Machaeroides

Machaeroides ("dagger-like") is an extinct genus of sabre-toothed predatory placental mammals from extinct subfamily Machaeroidinae within extinct family Oxyaenidae, that lived in North America (Wyoming) from the early to middle Eocene.

Not to be confused with Machairodus.

Machaeroides
Temporal range: early to middle Eocene
Machaeroides eothen skull
Machaeroides eothen restoration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Pan-Carnivora
Order: †Oxyaenodonta
Family: †Oxyaenidae
Subfamily: †Machaeroidinae
Genus: †Machaeroides
Matthew, 1909
Type species
†Machaeroides eothen
Matthew, 1909
Species
  • †M. eothen (Matthew, 1909)[1]
  • †M. simpsoni (Dawson, 1986)[2]
A map showing the fossil finds of
Machaeroides as well as other machaeroidinid genera.

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.[3]

M. eothen weighed an estimated 10–14 kg (22–31 lb), thus matching in size a small Staffordshire Terrier. M. simpsoni was probably smaller.[4]

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 Hyaenodonta, though as of 2014 the most recent studies favor the former.[5]

Phylogeny

The phylogenetic relationships of the genus Machaeroides are shown in the following cladogram.[6][7][8][9]

 Pan-Carnivora 
 †Hyaenodonta 

†Altacreodus

†Tinerhodon

 †Altacreodus/Tinerhodon clade
 ? 

†Wyolestidae

 ? 

†Simidectes

†Hyaenodonta (sensu stricto)

 sensu lato 

Carnivoramorpha

 †Oxyaenodonta 
 †Oxyaenidae 

†Tytthaeninae 

†Oxyaeninae

†Palaeonictinae

 †Machaeroidinae 
 †Machaeroides 

†Machaeroides eothen

†Machaeroides simpsoni

 ? 

†Isphanatherium

†Diegoaelurus

†Machaeroidinae sp. (CM 2386)

†Machaeroidinae sp. (FMNH PM 1506)

†Machaeroidinae sp. (USNM 173514)

†Apataelurus

See also

References
  1. W. D. Matthew. (1909.) "The Carnivora and Insectivora of the Bridger Basin, middle Eocene." Memoirs of the American Museum of Natural History 9:289-567
  2. M. R. Dawson, R. K. Stucky, L. Krishtalka and C. C. Black. (1986.) "Machaeroides simpsoni, new species, oldest known sabertooth creodont (Mammalia), of the Lost Cabin Eocene." Contributions to Geology, University of Wyoming, Special Paper 3:177-182
  3. Antón, Mauricio (2013). Sabertooth. Indiana University Press. ISBN 978-0-253-01049-0.
  4. 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.
  5. 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.
  6. Gunnel, Gregg F.; Gingerich, Philip D. (1991). "Systematics and evolution of late Paleocene and early Eocene Oxyaenidae (Mammalia, Creodonta) in the Clarks Fork Basin, Wyoming" (PDF). Contributions from the Museum of Paleontology. The University of Michigan. 28 (7): 141–180.
  7. Solé, Floréal; Ladevèze, Sandrine (2017). "Evolution of the hypercarnivorous dentition in mammals (Metatheria,Eutheria) and its bearing on the development of tribosphenic molars". Evolution & Development. 19 (2): 56–68. doi:10.1111/ede.12219. PMID 28181377. S2CID 46774007.
  8. Prevosti, F. J. & Forasiepi, A. M. (2018.) "Introduction. Evolution of South American Mammalian Predators During the Cenozoic: Paleobiogeographic and Paleoenvironmental Contingencies"
  9. Shawn P. Zack (2019). "A skeleton of a Uintan machaeroidine 'creodont' and the phylogeny of carnivorous eutherian mammals". Journal of Systematic Palaeontology. 17 (8): 653–689. doi:10.1080/14772019.2018.1466374. S2CID 89934728.
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