Conversation so far:
what can any mammal in the group theria do that prototherians cannot
All mammals except prototherians give birth to live young.
what is the etymology of the term mammal
The term Mammals comes from the Latin mamma meaning breast.
how many species of mammal are on earth
There are around 5,450 species of mammals.

Question: what is the largest order
Self-contained rewrite: what is the largest order of mammals