Until Now
Biology

Multituberculates reach their peak

The longest-lived mammal order of all time has its best moment — just before placentals push it aside.

When
Duration
10 million years
Known to
± 1 million years
Era
Paleocene, Cenozoic

Multituberculates are rodent-like mammals with bladed premolars and multi-cusped molars, and they persist for over 120 million years, longer than any other mammalian order. Their diversity peaks in the Paleocene as they exploit the seeds and fruit of recovering forests. Then it turns down. The standard explanation is competitive exclusion by the rising placental herbivores and early primates, though functional tests of that hypothesis have given mixed results, and their decline may owe as much to changing forests as to competitors.

Just before

Just after