|A Bactrian camel walking in the snow|
|Family:|| Camelidae |
| Camelus |
|Current range of camelids, all species|
Camelids are members of the biological family Camelidae, the only currently living family in the suborder Tylopoda. The seven extant members of this group are: dromedary camels, Bactrian camels, wild Bactrian camels, llamas, alpacas, vicuñas, and guanacos. Camelids are even-toed ungulates classified in the order Cetartiodactyla, along with species including whales, pigs, deer, cattle, and antelopes.
Camelids are large, strictly herbivorous animals with slender necks and long legs. They differ from ruminants in a number of ways.  Their dentition show traces of vestigial central incisors in the incisive bone, and the third incisors have developed into canine-like tusks. Camelids also have true canine teeth and tusk-like premolars, which are separated from the molars by a gap. The musculature of the hind limbs differs from those of other ungulates in that the legs are attached to the body only at the top of the thigh, rather than attached by skin and muscle from the knee upwards. Because of this, camelids have to lie down by resting on their knees with their legs tucked underneath their bodies.  They have three-chambered stomachs, rather than four-chambered ones; their upper lips are split in two, with each part separately mobile; and, uniquely among mammals, their red blood cells are elliptical.  They also have a unique type of antibodies, which lack the light chain, in addition to the normal antibodies found in other mammals. These so-called heavy-chain antibodies are being used to develop single-domain antibodies with potential pharmaceutical applications.
Camelids do not have hooves; rather, they have two-toed feet with toenails and soft foot pads (Tylopoda is Greek for "padded foot"). Most of the weight of the animal rests on these tough, leathery sole pads. The South American camelids have adapted to the steep and rocky terrain by adjusting the pads on their toes to maintain grip.  The surface area of Camels foot pads can increase with increasing velocity in order to reduce pressure on the feet and larger members of the camelid species will usually have larger pad area to help distribute weight across the foot.  Many fossil camelids were unguligrade and probably hooved, in contrast to all living species. 
Camelids are behaviorally similar in many ways, including their walking gait, in which both legs on the same side are moved simultaneously. While running, camelids engage a unique "running pace gait" in which limbs on the same side move in the same pattern they walk, with both left legs moving and then both right, which ensures that the fore and hind limb will not collide while in fast motion. During this motion, all four limbs momentarily are off the ground at the same time.  Consequently, camelids large enough for human beings to ride have a typical swaying motion.
Dromedary camels, bactrian camels, llamas, and alpacas are all induced ovulators. 
The three Afro-Asian camel species have developed extensive adaptations to their lives in harsh, near-waterless environments. Wild populations of the Bactrian camel are even able to drink brackish water, and some herds live in nuclear test areas. 
Comparative table of the seven extant species in the family Camelidae:
| Bactrian camel |
| Central and Inner Asia |
|300 to 1,000 kg (660 to 2,200 lb)|
| Dromedary |
|South Asia and Middle East|
|300 to 600 kg (660 to 1,320 lb)|
| Wild Bactrian camel |
|China and Mongolia||300 to 820 kg (660 to 1,800 lb)|
| Llama |
|(domestic form of guanaco)||130 to 200 kg (290 to 440 lb)|
| Guanaco |
|South America||about 90 to 120 kg (200 to 260 lb)|
| Alpaca |
|(domestic form of vicuña)||48 to 84 kg (106 to 185 lb)|
| Vicuña |
|South American Andes||35 to 65 kg (77 to 143 lb)|
|A family tree indicating different species within the Camelidae family |
Camelids are unusual in that their modern distribution is almost the inverse of their area of origin. Camelids first appeared very early in the evolution of the even-toed ungulates, around 50 to 40 million years ago during the middle Eocene,[ citation needed ] in present-day North America. Among the earliest camelids was the rabbit-sized Protylopus , which still had four toes on each foot. By the late Eocene, around 35 million years ago, camelids such as Poebrotherium had lost the two lateral toes, and were about the size of a modern goat.  
