Back To The Stone Age by Roy Krenkel and Frank Frazetta

Speak'n of stone age, I feel like I've been living under a rock for decades about this image.  Somehow, I've never bothered to look at the credits.  Is this like THE transition art that Roy used to get Fritz a gig at Ace?  Help a down-and-out fan here, folks!  yeah, now I see Krenkel, and over here I see Frazetta, but somehow it was always blocked to me.  I would really love to know if there's more collaborations of these two