Excerpts from Chapter 12 . . . FATAL FLAW

Before we begin, let me give you some background.

One of the mysteries of mass extinctions is that “big is bad.” During the dinosaur extinction, all animals where the adults weighed more than 55 pounds went extinct. Similarly, at the mammoth extinction, many mammals where the adults weighed more than 100 pounds went extinct, while smaller ones skated through almost unscathed. It’s the puzzle of the ice ages.

We pick up here toward the end of chapter 12, after having discussed how many hundreds of thousands of mammoths died at the end of the last ice age.

Let us begin . . . . . . . .

Entire herds of those giant beasts must have been wiped out! Just as entire herds of dinosaurs died.

Herds of dinosaurs?

Come on now. Dinosaurs didn’t herd together like cattle. Did they? Or clump together like a flock of bleating sheep. Did they? Don’t destroy all of my old illusions. Weren’t dinosaurs supposed to be big, mean, and macho? Weren’t dinosaurs supposed to be cold-blooded, lonesome bullies?

Not true. Some dinosaurs were veritable social butterflies, living together in herds so big that they make the American buffalo look like a hermit. An entire herd of dinosaurs was recently discovered by paleontologist Jack Horner. (The inspiration for Jurassic Park’s fictional hero Alan Grant, Horner is also a professor, and curator of the Museum of the Rockies at Montana State University.)

It was a herd of adult maiasaurs. (Maiasaurs were a type of hadrosaur best known as the duck-billed dinosaur.) Found at Montana’s Willow Creek anticline, the discovery was so important that Horner devoted an entire chapter in his 1988 book Digging Dinosaurs to “The Herd.”

The bones are gray-black in color, said Horner, and strangely battered. Shattered might be a better word. Stretching 1¼ miles east-to-west, and ¼ mile north-to-south, the bone bed contains more than 30 million fragments. There’s no way to count the bones, said Horner, but by a conservative estimate it holds the bones of at least 10,000 dead dinosaurs.

No freak accident of nature, said Horner, could have bunched the bones together like that, especially since they aren’t in a river or streambed. In fact he doesn’t know what they’re in; some sort of mudstone, he guesses. All massacred at the same time about 80 million years ago, they’re buried exactly 18 inches below a layer of bentonite (volcanic ash).

What turned the duckbills into sitting ducks? Maybe they got caught in a mud flow, one worker suggested. But why are the bones in such miserable shape?

Some are broken in half, others are sheared apart lengthwise. Even more mysteriously, right beside a badly damaged bone will lie a bone that hasn’t been touched. How could a mud flow be so selective?

Most perplexing of all, though, are the standing bones. Some bones are standing at attention, sticking straight into the ground. It looks like a giant’s game of mumblety-peg—played with dinosaur bones instead of knives.

Whoa. Floods don’t leave bones standing upright, thought Horner. Floods leave bones lying flat, or jumbled together in a mishmash.

Neither do mudslides. What kind of mudslide, he asked, no matter how big, could take a dead animal weighing two to three tons, two to three times more than a modern-day draft horse, and toss it around so hard that “its femur—still embedded in the flesh of its thigh—split lengthwise?”

Why are none of the bones chewed on? Ten thousand dead dinosaurs, doggy paradise, and nothing has gnawed on the bones?

Why are the bones lying east-to-west, the long dimension of the grave? And why are there no babies? Small bones are rare in the main part of the bone pit, said Horner, they’re all on the easternmost edge.

Three other digging sites, up to a mile further east, also hold “little” bones from nine-foot dinosaurs. Invariably, said Horner, the bones at the edge are better preserved than those in the middle.

Invariably! You’d think any predator with a lick of sense would go for the easy pickings first. Bones of the smaller animals at the edge should be the most damaged, not the least.

The volcanic ash must be the key, thought Horner. Look at Mount St. Helens. “That was a little volcano,” he said. “Volcanoes like that were a dime a dozen in the Rockies back in the late Cretaceous.” Much bigger volcanoes had erupted south of Willow Creek in the Elk Horn Mountains near Great Falls. Bigger volcanoes had erupted in the Rockies west of the site, too.

A volcanic eruption could explain why no predators had chewed on the bones; the predators had died along with their prey. Then a catastrophic flood moved the bones to their present location and buried them beneath a protective layer of mud.

Maybe. But I don’t buy it. Why are the bones at the edge in better shape than those in the center? Why are some bones so horribly battered while ones right beside them remain untouched? A volcano wouldn’t do any of those things. Neither would a flood.

But a snowstorm could!

Horner’s herd was caught in the biggest snowstorm in 14.1 million years … the same kind of snowstorm that will soon kill most of us!

With massive volcanic eruptions behind them, and six feet of snow per hour falling on their heads, the desperate maiasaurs stampeded. Eyes rolling, noses snorting, and lungs bellowing, the biggest, the hardiest, the meanest, tore to the front of the pack. (That’s how Mother Nature works, isn’t it? We call it survival of the fittest. It’s really survival of the nastiest. The young ones, the weak ones, the small ones, always get left in the rear.)

But it did no good. Flailing about in frantic attempts to stay above the snow, they instead dug deeper and deeper. Still it kept coming, burying the biggest among them.

It looked as if the meek really would inherit the earth. With no one left to walk on them, the ones in the rear had avoided the onslaught. Now it was their turn to climb the gory ladder of success. God help them, though, if they fell between the rungs. Instant pulverization in the grinding mass below.

Climbing ever higher on the bodies of their fallen comrades, they tried to stay above the ever deepening snow.

Still it kept coming. Four stories deep. Six stories deep. Nine. All in one day. Still they kept climbing, nine stories into the sky.

Millions of pounds of live dinosaurs, nine stories deep, biting and scratching and kicking and writhing and jumping on one another in panic would break a lot of bones, I would think, in a lot of funny ways. That’s how one bone could get shattered but not the one right beside it.

Reaching the top of the pulsating pile, still panicked, still running, they continued their deadly stampede. What a mistake! They didn’t know they were at the edge of a cliff; a cliff built of anguished dinosaur bodies on one side, and nine stories of soft snow on the other, ready to suck them down.

Off the edge of the pile they plowed. And down they went, sinking further and further into the snow. In front of the herd now, but on the bottom, they became living stepping stones for the next wave of their ever smaller brethren.

The smaller they were, the better to crawl on the backs of their heavier kin. The lighter they were, the better to swim through the snow and away from the belching volcanoes.

Exhausted, they stopped to catch their breath and maybe to take a nap. Too bad. Freezing is a peaceful way to go, I hear. You simply drift into a hypothermic sleep … and never wake up.

That’s why the bones of smaller animals are found at the edge of the pile. That’s why the bones at the edge are in better shape than those in the middle. There was no one left to stomp on them. Then the snow melted. And as it melted, nine stories of dead dinosaurs rotted and fell. Muscles and tendons disintegrated, and bones disarticulated themselves. Tumbling into the snowmelt, they came to rest pointing in the direction of the flow, east-to-west.

Some bones at the top, it seems logical, fell through the nine-story gridwork of rib cages below. Picking up speed as they went, by the time they hit bottom they rammed straight into the mud, just as Jack Horner found them.

What a desolate sound it must have made, with no one alive left to hear it, as the last lonely bone plinked down through the pile, to stand quivering in the macabre mud.

Now we know the dinosaur’s fatal flaw. Now we know the mammoth’s fatal flaw. They were too heavy. They couldn’t climb out of the snow.

Now we know our own fatal flaw!

Copyright © 2005 by Robert W. Felix

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