One level back to Vertebrates (red blood, new mouths) 2.3.3.3.1.2.3.3. Mammals 2.3.3.3.1.2.3.3.1. [Monotreme] (platypus, echidna) 2.3.3.3.1.2.3.3.2. [Marsupials] [Kangaroo, Koala] 2.3.3.3.1.2.3.3.3. [Umbilicals] (with placenta) One level further to [Monotreme] (platypus, echidna) One level further to [Marsupials] [Kangaroo, Koala] One level further to [Umbilicals] (with placenta)

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Mammals