Dino Boy in the Lost Valley was the backup feature on Space Ghost during the series' original run on CBS. However, when Space Ghost moved to NBC 10 years later as a mid-season replacement, Hanna-Barbera repackaged him with Frankenstein, Jr., leaving Dino Boy in the vaults. Hewey1972 uploaded this intro clip, narrated by the voice of Space Ghost himself, Gary Owens.
After The Flintstones had ended its prime-time run after 6 years, Hanna-Barbera wanted to take a more serious approach to the Stone Age, and Dino Boy was the first step in that direction. The next year brought Mightor, who fared about as well as Dino Boy did overall. Making such a sudden U-turn in that regard might actually have doomed Dino Boy in retrospect. Sadly, the studio's last two efforts, 1974's Valley of the Dinosaurs & Korg: 70,000 B. C., fared no better, either. Viewers simply preferred the humorous antics of The Flintstones over the concept of prehistoric heroes, and not even sending Captain Caveman back to his own time in the 80's could change that perception.
Not long ago, on a message board I frequent, I postulated an idea for a revival that would entail not only Dino Boy, but also Mightor & Valley of the Dinosaurs, with the idea that these three series could actually, if done right, have been linked together at some point, provided of course the creative personnel at Hanna-Barbera gave it serious consideration. Warner Bros. certainly is not in any hurry to try it, though, given Hollywood's general creative bankruptcy, they should.