Irish elk

The Irish elk (Megaloceros giganteus)[1][2] was a species of Megaloceros and one of the largest deer that ever lived. Its range extended across Eurasia, from Ireland to northern Asia and Africa, but a related form is recorded from China during the Late Pleistocene.[3] The most recent remains of the species have been carbon dated to about 7,700 years ago in Siberia.[4] 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). Recent phylogenetic analyses support the idea of a sister-group relationship between fallow deer (Dama dama) and the Irish Elk.[5][6] For this reason, the name "Giant Deer" is used in some publications.

Description
The Irish Elk stood about 2.1 metres (6.9 ft) tall at the shoulders carrying 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 kg (88 lb)). In body size, the Irish Elk matched the extant moose subspecies of Alaska (Alces alces gigas) as the largest known deer. The Irish Elk is estimated to have attained a total mass of 540–600 kg (1,190–1,320 lb), with large specimens having weighed 700 kg (1,500 lb) or more, roughly similar to the Alaskan Moose.[7][8][9] A significant collection of M. giganteus skeletons can be found at the Natural History Museum in Dublin.

Evolution
Physically, the Irish Elk is the heaviest known member of the “Old World deer”,[5] a division of the subfamily Cervinae whose groups the ”Old World deer” and “New World deer” are distinguished by foot structure rather than geographical origin.[10][citation needed][verification needed] Most remains of Irish Elk date from between 11,750 BP (Before Present)-with the first Megaloceros giganteus appearing about 400,000 years ago-and 10,950 BP.[11] Studies have shown they possibly evolved from M. antecedens. The earlier taxon — sometimes considered a paleosubspecies M. giganteus antecedens — is similar but had more complex and compact antlers.

The size of Irish Elk antlers are distinctive, and several theories have arisen as to their evolution. One theory was that their antlers, under constant and strong sexual selection, increased in size because males were using them in combat for access to females. It has also been suggested that they eventually became so unwieldy that the Irish Elk could not carry on the normal business of life and so became extinct. It was not until Stephen Jay Gould's important 1974 essay on Megaloceros that this theory was tested rigorously.

Gould demonstrated that for deer in general, species with a larger body size have antlers that are more than proportionately larger, a consequence of allometry, or differential growth rate of body size and antler size during development. Irish Elk had antlers of the appropriate size in correlation to their massive bodies. This does not mean that sexual selection played no part in maintaining large antler size, only that the antlers of the species' ancestors were already large to begin with. Indeed, Gould concluded that the large antler size and their position on the skull was very much maintained by sexual selection: they were morphologically ill-suited for combat between males, but their position was ideal to present them to intimidate rivals or impress females. Unlike other deer, M. giganteus did not even have to turn its head to present the antlers to best effect, but could accomplish this by simply looking straight ahead.[12] In 1987, Kitchener presented evidence that Irish Elk antlers were in fact used for fighting.[13] In addition, the Irish elk's antlers had several functions such as being a display for attraction of females and dominance of rival males.[14] The elks shed their antlers and re-grew a new pair during mating season.[15] Not much is known about the Irish elk's mating system, but according to Cedric O'Driscall Worman, often the norm was low male/female ratio and of these males, few bred successfully. The number of offspring produced by a female Irish elk was only 1 per mating season. Ultimately, the decrease in energy intake by the Late Pleistocene, influenced the ability to produce for Irish elk females.