100 ton animals are simply not possible under one G."
Hogwash. Utter ridiculous nonsense, and you people ought to be ashamed of yourselves, if you were even capable of shame, which obviously, you're not.
That makes you lesser forms of human beings, pal.
So don't be putting on "superior" airs...
First of all, as pointed out on this thread numerous times we have fossils of four-legged land-critters which grew over your magical 20,000 lb. limit not only from the age of Dinosaurs (65+ mya) but also the Oligocene (circa 25 mya) and even the current Holocene (10,000 bp).
So even without doing magical calculations, the facts refute your "gravity changes" hypothesis.
Second, all the calculations I've seen here are based on the weight lifting capacity of two-legged human beings, not four-legged slow-moving herbivorous beasts.
So, if you compare bone sizes of today's humans & elephants with those ancient beasts, you instantly see that they are scaled up to allow for their heavier weights.
Bigger beasts require bigger bones -- there's no magic to it, no fantasy "weight limit" and no change in gravity required, just bigger bones & muscles.
Third, real scientists (not phony-baloney nonsense peddlers) have actually studied this question, doing computer models based on sizes & weights estimated, and found them to work just fine, even up to 100 tons.
And, the problem over 100 tons is not bones or muscles, but rather joint strength, a matter about which the fossil record necessarily says very little.
Of course, if you had any interest in real science, you'd know all this already.
But you don't, because your real interest is anti-science, your desperate hope to discredit science enough to allow you to drive your own religious beliefs through whatever "holes" you can convince people exist.
Note to scale: human, Songhua River mammoth, today's African elephant.
Mammoth weight up to 20 tons, circa 10,000 years ago.
No magic calculations, no "gravity changes", just the observed facts: