Did you take into account that earth was heavier millions of years ago? Also, you would have to specify where on earth it weighed that amount.

Anyway, pound is an imperial unit for mass, just like slug. The "pound-force" is not part of the imperial units, jut rather of the "English Engineering Units" that differentiate between pound-mass, pound-force, pound-foot and others.

"Pound" is not a unit of force in ANY system. If you really meant force (I doubt that) you should have used lbf. Anyway, noone cares how many Newtons of force the earth exhibited on that animal, all the metric-using people in this thread are interested in its mass. All scales used to weigh something display kg (or pounds), so units of mass.