Ocepeia, Thomashuxleya, Periphragnis and Meniscotherium

Meniscotherium tapiacitum (Cope 1874; Williamson and Lucas 1992; Middle Eocene 54-38 mya; 25-50 cm long) nests in a marsupial clade near Monodelphis domestica.

Ocepeia daouiensis (Gheerbrant et al 2001, 2014; Paleocene, 60 mya; 9 cm skull length) is from Morocco. Here it nests with Coryphodon. The pneumatized skull contains many air spaces. Slightly larger skulls have larger canines and so are considered male, but may just be older. This specimen has only a tiny canine on a broken maxilla. The molar teeth are relatively large and the jugal deepens below the orbit, hiding the posterior molars in lateral view. Note the dorsal eyes, as in hippos. Ocepeia was found with aquatic taxa and was probably amphibious. The name Ocepeia derives from the initials of Office Chérifien des Phosphates (O.C.P.), the national Moroccan phosphate mining company.

Orthaspidotherium edwardsi (Ladeveze et al. 2010; Late Paleocene, 58 mya, 7.5cm skull length) nests with Meniscotherium. The skull is twice as wide as tall on this weasel-like terrestrial mammal. The jawline is convex at the canine and beneath the orbit. The lacrimal/jugal/zygomatic arch is quite robust.

Thomashuxleya externa (Ameghino 1901; Carrillo and Asher 2017; Eocene, 48-40 mya; 0.33m skull length, 1.3 m overall length, Middle Eocene) was named for the famous 19th century paleontologist. Thomashuxleya had four fingers and four toes. Considered a notoungulate, this taxon now nests basal to oreodonts and hippos. The large premaxillary fangs and flat teeth indicate this was a large herbivore was similar to hippos.

Periphragnis exauctus (Roth 1899 (genus), Ameghino 1902 (species), Middle Eocene to Early Oligocene; 1.5m long, skull length 10cm), is traditionally considered very close to Thomashuxleya. It has five hoof-like unguals on all four extremities, distinct from similar marsupials with four digits.

Ameghino F 1901. Notices préliminaires sur des ongulés nouveaux des terrains crétacés de Patagonie [Preliminary notes on new ungulates from the Cretaceous terrains of Patagonia]. Boletin de la Academia Nacional de Ciencias de Córdoba 16:349-429.

Ameghino F 1902. Cuadro sinoptico de las formaciones sedimentarias terciarias y cretacicas de la Argentina, en relacion con el desarrollo y descendencia de los mamiferos. An. Mus. Nac. Hist. Nat., vol. 8, pp. 1-12.

Argot C 2010. Morphofunctional analysis of the postcranium of Amphicyon major (Mammalia, Carnivora, Amphicyonidae) from the Miocene of Sansan (Gers, France) compared to three extant carnivores: Ursus arctos, Panthera leo, and Canis lupus. Geodiversitas 32 (1): 65-106.

Bergounious FM and Crouzel FC 1973. Amphicyon major Blainville du Miocene moyen de Sansan (Gers). Ann. Paleont., t. 59, fas. 1, pp. 3-76,47 fig. Paris.

Carrillo JD and Asher RJ 2017. An exceptionally well-preserved skeleton of Thomashuxleya externa (Mammalia, Notoungulata) from the Eocene of Patagonia, Argentina. Palaentologia Electronica 20.2.34A online PDF

Cope ED 1872. Descriptions of some new Vertebrata from the Bridger Group of the Eocene. Proceedings of the American Philosophical Society 12:460-465.

Cope ED 1874. Report of the Chief of Engineers for. 1874 Vol. II, Pt. II, Appendix FFa of Appendix FF, pp. 115-130.

Gheerbrant E, Sudre J, Iarochene M and Moumni A 2001. First ascertained African "condylarth" mammals (primitive ungulates: cf. Bulbulodentata & cf. Phenacodonta) from the Earliest Ypresian of the Ouled Abdoun Basin, Morocco. Journal of Vertebrate Paleontology 21(1): 107–118.

Gheerbrant E, Amaghzaz M, Bouya B, Goussard F, Letenneur C 2014. Ocepeia (Middle Paleocene of Morocco): The Oldest Skull of an Afrotherian Mammal. PLoS ONE 9(2): e89739. doi:10.1371/journal.pone.0089739

Lartet E 1836. Nomenclature des mammiféres et des coquilles qu’il a trouvés dans un terrain d’eau douce prés de Simorre et de Sansan (Gers). Bulletin de la Société Géologique de France 7: 217–220.

Osborn HF and Granger W 1932. Coryphodonts and uintatheres from the Mongolian expedition of 1930. American Museum Novitates 552:1-16.

Roth S 1899. Aviso preliminar sobre mamíferos mesozoicos encontrados en Patagonia. Revista del Museo de La Plata 9: 381–388.

Williamson TE and Lucas SG 1992. Meniscotherium (Mammalia, "Condylarthra") from the Palaeocene-Eocene of Westeran North America. New Mexico Museum of Natural Hstory and Science Bulletin 1.

wiki/Meniscotherium
wiki/Thomashuxleya
wiki/Periphragnis

Basal Mammalia

Monotremata

Basal Marsupialia

Akynodonta

Orcinus