JIM ALLEY LAY IN BED, THINKING. Lying around in bed was an unaccustomed luxury for the father of two boys five and eight years old, but Robyn and Bryan were still happily occupied with their Christmas aquisitions.

For a few minutes he savoured his solitude. Then with characteristic efficiency Jim began to wonder how he could best utilize his relaxed mental state. Mild-mannered but highly disciplined - he even sleeps in his gym shorts, as if ready to spring up for calisthenics at the buzz of an alarm - he could not resist the opportunity to find something to do with what otherwise would have been wasted time.

His thoughts wandered to his work. It was not an enormous leap for a toy-company executive on the day after Christmas. While his boys had ripped open their packages the previous morning, Jim had been imagining Christmas scenes all across the country. How many boys were opening Tyco train sets? How many preschoolers were squealing over Tyco's Super Blocks? The figures would not be in for a couple of weeks, so unlike his children, Jim had to remain in a state of suspense even after December 25.

He stopped thinking about sales figures. His boss, Tyco president Dick Grey, had told him to find new products, because the company needed to diversify. As head of marketing he was expected to know what the new trends would be.

Jim shared that expectation. I ought to be able to figure out the next fad, he mused. All the clues are out there floating around. All I have to do is fit them together. He searched for a major theme. Over the last year robots had predominated. Hasbro had Transformers, Tonka had GoBots, and three companies had been tripping over each other bringing out a third line of robots called Voltron. The usual host of imitators had crowded in as well, so it didn't take a genius to figure out that robots were already entering the final stage: death by oversaturation.

Military toys were always popular, but the industry leader, Hasbro, had locked up competition with its G.I. Joe line. Magical characters like wizards with swords had had their day, so Jim, who loved that sort of thing, regretfully eliminated them. Mattel's He-Man and Masters of the Universe line had been copied enough to exhaust the superhero theme.

The only new idea Jim had heard about was a line of space cowboys Mattel was planning. What else was there? Ordinary cowboys and Indians could be due for a revival, but Jim doubted it. Robyn and Bryan had never shown the slightest interest in anything western, although Jim, who was born in 1950, had followed the adventures of Davy Crockett, Wyatt Earp, and Matt Dillon with rapt attention.

Thinking about the generation gap gave him an idea. I should be approaching this from the other direction, he told himself. What are my kids interested in? What do they like hearing about that they aren't getting enough of at school? He immediately thought about dinosaurs. He had been fascinated with them in childhood, and he still enjoyed sharing his boys' interest in the subject. It amused Jim to hear their tiny voices pronounce the long names with such authority, and he had realized long ago that they already knew far more about the various species than he did. They knew which were the biggest (size is very important when you're five or eight), which ones ate meat and which did not. They also knew that there were no cavemen living at the same time as the dinosaurs.

Suddenly Jim wanted to make a line of toy dinosaurs. It was no secret that children loved dinosaurs. Everyone in the toy industry knew it, and the market had been full of dinosaur books and models for years. But Jim believed that he could create a formidible product if only he could find a gimmick, a niche - some concept that would give Tyco a new way of using the creatures.

If he could involve the dinosaurs with people, there would be all kinds of possibilities, but when one specied predeceases the other by 65 million years, the opportunities for interaction are limited. That hiatus, whose length his boys knew as well as their own ages, seemed insurmountable if he wanted to utilize the dinosaurs as real, rather than fantasy, creatures.

But why was he so concerned about realism, Jim asked himself. After all, he was only trying to invent a line of toys. He answered his own question: because the children would care. Notoriously finicky about details, children are very proud of their mastery of dinosaur names and facts, and Jim suspected that they would be scornful of a concept that tried to combine cavemen with dinosaurs. That impossibility was one of the most basic facts they were likely to know.

Suddenly it hit him. The dinosaurs would remain realistic; the fantasy would come from the people. We could bring people in from another place and another time, he thought withe excitement. They could come from outer space and we could use some kind of time travel to get them to earth. Then once they reached earth they could ride the dinosaurs like cowboys and Indians.

By now his mind was racing. Maybe the people could do more than just ride the dinosaurs. Maybe they could make them into vehicles. And there could be bad guys who would do bad things to the dinosaurs.

It sounded great. He was too excited to stay in bed. By the time he was dressed he had thought of a name for the toy line, and he could hardly wait to try some market research. He approached his test population of two sounding much calmer than he felt. "I have an idea for a toy," he told them. When he explained the concept, the boys liked it, so we went all the way and tried out the name of them too. Since the people from space were going to ride dinosaurs he'd call them . . . Dino-Riders!