Diacodexis

Diacodexis Temporal range: Early Eocene (Wasatchian-Bridgerian) ~55.4–46.2  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Jaw fragments of Diacodexis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Family:	† Diacodexeidae
Genus:	† Diacodexis Cope, 1882
Species
†D. antunesi †D. gracilis †D. ilicis †D. kelleyi †D. metsiacus †D. minutus †D. primus †D. secans †D. woltonensis ?†D. absarokae

Diacodexis is an extinct genus of small herbivorous mammals belonging to the family Diacodexeidae ^{[1] [2] [3]} that lived in North America and Europe from 55.4 mya to 46.2 mya, existing for approximately 9.2 million years.

Description

Diacodexis is the oldest known even-toed ungulate. In life, it would have resembled a modern duiker, measuring about 50 centimetres (1.6 ft) in body length, but with a much longer tail. Unlike most later species of artiodactyl, it still had five toes on each foot, although the third and fourth toes were already elongated. It may also have had small hooves on each toe. Its teeth suggest that it was a herbivorous browser. ^[4]

D. ilicis possessed a very simple neocortex, characterised by an almond-shaped gyrus instead of parallel sulci as some earlier authors had believed. ^[5]

As suggested by its long legs, Diacodexis is believed to have been fast-running, capable of leaping relatively far.

Fossil distribution

Diacodexis was widespread, with fossils having been found throughout Europe and North America. However, the genus is currently considered paraphyletic, with the various species likely being a loose conglomerate of basal artiodactyls, rather than a natural grouping. ^[6]

References

1. Orliac, M.J.; Benoit, J.; O'Leary, M.A. (November 2012). "The inner ear of Diacodexis, the oldest artiodactyl mammal". Journal of Anatomy. 21 (5): 417–426. doi:10.1111/j.1469-7580.2012.01562.x. PMC   3482349 . PMID   22938073.
2. Theodor, Jessica M.; Erfurt, Jörg; Grégoire Métais (2007-10-23). "The earliest artiodactyls: Diacodexeidae, Dichobunidae, Homacodontidae, Leptochoeridae and Raoellidae". In Prothero, Donald R.; Foss, Scott E. (eds.). Evolution of Artiodactyls. Johns Hopkins University. pp. 32–58. ISBN   9780801887352.
3. Boivin, M.; Orliac, M.J.; et al. (September 2018). "New material of Diacodexis (Mammalia, Artiodactyla) from the early Eocene of Southern Europe" (PDF). Geobios. 51 (4): 285–306. Bibcode:2018Geobi..51..285B. doi:10.1016/j.geobios.2018.06.003. S2CID   134967454.
4. Palmer 1999 , p. 266
5. Orliac, M. J.; Gilissen, E. (22 September 2012). "Virtual endocranial cast of earliest Eocene Diacodexis (Artiodactyla, Mammalia) and morphological diversity of early artiodactyl brains". Proceedings of the Royal Society B: Biological Sciences . 279 (1743): 3670–3677. doi:10.1098/rspb.2012.1156. ISSN   0962-8452. PMC   3415922 . PMID   22764165.
6. Rautela, A., & Bajpai, S. (2023). Gujaratia indica, the oldest artiodactyl (Mammalia) from South Asia: new dental material and phylogenetic relationships. Journal of Systematic Palaeontology, 21(1). https://doi.org/10.1080/14772019.2023.2267553

Bibliography

• Palmer, D. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. ISBN   1-84028-152-9.