It was a mild day, late into the Cretaceous period. A Pachycephalosaurus walked the forest, the body of a Vegavis in its mouth. Several hours had passed since it had collected its prize, but still it journeyed. Resisting the urge to eat for this long was proving difficult, but it would persevere.
After some time, it spotted something soaring through the sky, a mere silhouette against the sun. The Pachycephalosaurus hurried after the silhouette. The being took perch on its usual spot, on the highest branch of a tree in the middle of a clearing. It was the only branch that kept it safe from even the biggest predators.
Standing on one of the tree's many roots was a creature the Pachycephalosaurus recognized, but did not quite understand. It was a furry thing, a quadruped, a little smaller than the Vegavis the Pachycephalosaurus carried. There were many like it, all following the winged one, all identical. But only one sat on the root that day. The two watched each other for some time before the flighted one let out a call. The Pachycephalosaurus understood this meant it could approach.
The Pachycephalosaurus understood the winged one was no Archaeopteryx. The fact that Archaeopteryx had gone extinct almost one hundred million years ago was lost on the Pachycephalosaurus, nor did the true origin of the creature matter too much to the Pachycephalosaurus. It wasn't all that smart. Silly dinosaur. It couldn't even sense the suppressing amount of mirth emanating from the winged one. The Pachycephalosaurus dropped the carcass at the foot of the tree, as it had done for the past fifty days. The winged one let out another cry, and the furry thing dragged the carcass into a hole under the tree.
Three of the furred creatures exited the hole, each carrying assorted rocks. They displayed their wares and wagged their little tails. But the Pachycephalosaurus desired none of them. It had, after all, bought instances of each presented. The Pachycephalosaurus was a rock collector, a veritable Connoissaur. While the company of Mastodon, Carnotaurus & Dark certainly rewarded oneself with interesting rocks, none could beat the winged one. It had ran up a deposit over the past fifty days, and it wished to use it all on something more grand. After some time the winged one bobbed its head up and down. It let out yet another cry, and another one of the furry things walked out from under the tree. This one held a piece of wood, odd runes scratched into it.
The Pachycephalosaurus did not understand. This was not a rock. It desired a rock, and a fancy one at that. It growled, and each creature growled back in unison, their adorable little ears pressed back. This gave the Pachycephalosaurus pause. The winged one let out a strange sound, alternating in pitch. Almost like a laugh. It conveyed that the wood was simply a formality, a sign of respectability. Very fancy. Now understanding that what it held was not simply wood, the Pachycephalosaurus attempted to chew it. It decided that whatever formalities were, they were not very tasty. In fact, formalities tasted a lot like wood.
After an odd motion where it held its right wing to its crest and leaned forward, the wondrous creature lifted itself from the branch. It thanked the Pachycephalosaurus for all of its business, then simply flew up into the sky. The Pachycephalosaurus watched it go helplessly, thinking all it got was some poor tasting formality. Fifty meals, and not a fancy rock to show for it. Curses flowed from the Pachycephalosaurus's maw as it watched the winged one depart.
The Pachycephalosaurus's tiny mind lapsed for a moment as it stared at the departing salesbirdinosaur. Instead of a sun, its details were hidden by a massive flaming rock. The most fanciest rock of all rocks. The Pachycephalosaurus felt satisfied with its purchase. It would look so nice on the mantle. If Pachycephalosaurusi had mantles.
The most fanciest awesome rock itself was at least ten kilometers in diameter, which according to modern rock enthusiasts is indeed quite fancy. The most fanciest gloriously awesome rock certainly brightened up the Pachycephalosaurus's life. And even Mastodon and Carnotaurus's lives were brightened up, as deep in their caves as they were. In fact, it brightened up the lives of three-fourths of the planet's flora and fauna. One could argue it even brightened up the day of the planet itself!
Then the most fanciest gloriously awesome fantastic rock (later marketed simply as Dr. Wondertainment's Marvelous Meteor™) arrived at its destination; Chicxulub, Mexico - 66,462,579 BC. Right on time.