Machaeroides

Machaeroides; Temporal range: 50.3–46.2 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ early to middle Eocene
	Machaeroides eothen skull
	Machaeroides eothen head restoration
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Oxyaenodonta
Family:	†Oxyaenidae
Subfamily:	†Machaeroidinae
Genus:	†Machaeroides; Matthew, 1909
Type species
	Machaeroides eothen; Matthew, 1909
Species
	†M. eothen (Matthew, 1909); †M. simpsoni (Dawson, 1986);

Machaeroides ("dagger-like") is a genus of sabre-toothed predatory mammal that lived during the Eocene (50.3 to 46.2 mya). Its fossils were found in the U.S. state of Wyoming.

Description

Both species bore a passing or superficial resemblance to a very small, dog-sized saber-toothed cat. Machaeroides could be distinguished from actual saber-toothed cats by their more-elongated skulls, and their plantigrade stance. Machaeroides species are distinguished from the closely related Apataelurus 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.[1]

M. eothen weighed an estimated 10–14 kg (22–31 lb), thus matching in size a small Staffordshire Terrier. M. simpsoni was probably smaller.[2]

Taxonomic placement

Its position within the mammals has been in dispute. Experts have been equally divided over whether Machaeroides and its sister-genus, Apataelurus, belong in Oxyaenidae or Hyaenodontidae, though the most recent studies favor the former.[3]

References

Antón, Mauricio (2013). Sabertooth. Indiana University Press. ISBN 978-0-253-01049-0.
Egi, Naoko1 (2001). "Body Mass Estimates in Extinct Mammals from Limb Bone Dimensions: the Case of North American Hyaenodontids". Palaeontology. 44 (3): 497–528. doi:10.1111/1475-4983.00189.
Zack, S. (2014). "Saber-tooth origins: a new skeletal association and the affinities of Machaeroidinae (Mammalia, Creodonta)". Journal of Vertebrate Paleontology, Program and Abstracts: 259–260.

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[1] Antón, Mauricio (2013). Sabertooth. Indiana University Press. ISBN 978-0-253-01049-0.

[2] Egi, Naoko1 (2001). "Body Mass Estimates in Extinct Mammals from Limb Bone Dimensions: the Case of North American Hyaenodontids". Palaeontology. 44 (3): 497–528. doi:10.1111/1475-4983.00189.

[3] Zack, S. (2014). "Saber-tooth origins: a new skeletal association and the affinities of Machaeroidinae (Mammalia, Creodonta)". Journal of Vertebrate Paleontology, Program and Abstracts: 259–260.