 00:22:09,375 --> 00:22:18,841 and see Rodolfo and all the fantastic finds he'd made, I jumped at it. 243 00:22:23,722 --> 00:22:26,418 (NARRATOR) Currie had always believed 244 00:22:26,592 --> 00:22:30,722 the mega-carnivores were solitary and didn't hunt in packs. 245 00:22:30,896 --> 00:22:35,697 But over time, as he began to think things through, he made a connection. 246 00:22:37,069 --> 00:22:39,094 Looking at modern animals, 247 00:22:39,271 --> 00:22:42,604 it became clear that it wasn't such an unusual thing 248 00:22:42,775 --> 00:22:46,541 that big meat-eating dinosaurs were pack animals. 249 00:22:46,712 --> 00:22:51,376 We'd had good indications that the plant-eaters were herding animals. 250 00:22:51,550 --> 00:22:53,177 It made sense 251 00:22:53,352 --> 00:22:58,722 that if the carnivores wanted to break the defenses of a plant-eater's herd, 252 00:22:58,891 --> 00:23:02,258 the only way they could do that is by strength of numbers. 253 00:23:02,428 --> 00:23:06,296 One of the responses that happens in a wide range of animals 254 00:23:06,465 --> 00:23:09,798 is that the meat-eaters become pack hunters. 255 00:23:15,474 --> 00:23:17,499 (NARRATOR) Currie now began to think 256 00:23:17,676 --> 00:23:22,875 the idea of large meat-eating dinosaurs as pack hunters was a possibility. 257 00:23:23,816 --> 00:23:27,149 But to prove his hunch, he needed hard evidence, 258 00:23:27,319 --> 00:23:30,914 like that which had been found for the plant-eaters. 259 00:23:31,090 --> 00:23:33,115 What he needed was to find a bone bed 260 00:23:33,292 --> 00:23:39,492 where a group of mega-carnivores, no matter what species, lay buried together. 261 00:23:40,733 --> 00:23:44,794 (CURRIE) If we can find a bone bed with a lot of carnivores in one place, 262 00:23:44,970 --> 00:23:48,235 we have an indication that they died together. 263 00:23:48,407 --> 00:23:50,068 If they died together, 264 00:23:50,242 --> 00:23:54,872 there's a high probability they may have been living together. 265 00:23:55,414 --> 00:23:59,111 The only way to demonstrate an animal's a group hunter, 266 00:23:59,284 --> 00:24:03,414 or even come close to thinking about that, is by finding an assemblage 267 00:24:03,589 --> 00:24:06,922 with multiple individuals of different age sizes, 268 00:24:07,092 --> 00:24:12,394 from small individuals all the way to big adults, buried together at the same time. 269 00:24:16,101 --> 00:24:21,061 So for Currie, the search was on around the world for just such a site. 270 00:24:34,753 --> 00:24:37,221 And then...he remembered something. 271 00:24:46,832 --> 00:24:50,791 Several years earlier, he had read a very old magazine article 272 00:24:50,969 --> 00:24:54,564 by one of the most famous early dinosaur hunters. 273 00:24:55,808 --> 00:24:57,799 (CURRIE) I read an article by Brown. 274 00:24:57,976 --> 00:25:03,004 The article was basically about his experiences in southern Alberta. 275 00:25:03,182 --> 00:25:08,552 In that article is basically a one-liner, which suggests that he found somewhere 276 00:25:08,720 --> 00:25:13,623 where there was a lot of tyrannosaurs' remains in one single bone bed. 277 00:25:13,792 --> 00:25:16,556 (NARRATOR) Currie realized this might be 278 00:25:16,728 --> 00:25:20,095 the multiple-carnivore bone bed he had been looking for, 279 00:25:20,265 --> 00:25:25,726 a place which showed that several tyrannosaurs had lived and died together. 280 00:25:25,904 --> 00:25:29,772 Buried in the pages of ''National Geographic'' for over 80 years, 281 00:25:29,942 --> 00:25:32,843 the reference to the bone bed site had long been forgotten. 