Tylopoda (meaning "calloused foot") is a

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

of terrestrial herbivorous

even-toed ungulate The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...

s belonging to 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 ...

Artiodactyla. They are found in the wild in their native ranges of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

and

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

, while Australian feral camels are introduced. The group has a long fossil history in

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 th ...

and

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...

. Tylopoda appeared during the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

around 50 million years ago. Tylopoda has only one

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, ...

family,

Camelidae 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 ...

, which includes

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. ...

llama The llama (; ) (''Lama glama'') is a domesticated South American camelid, widely used as a meat and pack animal by Andean cultures since the Pre-Columbian era. Llamas are social animals and live with others as a herd. Their wool is soft ...

s, guanacos,

alpaca The alpaca (''Lama pacos'') 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 success ...

s and vicuñas. This group was much more diverse in the past, containing a number of extinct families in addition to the ancestors of living camelids (see below). Tylopods are not

ruminants Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...

Taxonomy and systematics

Tylopoda was named by Illiger (1811) and considered

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

by Matthew (1908). It was treated as an unranked clade by Matthew (1908) and as a suborder by Carroll (1988), Ursing et al. (2000) and Whistler and Webb (2005). It was assigned to

Ruminantia Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...

by Matthew (1908); to Artiodactyla by Flower (1883) and Carroll (1988); to Neoselenodontia by Whistler and Webb (2005); and to

Cetartiodactyla The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poste ...

by Ursing et al. (2000) and by Agnarsson and May-Collado (2008).R. L. Carroll. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698 The main problem with circumscription of Tylopoda is that the extensive fossil record of camel-like mammals has not yet been thoroughly examined from a

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

standpoint. Tylopoda is a highly distinctive lineage among the artiodactyls, but its exact relationships are somewhat elusive because the six living species are all closely related and can be considered "

living fossil A living fossil is an extant taxon that cosmetically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living foss ...

s", the sole surviving lineage of a prehistorically wildly successful

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

. More recent studies suggest that tylopods are not as closely related to ruminants as traditionally believed, expressed in

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

form as:Spaulding, M., O'Leary, M.A. & Gatesy, J. (2009): Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution. '' PLoS ONE'' no 4(9): e7062.
article
/ref>(see e.g. Fig S10) Tylopoda are extremely conservative in their lifestyle and (like ruminants) seem to have occupied the same

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...

since their origin over 40 million years ago. Thus, it seems that the previous assumption of a close relationship between Tylopoda and ruminants is simply because all other close relatives (whales, pigs etc.) are so divergent in their adaptations as to have obscured most indications of relationship, or at least those visible to phenetic analyses. However, the rather basal position that Tylopoda appears to have among the

s and relatives means that the oldest members of this lineage are still morphologically very primitive and hard to distinguish from the ancestors of related lineages. The first major modern and comprehensive analysis of the problem (in 2009) supported this; while some taxa traditionally considered Tylopoda could be confirmed to belong to this suborder (and a few refuted), the delimitation of this group is still very much disputed despite (or because of) an extensive fossil record. Agriochoerus

The taxa currently assigned (with some reliability) to Tylopoda are: Basal and '' incertae sedis'' * Genus †'' Gobiohyus''? * Family † Homacodontidae Superfamily † Anoplotherioidea * Family †

Anoplotheriidae Anoplotheriidae is an extinct family of even-toed ungulates ( order Artiodactyla). They were endemic to Western Europe during the Eocene and Oligocene epochs about 48—23 million years ago (Mya), existing for about 25 million years. They disapp ...

* Family †

Cainotheriidae Cainotheriidae is an extinct family of artiodactyls known from the Late Eocene to Middle Miocene of Europe. They are mostly found preserved in karstic deposits. These animals were small in size, and generally did not exceed in height at the ...

* Family † Dacrytheriidae Superfamily Cameloidea * Family †

Oromerycidae Oromerycidae is a small (both in size and diversity), extinct family of artiodactyls (even-toed hoofed mammals) closely related to living camels, known from the early to late Eocene of western North America. Oromerycids are placed in the artiod ...

* Family

Superfamily †

Merycoidodontoidea Merycoidodontoidea, sometimes called "oreodonts" or "ruminating hogs", is an extinct superfamily of prehistoric cud-chewing artiodactyls with short faces and fang-like canine teeth. As their name implies, some of the better known forms were gene ...

(=Oreodontoidea) * Family †" Agriochoeridae" (

paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

) * Family †

Merycoidodontidae Merycoidodontoidea, sometimes called "oreodonts" or "ruminating hogs", is an extinct superfamily of prehistoric cud-chewing artiodactyls with short faces and fang-like canine teeth. As their name implies, some of the better known forms were gene ...

Superfamily † Xiphodontoidea * Family †

Xiphodontidae Xiphodontidae is an extinct family of even-toed ungulates ( order Artiodactyla), endemic to Europe during the Eocene 40.4—33.9 million years ago, existing for about 7.5 million years. They were, most likely, all terrestrial herbivor ...

Disputed Tylopoda

Several additional prehistoric (cet)artiodactyl taxa are sometimes assigned to the Tylopoda, but other authors consider them ''incertae sedis'' or basal lineages among the (Cet)artiodactyla: * Family † Antiacodontidae * Family †

Choeropotamidae Choeropotamidae, also known as Haplobunodontidae, are a family of extinct mammals, extinct herbivores, belonging to artiodactyls. They lived between the lower/middle Eocene and lower Oligocene (about 48 - 30 million years ago) and their remain ...

(= Haplobunodontidae) * Family †" Diacodexeidae" (

) * Family † Leptochoeridae The Cebochoeridae and Protoceratidae, on the other hand, are prehistoric families that were occasionally placed within Tylopoda in the past, but are now considered more closely related to cetaceans and ruminants respectively than to camels.

References

External links

* * {{Taxonbar, from=Q1077169 Even-toed ungulates Extant Eocene first appearances de:Kamele