the paper itself
Scepticism is of course warranted. I read the paper. All it claims is given that extraneous body interactions were common in the early solar (Saturnian) system, such a body peturbed Iapetus' primordial closer to Saturn orbit and the ridge feature, quite reasonably it seems to me, was a demonstrable result of a collision with an earlier Saturnian ring. It's an easy read.
-p