Chacoan pygmy opossum
The Chacoan pygmy opossum is the smallest known species of opossum. The head-body length is 68 mm, the tail is 55 mm long and the hind foot is 11 mm. It differs from other "marmosine" or mouse opossums in having a long third manual digit, no distinctly tricolored pelage, a long fourth pedal digit, and a tail shorter than head-body. No other marmosine genera have this combination of characters.