Uncovering the Rapid Growth of Prehistoric Thunder Beasts.

Brontotheres, the rhino-like herbivorous mammals that lived during the Eocene Epoch, evolved from dog-size animals to nearly elephant-sized creatures relatively quickly due to competition and extinction of smaller species. The study suggests that becoming large herbivores benefited brontotheres, and smaller species were more vulnerable to competition and predation. However, the herbivorous titans lost their survival edge when the Eocene’s humid greenhouse conditions started winding down, causing their extinction. The study provides a new perspective on what drives the evolution of body size and proposes a pathway to reach megaherbivory that needs to be tested in other mammalian groups.