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Condylarthra is an informal group – previously considered an order – of extinct
placental mammal Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguish ...
s, known primarily from the
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''palai ...
and
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'', "da ...
epochs. They are considered early, primitive
ungulates Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...
. It is now largely considered to be a
wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically define ...
, having served as a dumping ground for classifying ungulates which had not been clearly established as part of either Perissodactyla or Cetartiodactyla, being composed thus of several unrelated lineages.


Taxonomic history

Condylarthra always was a problematic group. When Condylarthra was first described by , Phenacodontidae was the type and only family therein. , however, raised Condylarthra to an order and included a wide range of diverse placentals with generalized
dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolog ...
s and postcranial skeletons. More recent researchers (i.e. post-WW2) have been more restrictive; either including only a limited number of taxa, or proposing that the term should be abandoned altogether. Due to their primitive characteristics condylarths have been considered ancestral to several ungulate orders, including the living
Artiodactyla 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 ...
,
Cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel the ...
, Perissodactyla,
Hyracoidea Hyraxes (), also called dassies, are small, thickset, herbivorous mammals in the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Typically, they measure between long and weigh between . They are superficially simil ...
,
Sirenia The Sirenia (), commonly referred to as sea-cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The Sirenia currently comprise two distinct ...
, and
Proboscidea The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Fro ...
, as well as the extinct
Desmostylia The Desmostylia (from Greek δεσμά ''desma'', "bundle", and στῦλος ''stylos'', "pillar") are an extinct order of aquatic mammals that existed from the early Oligocene ( Rupelian) to the late Miocene (Tortonian) (). Desmostylians a ...
, Embrithopoda, Litopterna,
Notoungulata Notoungulata is an extinct order of mammalian ungulates that inhabited South America from the early Paleocene to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resem ...
, and Astrapotheria. delimited condylarths as those having the following characters, but lacking the specializations present in more derived orders: * superior ramus of
stapedial artery In human anatomy, the stapedial branch of posterior auricular artery, or stapedial artery for short, is a small artery supplying the stapedius muscle in the inner ear. Structure In humans In humans, the stapedial artery is normally present in th ...
shifted to petrosal or lost * mastoid foramen lost * bulla if present composed of
ectotympanic The ectotympanic, or tympanicum, is a bony structure found in all mammals, located on the tympanic part of the temporal bone, which holds the tympanic membrane (eardrum) in place. In catarrhine primates (including humans), it takes a tube-shape. I ...
* relatively bunodont teeth with low cusp relief * trigonids of lower molars shortened anteroposteriorly * large, posteriorly projecting hypoconulid on M3 (lower third molar) * head of
astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...
is short and robust


Evolutionary history

The disappearance of the dinosaurs opened up an
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 ...
for large mammalian
herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...
s. Some condylarths evolved to fill the niche, while others remained insectivorous. This may explain, in part, the tremendous
evolutionary radiation An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. Radiations may affect one clade or many, and be rapid ...
of the condylarths that we can observe throughout the Paleocene, resulting in the different groups of
ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraff ...
s (or "
hoof The hoof (plural: hooves) is the tip of a toe of an ungulate mammal, which is covered and strengthened with a thick and horny keratin covering. Artiodactyls are even-toed ungulates, species whose feet have an even number of digits, yet the r ...
ed mammals") that form the dominant herbivores in most
Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...
animal communities on land, except on the
island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island ...
continent of
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country b ...
. Among recent mammals,
Paenungulata Paenungulata (from Latin ''paene'' "almost" + ''ungulātus'' "having hoofs") is a clade of "sub-ungulates", which groups three extant mammal orders: Proboscidea (including elephants), Sirenia ( sea cows, including dugongs and manatees), and Hyr ...
(
hyrax Hyraxes (), also called dassies, are small, thickset, herbivorous mammals in the order Hyracoidea. Hyraxes are well-furred, rotund animals with short tails. Typically, they measure between long and weigh between . They are superficially simi ...
es,
elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae ...
s, and sea cows), Perissodactyla (
horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million ...
s,
rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species ...
es, and
tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inhabi ...
s),
Artiodactyla 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 ...
(
pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus ...
s,
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the rei ...
,
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 mamm ...
, cows,
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 ...
s, hippos, and their relatives),
Cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel the ...
(
whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s), and
Tubulidentata Orycteropodidae is a family of afrotherian mammals. Although there are many fossil species, the only species surviving today is the aardvark, ''Orycteropus afer''. Orycteropodidae is recognized as the only family within the order Tubulidentata ...
(
aardvark The aardvark ( ; ''Orycteropus afer'') is a medium-sized, burrowing, nocturnal mammal native to Africa. It is the only living species of the order Tubulidentata, although other prehistoric species and genera of Tubulidentata are known. Unlik ...
s) are traditionally regarded as members of the Ungulata. Besides these, several extinct animals also belong to this group, especially the
endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
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 sout ...
n orders of ungulates, ( Meridiungulata). Although many ungulates have hooves, this feature does not define the Ungulata. Indeed, some condylarths had small hooves on their feet, but the most primitive forms are
claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes ( mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or t ...
ed. Recent molecular and DNA research has reorganised the picture of mammalian evolution. Paenungulates and tubulidentates are seen as
afrotheria Afrotheria ( from Latin ''Afro-'' "of Africa" + ''theria'' "wild beast") is a clade of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews (also ...
ns, and no longer seen as closely related to the
laurasiatheria Laurasiatheria ("laurasian beasts") is a superorder of placental mammals that groups together true insectivores ( eulipotyphlans), bats ( chiropterans), carnivorans, pangolins ( pholidotes), even-toed ungulates ( artiodactyls), odd-toed ungula ...
n perissodactyls, artiodactyls, and cetaceans, implying that hooves were acquired independently (i.e. were analogous) by at least two different mammalian lineages, once in the Afrotheria and once in the Laurasiatheria. Condylarthra itself, therefore, is
polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
: the several condylarth groups are not closely related to each other at all. Indeed, Condylarthra is sometimes regarded as a 'wastebasket' taxon. True relationships remain in many cases unresolved. In addition to meridiungulates and living ungulates, a condylarthran ancestry has been proposed for several other extinct groups of mammals, including
Mesonychia Mesonychia ("middle claws") is an extinct taxon of small- to large-sized carnivorous ungulates related to artiodactyls. Mesonychids first appeared in the early Paleocene, went into a sharp decline at the end of the Eocene, and died out entirely ...
and
Dinocerata Dinocerata (from the Greek (), "terrible", and (), "horn") is an extinct order of plant-eating hoofed mammals with horns and protuberant canine teeth. Classification A 2015 phylogenetic study recovered Dinocerata as closely related to '' ...
.


