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Temporal range: Late Paleocene–Late Eocene
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
(unranked): Carnivoraformes
Superfamily: Miacoidea
Family: Miacidae
Genus: Miacis
Cope, 1872
Type species
Miacis parvivorus
Cope, 1872
Miacis fossil sites.PNG
Sites where Miacis fossils have been found.

Miacis is a genus of extinct carnivorous mammals that appeared in the late Paleocene and continued through the Eocene. The genus Miacis is not monophyletic but a diverse collection of species that belong to the stemgroup within the Carnivoramorpha.[2] As such, most Miacis species belong to the group of early carnivores that represent the ancestors of the modern order, the crown-group Carnivora. However, the species Miacis cognitus (now Gustafsonia) is placed not in the stem-group but among the Caniformia,[3] one of the two suborders of the crown-group Carnivora.

Miacis species were five-clawed, about the size of a weasel (~30 cm), and lived on the North American and Eurasian continents. They retained some primitive characteristics such as low skulls, long slender bodies, long tails, and short legs. Miacis retained 44 teeth, although some reductions in this number were apparently in progress and some of the teeth were reduced in size.

The hind limbs were longer than the forelimbs, the pelvis was dog-like in form and structure, and some specialized traits were present in the vertebrae. It had retractable claws, agile joints for climbing, and binocular vision. Miacis and related forms had brains that were relatively larger than those of the creodonts, and the larger brain size as compared with body size probably reflects an increase in intelligence.[citation needed]

Like many other early carnivoramorphans, it was well suited for an arboreal climbing lifestyle with needle sharp claws, and had limbs and joints that resemble those of modern carnivorans. Miacis was probably a very agile forest dweller that preyed upon smaller animals, such as small mammals, reptiles, and birds, and might have also have eaten eggs and fruits.[4]


Since Edward Drinker Cope first described the genus Miacis in 1872, at least twenty other species have been assigned to Miacis. However, these species share few synapomorphies other than plesiomorphic characteristics of Miacids in general. This reflects the fact that Miacis has been treated as a wastebasket taxon and contains a diverse collection of species that belong to the stemgroup within the Carnivoramorpha.[2] Many of the species originally assigned to Miacis have since been assigned to other genera and, apart from the type species, Miacis parvivorus, the remaining species are often referred to with Miacis in quotations (e.g. "Miacis" latidens). The following table lists the Miacis species in chronological order of their original description and notes the reassignments to other genera.

Species Authority Type locality Status and notes
M. parvivorus Cope, 1872[5] Black's Fork of Green River, Bridger Formation (Wyoming, USA) Type species. Alteratively Viverravus parvivorus and Vulpavus parvivorus
M. sylvestris Marsh, 1872[6] Bridger Formation (Wyoming, USA) Harpalodon sylvestris according to J. L. Wortman 1901[7]
M. vulpinus Scott & Osborn, 1887[8] Uinta Basin (Utah, USA) Described as Amphicyon vulpinum; assigned to Miacis by Matthew (1909)[9]
M. uintensis Osborn 1895[10] Uinta Basin (Utah, USA) now assigned to Prodaphaenus uintensis Friscia & Rasmussen 2010[11]
M. hargeri Wortman, 1901[12] Bridger Formation (Wyoming, USA)
M. washakius
M. medius Matthew, 1909[9] Bridger Formation (Wyoming, USA)
M. exiguus Matthew & Granger, 1915[13] Clark's Fork Basin (Wyoming, USA)
M. latidens
M. invictus Matthew & Granger, 1925[14] Irdin Manha Formation (Inner Mongolia, China)
M. hookwayi Stock, 1934[15] Tapo Canyon (California, USA)
M. gracilis Clark, 1939[16] Uinta Basin (Utah, USA) now assigned to Procynodictis vulpiceps
M. latouri Quinet, 1966 Dormaal (Flemish Brabant), Belgium now assigned to Dormaalocyon latouri[17]
M. lushiensis Chow, 1975 Shanghuang Quarry (Jiangsu, China)
M. deutschi Gingerich, 1983[18] Clark's Fork Basin (Wyoming, USA)
M. petilus
M. winkleri Clark's Fork Basin, Wyoming Assigned to new genus as type species Gracilocyon winkleri [19]
M. australis Gustafson, 1986[20] Rifle Range Hollow or Blue Cliff Horizon (Texas, USA) now assigned to Angelarctocyon australis[21]
M. cognitus Reeves Bonebed (Texas, USA) now assigned to Gustafsonia cognita in Caniformia[21]
M. boqinghensis Huang et al., 1986[22] Huoshipo, Guojiazhuang Village, Hedi Formation (China)
M. thailandicus Ducrocq et al 1992[23]
M. rosei Heinrich et al., 2008[1] Recombined as Gracilocyon rosei[19]
M. rundlei Hooker, 2010 Abbey Wood, England now assigned to Gracilocyon rundlei [17]
M. solei Smith & Smith, 2010[19] Dormaal (Flemish Brabant), Belgium Gracilocyon solei[19]


