"Don't be Triassic," snapped the Troodon. "This is the wave of the future."

The Ankylosaurus swished his massive tail dejectedly, crushing a small tree. "I can't help it my brain's the size of a golf ball," he said.

"Well, lucky you've got me around," said the Troodon, adjusting a piston. "So long as I don't eat you." He smiled in that toothy way theropods had, which the Ankylosaurus had never liked, and examined his work. "There, lovely. Drag that fuel over, will you?"

The Ankylosaurus, glad to be doing something the Troodon couldn't, walked carefully up to and past the invention, dragging the bundle of wood the Troodon had harnessed to him right up to the maw of the machine. The Troodon plucked several pieces out and threw them in, then struck a match (invented a century before by another Troodon) and tossed it into the piles of kindling already inside. A flame leapt up, and the Anklylosaurus watched the fire grow with a kind of anxious fascination.

"It's not doing anything," he said after a while.

"Shut up," said the Troodon, and the Ankylosaurus thought he sounded worried. "It just needs to heat up enough to ... oh! Ha! Ha ha ha! Yes! Look! Yes! It works! I'm a genius! It works!"

It did seem to be working. The flames were leaping up to caress the container of water, and through some means that the Ankylosaurus couldn't understand at all, this was moving a rod back and forth, which made a wheel turn. Smoke poured out of a small smokestack, and steam squirted out elsewhere. The Ankylosaurus waited, hoping there was more to it.

"That's it?" he said, finally.

"That's it? You lump! I've invented the steam engine! Can't you see what this means?"

"I don't know," said the Ankylosaurus. "It seems to be spitting up a lot of smoke."

"Pollution, bah!" scoffed the Troodon. " The sky is infinite, the waters are infinite ... what do you think's going to happen? We'll dirty ourselves to death? Ha! Dinosaurs have reached their rightful place as masters of the planet! You just wait!"

# # #

Fifteen hundred years later ...

A massive asteroid, more than six miles across, barreled toward a planet nearly covered in black, sooty clouds, though glimpses of brownish-blue and brownish-green were visible through small gaps. When it impacted, it would raise a lot of dust over the corpses of the last dinosaurs, who had starved to death on their choked planet only a hundred years before.