I'm very much into studying the Pleistocene age, and I started a personal project about a Megatherium Americanum (one of the largest animals in its habitat, weighing up to 4 t (8,800 lb), with a shoulder height of 2.1 m (6 ft 11 in) and length of 6 m (20 ft) from head to tail. It was one of the largest ground sloths, about as big as modern Asian elephants, cit. Google).
I started creating the whole skeleton and attaching dynamic muscles to it, and produce a work in progress showcase animation to show current stage.
Skeleton it's about done (even if some deformations are broken), while the muscle system it's about 70% complete. As the whole skeleton-muscle system is done, I will model the soft tissues, apply the skin and see how the physics will work: if successful, the muscle deformation will extend to the skin producing a great result. Stay tuned...