The Mammals of the Lower Cretaceous

Abstract

The next 40 × 106 years spanning the Lower Cretaceous was a critical period in mammalian evolution, as it was during this time that the primitive mammals known in the Jurassic evolved into marsupials and placentals. In other words it was in the Lower Cretaceous that modern mammals first appeared; unfortunately much less is known about early Cretaceous mammals than about those from the Jurassic.