''Machaeroides'' ("dagger-like") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of sabre-toothed predatory placental mammals from extinct subfamily

Machaeroidinae Machaeroidinae ("dagger-like") is an extinct subfamily of carnivorous saber-toothed placental mammals, from the extinct family Oxyaenidae, that lived from the early to middle Eocene of Asia and North America.Malcolm C. McKenna, Susan K. Bell: ' ...

within extinct family

Oxyaenidae Oxyaenidae ("sharp hyenas") is a family of extinct carnivorous placental mammals. Traditionally classified in order Creodonta, this group is now classified in its own order Oxyaenodonta ("sharp tooth hyenas") within clade Pan-Carnivora in mirord ...

, that lived 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 ...

(

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

) from the early to middle

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 ...

Description

Both species bore a passing or superficial resemblance to a very small, dog-sized

saber-toothed cat Machairodontinae (from Ancient Greek μάχαιρα '' machaira,'' a type of Ancient Greek sword and ὀδόντος ''odontos'' meaning tooth) is an extinct subfamily of carnivoran mammals of the cat family Felidae, representing the earliest ...

. ''Machaeroides'' could be distinguished from actual saber-toothed cats by their more-elongated skulls, and their

plantigrade 151px, Portion of a human skeleton, showing plantigrade habit In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. ...

stance. ''Machaeroides'' species are distinguished from the closely related ''

Apataelurus ''Apataelurus'' ("false cat") is an extinct genus of saber-toothed placental mammals from the extinct family Oxyaenidae, that lived in North America and East Asia from the early to middle Eocene, 48-40 million years ago. This genus was defined b ...

'' by the fact that the former genus had smaller saber-teeth. Despite its small size, the genus ''Machairoides'' was well-equipped to hunt prey larger than itself, such as the small, primitive horses and rhinoceroses present at the time, as it was equipped with saber teeth and powerful forelimbs to subdue prey. ''M. eothen'' weighed an estimated , thus matching in size a small Staffordshire Terrier. ''M. simpsoni'' was probably smaller.

Taxonomic placement

Its position within the mammals has been in dispute. Experts have been equally divided over whether ''Machaeroides'' and its sister-genus, ''

'', belong in

Hyaenodonta Hyaenodonta (" hyena teeth") is an extinct order of hypercarnivorous placental mammals of clade Pan-Carnivora from mirorder Ferae. Hyaenodonts were important mammalian predators that arose during the early Paleocene in Europe and persisted w ...

, though the most recent studies favor the former.

References

Oxyaenidae Eocene mammals of North America Prehistoric placental genera Paleogene geology of Wyoming Eocene genus first appearances Eocene genus extinctions Paleontology in Wyoming {{paleo-mammal-stub