Ectocion and Elophiodon

Ectocion ralstonensis (Cope 1882 a, e, Granger 1915; Late Paleocene; 11 cm skull length) is generally considered a member of the Phenacodontidae, like Phenacodus, but here nests It nests close to Agriochoerus latifrons, perhaps as a juvenile given its small size, large orbit and short rostrum.

Ectocion cedrus (Cope 1882a, e, Thewissen 1990; UM 86155; Paleocene, 50mya)
This genus is known from a fragmentary skull and several partial skeletons. The dental morphology is lophodont with a narrow rostrum.

Eolophiodon laboriense (Robinet et al. 2015; early Eocene; MHNT.PAL.2010.19.3.1, scale bar = 5cm) is widely considered a smaller relative of Lophiodon and living tapirs with a very narrow skull. Here it nests instead with Ectocion ralstonensis among the hippos. Note the convergence with unrelated Sinonyx.

Cope ED 1882a. Contributions to the history of the Vertebrata of the lower Eocene of Wyoming and New Mexico, made during 1881. Proceedings of the American Philosophical Society: 139-197.

Cope ED 1882e. Note on Eocene Mammalia. American Naturalist 16:522.

Filhol H 1881. Etude sur les mammifères fossiles de Ronzon (Haute-Loire). Bibliothèque Ecole des Hautes Etudes. Section Sciences Naturelles, Masson éd. (Paris), T. 24, art. 4: 1-270, 26 pl.

Finarelli JA 2008. A Total Evidence Phylogeny of the Arctoidea (Carnivora: Mammalia): Relationships Among Basal Taxa. Journal of Mammalian Evolution. 15(4): 231–259.

Granger W 1915. A revision of the lower Wasatch and Wind River faunas, Part III: Order Condylarthra, families Phenacodontidae and Meniscotheriidae. Bulletin of the American Museum of Natural History 34:329-361.

Robinet et al. 2015. A new genus of Lophiodontidae (Perissodactyla, Mammalia) from the early Eocene of La Borie (Southern France) and the origin of the genus Lophiodon Cuvier, 1822. Geobios 48 (2015) 25–38.

Thewissen JGM 1990. Evolution of Paleocene and Eocene phenacodontidae (Mammalia, Condylarthra). University of Michigan Papers on Paleontology 29:1-107.

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Basal Mammalia

Monotremata

Basal Marsupialia

Akynodonta

Orcinus