The Irish Elk (Megaloceros giganteus), was a species of Megaloceros and one of the largest deer that ever lived. Its range extended across Eurasia, from Ireland to east of Lake Baikal, during the Late Pleistocene. The latest known remains of the species have been carbon dated to about 7,700 years ago. Although most skeletons have been found in Irish bogs, the animal was not exclusively Irish and was not closely related to either of the living species currently called elk - Alces alces (the European elk, known in North America as the moose) or Cervus canadensis (the North American elk or wapiti); for this reason, the name “Giant Deer” is used in some publications.
Megaloceros giganteus first appeared about 400,000 years ago. It possibly evolved from M. antecedens. The earlier taxon — sometimes considered a paleosubspeciesM. giganteus antecedens — is similar but had more complex and compact antlers.
The Irish Elk stood about 2.1 metres (6.9 ft) tall at the shoulders, and it had the largest antlers of any known cervid (a maximum of 3.65 m (12.0 ft) from tip to tip and weighing up to 40 kilograms (88 lb)). In body size, the Irish Elk matched the extant moose subspecies of Alaska (Alces alces gigas) as the largest known deer.
Antlers were so large that it required large amounts of calcium and phosphate to form occurring cases of osteoporosis among male Irish elk, so that mortality, already high, increased in bad years.