282 00:25:34,980 --> 00:25:40,680 I got really excited. I knew that this was a really special site. 283 00:25:40,853 --> 00:25:43,754 And I felt that we had to refind this site. 284 00:25:43,922 --> 00:25:48,484 It wasn't a matter any more that there was a bone bed that we might find. 285 00:25:48,660 --> 00:25:50,389 I had to find that site. 286 00:25:53,565 --> 00:25:59,401 (NARRATOR) Although finding this site had become crucial, there was a problem. 287 00:26:00,038 --> 00:26:04,065 Barnum Brown had never written down where the site was. 288 00:26:04,243 --> 00:26:08,270 He died, taking the secret of its location to the grave. 289 00:26:09,681 --> 00:26:14,345 This is one of Barnum Brown's field books. There aren't too many of these, 290 00:26:14,519 --> 00:26:18,011 just because Barnum Brown didn't take any notes. 291 00:26:18,357 --> 00:26:22,418 All it is is just a list of specimens and field numbers. 292 00:26:22,594 --> 00:26:24,858 There's not much about his activities, 293 00:26:25,030 --> 00:26:28,363 about the geology of particular localities, 294 00:26:28,533 --> 00:26:31,058 except that the rocks were grey, 295 00:26:31,236 --> 00:26:34,228 or it took him three days to get a specimen out. 296 00:26:34,406 --> 00:26:38,638 Unlike a lot of paleontologists of his time, or even today, 297 00:26:38,810 --> 00:26:41,074 he wasn't much of a note taker. 298 00:26:46,051 --> 00:26:48,679 (NARRATOR) Currie needed to find the site. 299 00:26:48,854 --> 00:26:52,551 So he scoured Brown's archive, looking for clues. 300 00:27:01,566 --> 00:27:05,161 (CURRIE) We looked at everything we could get our hands on. 301 00:27:05,337 --> 00:27:10,502 Amongst all that material were four photographs which were pretty good. 302 00:27:15,113 --> 00:27:20,551 (NARRATOR) The photographs had been taken by Brown around the dig site in 1910. 303 00:27:20,719 --> 00:27:26,021 Currie hoped that he could use the photos to pinpoint Brown's excavation. 304 00:27:27,025 --> 00:27:30,859 All that was known was that the site lay somewhere in the Badlands, 305 00:27:31,029 --> 00:27:34,021 near the Red Deer River in western Canada. 306 00:27:44,009 --> 00:27:49,447 So in 1997, Currie and a team of paleontologists set off by boat 307 00:27:49,781 --> 00:27:53,273 down a hundred-mile stretch of the Red Deer River, 308 00:27:53,452 --> 00:27:58,412 following the paddle strokes of Barnum Brown, looking for the site. 309 00:28:01,493 --> 00:28:05,122 The Badlands of Canada stretch over hundreds of square miles, 310 00:28:05,297 --> 00:28:10,496 with endless crags, hills and gullies that all look exactly the same. 311 00:28:13,772 --> 00:28:15,433 In all this vast land, 312 00:28:15,607 --> 00:28:20,408 no one knew where this potential goldmine of fossils was located. 313 00:28:22,414 --> 00:28:26,544 (CURRIE) The Badlands are very, very complex. 314 00:28:27,853 --> 00:28:30,287 Unless you have exactly the right angle, 315 00:28:30,455 --> 00:28:33,754 at the same time of day as he took the photograph, 316 00:28:33,925 --> 00:28:39,329 the chances are pretty good you can't relocate sites by using photographs. 317 00:28:41,767 --> 00:28:46,227 (NARRATOR) But as he studied the photographs, Currie noticed something. 318 00:28:46,405 --> 00:28:51,206 In one of them, Brown's assistant was working at the elusive site. 319 00:28:52,744 --> 00:28:55,440 Behind him was a distinctive ridge of hills. 320 00:28:55,614 --> 00:28:59,812 If Currie could find that ridge, he could find the site. 321 00:29:01,987 --> 00:29:04,182 If you look at this photograph, 322 00:29:04,356 --> 00:29:08,224 you can see a series of ridges with trees behind them. 323 00:29:08,994 --> 00:29:14,261 There's not that many places around with that combination of ridges and trees. 