Well I finally got down to it and have started modeling the the bones in the body. I thought I'd start with the most complex bones to model, and then work my way down from there. Next I'll do the spine and the femur. Also since the back half of the gryphon is a Lion it will work out quite nicely when I start modeling an actual Lion.

I've just about finished the Pelvis, then I'll move on to the other bones in the body.

I got the reference images from http://digital.library.wisc.edu/1711.dl/Science.VetAnatImgs
Some of the best anatomical drawings on the planet for horses, dogs, lions, cows, and more. You have probably seen some of them already in books and online.