The family diversified and prospered, with the two living tribes, the Camelini and Lamini, diverging in the late early Miocene around 17 million years ago, but remained confined to the North American continent until about seven million years ago, when Paracamelus crossed the Bering land bridge into Eurasia, giving rise to the modern camels, and about three million years ago, when Hemiauchenia emigrated into South America (as part of the Great American Interchange, giving rise to the modern llamas.[ citation needed ] A population of Paracamelus continued living in North America and evolved into the high arctic camel, which survived until the middle Pleistocene.
The original camelids of North America remained common until the quite recent geological past, but then disappeared, possibly as a result of hunting or habitat alterations by the earliest human settlers, and possibly as a result of changing environmental conditions after the last ice age, or a combination of these factors. Three species groups survived - the dromedary of northern Africa and southwest Asia; the Bactrian camel of central Asia; and the South American group, which has now diverged into a range of forms that are closely related, but usually classified as four species - llamas, alpacas, guanacos, and vicuñas. Camelids were domesticated by early Andean peoples,  and remain in use today.
Fossil camelids show a wider variety than their modern counterparts. One North American genus, Titanotylopus , stood 3.5 m at the shoulder, compared with about 2.0 m for the largest modern camelids. Other extinct camelids included small, gazelle-like animals, such as Stenomylus . Finally, a number of very tall, giraffe-like camelids were adapted to feeding on leaves from high trees, including such genera as Aepycamelus and Oxydactylus . 
Whether the wild Bactrian camel (Camelus ferus) is a distinct species or a subspecies (C. bactrianus ferus) is still debated.   The divergence date is 0.7 million years ago, long before the start of domestication. 
|Aepycamelus||Miocene||Tall, s-shaped neck, true padded camel feet|
|Camelops||Pliocene-Pleistocene||Large, with true camel feet, hump status uncertain|
|Eulamaops||Pleistocene||From South America|
|Floridatragulus||Early Miocene||A bizarre species of camel with a long snout|
|Hemiauchenia||Miocene-Pleistocene||A North and South American lamine genus|
|Megacamelus||Miocene-Pleistocene||The largest species of camelid|
|Megatylopus||Miocene-Early Pleistocene||Large camelid from North America|
|Oxydactylus||Early Miocene||The earliest member of the "giraffe camel" family|
|Palaeolama||Pleistocene||A North and South American lamine genus|
|Poebrotherium||Oligocene||This species of camel took the place of deer and antelope in the White River Badlands.|
|Procamelus||Miocene||Ancestor of extinct Titanolypus and modern Camelus|
|Protylopus||Late Eocene||Earliest member of the camelids|
|Stenomylus||Early Miocene||Small, gazelle-like camel that lived in large herds on the Great Plains|
|Titanotylopus||Miocene-Pleistocene||Tall, humped, true camel feet|
A camel is an even-toed ungulate in the genus Camelus that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provide food and textiles. Camels are working animals especially suited to their desert habitat and are a vital means of transport for passengers and cargo. There are three surviving species of camel. The one-humped dromedary makes up 94% of the world's camel population, and the two-humped Bactrian camel makes up 6%. The wild Bactrian camel is a separate species and is now critically endangered.
The llama is a domesticated South American camelid, widely used as a meat and pack animal by Andean cultures since the Pre-Columbian era.
The even-toed ungulates are ungulates—hoofed animals—which bear weight equally on two of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, odd-toed ungulates bear weight on an odd number of the five toes. Another difference between the two is that many other even-toed ungulates digest plant cellulose in one or more stomach chambers rather than in their intestine as the odd-toed ungulates do.
Tylopoda is a suborder of terrestrial herbivorous even-toed ungulates belonging to the order Artiodactyla. They are found in the wild in their native ranges of South America and Asia, while Australian feral camels are introduced. The group has a long fossil history in North America and Eurasia. Tylopoda appeared during the Eocene around 50 million years ago.
The dromedary, also known as the dromedary camel, Arabian camel, or one-humped camel, is a large even-toed ungulate, of the genus Camelus, with one hump on its back.
