Prehistorik is a platform game developed by Titus Interactive for the Amiga, Atari ST, Amstrad CPC and DOS. Titus Interactive also published it, and released the game in 1991.
The playable character is a neanderthal armed with a club. In a search for food, the neanderthal must hit dinosaurs and other animals that come in his way. Some hostile beings can't be beat, so the player must dodge them. A boss awaits in every even numbered level. There are seven levels.
Prehistorik's vivid colors and large, outrageous bosses were part of the game's appeal. While the movements could have benefitted from smooth sprites, and required the wearing down of a space bar in order to progress in the game, the game was favored by the BBS Scene, accidentally (?) finding its way into shareware uploads on at least one BBS.
Source: Wikipedia, "Prehistorik," available under the CC-BY-SA License.