- [Narrator] Right now,
paleontologists discover a new species of dinosaur
every week, and it's no wonder. Dinosaurs dominated the
planet for 135 million years, but they didn't start out on top. The first dinosaurs emerged
around 230 million years ago, during the Triassic Period. Back then, Earth looked very different. Instead of seven continents,
there was just one, Pangaea. Even early dinosaurs were nothing like those Hollywood giants. Eoraptor, possibly the first
true dinosaur, was puny, especially compared to
top predators of the day, like some of the giant Rauisuchians. Over the next 30 million years, new species of dinosaurs
and amphibians developed, along with the first mammals. Life was flourishing. Then, 201 million years
ago, everything changed. Pangaea began to tear apart. The shifting tectonic plates
sparked volcanic eruptions, which, over tens of thousands of years, tripled the amount of greenhouse
gasses in the atmosphere, and warmed the planet by
three to four degrees Celsius. It vanquished at least 30%
of all life in the process. But for some reason, maybe luck,
or some helpful adaptation, the dinosaurs sailed on through to the dawn of the Jurassic Period, and over the next 135 million years, they continued to spread,
diversify, and evolve into some familiar faces. For example, the first Tyrannosaurus sprouted up some time around
170 million years ago. But don't get your hopes up. These guys were no T-Rex. The real sovereign of the
era was the Allosaurus. It dined on sauropods with
its meat cleaver teeth. Meanwhile, Pangaea
continued to pull apart. By 145 million years ago, it began to resemble what we see today, forming isolated pockets where dinosaurs grew
increasingly different. It was the heyday of dinosaur diversity, and a new period, the Cretaceous. In Argentina, giants like Petagotitan, the biggest dinosaur on record, turned up around 100 million years ago. But the most frightening of
all appeared in the western US, around 68 million years ago. T-Rex, the largest carnivore in history. On its own, it was a formidable predator. But it turns out the T-Rex
likely hunted in packs, and where T-Rex did not roam, other pack hunters filled the niche. In Asia, the small yet
cunning Velociraptor roamed. It was a bad time to be a mammal. And then, 66 million years ago, the Chicxulub asteroid
wiped out all the dinosaurs. Well, almost all of them. One group remained. Their descendants might be
sitting outside your window right now. Birds. That's right, modern birds are dinosaurs. Turns out the legacy of these
titans today is, well, dinner. This video is made in large part thanks to Steve Brusatte, and the information in his new book, The Rise and Fall of the Dinosaurs. What interesting dinosaur facts
do you want to know about? Let us know in the comments.