324 00:29:14,433 --> 00:29:17,960 If you can line yourself up with those ridges and trees, 325 00:29:18,136 --> 00:29:23,096 you're in the right area and you have a good chance of finding the quarry. 326 00:29:23,275 --> 00:29:27,575 Even so, it's still like looking for a needle in a haystack. 327 00:29:32,751 --> 00:29:35,743 We spent a couple of days scouring the area, 328 00:29:35,921 --> 00:29:41,791 looking for the right combination of Badlands as revealed in the photographs. 329 00:29:41,960 --> 00:29:45,327 The first day went by and we had no luck. 330 00:29:45,497 --> 00:29:48,591 The next day turned out to be the hottest day of the year. 331 00:29:48,767 --> 00:29:54,330 The expedition, which numbered about 16 people, basically ran out of water. 332 00:29:57,576 --> 00:30:01,945 By lunch time, everybody had gone back to camp except for me. 333 00:30:02,114 --> 00:30:04,674 I'm crazy enough that I kept at it. 334 00:30:04,850 --> 00:30:07,785 I went through all the Badlands here. 335 00:30:07,953 --> 00:30:10,649 These canyons are quite deep, 336 00:30:10,822 --> 00:30:15,452 so going up and down them on the hottest day of the year was quite an effort. 337 00:30:15,627 --> 00:30:18,357 There was a point when I suddenly realized 338 00:30:18,530 --> 00:30:25,231 a ridge in this region looked like it might just have the right viewpoint. 339 00:30:28,573 --> 00:30:33,340 I got to the top, and as I mounted this ridge over here, 340 00:30:33,512 --> 00:30:38,347 I could see that the trees and the ridge lined up perfectly. 341 00:30:38,517 --> 00:30:40,508 I knew I had the site. 342 00:31:30,302 --> 00:31:34,466 (NARRATOR) Currie and his team pounced on this unique site and started digging. 343 00:31:36,374 --> 00:31:38,365 And it was worth it. 344 00:31:38,543 --> 00:31:43,947 What they found were the remains of several tyrannosaurs, all in one place. 345 00:31:53,225 --> 00:31:58,720 One after another, they kept unearthing the bones of these huge carnivores. 346 00:32:02,567 --> 00:32:04,797 I don't know if Brown did a head count, 347 00:32:04,970 --> 00:32:09,839 but the minimum number of animals in this quarry is definitely 12. 348 00:32:14,145 --> 00:32:19,208 (NARRATOR) 12 large meat-eating dinosaurs buried in the same place. 349 00:32:19,384 --> 00:32:21,545 It was an unprecedented find. 350 00:32:21,720 --> 00:32:27,522 Phil Currie had found the site that he had dreamed of. But there was more. 351 00:32:27,692 --> 00:32:30,160 As they examined the bones, 352 00:32:30,328 --> 00:32:33,889 it was clear that the dinosaurs were of every age, 353 00:32:34,065 --> 00:32:36,829 from babies up to fully mature adults. 354 00:32:37,002 --> 00:32:38,993 It looked like a pack. 355 00:32:41,773 --> 00:32:45,607 (CURRIE) The range of material is such that we can see 356 00:32:45,777 --> 00:32:50,646 that the smallest individual in the bone bed was about four meters long. 357 00:32:50,815 --> 00:32:54,546 And the largest individual is about 11 meters long. 358 00:32:54,719 --> 00:32:57,347 So it's a pretty big range in size. 359 00:32:59,958 --> 00:33:02,153 (NARRATOR) They had found a whole pack. 360 00:33:02,327 --> 00:33:07,594 Here at last was proof that the giant meat-eaters were not solitary creatures, 361 00:33:07,766 --> 00:33:10,496 that the traditional image was wrong. 362 00:33:12,570 --> 00:33:17,974 Instead, the mega-carnivores may really have lived and hunted in groups. 363 00:33:19,110 --> 00:33:21,874 If that was true, then down in South America, 364 00:33:22,047 --> 00:33:25,073 packs of Giganotosaurus might have attacked prey 365 00:33:25,250 --> 00:33:28,583 as enormous as the immense Argentinosaurus. 