Random

A long time ago, I read a story about how an Apatosaurus, what we used to call Brontosaurus, had too long a neck for its heart to pump enough blood to its brain. The animal couldn't exist, yet there it was. Later I'd heard a narrator state that after a certain period, no animals larger than our modern elephant existed. Anything larger than an African Elephant had died off.

There's a layer of soot colored earth under the ground, sometimes exposed. Over the entire earth. That's the main evidence for the comet/meteor theory. This crater or that crater is the other.

My theory: Not one, but thousands, maybe millions of meteors hit the earth. But not single or even multiple catastrophic meteor like Shoemaker-Levy 9, the series of objects that hit Jupiter. I theorize that it was a shower of meteors that mostly burned out in the sky, raining iridium-laden ash and rock, smoking to the Earth. A meteor shower, rather than a bombardment, over a long period of time, maybe centuries. Perhaps a large impact or two to explain the craters. Enough to explain the vegetation dieing off. Enough to explain why there's this layer over the entire Earth. And also to explain why animals over a certain size died, but not because life got harder or size made them more tempting prey for desperate predators.

All those micro-meteors raining down added mass to the planet. They laid down a roughly 2 to 3 inch layer over the entire planet. I don't know the math at all, but I would imagine that that much mass added would increase the gravitational pull of the planet itself. This was all new material, not the same finite matter spewed up form volcanoes, as one theory posits. I think those animals were just too big to live after the added mass. Maybe they didn't die because of it, maybe they adapted and evolved because of it, but I can't see animals that size surviving now, even in a zoo. Their mass would kill them. Reverse that thinking and ask what would have to change to imagine the same creature living 65 million years ago.