Sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest herbivores ever to have evolved, commonly exceeding body masses of 30 tons or more .

In many forms, the small head and weak dentition appear ill suited for oral processing of the enormous quantity of plant matter required to support their high growth rates , if not endothermic metabolism 

Polished pebbles occasionally found with sauropod skeletons are generally interpreted as gastroliths or stomach stones, i.e. stones ingested voluntarily by the animal and retained in its digestive tract

This gastrolith is from the Jursasic age fromt utah usa

size  27 x 25 x 7 MM