Thanks John!!
To do that animation I used 3ds max biped, then add it to your mesh (the process can be tricky the firsts tries but do notgive up^^) then you can do the animation as if you were moving a puppet you, and when your animation is finished you have to export it to Hyperion(in fact you will export a model for each keyframe you want). The problem with this technic is that your animation will be really ressource consuming : for the predator the animation is made of 134 models and its weight without the texture is around 40 Mo and the real problem is that it takes even much more RAM (for this demo you need at least 2Go RAM !!

) .
However if you reached this stage and you want to export it you should make a maxscript to help exporting each meshes or bother export them manually.
Here is a sample script that you can use as a base for the export:
frame = 0
for i = STARTING_FRAME to ENDING_FRAME by STEPS do
(
path = "F:\\3dsmax7\\meshes\\SiunimTao\\"
extension = ".3ds"
frame_string = frame as string
fullpath = path + frame_string + extension
exportFile fullpath #noPrompt selectedOnly:true
frame += 1
sliderTime += STEPS
)
Where the STEPS is the precision you want for your animation, the greater the STEPS are the less precise your animation will be, but you will save then some ressources when packaging /playing your demos.
Replace
STARTING_FRAME and ENDING_FRAME with the corresponding values, and one more important thing : BE SURE THE FOLDER IN WHICH YOU WANT TO EXPORT YOUR ANIMATION EXISTS OR THAT THE PATH YOU INPUT IS CORRECTLY TYPED!! don't forget the "\\" escape sequence to type a "\".