You can download a free plesiosaur-like Loch Ness Monster (shown above) in LightWave .lwo format at [Fantastic Arts](http://www.fantasticarts.com/3dmodels/3dcreature.htm).

A few caveats:

It's a static mesh (not poseable), it has no uv-mapping (it won't accept textures), and it has a few degenerate vertices around the eyesockets and jaw (the black spots).

The latter two problems can be fixed with a freeware utility like LithUnwrap, which can remap the mesh, remove the degenerate vertices, and save the mesh in Poser-friendly .obj format.

As far as posing is concerned, you'd either have to make the mesh into a Poser figure, or treat it as a prop and create new morphs using Poser's magnets or a modeling program.