Specifically, the researchers knew that if they found a feature in birds that was also present in monotremes (or marsupials or eutherians), this would mean that the feature was most likely also ...

Monotremes diverged from the therian mammal ... Therian mammals with common characters split into marsupials and eutherians around 148 Myr ago (dark-red text). Geological eras and periods with ...

"Today, Australia is known as a land of marsupials, but discovering these new fossils is the first indication that Australia was previously home to a diversity of monotremes." Only five of these ...