Eric Flint: Boundary

"Cut it out, Joe!"

Jackie came clattering down the stairs, holding something behind her. "Ready?"

"Let's see it."

A few minutes later, Helen looked up. "Joe, take a look at this."

Joe put down the lemonade Mrs. Secord had handed him, rose from the couch and joined Helen in staring at the object.

It resembled nothing so much as a large blackish shoehorn- Helen estimated it at around fifteen centimeters long and ranging from three to six centimeters wide, with a concave side and a little hook on the narrow end.

"Some kind of brachiopod relative?"

"Not one I'm familiar with. Look at these marks here."

Joe frowned, then took the object and studied it more closely. "Well, it's definitely a fossil, and… those sure look like muscle attachment scars. But what're they doing on both sides of this thing, if it's a shell? Should run down only one side, shouldn't they?"

"That'd be my expectation, too. But if this is a bone, why is it so thin and concave? I've never even heard of anything like that."

Joe was good at visualizing anatomy-much better than Helen, in fact, who always had to sit down and sketch it out a piece at a time. His face now screwed up in concentration. "If you had a… no, no, that wouldn't make sense. Oh, but maybe… no, not that either. I suppose if…"

He turned the fossil over, examining the backside carefully. "Darn. No sign of it being a piece of something else, either, which might have explained it." He turned it over and over a couple more times, shifting his point of view as though it might suddenly become an obvious and familiar fossil from some different angle, then handed it back to Helen.

"Okay, you win, Jackie. I'm beat. Do you know what it is?"

Jackie shook her head, looking excited and trying not to-after all, she wasn't a high school girl any longer, and hadn't been for a number of years. "No, not really. I knew it didn't look like anything I'd seen before, but I was sure you people would know right away. Are you guys putting me on? You really, truly don't know what it is?"

"Really, truly, Jackie," Helen said. "I've never seen anything like it, or heard of anything like it. You say you know where you found it?"

Jackie looked hurt. "Of course I do, Helen! Haven't I been keeping a journal since my second year doing this?"

"I'm sorry. I should have said: will you show us where you found it, and where you think it came from?"

"Of course. Let me get my hiking boots on, and we'll go out there now."

"There" turned out to be a few miles out, not all that far from the old dig site, but to the northwest up a small arroyo. "I found it lying over here, half under some sand. I think it washed down from somewhere up the arroyo."

Helen measured the area by eye, trying to visualize the rains, the wash coming down, the size of the fossil.

She thought Jackie was right. "Let's go up a ways, then, and see if we find anything."

Luck, luck, luck.

The word kept repeating itself over and over in Helen's mind, as she stood there looking at the wall of the arroyo in a state of half-shock.

"Jesus Christ," Joe repeated for the fifth time, finally straightening up from his examination. "Helen, that's a Deinonychus, or I'm just a first-year student."

"And if the rest is in the same condition, we've got ourselves a fully articulated skeleton."

Amateur or not, Jackie understood how very rare that was, and her excitement was only restrained by an attempt to be more professional and dignified than the professionals around her. Theropod skeletons, like the Deinonychus, were rare enough to be noteworthy, but fully articulated skeletons-skeletons that had remained pretty much connected as they had been in life-were vanishingly rare.

Helen glanced down the arroyo, frowning. "Odd, though."

"What's odd?"

She pulled out the unknown fossil. "If this came from here, there's no way it's a shell. Not of a water dweller, anyway."

Joe nodded. "These are land formations; late Cretaceous, maybe even Maastrichtian."

"No 'maybe' involved, Joe. Look at where your hand is."

Joe looked at the rock wall he'd been leaning against. "What-"

He suddenly started laughing. "You can't be serious, Helen! It's like pulling three jackpots in a row at Vegas!"

"What is it?" Jackie asked, seeing the narrow, dark band both Joe and Helen were staring at. Then she whipped around, eyes wide.

"You mean…?"

"Yes." Helen was hardly able to believe it herself. "It looks like our fossil is sitting right smack on the K-T boundary."

"Where the comet-um, sorry." Jackie caught herself before finishing the sentence. She tended to forget that the Alvarez Hypothesis was still a touchy subject for a lot of paleontologists, even if she herself thought it was a darn neat idea.

"Yes, where the comet." Helen said the words with a half-snort, half-chuckle.

Fortunately for Jackie, Helen was less hostile to the Alvarez Hypothesis than most members of her profession. She didn't doubt at all that an impact had happened at the K-T Boundary, which marked the end of the Mesozoic Era. She simply questioned whether it had the worldwide cataclysmic effects that the hypothesis proposed. There were other impact craters about as big as the one in Yucatan, after all. The Manicouagan, to name just one. But they'd had no discernable ecological effects at all; not even regional ones, so far as anyone could determine.

Nor had anyone ever really explained, to Helen's satisfaction, exactly how the impact had killed off so many species. Nor the peculiar mechanism by which it had killed off some, but not others. In what mystifying manner, for instance, had it killed off all ammonites-but spared their close relatives, the squids and the octopi? These were the sort of nitty-gritty questions that paleontologists focused on, and that physicists tended to ignore.

Still, she was willing to entertain it as a valid and testable hypothesis. In truth, she'd privately admit to herself, Helen's residual animosity toward the Alvarez Hypothesis was emotional rather than intellectual. Like most paleontologists, she was often rankled by the overbearing arrogance of many of the physicists who were so charmed by the hypothesis and took it as Revealed Truth. When they pontificated on the subject, physicists tended to dismiss the inconvenient facts paleontologists kept bringing up, much like an exasperated adult brushes aside the foolish questions of little children.

One of those facts, however, was that there was no evidence that any dinosaur had survived till the end of the Cretaceous. But now…

It looked as if they'd found the evidence.

"Yes, where the comet," she repeated.

She dusted her hands off on her jeans, and straightened up. "It's going to be a hike back and it'll be getting dark in a few hours. Even if it weren't, we can't do anything yet. This is on your folks' land, Jackie. We'll have to get their permission to dig here, and I've absolutely got to call the Museum of the Rockies. Probably a few other people."

She took a long, slow breath. "This is going to be a big dig, Jackie. Whatever your funny fossil is, it's led us to the mother lode."

That night, on the telephone from her motel room, she conveyed her excitement to the director of the Museum of the Rockies. It wasn't hard, actually. Ever since the days of Jack Horner, the museum had prided itself on its eminence in the world of paleontology, especially dinosaur paleontology. Director Bonds immediately grasped the significance of finding what appeared to be an articulated velociraptor skeleton on the very edge of the K-T boundary. He promised to give her the full support of the museum.

In fact, he even came out himself, three days later. By then, Helen, Joe, and Jackie had been joined by Carol Danvers and Bill Ishihara, the other members of Helen's team. Three days of careful digging had uncovered the entire lower half of the fossil. And, in the process, they had found the leg bone of another velociraptor underneath it, the body apparently extending off to the side of the first.