A phylogenetic analysis of "Miacis" species and other carnivoramorphans reveals the paraphyletic nature of the genus Miacis. Some are found in a basal position among the stem carnivoraform groups, others are clustered in the middle near Miacis parvivorous, and one, "M". cognitus, within Caniform family Amphicyonidae. The cladogram is based on a morphological analysis of dental, cranial, and postcranial features.[17][24]




Uintacyon group (includes Zodiocyon and Xinyuictis)

Oodectes group

Gracilocyon winkleri

Gracilocyon rundlei

Gracilocyon solei


Oodectes herpestoides

Oodectes jepseni

"Miacis" petilus

"Miacis" exiguus

Dormaalocyon latouri

"Miacis" deutschi

Vulpavus group


Vulpavus (including Palaearctonyx)

"Miacis" latidens

Miacis parvivorous

Dawsonicyon isami

"Miacis" uintensis

"Miacis" washakius

'"Miacis" medius

PM 3868

"Miacis" sylvestris

Procyonodictis vulpiceps

Tapocyon robustis

Quercygale augustidens









"Miacis" cognitus


  1. ^ a b Heinrich, R.E.; Strait, S.G.; Houde, P. (2008). "Earliest Eocene Miacidae (Mammalia: Carnivora) from northwestern Wyoming". Journal of Paleontology. 82 (1): 154–162. doi:10.1666/05-118.1.
  2. ^ a b Wesley-Hunt, G.D.; Flynn J.J. (2005). Phylogeny of the Carnivora: Basal Relationships Among the Carnivoramorphans, and Assessment of the Position of 'Miacoidea' Relative to Carnivora. Journal of Systematic Palaeontology, 3: 1-28. doi:10.1017/S1477201904001518
  3. ^ Spaulding, M.; Flynn J.J.; Stucky, R.K. (2010) Anew basal Carnivoramorphan (Mammalia) from the ‘Bridger B’ (Black’s Fork Member, Bridger Formation, Bridgerian NALMA, Middel Eocene) of Wyoming, USA. Paleontology 53: 815-832. doi:10.1111/j.1475-4983.2010.00963.x
  4. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 214. ISBN 1-84028-152-9.
  5. ^ E. D. Cope. 1872. Third account of new Vertebrata from the Bridger Eocene of Wyoming Valley. Proceedings of the American Philosophical Society (separate) 1-4 [M. Carrano/M. Carrano]
  6. ^ O. C. Marsh. 1872. Preliminary description of new Tertiary mammals. Part II. American Journal of Science 4(21):202-224
  7. ^ J. L. Wortman. 1901. Studies of Eocene Mammalia in the Marsh Collection, Peabody Museum. The American Journal of Science, series 4 12:193-206 [M. Carrano/M. Carrano]
  8. ^ W. B. Scott and H. F. Osborn. 1887. Preliminary Report on the Vertebrate Fossils of the Uinta Formation, Collected by the Princeton Expedition of 1886. Proceedings of the American Philosophical Society 24(126):255-264 [J. Marcot/J. Marcot]
  9. ^ a b 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
  10. ^ H. F. Osborn. 1895. Fossil mammals of the Uinta Basin. Expedition of 1894. Bulletin of the American Museum of Natural History 7(2):71-105
  11. ^ A. R. Friscia and D. T. Rasmussen. 2010. Middle Eocene Carnivoramorpha of the Uinta Basin, Utah. Annals of Carnegie Museum 79(1):51-63 [J. Alroy/J. Alroy]
