Simplify the following text for a Grade 4 native English-speaking person.
Original: Prototheria ( , from Greek prÅ tos , first , + thÄ `` r , wild animal ) is a taxonomic group , or taxon , to which the order Monotremata belongs .
Simplified: The Prototheria is a subclass of mammals . The name comes from Greek prÅ tos means ` first ' , and thÄ `` r , ` beast ' .