Maximucinus muirheadae lived from the late Oligocene to middle Miocene and is the largest thylacinid species known to have lived in Australia from the late Oligocene to the middle Miocene. M. muirheadae was a quadrupedal marsupial predator, that in appearance looked similar to a dog with a long snout. Its molar teeth were specialized for carnivory; the cups and crest were reduced or elongated to give the molars a cutting blade. It is estimated to have weighed about 18 kilograms.