Amynodontidae ("defensive tooth") is a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of extinct

perissodactyl Odd-toed ungulates, mammals which constitute the taxonomic order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still using four toes on the front legs) o ...

s related to true

rhinoceroses 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 ...

. They are commonly portrayed as semiaquatic hippo-like rhinos but this description only fits members of the Metamynodontini; other groups of amynodonts like the cadurcodontines had more typical

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, giraffes, cam ...

proportions and convergently evolved a

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 inhabit ...

-like

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

. The Greek name of the family describes their tusks, derived from enlarged canine teeth. Odd-toed ungulates are herbivores, so these tusks would have been used either to deter or defend against predators (as suggested by the name) or perhaps in fights among males.http://www.rhinoresourcecenter.com/pdf_files/141/1415340780.pdf Their fossils have been found 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 the Car ...

, 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 archipelago a ...

ranging in age from the

Middle 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'', "dawn ...

to the

Early Oligocene The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chatti ...

, with a single genus (''Cadurcotherium'') surviving into the

Late Oligocene The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...

in South Asia (Pakistan). The genus ''

Metamynodon ''Metamynodon'' is an extinct genus of Amynodontidae, amynodont Rhinocerotoidea, rhino that lived in North America (White River Fauna) and Asia from the late Eocene until early Oligocene, although the questionable inclusion of ''M. mckinneyi'' co ...

'' may have survived into the early

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Taxonomy

†Amynodontidae *Subfamily Amynodontinae **Tribe Cadurcodontini ***Genus ''

Cadurcodon ''Cadurcodon'' is an extinct genus of amynodont rhino that lived during the Late Eocene to the Oligocene period. Fossils have been found throughout Mongolia and China. It may have sported a tapir-like proboscis A proboscis () is an elongat ...

'' ***Genus '' Lushiamynodon'' ***Genus '' Sharamynodon'' **Tribe Metamynodontini ***Genus '' Gigantamynodon'' ***Genus ''

'' ***Genus '' Paramynodon'' ***Genus '' Zaisanamynodon'' **Tribe ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...

'' ***Genus '' Amynodon'' *Subfamily ''incertae sedis'' **Genus '' Amynodontopsis'' **Genus '' Armania'' **Genus '' Cadurcotherium'' **Genus '' Caenolophus'' **Genus '' Hypsamynodon'' **Genus '' Megalamynodon'' **Genus '' Penetrigonias'' **Genus '' Procadurcodon'' **Genus '' Rostriamynodon'' **Genus '' Teilhardia''

References

Prehistoric odd-toed ungulates Miocene extinctions Eocene first appearances Prehistoric mammal families {{paleo-oddtoedungulate-stub