Acinonyx is very cheetah like. Not only was he a Solitary hunter, which
already decreases his danger to hominids, but moreover the acynonyx species
didn't distribute over the world until 3 (to 1) mln years ago. I think this
rules out that the big cats could have been a serious danger to the survival
as a species of Australopithecus Afarensis, simply because there were no big
cats around at the time in Africa.
by the way there was one big acynonix (called pardinensis), the size of a
lion, but this one too only developed in the pleistocene. When man had
already learned to use his tools!
Look for your aquatic ape theory predator among hyeanids, as other canine
didn't develop until the pleistocene.
J. de Lyser.