Typically I can't find the thread now, but not so long ago somebody was asking which turtles have Shell Shield (without being trained).
Petopia is a little vague as it only states that they can all be trained Shell Shield, and not which have it already.
I can confirm then, that the snapjaws in Hinterlands have it. (L30-32)
I tamed Sherman (my tank ;) ) over the weekend :)
Edited, Feb 11th 2008 8:39am by Reknotz