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Camelids are members of the biological family Camelidae, the only currently living family in the suborder Tylopoda. The seven
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
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 Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Cetartiodactyla, along with species like whales, pigs, deer, cattle, and
antelope The term antelope is used to refer to many species of even-toed ruminant that are indigenous to various regions in Africa and Eurasia. Antelope comprise a wastebasket taxon defined as any of numerous Old World grazing and browsing hoofed mammals ...
s.


Characteristics

Camelids are large, strictly herbivorous animals with slender necks and long legs. They differ from ruminants in a number of ways.Fowler, M.E. (2010). ''Medicine and Surgery of Camelids'', Ames, Iowa: Wiley-Blackwell. Chapter 1 "General Biology and Evolution" addresses the fact that camelids (including camels and llamas) are not ruminants, pseudo-ruminants, or modified ruminants. 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 An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
, which lack the light chain, in addition to the normal antibodies found in other mammals. These so-called
heavy-chain antibodies A heavy-chain antibody is an antibody which consists only of two heavy chains and lacks the two light chains usually found in antibodies. In common antibodies, the antigen binding region consists of the variable domains of the heavy and light c ...
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, this ensures that the fore and hind limb will not collide while in fast motion. During this motion there is a moment where all four limbs 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:


Evolution

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, in present-day
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
. Among the earliest camelids was the rabbit-sized ''
Protylopus ''Protylopus'' is an extinct genus of camel that lived during middle to late Eocene some 50-40 million years ago in North America. Along with being the oldest camel known, it was also the smallest, reaching a length of , and probably weighing a ...
'', which still had four toes on each foot. By the late Eocene, around 35 million years ago, camelids such as ''
Poebrotherium ''Poebrotherium'' ( ) is an extinct genus of camelid, endemic to North America. They lived from the Eocene to Miocene epochs, 46.3—13.6 mya, existing for approximately . Discovery and history ''Poebrotherium'' was first named by scientist J ...
'' had lost the two lateral toes, and were about the size of a modern goat. The family diversified and prospered, but remained confined to the North American continent until only about two to three million years ago, when representatives arrived in Asia, and (as part of the
Great American Interchange The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which lan ...
that followed the formation of the
Isthmus of Panama The Isthmus of Panama ( es, Istmo de Panamá), also historically known as the Isthmus of Darien (), is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country ...
) South America. A
high arctic camel The High Arctic camel, from the mid-Pliocene epoch, is a fossil camel related to the fossil genus ''Paracamelus'' from which modern camels arose. It is also related to the extinct Ice Age Yukon giant camel. Collagen-containing fossils were found i ...
from this time period has been documented in the far northern reaches of Canada. 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 m for the largest modern camelids. Other extinct camelids included small, gazelle-like animals, such as ''
Stenomylus ''Stenomylus'' is an extinct genus of miniature camelid native to North America that died out around 30 million years ago. Its name is derived from the Greek (, "narrow") and (, "molar"). ''Stenomylus'' was extremely diminutive compared to ...
''. 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 in fact a distinct species or a subspecies (''Camelus bactrianus ferus'') is still debated. The divergence date is 0.7 million years ago, long before the start of domestication.


Scientific classification

Family Camelidae * †Subfamily Poebrotheriinae * †Subfamily Miolabinae * †Subfamily
Stenomylinae 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, ...
* †Subfamily Floridatragulinae * Subfamily
Camelinae Camelinae is a subfamily of artiodactyls of the family Camelidae, known from Asia, Eurasia, South America, North America, and Africa appearing during the Eocene 38 mya, existing for approximately . Camelinae include the tribes Camelini and Lami ...
** Tribe
Lamini Lamini (members are called ''laminoids'') 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 specie ...
*** Genus: ''
Lama Lama (; "chief") is a title for a teacher of the Dharma in Tibetan Buddhism. The name is similar to the Sanskrit term ''guru'', meaning "heavy one", endowed with qualities the student will eventually embody. The Tibetan word "lama" means "hi ...
'' **** Llama, ''Lama glama'' **** Guanaco, ''Lama guanicoe'' **** Alpaca, ''Lama pacos'' **** Vicuña, ''Lama vicugna'' *** Genus: '' Hemiauchenia'' **** †''
Hemiauchenia macrocephala ''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 Early Pleistocene, as part of the Great American Biotic I ...
'' **** †'' Hemiauchenia minima'' **** †'' Hemiauchenia blancoensis'' **** †'' Hemiauchenia vera'' **** †'' Hemiauchenia paradoxa'' *** Genus '' Palaeolama'' **** †''
Palaeolama mirifica ''Palaeolama'' () is an extinct genus of laminoid camelid that existed from the Late Pliocene to the Early Holocene (). Their range extended from North America to the intertropical region of South America. Description ''Palaeolama'' were relat ...
'' ** Tribe Camelini *** Genus: ''
Camel A camel (from: la, camelus and grc-gre, κάμηλος (''kamēlos'') from Hebrew or Phoenician: גָמָל ''gāmāl''.) is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. C ...
us'' **** Bactrian camel, ''Camelus bactrianus'' **** Dromedary, ''Camelus dromedarius'' **** Wild Bactrian camel, ''Camelus ferus'' **** † Syrian camel, '' Camelus moreli'' **** †'' Camelus sivalensis'' ***Genus: '' Camelops'' **** †''
Camelops hesternus ''Camelops''Being occasionally called ''Western Camel'' or ''Yesterday's Camel''. is an extinct genus of camels that lived in North and Central America, ranging from Alaska to Guatemala, from the middle Pliocene to the end of the Pleistocene. It ...
'' ***Genus: '' Paracamelus'' **** †''
Paracamelus gigas ''Paracamelus'' is an extinct genus of camel in the family Camelidae. It originated in North America during the Middle Miocene but crossed the Beringian land bridge into Eurasia during the Late Miocene, approximately 7.5–6.5  million y ...
''


Phylogeny


Extinct genera


References


External links


Pictures of camelid species
{{Authority control Extant Lutetian first appearances Mammal families Taxa named by John Edward Gray Tylopoda