Front View of Muntjac Skull
The muntjac is native to South Asia, but has been introduced to some parts of England, and is considered an invasive species there. The general build of this small deer is similar throughout the genus, with a short stature, short and single-pointed antlers, and tusks.
Muntjacs are also considered the oldest genus of deer extant, having originated at least 30 million years ago (as compared to white-tailed and mule deer, whose direct ancestor evolved less than 5 million years ago). Despite this, and their genetic similarities on an mtDNA level, the various species of the genus are very interesting to geneticists on account of their chromosomal differences. The Indian Muntjac has a diploid number of only 7 in the males, and 6 in the females, while the Reeve's Muntjac has a diploid number of 46. That's a huge difference in one genus, and we're still trying to make sense of how the species can be so similar, yet so incredibly different!
The Naturalist's Library: Vol XXI - Mammalia: Deer, Antelopes and Camels. Sir William Jardine, 1878.