A roadside Alligator/Reptile Show is robbed by a guy who may be an escaped felon. The proprietor has a tunnel entrance down some stairs which are behind a jailbar type door. A bipedal monster lurks below. I think the felon sees the bars and assumes there is some sort of great wealth to be obtained. A good looking gal and another man/her boyfriend become part of the story. The robber might shoot the owner and the monster gets the robber. The boyfriend kills the monster... I think. BW and saw it during the 70s on broadcast TV.

Nobody I've ever mentioned it to, can remember such a movie. Any ideas ? Thanks.