Actually, the crappy '90s version, Porta.

This movie seems suspiciously similar to "By the Waters of Babylon," a novella by Stephen Vincent Benet. I'm not, however, insisting that Corman ripped it off.

There were prints out there with the PREHISTORIC WORLD title; in at least one interview, Corman was surprised to learn, many years later, that that WASN'T the standard title.