The most efficient creature is hands down the Carno. Easy to tame and gives a third of the XP a Wyvern of similar level would give. Just be sure to weaken them beforehand because the night isn't long enough to watch a Troodon eat 3 lvl 200+ Carnos all the way through their 2,4k-4k HP.

Oh and start the tame as soon as the night falls, not sooner, not later.

More Troodon Taming & KO Tips