The Bactrian camel, also known as the Mongolian camel or domestic Bactrian camel, is a large even-toed ungulate native to the steppes of Central Asia. It has two humps on its back, in contrast to the single-humped dromedary. Its population of 2 million exists mainly in the domesticated form. Their name comes from the ancient historical region of Bactria.
The guanaco is a camelid native to South America, closely related to the llama. Guanacos are one of two wild South American camelids, the other being the vicuña, which lives at higher elevations.
Lama is a genus containing four South American camelids, the wild guanaco and vicuña, and the domesticated llama and alpaca. Before the Spanish conquest of the Americas, llamas and alpacas were the only domesticated ungulates of the continent. They were kept not only for their value as beasts of burden, but also for their flesh, hides, and wool.
A cama is a hybrid between a male dromedary camel and a female llama, and has been produced via artificial insemination at the Camel Reproduction Centre in Dubai. The first cama was born on January 14, 1998. The aim was to create an animal capable of higher wool production than the llama, with the size and strength of a camel and a cooperative temperament.
Camelops is an extinct genus of camels that lived in North and Central America, ranging from Alaska to Honduras, from the middle Pliocene to the end of the Pleistocene. It is more closely related to the Old World dromedary and bactrian and wild bactrian camels than to the New World guanaco, vicuña, alpaca and llama; making it a true camel of the Camelini tribe. Its name is derived from the Ancient Greek κάμηλος and ὄψ, i.e. "camel-face".
Titanotylopus is an extinct genus of terrestrial herbivore in the family Camelidae, endemic to North America from the late Hemphillian stage of the Miocene through the Irvingtonian stage of the Pleistocene. It was one of the last surviving North American camels, after its extinction, only Camelops remained. Its closest living relative is the Bactrian camel.
A huarizo is a cross between a male llama and a female alpaca. The most common hybrid between South American camelids, huarizo tend to be much smaller than llamas, with their fibre being longer. Misti, a similar hybrid is a cross between a male alpaca and a female llama. Huarizo are sterile in the wild, but recent genetic research conducted at the University of Minnesota Rochester suggests that it may be possible to preserve fertility with minimal genetic modification. Many owners have reported that their Huarizos and Mistis are fertile. Quite a shock when everyone says they are sterile. Presumably, by "wild", feral is actually intended as both alpacas and llamas are domestic creations.
The alpaca is a species of South American camelid mammal. It is similar to, and often confused with, the llama. However, alpacas are often noticeably smaller than llamas. The two animals are closely related and can successfully crossbreed. Both species are believed to have been domesticated from their wild relatives, the vicuña and guanaco. There are two breeds of alpaca: the Suri alpaca and the Huacaya alpaca.
Hemiauchenia is a genus of laminoid camelids that evolved in North America in the Miocene period about 10 million years ago. This genus diversified and moved to South America in the Late Pliocene approximately 3 to 2 million years ago, as part of the Great American Biotic Interchange, giving rise to modern lamines. The genus became extinct at the end of the Pleistocene.
Palaeolama is an extinct genus of laminoid camelids that existed from the Late Pliocene to the Early Holocene. Their range extended from North America to the intertropical region of South America.
Lamini is a tribe of the subfamily Camelinae. It contains one extant genus with four species, all exclusively from South America: llamas, alpacas, vicuñas, and guanacos. The former two are domesticated species, while the latter two are only found in the wild. None display sexual dimorphism. The four species can interbreed and produce fertile offspring. Additionally, there are two extinct genera known from the fossil record.
A hybrid camel is a hybrid between a Bactrian camel and dromedary.
The wild camel is a critically endangered species of camel living in parts of northwestern China and southwestern Mongolia. It is closely related to the Bactrian camel. Both are large, double-humped even-toed ungulates native to the steppes of central Asia. Until recently, wild camels were thought to have descended from domesticated Bactrian camels that became feral after being released into the wild. However, genetic studies have established it as a separate species which diverged from the Bactrian camel about 1.1 million years ago.