Irish elk
Large deer with impressive antlers evolved during the early Pleistocene, probably as a result of abundant resources to drive evolution. The early Pleistocene cervid † "Eucladoceros" was comparable in size to the modern elk. † "Megaloceros" (Pliocene–Pleistocene) featured the Irish elk ("M. giganteus"), one of the largest known cervids. The Irish elk reached at the shoulder and had heavy antlers that spanned from tip to tip. These large animals are thought to have faced extinction due to conflict between sexual selection for large antlers and body and natural selection for a smaller form. Meanwhile, the moose and reindeer radiated into North America from Siberia.