What era did large mammals first appear?

The era during which large mammals first appeared is known as the Cenozoic Era, also commonly referred to as the Age of Mammals. It began approximately 66 million years ago with the extinction of non-avian dinosaurs and continued into the present.

The early Cenozoic Era, including the Paleocene and Eocene epochs, was a critical period in mammalian evolution. It witnessed the rise of various large mammal groups, marking a dramatic diversification in mammalian size and ecological roles. Some of the early large mammals to emerge during this time included:

1. Condylarths: These were herbivorous animals considered ancestral to later diverse ungulate groups such as horses, pigs, and hippos.

2. Uintatheres: Large herbivores known for their distinctive three-horned skulls reminiscent of rhinos.

3. Brontotheres: Enormous herbivores related to horses but more massive in size, recognizable by their large horns on the snout.

4. Andrewsarchus: One of the largest carnivorous mammals recorded in history, comparable in size to a small elephant.

5. Basilosaurus: A whale-like mammal that flourished in ancient oceans, predating the evolution of modern cetaceans like dolphins and whales.

The Cenozoic Era was significant for mammalian evolution with diverse large mammals taking on different ecological niches vacated by the extinction of many dinosaur species at the end of the Cretaceous period.