ive always considered optimus primal to be optimus prime and they just changed there names to suit the enviroment, like maximals and predicons.it was one of those things that did bother me in the series when they introduced optimus prime in the ark.so if hes not optimus prime who is he and how do's he come by primes face and name because,same as megatron. i always thought that the time line for beastwars was set somewhere after (about 500 to 1000 years) the original series but set in prehistoric earth.