It may look mouse-like but it's actually a marsupial of the dasyurid family - the family that includes quolls, Tasmanian devils and the Thylacine. All dasyurids are carnivores and most are tiny and feed mainly on insects, but won't reject a small lizard or anything else they may find that's meaty.
Head-body length is usually 55-65mm and they barely weigh over 4 grams. The head is unusually flattened (3-4mm top to bottom) so it can easily dash through the cracks formed in the mud in the arid areas of Northern Australia.
Long-tailed Planigale at Wikipedia.