Which was the biggest mammal of all?

The first mammal was small and inconspicuous, and they were vulnerable to all the fierce dinosaur predators. Once the dinosaurs died out, the mammals were able to develop and evolve. Eventually the mammals grew into forms that were almost as gigantic as their dinosaur predecessors. Indricotherium, which was a member of the rhinoceros family, developed into something resembling the giant sauropods but with a shorter neck and tail. It grew to a height of 5 meters at the shoulder and weighed 15 tonnes. it probably grazed on trees, like the modern giraffe. Indricotherium had four large teeth, two in the upper and two in the lower jaw. It also had three toes on each foot. In many ways, it resembled a gigantic tapir.