It’s just like with the original Universal film THE WOLF MAN. The title has with time been altered, by some people, anyway. “Wolf” and “Man” are combined. This makes for the more grammatically correct and aesthetically pleasing THE WOLFMAN. When Universal remade the classic werewolf yarn a few years back they corrected themselves and released the flick as THE WOLFMAN. The same goes for THE TEXAS CHAINSAW MASSACRE. Originally it was THE TEXAS CHAIN SAW MASSACRE, with “chain” and “saw” being two separate words. You’ll still see it spelled that way sometimes, and it’s that way on old posters and such. But “chain saw” is grammatically incorrect. It should be one word. “Chainsaw.” Most times when the movie is referenced today you’ll see this correction applied.
Almost Universally the Lizard Man of Scape Ore Swamp in South Carolina is referred to in that manner, as “Lizard Man”. But it’s incorrect. It should either be hyphenated as “Lizard-Man” (the way Spider-Man’s name is hyphenated, or the X-Men) or the words should be combined (as with Batman) into “Lizardman.” I don’t mind being the first to start this movement. I will henceforth refer to the creature as “Lizardman.” You should as well.