First skin-breathing mammal

The first species of mammal shown to breathe through its skin, at least for part of its life, is the Julia Creek dunnart (Sminthopsis douglasi), a tiny species of Australian marsupial mouse. McGill University (Australia) physiologist Dr Jacopo Mortola (Canada) has discovered that although as an adult this shrew-like marsupial breathes through its lungs like other mammals, when first born it is so small – only 4 mm (0.15 in) long – that its muscles are too weak to inflate its lungs. Consequently, it absorbs oxygen directly through its skin, a process continuing until it leaves its mother's pouch, by which time it is large enough to inflate its lungs.