366 00:33:38,830 --> 00:33:41,390 Currie's site seemed to prove it all. 367 00:33:41,566 --> 00:33:45,332 But other paleontologists were not yet convinced. 368 00:33:47,105 --> 00:33:49,573 (CARRANO ) Bone beds are tantalizing, 369 00:33:49,741 --> 00:33:54,337 because you have a tremendous number of bones in one single layer. 370 00:33:54,512 --> 00:33:58,505 It's tempting to look at that as evidence for a herd of animals, 371 00:33:58,683 --> 00:34:00,742 living in one place at one time. 372 00:34:00,919 --> 00:34:04,787 There are times the information supports that interpretation. 373 00:34:04,956 --> 00:34:07,516 But there are times when it does not. 374 00:34:08,526 --> 00:34:11,154 (NARRATOR) Before anyone would endorse Currie, 375 00:34:11,329 --> 00:34:15,425 he would have to verify some key details about the dig site. 376 00:34:19,137 --> 00:34:25,474 (MILNER) A bone bed doesn't automatically mean that the animals lived together. 377 00:34:25,643 --> 00:34:29,545 Sometimes bone beds accumulate from large areas, 378 00:34:29,714 --> 00:34:33,616 where floods have brought all kinds of remains together. 379 00:34:33,785 --> 00:34:37,516 You might be looking at an accumulation of many animals, 380 00:34:37,689 --> 00:34:39,418 from miles and miles away. 381 00:34:41,659 --> 00:34:43,854 (NARRATOR) This was the first problem. 382 00:34:44,028 --> 00:34:46,929 Flood waters could have washed together 383 00:34:47,232 --> 00:34:50,827 the remains of several unrelated tyrannosaurs. 384 00:34:52,137 --> 00:34:54,731 Buried in the same place millions of years ago, 385 00:34:54,906 --> 00:34:57,306 today they might look like a pack. 386 00:35:02,213 --> 00:35:04,977 But Currie felt he had an answer to this. 387 00:35:05,150 --> 00:35:07,482 Tyrannosaurs were rare dinosaurs. 388 00:35:07,652 --> 00:35:12,055 They would have made up only five per cent of the animal life in this area. 389 00:35:12,223 --> 00:35:16,592 The chances that 12 unrelated tyrannosaurs died separately 390 00:35:16,761 --> 00:35:20,356 and were washed together to this spot were minute. 391 00:35:22,233 --> 00:35:25,293 To find 12 tyrannosaurs by chance, 392 00:35:25,470 --> 00:35:28,166 at this level, in this bone bed... 393 00:35:28,339 --> 00:35:32,605 The chances of that happening are about one in 64 million. 394 00:35:32,777 --> 00:35:35,974 It isn't likely that it's going to happen by chance. 395 00:35:37,048 --> 00:35:39,778 (NARRATOR) There could be an even more dramatic reason 396 00:35:39,951 --> 00:35:44,411 why the bones of Currie's tyrannosaurs were all in one place. 397 00:35:44,589 --> 00:35:47,649 They could all have been caught in a predator trap. 398 00:35:55,567 --> 00:35:57,558 This is a predator trap. 399 00:36:00,205 --> 00:36:02,765 In this strange swamp-like place, 400 00:36:02,941 --> 00:36:05,933 molten tar has bubbled up from deep within the Earth 401 00:36:06,110 --> 00:36:08,340 for tens of thousands of years. 402 00:36:10,148 --> 00:36:13,709 The sticky tar is lethal to any animal that wanders into it. 403 00:36:13,885 --> 00:36:16,786 Within seconds, the creature will become stuck, 404 00:36:16,955 --> 00:36:18,946 and then its fate is sealed. 405 00:36:22,694 --> 00:36:26,562 Predator traps have been found all around the world. 406 00:36:28,299 --> 00:36:30,859 This one is in downtown Los Angeles. 407 00:36:34,072 --> 00:36:39,009 John Harris has been investigating these tar pits for the past 20 years. 