ANDREWS AIR FORCE BASE, Md. (AP) _ The giant pterodactyl, a flying reptile, died with the dinosaurs 65 million years ago. It didn't fare so well Saturday either, trying to make a comeback in a year of space failures.

A one-of-a-kind, 44-pound, radio controlled, motorized, fur-covered replica with 18-foot-long fierce flapping wings, a heart of nickel cadmium batteries and a pricetag of $700,000 was making its public debut.

It was towed swiftly down a flight line often used by President Reagan, rose dramatically 600 feet into the morning sky and, when left to solo, did a couple of agonized turns and headed straight for the ground. A blue parachute popped out, alas too late.

There was not even an awk.

''Now we know what happened to the dinosaur,'' said an Air Force colonel who didn't stay around long enough for his name to go into books of great quotations.

Like the failures of the space shuttle, and the Titan and Delta rockets earlier in the year, the event took place in front of news cameras. They had been poised to record the modern-day gliding and soaring of quetzalcoatlus northropi, one of a group of flying reptiles termed pterosaurs.

The pterosaurs were distantly related to the dinosaurs and the group to which quetzalcoatlus belonged are known as pterodactyls. The fossilized bones of quetzalcoatlus were found in the Big Bend National Park in west Texas in 1972.

For the first public demonstration, there was a successful dress rehearsal with a dummy pterodactyl earlier Saturday. Then the Air Force decided the 100 or more photographers were too close and moved them back 500 feet. And only then did the reptile begin to move.

Its free flight was to have lasted two or three minutes. It was about that many seconds. From rollout to crash, only 45 seconds expired. A crowd, expected to number up to three quarter of a million later in the day, was at Andrews for an air show to mark Armed Services Day but probably could see little of the dinaflop which was at least a half mile away.

Paul MacCready, who built the ''Gossamer Condor,'' - the first sustained, controlled flight by a heavier-than aircraft powered solely by its pilot's muscles, was commissioned by the Smithsonian Institution to recreate the pterodactyl for a large screen film, ''On the Wing,'' that opens June 20.

It did its thing earlier this year successfully filling MacCready's instructions that the creature fly realistically, propelling itself by wing flapping; that it be fully controllable in normal flying conditions and that it use an electric power system that would allow a few minutes of powered flight.

The reptile, loaded with sensors and 13 ''muscles'' connected to a computer, is ''sophisticated by airplane standards, crude by nature's standards,'' he said before the flight. ''It's a temperamental, overweight adolescent actor, with draggy hair.''

Like the original, the replica has no tail - but to get it into the air, a drop-off rudder had to be affixed. When the rudder and the tow line were let go, the pterodactyl did its swan dive.

''The head, which controls the yaw, seemed to deflect in the right turn so it acted like a speed brake slowing it down,'' said Steve Fitch, technical manager for the Air and Space Museum.

On the ground, the replica looked like a headless turkey. The head was severed from the neck. MacCready and his crew said they could put it together again and the Smithsonian said it would have an honored place in the museum.

It was the 32nd flight for the strange creature, which has three claws on each wing. It had crashed before only to rise again.

Except for embarrassment, no harm was done.

''Our sole focus was to make it suitable for the film,'' said Professor Wann Langston of the University of Texas, who was the project's paleontological adviser.