From Halopedia, the Halo wiki
Brontotheres lived in east Africa as late as 97,445 BCE. They were among the creatures that were preserved as part of the Librarian's Conservation Measure. At one point during the Librarian's last days on Earth before the firing of the Halo Array, a two-meter high brontothere was one of the animals that approached her, nuzzling her hand. She surmised that they no longer had any fear since all the humans had been removed.
Behind the scenes
Outside of the Halo universe, brontotheres are believed to have gone extinct around 33.9 million years ago, as opposed to still existing on Earth just around 100,000 years ago. Brontotheres were modeled for Halo Infinite's announcement trailer at E3 2018. During the trailer's production, they were internally referred to as "space rhinos" by members of 343 Industries.
List of appearances