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Mammal size maxed out after dinos’ demise

Opening new ecological niches led to worldwide boom in size

By Susan Milius

- More than 2 years ago

After dinosaurs went extinct 65 million years ago, land mammals tended to supersize and then hit a limit, roughly at the same time worldwide.

BIG Once the dinosaurs disappeared, mammal lineages evolved some whoppers. The now-extinct Indricotherium (biggest below) weighed in at 15,000 kilograms, and Deinotherium (just behind elephant) reached as much as 17,000 kilos.