After the dinosaurs went extinct, mammals got 1,000 times bigger, and here’s why. With the dinosaurs out of the picture, there was a lot more space and food available for the surviving mammals. This allowed them to grow larger and take over the ecological roles that the massive dinos had filled. Bigger mammals could better defend themselves, explore new environments, and find diverse food sources. Plus, the climate and habitats favored these larger mammals, leading to the giants we see in the fossil record. Credit:
Brontotherium hatcheri: By Postdlf, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0/, https://commons.wikimedia.org/w/index.php?curid=2655565
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Brontotherium hatcheri: By Postdlf, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0/, https://commons.wikimedia.org/w/index.php?curid=2655565
Animation is created by Bright Side.
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FunTranscript
00:00Bam!
00:09The giant asteroid slammed into Earth and a while after that, dinosaurs were gone.
00:14You'd think there's nothing to be afraid of now, but nope, some pretty unique and scary
00:19beasts started to evolve after that.
00:22Back at that time, mammals were going through significant changes.
00:25It seems that some of them, like those similar to horses and rhinos, became giant and powerful
00:31very soon after the dinosaurs were gone.
00:35When dinosaurs were in charge, which was about 145 to 66 million years ago, mammals were
00:41relatively small creatures.
00:43Most of the time, they lived in the shadows of their much bigger enemies to avoid ending
00:47up as their dinner.
00:49Many of them weighed around 22 pounds or even less.
00:54But when the dinosaurs went extinct, mammals finally had a chance to take advantage of
00:58the new environment.
01:00For example, Brontotheris.
01:03It took this opportunity and grew to enormous sizes.
01:06They started at around 40 pounds and eventually reached weights of 4 to 5 tons in just 16
01:13million years.
01:14This sounds long, but it's relatively short in geological terms.
01:18Their large body size gave them and some other mammals an advantage after the dinosaurs disappeared.
01:24Now, they were the dominant and ferocious creatures others were afraid of.
01:29Brontotheris, whose fossils have been found in North America, got this cool name, Thunder
01:34Beasts, from the Sioux people because they believed these fossils came from giant thunder
01:39horses that would roam the plains during thunderstorms.
01:44And it's still a mystery how these Thunder Beasts got to grow so big so quickly.
01:50One of the theories says that they gradually increased in size over time.
01:54Another option is they went through rapid bursts of growth but also had periods where
01:58they didn't quite change.
02:00Or maybe there was a mix of species.
02:02Some were small and some were bigger, but in general, more of them ended up growing
02:07large.
02:08And scientists studied a family tree of 276 Thunder Beasts and realized the third option
02:14fits the best.
02:18It's all competition in nature.
02:20Back in that time, most mammals were small, so there was fierce competition among smaller
02:24plant-eating animals when it came to food.
02:27The larger ones, like Thunder Beasts, faced less competition for the resources they needed
02:32to survive.
02:33So bigger species had more chances to stay, while the smaller ones went extinct quickly.
02:41So yeah, the end of the dinosaur era doesn't mean the end of impressive and giant animals
02:46you'd also run away from.
02:48For example, I definitely wouldn't like to face this fella.
02:52It kind of reminds me of a giant sloth at first, but those evolved tens of millions
02:57of years later.
02:59This giant lived somewhere between 50 and 60 million years ago in North America.
03:04It was around 8 feet long and had an unusually massive and thick body and legs.
03:10Its tail was very thick as well.
03:12This beast must have used it to support itself and stand on its hind legs.
03:17Its skull was relatively short and small compared to its large body.
03:21What's interesting is that it still had collar bones, which are bones that most hooved
03:26animals don't have anymore.
03:29Here's something comforting that makes it less scary though.
03:31They probably ate plants that were soft enough to chew easily.
03:38Now imagine a snake so big it could easily rival the size of a T-Rex.
03:43It's not some mythical creature from fiction movies, but Titanoboa, the incredible beast
03:49that lived around 60 million years ago in the lush forests and rivers of South America.
03:55It was the largest snake ever that we know about.
03:57It was actually like the ancient ancestor of today's boas and anacondas that still
04:02live in the same region.
04:04Its body was a mind-boggling 42.7 feet long, which is longer than a school bus!
