It sometimes appears that just about every sort of animal was larger in prehistoric times. That this cannot be a universal rule is shown by the fact that the largest animal ever to have lived is the blue whale, which is still around today (albeit as an endangered species). Still, it is true that many prehistoric animals were larger than those alive today, and dinosaur researchers do seem to be engaged in a constant battle to find the "biggest land animal ever" - although this is likely a reflection of what sort of palaeontology stories get into the regular news media.
The largest land animal ever to have lived was surely a dinosaur, most likely a member of the aptly named titanosaur group. But what about the largest land mammal? It's hard to know for sure, partly because "largest" is a vague term that could be interpreted in different ways - do we mean weight or linear dimensions? But it's also just difficult to know when all you have to go on is the skeleton, and that's probably incomplete.
