prototherian
Concise Oxford English Dictionary © 2008 Oxford University Press:
prototherian /ˌprəʊtə(ʊ)ˈθɪərɪən/ Zoology
▶noun a mammal of the subclass Prototheria, which comprises the monotremes and their extinct relatives. ▶adjective relating to prototherians.
'prototherian' also found in these Oxford entries:

