Horse
The horse adapted to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not. Horses and other equids are odd-toed ungulates of the order Perissodactyla, a group of mammals that was dominant during the Tertiary period. In the past, this order contained 14 families, but only three—Equidae (the horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)—have survived to the present day.
Deer
The subfamily Capreolinae consists of 9 genera and 36 species, while Cervinae comprises 10 genera and 55 species. Hydropotinae consists of a single species, the water deer ("H. inermis"); however, a 1998 study placed it under Capreolinae. The following list is based on molecular and phylogenetic studies by zoologists such as Groves and Grubb.The following is the classification of the extinct cervids with known fossil record:Deer were an important source of food for early hominids. In China, "Homo erectus" fed upon the sika deer, while the red deer was hunted in Germany. In the Upper Palaeolithic, the reindeer was the staple food for Cro-Magnon people, while the cave paintings at Lascaux in southwestern France include some 90 images of stags.