04:11To support its giant body, Titanoboa had about 250 vertebrae, which are the bones that make
04:17up the backbone of animals.
04:20Imagine how much it needed to eat to maintain such a massive body that was as heavy as a
04:25small car!
04:26It went after fish and crocodiles that lived in the waters and rivers of its home.
04:31A snake taking down a crocodile?
04:33It had to be a powerful beast.
04:36Titanoboa holds the record at the moment, but scientists believe we might discover more
04:41fossils of snakes that could be even bigger than this one!
04:47You know there has to be some scary crocodile on the list.
04:51Back in the dino era, there were even crocodiles that were 40 feet long and enjoyed snacking
04:55on dinosaurs.
04:57You can tell they haven't become less scary even after that!
05:01This beast lived between 15 million and 55 million years ago in what is now Venezuela,
05:06Peru and Argentina.
05:08It belonged to a group that was there during the time of the dinosaurs, but like many others,
05:13got to live their best years and thrived after the dinos disappeared.
05:18Unlike most crocodiles that stick to the edge of the water, you could easily come across
05:23this one since it liked to take walks on the land to check what was happening around.
05:28Check out its flattened blade-like teeth.
05:30They remind of those carnivorous dinosaurs even more than other crocodiles!
05:35This adaptation helped with catching prey during its chill afternoon walks on land.
05:40This fearsome creature could grow to over 20 feet long and weigh more than 3,000 pounds,
05:46which is bigger than today's saltwater crocodiles!
05:53Even a rhinoceros came in the XXL size in those post-dino times!
05:58This one, whose name I can't even try to pronounce, was a massive herbivore that lived
06:03in eastern Eurasia.
06:05It looked like a rhino, but it still had some differences, like its neck that was stretching
06:10over 6 feet long, which made it look like a rhino with a giraffe's neck.
06:15The creature stood more than 15 feet tall at the shoulder, towering over most other
06:20animals of its time.
06:22It looked slender, but it's still incredibly heavy with its 33,000 pounds, which is like
06:28two to three grown African elephants, or even a small house!
06:35One of the biggest carnivores that wandered Ice Age Australia wasn't a mammal, but this
06:40frightening reptile called Megalania.
06:43It could grow to be over 18 feet long, which is more than twice longer than the Komodo
06:47dragon, one of the largest lizards alive today!
06:51Megalania had sharp curved teeth similar to those of Komodo dragons, which means its bite
06:57was extremely powerful, and maybe even venomous.
07:01This venom worked in a way it could have prevented its prey from healing property, which means
07:06the poor animal would become weaker, so Megalania didn't even have to work that much to catch
07:10it after that first bite, no matter where its prey would try to escape!
07:17Moving on to birds now!
07:20An elephant bird stood almost 10 feet tall and weighed over a thousand pounds!
07:25You could see it on the island of Madagascar more than a thousand years ago, which is
07:30not even that long ago compared to the others!
07:33One of the multiple species of elephant bird was so big that it could rival some non-avian
07:38dinosaurs such as Euteraptor when it came to size!
07:42And its eggs were gigantic too!
07:45Just one egg could weigh more than 20 pounds, which is heavier than a bowling ball!
07:50The interior of its egg had a lot of space, so much you could hold more than a hundred
07:55chicken eggs inside!
07:59Land and air weren't safe from big beasts where you couldn't be sure if it wanted to
08:03eat you or your salad.
08:05And it was not much different in the water either.
08:08You've heard of Livyatan, right?
08:10It was an ancient, powerful predator and a type of sperm whale, but much larger and more
08:16fearsome than those we know today.
08:18While modern sperm whales mostly eat squid, Livyatan probably had a little bit different
08:24diet, which included other whales.
08:28Another giant predator was also roaming around the same time and place as Livyatan.
08:34Who else but our dear Megalodon shark!
08:37Scientists believed Megalodon also went after other whales, and the fight for the sweetest
08:42bite or even among each other was probably spectacular!
08:47That's it for today!
08:48So hey, if you pacified your curiosity, then give the video a like and share it with your
08:53friends.
08:54Or if you want more, just click on these videos and stay on the Bright Side!