Megaloceros giganteus or Irish Elk
Megaloceros giganteus (Megaloceros from Greek meaning Great Horn and giganteus from Latin meaning Giant) or the Irish Elk was one of if not the largest deer to ever exist. Though it is called “Irish Elk,” it is not closely related to the American Elk (Cervus canadensis,) or the Eurasian Elk, known in North America as the Moose (Alces alces,) and as such has been referred to as the Giant Deer in some publications.
We first have evidence of it arising in the mid Pleistocene, ~400,000 years ago, lasting until the early Holocene, about 7,700 years ago (from the latest known specimen.) It ranged from Ireland, where most specimens have been found in peat bogs, all the way across Eurasia to East of Lake Baikal, the world’s oldest lake, which is at least 25 myo. It stood about 2.1 meters high (6.9 feet,) and had magnificent antlers, with the largest known being 3.65 meters in width (12 feet,) it had the largest known antlers of any other cervid (deer.)
This is my picture of the mounted specimen at the Cleveland Museum of Natural History, forgive me for its blurriness, I was using a phone camera, and I do not have the steadiest of outstretched arms.