Mammals' best hope for survival through Earth's Pangea Ultima era could look something like the North African gerbil, he said — a small rodent that thrives in the harsh conditions of the Sahara ...

The early mammals in this study — like many during the Mesozoic Era — were small creatures much like rodents, shrews or moles. They also appear to have had similarly gray and brown coats.

Dolphins are the best-studied marine mammals capable of this style of sleeping. Brain scans on captive dolphins show that while one hemisphere is in slow-wave, deep sleep, the other hemisphere is ...

In almost all mammals, male sex-determination occurs via the SRY gene on the male Y chromosome. Monotremes have evolved a totally different sex chromosome system that lacks the SRY gene.