In which era the first mammals evolved in the earth?

Question

Which of these does not hold true for mammals?
[A] All Have a Backbone
[B] All have hair at some stage
[C] All Females have mammary gland
[D] All females give birth to live young

Answer 1

In Triassic era the first mammals evolved in the earth. The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.