LOL!
Ed Huble has a gun (maybe more) for those - the .577 Tyrannosaurus is rather weak kneed to some of Ed's Stuff. Think in the 20,000FPE range for the really big ones. Of course, numbers are only numbers and formulae used to expand numbers are for accountants. If you're going to hit something, hit hard with something big. Small bores are, well, small bores.

The 20 bore (.615") was deemed too small for really big animals in India mid 1800's - that is why big bore rifles were developed. They started at 16 bore and leveled at 14 bore as the most popular for 'lighter big game', but would suffice for the big stuff.

For dinos - explosive 'shells' in 8 to 4 gauge might come in handy - thank you Lt. James Forsyth, for your teachings.

PSSST - I personally think this is where Elmer got his early schooling