408 00:36:40,378 --> 00:36:44,610 A horse or a ground sloth or a camel would wander along, 409 00:36:44,782 --> 00:36:49,048 and get stuck and... Just demonstrating here... 410 00:36:49,787 --> 00:36:53,985 Once it's in, it takes a great deal of strength to pull it out. 411 00:36:54,158 --> 00:36:56,991 If an animal gets stuck on the surface like this, 412 00:36:57,161 --> 00:37:00,927 when it's trying to pull out one leg, it's pushing in three others. 413 00:37:01,099 --> 00:37:03,863 Very soon it will get totally immobilized. 414 00:37:06,337 --> 00:37:09,966 (NARRATOR) The trapped animal would lure predators to the swamp, 415 00:37:10,141 --> 00:37:12,439 who would, in turn, become stuck. 416 00:37:13,545 --> 00:37:19,347 (HARRIS) It would be meat on the hoof, waiting for the sabre-tooths to feed. 417 00:37:19,517 --> 00:37:22,145 They would come in and, in turn, get stuck. 418 00:37:22,320 --> 00:37:25,016 Down would come vultures and they'd get stuck. 419 00:37:25,189 --> 00:37:27,851 In would come the flies, and they'd get stuck. 420 00:37:28,026 --> 00:37:31,928 In short order, you'd build up the whole food chain. 421 00:37:36,434 --> 00:37:40,996 (NARRATOR) Over time, hundreds of dinosaurs would have sunk into traps. 422 00:37:41,172 --> 00:37:45,871 Millions of years later, the tar and mud has turned to rock, 423 00:37:46,044 --> 00:37:51,607 the bones fossilized, and the site would look like any normal rocky bone bed. 424 00:37:56,387 --> 00:37:59,982 If Currie's site was actually a prehistoric predator trap, 425 00:38:00,158 --> 00:38:04,857 it would destroy his theory that the tyrannosaurs hunted in packs. 426 00:38:05,730 --> 00:38:08,631 But how could the paleontologists tell? 427 00:38:10,268 --> 00:38:14,637 There is always one telltale feature of all predator traps. 428 00:38:15,573 --> 00:38:20,977 They trap and kill every animal that is unlucky enough to cross their path. 429 00:38:22,680 --> 00:38:27,913 They contain the bones of many different species that lived for miles around. 430 00:38:34,726 --> 00:38:39,425 Over the last century, we've recovered three and a half million fossils, 431 00:38:39,597 --> 00:38:43,465 representing more than 650 species of animals and plants. 432 00:38:43,635 --> 00:38:46,729 They include a great diversity of large animals, 433 00:38:46,904 --> 00:38:52,171 mammoths, mastadons, sabre-tooth cats, lions, dire wolves and so on. 434 00:38:55,413 --> 00:38:59,611 (NARRATOR) If Currie's team discovered many species at their site, 435 00:38:59,784 --> 00:39:05,450 they would have to consider whether they were the leftovers of a predator trap. 436 00:39:07,358 --> 00:39:10,191 But after three years of painstaking digging, 437 00:39:10,361 --> 00:39:14,457 there's been one extraordinary finding about this site. 438 00:39:15,566 --> 00:39:20,697 (CURRIE) So far, all of the animals that we've found in here as parts of skeletons 439 00:39:20,872 --> 00:39:23,807 are one species, and that's this big meat-eater, 440 00:39:23,975 --> 00:39:26,466 a tyrannosaur known as Albertosaurus. 441 00:39:26,644 --> 00:39:30,307 There are no other carnivorous dinosaurs in this bone bed. 442 00:39:30,481 --> 00:39:33,644 Given that we're dealing with only one type of carnivore, 443 00:39:33,818 --> 00:39:36,981 we can rule out things like predator traps. 444 00:39:37,355 --> 00:39:41,451 It's almost certain these dinosaurs died here together 445 00:39:41,626 --> 00:39:43,617 because they were living together. 446 00:39:57,508 --> 00:40:00,875 (NARRATOR) Phil Currie seemed to have proved his case. 447 00:40:02,213 --> 00:40:04,204 But he hadn't. 448 00:40:04,382 --> 00:40:09,877 Although he was convinced, his fellow paleontologists still weren't sure. 449 00:40:10,455 --> 00:40:14,551 If we just found one site with large predatory dinosaurs, 450 00:40:14,726 --> 00:40:19,527 found as a group with multiple individuals of different age sizes, 451 00:40:19,697 --> 00:40:22,461 that could be a fluke, a chance. 452 00:40:22,633 --> 00:40:25,261 The evidence is a little bit equivocal. 453 00:40:25,436 --> 00:40:28,769 It's not definite. It's a little circumstantial. 454 00:40:30,641 --> 00:40:35,669 (NARRATOR) Despite all his efforts, Currie's case was not yet proven. 455 00:40:35,847 --> 00:40:37,678 He needed a second site 456 00:40:37,849 --> 00:40:41,785 to convince his colleagues that the first dig wasn't a fluke, 457 00:40:41,953 --> 00:40:46,413 that large meat-eating dinosaurs really were pack hunters. 458 00:40:49,060 --> 00:40:52,188 And then he got some unexpected news. 459 00:41:02,073 --> 00:41:07,204 Patagonia, which had harbored the bones of Argentinosaurus and Giganotosaurus, 460 00:41:07,378 --> 00:41:09,869 had yielded one further treasure. 461 00:41:13,217 --> 00:41:16,914 Phil Currie's colleague, Rodolfo Coria, had made a new discovery. 462 00:41:19,557 --> 00:41:22,822 We came here because a local farmer called us 463 00:41:23,027 --> 00:41:25,860 because of some fossils that he had found. 464 00:41:26,030 --> 00:41:29,932 We were very lucky, because looking in the slope of this hill, 465 00:41:30,101 --> 00:41:32,763 we found this bone. 466 00:41:35,907 --> 00:41:41,140 (NARRATOR) This is a toe bone of what was to prove to be an enormous dinosaur. 467 00:41:41,879 --> 00:41:45,508 Rodolfo had recognized that the bone was from a meat-eater, 468 00:41:45,683 --> 00:41:49,813 and the following year he persuaded Phil Currie to join him in Patagonia, 469 00:41:49,987 --> 00:41:52,820 to try and find the rest of the skeleton. 470 00:41:55,493 --> 00:41:59,224 (CURRIE) We found the level where the bones were coming from. 471 00:41:59,397 --> 00:42:03,299 As we dug in, we realized there was a good part of a skeleton there. 472 00:42:04,936 --> 00:42:07,496 It far surpassed our expectations. 473 00:42:10,007 --> 00:42:14,205 (NARRATOR) Phil and Rodolfo thought the bones belonged to Giganotosaurus. 474 00:42:18,683 --> 00:42:21,413 But as they examined their new discoveries, 475 00:42:21,586 --> 00:42:27,320 they noticed that the bones had different shapes from those of Giganotosaurus. 476 00:42:31,295 --> 00:42:34,423 (CORIA) These differences in the shape of the bones 477 00:42:34,599 --> 00:42:39,434 are a clue for a paleontologist to identify a new species. 478 00:42:40,438 --> 00:42:46,308 And the shape is telling us that we are dealing with a new species of meat-eater. 479 00:42:47,879 --> 00:42:51,645 (NARRATOR) They began to measure the bones of their new beast. 480 00:42:51,816 --> 00:42:56,651 They were bigger than any meat-eater bones ever found anywhere in the world. 481 00:42:56,821 --> 00:43:00,757 Bigger than T-rex, bigger even than Giganotosaurus. 482 00:43:03,060 --> 00:43:10,091 A full-sized Tyrannosaurus rex was between 12 and 13 meters in total length. 483 00:43:11,435 --> 00:43:16,236 That means that the new one was somewhere between 14 and 15 meters. 484 00:43:36,661 --> 00:43:41,621 It looks like we've probably got the biggest meat-eater in the world. 485 00:43:43,734 --> 00:43:45,964 (NARRATOR) But there was more. 486 00:43:46,137 --> 00:43:49,573 When Rodolfo and his team began to study the bones in detail, 487 00:43:49,740 --> 00:43:52,140 they noticed something strange. 488 00:43:53,511 --> 00:43:55,274 As they analyzed the bones, 489 00:43:55,446 --> 00:43:59,473 Rodolfo realized that they had found four leg bones... 490 00:44:00,451 --> 00:44:02,885 ..for a two-legged creature. 