Amblypoda was a taxonomic hypothesis uniting a group of extinct, herbivorous

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s. They were considered a suborder of the primitive

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

mammals and have since been shown to represent a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

group.

Characteristics

The Amblypoda take their name from their short and stumpy feet, which were furnished with five toes each and supported massive pillar-like limbs. The brain cavity was extremely small and insignificant in comparison to the bodily mass, which was equal to that of the largest

rhinoceros A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

es. These animals were descendants of the small ancestral ungulates that retained all the primitive characteristics of the latter, accompanied by a huge increase in body size. The Amblypoda were confined to the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

and

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

periods and occurred in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

(especially

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

) and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. The cheek teeth were short-crowned (

brachyodont The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth ...

), with the tubercles more-or-less completely fused into transverse ridges, or cross-crests (

lophodont The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth ...

type), and the total number of teeth was in one case the typical 44, but in another was fewer. The

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

of the neck unite on nearly flat surfaces, the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

had lost the foramen, or perforation, at the lower end, and the third trochanter to the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

may have also been wanting. In the forelimb, the upper and lower series of

carpal The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The terms "carpus" and "carpal" are derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In huma ...

(finger) bones scarcely alternated, but in the hind foot, the astragalus overlapped the cuboid, while the

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

, which was quite distinct from the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

(as was the

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

from the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

in the forelimb), articulated with both astragalus and calcaneum.

Types of amblypods

The most generalized type was ''

Coryphodon ''Coryphodon'' (from Greek , "point", and , "tooth", meaning ''peaked tooth'', referring to "the development of the angles of the ridges into points n the molars") is an extinct genus of pantodonts of the family Coryphodontidae. ''Coryphodo ...

'', representing the family

Coryphodontidae Coryphodontidae is an extinct family of pantodont mammals known from the Late Paleocene to the Middle Eocene of Eurasia and North America. The type genus '' Coryphodon'' is known from around the Paleocene-Eocene transition in Europe, western Uni ...

, from the lower Eocene of Europe and North America, in which there were 44 teeth and no horn-like excrescences on the long skull, while the femur had a third trochanter. The canines were somewhat elongated and were followed by a short gap in each jaw, and the cheek-teeth were adapted for succulent food. The length of the body reached about six feet in some cases. In the middle Eocene formations of North America occurred the more specialized ''

Uintatherium ''Uintatherium'' ("Beast of the Uinta Mountains") is an extinct genus of herbivorous dinoceratan mammal that lived during the Eocene epoch. Two species are currently recognized: ''U. anceps'' from the United States during the Early to Middle Eoc ...

'' (or ''Dinoceras''), typifying the family Uintatheriidae. Uintatheres were huge creatures with long narrow skulls, of which the elongated facial portion carried three pairs of bony horn-cores, probably covered with short horns in life, the hind-pair having been much the largest. The dental formula was i. 0/3, c. 1/1, p. 3/3·4, m. 3/3, the upper canines having been long sabre-like weapons, protected by a descending flange on each side of the lower front jaw. In the basal Eocene of North America, the Amblypoda were represented by extremely primitive, five-toed, small ungulates such as '' Periptychus'' and '' Pantolambda'', each of these typifying a family. The full typical series of 44 teeth was developed in each, but whereas in the

Periptychidae Periptychidae is a family of Cretaceous–Paleocene placental mammals, known definitively only from North America. The family is part of a radiation of early herbivorous and omnivorous mammals formerly classified in the extinct order " Condylart ...

, the upper molars were

bunodont The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone tooth ...

and tritubercular, in the

Pantolambdidae Pantolambdidae is an extinct family of pantodont mammal in the order Pantodonta Pantodonta is an extinct suborder (or, according to some, an Order (biology), order) of eutherian mammals. These herbivorous mammals were one of the first groups ...

, they had assumed a

selenodont Selenodont teeth are the type of molars and premolars commonly found in ruminant herbivores. They are characterized by low crowns, and crescent-shaped cusps when viewed from above (crown view). The term comes from the Ancient Greek roots (, ' ...

structure.

Creodont Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ance ...

characters were displayed in the skeleton.

Current taxonomy of animals once classified in Amblypoda

Few authorities recognize Amblypoda in modern classifications. The following mammals were once considered part of this group: *Order

Pantodonta Pantodonta is an extinct suborder (or, according to some, an Order (biology), order) of eutherian mammals. These herbivorous mammals were one of the first groups of large mammals to evolve (around 66 million years ago) after the K-T boundary, en ...

**Family Wangliidae **Family Harpyodidae **Family

Bemalambdidae Bemalambdidae is an extinct family of pantodont mammals known from Early and Middle Paleocene of China. Description The bemalambdids are, along with '' Harpyodus'' and ''Alcidedorbignya'', the most primitive pantodonts. ''Hypsilolambda'' is k ...

**Family Pastoralodontidae **Family

Titanoideidae ''Titanoides'' is an extinct genus of Pantodonta, pantodont mammal that lived in North Dakota and as far north as central Alberta. They were up to long and up to in weight, being the largest mammals of their habitat, a tropical swampland where ...

**Family

(including '' Pantolambda'') **Family

Barylambdidae Barylambdidae is an extinct family of pantodont mammals from North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Ar ...

**Family Cyriacotheriidae **Family Pantolambdodontidae **Family

(including ''

'') *Order

Dinocerata Dinocerata, from Ancient Greek (), "terrible", and (), "horn", or Uintatheria, is an extinct order of large herbivorous hoofed mammals with horns and protuberant canine teeth, known from the Paleocene and Eocene of Asia and North America. With ...

**Family Uintatheriidae (includes ''

'', ''Eobasileus'', ''Tetheopsis'', etc. '' Gobiatherium'' is sometimes placed in its own family.) *a part of the order Condylarthra, mainly the family

(including '' Periptychus'')

References

{{reflist Obsolete mammal taxa