Well. If a sauropod was endothermic, it could gather food much more quickly than an ectothermic counterpart could. More important, it would have much more efficient digestion (recall that in general a ten degree difference in temperature doubles the speed of all chemical reactions).
(Though... keep in mind that this is about degrees Celsius.)
The biggest tortoises and lizards (e.g. _Geochelone_ and _Megalania_) may have approached a tonne, but we have no evidence that the significantly exceeded it.
Same for pareiasaurs. (Plus, those may have been amphibious.)
So this thing was averaging a tonne of growth per year, or nearly 3 kg per day.
GAH!