Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Six species of "camels" exist in the world today: the llama (Lama glama) and alpaca (Lama pacos) were domesticated in South America 4-5 thousand years ago, while the guanaco (Lama guanicoe) and vicuna (Vicugna vicugna) still exist in the wild. The more familiar bactrian camel (Camelus bactrianus) of Asia and the African dromedary camel (Camelus dromediarus) make up the balance of the camelids. The four species of South American camelids are ancestors of "llama-like" creatures that stalked North America in the Pliocene Epoch. As their resources depleted they moved south toward South America while their relatives, the camels, went east to Asia and Africa.
Smith, Timothy M.
"Reproduction in South American Camelids,"
Iowa State University Veterinarian: Vol. 47
, Article 6.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol47/iss2/6