491 00:44:07,558 --> 00:44:12,086 There was more than one carnivore in this dinosaur graveyard. 492 00:44:24,709 --> 00:44:28,668 So far, our record is indicating 493 00:44:28,846 --> 00:44:34,079 that at least six individuals have been preserved. 494 00:44:35,453 --> 00:44:38,820 (NARRATOR) What's more, they were all different ages. 495 00:44:38,990 --> 00:44:43,825 With six specimens of the new meat-eating dinosaur found at the Argentinian site, 496 00:44:43,995 --> 00:44:48,955 Phil Currie had what he needed - the second pack of mega-carnivores. 497 00:44:57,174 --> 00:44:59,142 I just couldn't believe it. 498 00:44:59,310 --> 00:45:05,215 Suddenly we had two large meat-eating dinosaurs in two parts of the world 499 00:45:05,383 --> 00:45:08,181 which were showing packing behavior. 500 00:45:10,421 --> 00:45:13,254 It seems to me that we have convincing evidence 501 00:45:13,424 --> 00:45:18,418 that large meat-eating dinosaurs formed these social groups, 502 00:45:18,596 --> 00:45:23,556 where the young and the old hunted together and lived together. 503 00:45:29,807 --> 00:45:34,744 (NARRATOR) Finally, Currie's discoveries are beginning to convince others. 504 00:45:34,912 --> 00:45:37,142 (HOLTZ) On the basis of these discoveries, 505 00:45:37,314 --> 00:45:43,446 we're beginning to have to change our ideas on how large predators behaved. 506 00:45:43,654 --> 00:45:46,487 If they're operating as a group, as a pack, 507 00:45:46,657 --> 00:45:51,651 a group of Giganotosaurus might have been able to mob 508 00:45:51,829 --> 00:45:56,061 even a big Argentinosaurus - something no one suspected before. 509 00:45:58,169 --> 00:46:02,538 (NARRATOR) But for Phil Currie, this idea was more than a suspicion. 510 00:46:02,706 --> 00:46:08,008 It made sense to him that the giant meat-eaters preyed upon the long-necks. 511 00:46:08,179 --> 00:46:10,670 He was convinced by their teeth. 512 00:46:11,582 --> 00:46:17,748 (CURRIE) The teeth are better adapted for going after really big dinosaurs, 513 00:46:17,922 --> 00:46:21,289 like the long-necked plant-eaters in that region. 514 00:46:21,459 --> 00:46:25,122 If you look at the teeth, the teeth are very blade-like. 515 00:46:25,296 --> 00:46:28,197 They have serrations down the front and the back, 516 00:46:28,365 --> 00:46:32,734 and the teeth themselves are very narrow and knife-like. 517 00:46:33,871 --> 00:46:38,103 This is a slicing tooth, designed to cut through meat. 518 00:46:38,409 --> 00:46:42,743 So this new form could bite and slice out big chunks of flesh. 519 00:46:44,615 --> 00:46:47,675 (NARRATOR) The long-necks had massive bones, 520 00:46:47,852 --> 00:46:50,650 impossible to crunch through. 521 00:46:50,821 --> 00:46:54,450 So the giant South American carnivores didn't even try. 522 00:46:54,625 --> 00:46:58,823 Instead, Currie believes they used their thin steak-knife teeth 523 00:46:58,996 --> 00:47:02,955 to strip flesh from around the enormous bones. 524 00:47:04,101 --> 00:47:07,559 They were probably moving in to take quick bites, 525 00:47:07,738 --> 00:47:11,174 slicing off only the flesh and not biting very deep at all. 526 00:47:11,342 --> 00:47:14,675 Then they'd come in again and take another bite, 527 00:47:14,845 --> 00:47:17,780 until the prey was weak enough to kill. 528 00:47:19,617 --> 00:47:23,280 (NARRATOR) So when a group attacked together in a pack, 529 00:47:23,454 --> 00:47:27,447 even a huge Argentinosaurus was doomed. 530 00:47:29,760 --> 00:47:34,993 It looks like the clash of titans could really have happened, after all. 531 00:47:38,269 --> 00:47:40,260 (ROARING) 532 00:47:44,141 --> 00:47:45,574 (DEEP GROWLING)