  12. ^ J. L. Wortman. 1901-1902. Studies of Eocene Mammalia in the Marsh Collection, Peabody Museum,- Part 1: Carnivora. American Journal of Science
  13. ^ W. D. Matthew and W. Granger. 1915. A revision of the Lower Eocene Wasatch and Wind River faunas. Bulletin of the American Museum of Natural History 34(1):1-103
  14. ^ W. D. Matthew and W. Granger. 1925. New mammals from the Irdin Manha Eocene of Mongolia. American Museum Novitates (198)1-10 [K. Beard/K. Beard]
  15. ^ C. Stock. 1934. Proceedings of the National Academy of Sciences 20(7)
  16. ^ Clark, John. 1939. Miacis gracilis, a new carnivore from the Uinta Eocene. Annals of The Carnegie Museum 27, 349--370
  17. ^ a b c Solé, Floréal; Smith, Richard; Coillot, Tiphaine; de Bast, Eric; Smith, Thierry (2014). "Dental and tarsal anatomy of 'Miacis' latouri and a phylogenetic analysis of the earliest carnivoraforms (Mammalia, Carnivoramorpha)". Journal of Vertebrate Paleontology. 34 (1): 1–21. doi:10.1080/02724634.2013.793195. ISSN 0272-4634.
  18. ^ P. D. Gingerich. 1983. Systematics of Early Eocene Miacidae (Mammalia, Carnivora) in the Clark's Fork Basin, Wyoming. Contributions from the Museum of Paleontology, University of Michigan 26(10):197-225
  19. ^ a b c d Smith, Thierry; Smith, Richard (2010). "A New Genus of "Miacid" Carnivoran from the Earliest Eocene of Europe and North America". Acta Palaeontologica Polonica. 55 (4): 761–764. doi:10.4202/app.2009.0125. ISSN 0567-7920.
  20. ^ E. P. Gustafson. 1986. Carnivorous mammals of the Late Eocene and Early Oligocene of Trans-Pecos Texas. Texas Memorial Museum Bulletin 33:1-66 [J. Alroy/J. Alroy/J. Marcot]
  21. ^ a b Tomiya, Susumu; Tseng, Zhijie Jack (2016). "Whence the beardogs? Reappraisal of the Middle to Late Eocene 'Miacis' from Texas, USA, and the origin of Amphicyonidae (Mammalia, Carnivora)". Royal Society Open Science. 3 (10): 160518. doi:10.1098/rsos.160518. ISSN 2054-5703.
  22. ^ X.-S. Huang, Y.-S. Tong, and J.-W. Wang. 1999. A new Miacis (Mammalia Carnivora, Miacidae) from the Middle Eocene of Yuanqu Basin, Shanxi Province. Vertebrata PalAsiatica 37(4):291-299 [P. Mannion/P. Mannion]
  23. ^ Ducrocq S., Buffetaut E., Buffetaut-Tong H., Helmcke-Ingavat R., Jaeger J.-J., Jongkanchanasoontorn Y., and Suteethorn V. (1992) A lower Tertiary vertebrate fauna from Krabi (South Thailand). N. Jb. Geol. Palaont. Abh., 184,101-122.
  24. ^ Solé, Floréal; Smith, Thierry; De Bast, Eric; Codrea, Vlad; Gheerbrant, Emmanuel (2016). "New carnivoraforms from the latest Paleocene of Europe and their bearing on the origin and radiation of Carnivoraformes (Carnivoramorpha, Mammalia)". Journal of Vertebrate Paleontology. 36 (2): e1082480. doi:10.1080/02724634.2016.1082480. ISSN 0272-4634.

External links[edit]

  • Data related to Miacis at Wikispecies
  • Media related to Miacis at Wikimedia Commons