All across the world, the great reptilian beasts known as dinosaurs were in a state of decay. For 160 million years, these wonderous monsters had reigned planet Earth with an iron fist, sweeping aside all other creatures standing in their way, as well as each other. But now, that reign had been showing telltale signs that it was nearing a sickly end.
For the past few centuries, volcanoes (or smoking mountains, as they were called back then) everywhere had sprung to life like wildfire, erupting nonstop for years and years, blanketing the Earth's atmosphere with all sorts of poisonous gases and debris. Quality oxygen had become more difficult to come by, as it has been coated with acidic pollution the likes of which had not been seen before. Said pollution had made it rather a miracle even for new dinosaurs and other related creatures to be hatched into their world, as it had prevented eggshells from forming properly, leaving embryos unprotected from the elements and causing them to die while still in their eggs. Even the ones that survived had even tougher times than before doing so, as food and drinkable water had become more and more scarce from the poisoning of the atmosphere. With all of these hardships, life on Earth appeared as if it were choking to death.
Even so, life in the Great Valley continued on as peaceful and prosperous as it always had. The Great Valley was an oasis located in the middle of a vast, barren landscape known simply to its inhabitants as the Mysterious Beyond; rivers that flowed underground broke the surface in the valley, feeding it the clean, fresh water that its inhabitants lived on, as well as providing nourishment for the plants that the dinosaurs feasted on. Additionally, the mountains around the valley (known colloquially as the Great Wall), protected these gentle giants from the carnivorous theropd dinosaurs (which they called "Sharpteeth") who sought to feed on them for their own sustinence.
This particular day was another one of those typical peaceful, sunny occasions. In a clearing just outside of the undergrowth, a pair of juvenile dinosaurs were having a playful jousting match. One of these dinos was called Littlefoot; a friendly little Apatosaurus (a type of sauropod, which was something known to his peers as "Longnecks") who liked making friends with all sorts of creatures - a practice many in the dinosaur kingdom frowned upon due to personal prejudices. One of these friends was a female Triceratops (a type of "Three-horn", as they called them) named Cera; an aggressive, emotionally insecure sort of creature - she's the one who Littlefoot is jousting with at the moment.
Though the two were the best of friends, they did tend to pick fights, whether they were playful or serious. Fortunately, this was just a little playful contest, which was closely watched by their other friends - Petrie, the timid Pteranodon (or Flyer), Ducky, the sweet innocent Saurolophus (or Swimmer), and Spike, the dimwitted, illiterate Stegosaurus (or Spike-Tail) and Ducky's adoptive brother.
"Nine wins in a row for me," Cera smirked as she pawed the ground, prepping for another round. "I really don't know why you keep trying, Littlefoot. Face it, you just can't beat me!"
Trying not to let her mind games get through to him, Littlefoot simply scoffed it off. "Oh, this time will be the charm for sure!"
"That's what you said the last seven times!" Cera blustered. "Now charge at me, you!"
And with a great collective leap, the two friends charged at each other, looking to dish out some damage...
"Ha! Got ya again!" Cera celebrates as Littlefoot was thrown over onto his backside by the impact as their other friends looked on.
"Look like Cera win again, I suppose." shrugged Petrie.
"It would be nice if Littlefoot could take her down once in a while," affirmed Ducky. "It would, it would."
Spike said nothing; he simply let out a grunt of agreement as Littlefoot rolled himself back up onto his feet.
"OK, fine, I can't beat you," Littlefoot nonchalantly acknowledged. "Now can we do something else? Besides, your horn is making me bruise."
"Yeah, this is getting quite repetitive," Cera admitted. "So, uh, now whaddya wanna-"
"WHOA!" Littlefoot suddenly exclaimed. "Who turned on the lights?!"
"Is the Bright Circle (we call that the Sun) acting up or something?" added Cera.
"Me no know!" whimpered Petrie as he shielded his eyes with his wings.
Indeed, the sky has suddenly turned into a bright white - almost as bright as the Bright Circle itself. Our prehistoric pals shielded their eyes as best as they could, trying to protect themselves from this sudden burst of burning light.
But then, just like that, the light faded out, and for a moment everything seemed to have proceeded back to normal.
"Whew, I am glad that is-"
But before Ducky could finish her sentence, a sudden jolt shook the very ground underneath them. Said shaking only lasted for a second, but it was more than enough to scare our pals senseless.
"What was THAT?!" Ducky cried out. "Was it an earthquake? Huh? Huh?!"
At that precise moment, Petrie glanced over and saw something advancing towards them over the horizon, something that was hellbent on consuming them all alive; something that could spell the end for all life on Earth.
"Uh, guys," he squeaked. "THAT NO EARTH SHAKE!"