Achaenodon is an extinct artiodactyl mammal, possibly belonging to the family Helohyidae. It lived in the mid-late Eocene (about 43-39 million years ago) and its fossil remains have been found in North America.[1]
| Achaenodon Temporal range: Mid-to-Upper Eocene
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| Reconstruction of the skull of Achaenodon robustus | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | †Helohyidae |
| Genus: | †Achaenodon Cope, 1873 |
| Type species | |
| †Achaenodon insolens Cope, 1873
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| Other species | |
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Description edit
Achaenodon was around the size of a pig[2] or a black bear,[3] with a body mass of around 200–285 kilograms (441–628 lb).[2] The skull had a relatively short muzzle and large sideways (laterally) expanded zygomatic arches, making the skull nearly as wide as it is long. There was a very high sagittal crest, which connected later to an expanded nuchal crest; these two structures, together with the large cheekbone arches, indicate that the musculature of the jaws was extremely powerful. The teeth of Achenodon were bunodont and quite large in size. The dental formula was the primitive (ancestral) condition of artiodactyls with three incisors, a canine, four premolars and three molars; the first lower premolar was present in juveniles but were absent in adults. The upper molars had greatly thickened enamel. The limbs were short, with the forelimbs being slightly shorter than the hindlimbs, with the manus having four digits.[3]
Classification edit
First described in 1873 by Edward Drinker Cope, Achaenodon is best known for fossil remains from the Wyoming Middle Eocene. The type species is Achaenodon insolens. Other species are known, from California,[4] Oregon (A. fremdi[5]), Utah (A. uintense), and Wyoming (A. robustus). Archaenodon has generally either been assigned to the family Helohyidae,[3] or to its own family Achaenodontidae.[5] Some studies have suggested that Achaenodon could be a basal representative of Cetancodontamorpha, and closely related to entelodonts.[6]
References edit
- ^ "Achaenodon (Mammalia, Artiodactyla) from the Eocene Clarno Formation, Oregon, and the age of the Hancock quarry local fauna | Celebrating New Mexico Statehood". nmstatehood.unm.edu.
- ^ a b Burger, B.J.; Jolley, L.A. (2020). "A new large body helohyid (Artiodactyla) from the Bridgerian Middle Eocene Washakie Formation of southern Wyoming". Paludicola. 12 (4): 175–184. Retrieved 2020-06-28 – via ResearchGate.
- ^ a b c Foss, S. E. (2007). Family Helohyidae. In The evolution of artiodactyls (ed. D. R. Prothero and S. E. Foss), pp. 85–88. The Johns Hopkins University Press, Baltimore.
- ^ Atwater, Amy L.; Kirk, E. Christopher (November 2018). "New middle Eocene omomyines (Primates, Haplorhini) from San Diego County, California". Journal of Human Evolution. 124: 7–24. doi:10.1016/j.jhevol.2018.04.010. PMID 30149995.
- ^ a b Lucas, S. G., Foss, S. E. & Mihlbachler, M. C. 2004. Achaenodon (Mammalia, Artiodactyla) from the Eocene Clarno Formation, Oregon, and the age of the Hancock quarry local fauna. New Mexico Museum of Natural History and Science Bulletin, 26, 89–96.
- ^ Yu, Yang; Gao, Hongyan; Li, Qiang; Ni, Xijun (2023-01-01). "A new entelodont (Artiodactyla, Mammalia) from the late Eocene of China and its phylogenetic implications". Journal of Systematic Palaeontology. 21 (1). Bibcode:2023JSPal..2189436Y. doi:10.1080/14772019.2023.2189436. ISSN 1477-2019. S2CID 257895430.