Mammals of Australia introductions of placental mammals into Australian fauna were about (rats), several thousand years ago (dingo), and 200 years ago (many species); the last two were made by humans. Some claims were made about placental mammal fossils from the Eocene of Australia, called "Tingamarra". These claims are based on only one found tooth having some characteristic features of condylarth, and were discussed widely. But both the age and placental nature of these fossils were challenged by other researchers. Monotremes are mammals with a unique method of reproduction: they lay eggs instead of giving birth to live young. Two of the five
What Love Is Made Of extremely positive about "What Love Is Made Of", describing it as "darker than anything" from "On a Mission", while calling it "slinky". The reviewer went on to commend the "irresistibly pouty" chorus. Pitchfork Media's Katherine St. Asaph commented that, in the song, the singer "sound[ed] completely enthralled, by either her lover or the music" and complimented her voice, noting that it seemed "ten times bigger than before". Jordan Sargent of "Spin" magazine called the track "exuberant" and highlighted Katy's vocal performance, which he deemed "typically fantastic", while the team from pop music website Popjustice gave "What Love Is Made Of"