Taxonomy

*Family Arctocyonidae (possibly
polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
assemblage) **Genus '' Arctocyon'' **Genus '' Chriacus'' *Family Periptychidae **Genus '' Ectoconus'' **Genus '' Oxyacodon'' *Family Hyopsodontidae (now established as within Perissodactyla) **Subfamily '' Tricuspiodontinae'' ***Genus '' Litomylus'' ***Genus '' Paratricuspiodon'' ***Genus '' Tricuspiodon'' **Genus ''
Aletodon ''Aletodon'' is a genus of ground dwelling insectivores, now extinct. The genus flourished from around 58.7 to 55.8 Ma. It was native to Colorado, Wyoming Wyoming () is a state in the Mountain West subregion of the Western United St ...
'' **Genus '' Decoredon'' **Genus '' Dipavali'' **Genus '' Dorraletes'' **Genus '' Haplaletes'' **Genus '' Haplomylus'' **Genus '' Hyopsodus'' **Genus '' Louisina'' **Genus '' Microhyus'' **Genus '' Midiagnus'' **Genus '' Oxyprimus'' **Genus '' Palasiodon'' **Genus ''
Paschatherium ''Paschatherium'' is a small extinct mammal of the Perissodactyla order, with an insectivore-like dentition. Its morphology indicates an arboreal form, adapted climbing and running on trees. ''Paschatherium'' must have been extremely numerous in ...
'' **Genus '' Utemylus'' **Genus '' Yuodon'' *Family Mioclaenidae *Family Phenacodontidae (established as stem- Perissodactyla) **Subfamily Meniscotheriinae ***Genus '' Ectocion'' ***Genus '' Meniscotherium'' **Genus '' Almogaver'' **Genus '' Copecion'' **Genus '' Eodesmatodon'' **Genus ''
Phenacodus ''Phenacodus'' (Greek: "deception" (phenax), "tooth' (odus)) is an extinct genus of mammals from the late Paleocene through middle Eocene, about 55 million years ago. It is one of the earliest and most primitive of the ungulates, typifying the ...
'' *Family Pleuraspidotheriidae **Genus '' Hilalia'' **Genus '' Orthaspidotherium'' **Genus '' Parabunodon'' **Genus '' Pleuraspidotherium'' *Family Didolodontidae (stem- Meridiungulata) *Family Sparnotheriodontidae? ( Litopterna) *Genus '' Tingamarra''? (non-descript therian mammal) *Genus '' Protungulatum'' (either non-placental eutherian or basal artiodactyl). *Genus '' Kharmerungulatum'' (a zhelestidJames David Archibald · Alexander Olegovich Averianov
Phylogenetic analysis, taxonomic revision, and dental ontogeny of the Cretaceous Zhelestidae (Mammalia: Eutheria)
Article · Feb 2012 · Zoological Journal of the Linnean Society
)


See also

*
Evolution of mammals The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synapsid species that looked l ...
*
List of prehistoric mammals This is an incomplete list of prehistoric mammals. It does not include extant mammals or recently extinct mammals. For extinct primate species, see: list of fossil primates.Mikko's Phylogeny Archiv Mammaliaformes ' *Genus †'' Adelobasileu ...


Notes


References

* * * * * * * * * * *


External links

{{Authority control Obsolete mammal taxa