Interatherium rodens (Ameghino 1887, 1894; Middle Miocene; 50cm in length) the Interatheridae and Interatherium were long considered members of the Notoungulata, a clade that has broken up in the large reptile tree. Here Interatherium nests at the base of the kangaroos and Toxodon, derived from the more basal marsupials like Didelphis. Interatherium retains several small incisors, but apparently has lost its thumb, unlike kangaroos.

Miocochilius anomopodus (Stirton 1953; Croft 2007; Late Miocene; 30cm in length) originally considered a notoungulate, this cat-sized interathere had long legs and ran on just two digits per manus and pes. A third vestige on the manus did not touch the ground.

Paedotherium typicum (Burmeister 1888, Cerdeño E and Bond M 1998; Miocene-Pleistocene) was originally considered a rabbit-like typothere notoungulate, but here nests with Interatherium. The maxillary notch was just noticeable here, in the photo, hot in the drawing. The top of the squamosal appears to be lost here, in comparison to Interatherium (above). The four molars and two premolars are flattened. The incisors are procumbent. The lacrimal has an odd anterior process. As in Interatherium, the anterior jugals are squanred off. Like Vintana, the orbit is in the posterior half of the skull. Unlike Interatherium, the legs of Paedotherium are much longer relative to the dorsal vertebrae. The ?tabulars (known as mastoid bullae) are expanded to form spheres.

Protypotherium antiquum (Ameghino 1882; Miocene, 25mya; 40cm in length) was originally considered a small, sheep-like notoungulate and an interethere. A full set of teeth (11 per side) lined the jaws and all had deep roots. The canine was tiny on this herbivore. The upper rostrum has several fenestrations.

Procavia capensis (Pallas 1756, 50cm) is the living rock hyrax and a traditonal relative of Elephas and Dusisiren. Superficially it resembled a guinea pig. Closest relatives in the LRT include the African Phosphatherium and South American notoungulates like Hegetotherium. The hyrax inhabits rock crevices and lives in groups of 10-80 with some acting as sentries to sound the alarm at the sight of predators. They use at least 21 vocal signals. Note the tusk-like incisors with deep roots. The soles of the feet are heavily padded. The testes are held within the abdomen. It rests most of the time, often basking in the equatorial sun.

Hegetotherium mirabile (Ameghino 1887; Mid Miocene, 17mya; skull length 10cm) was originally considered a notoungulate. Here it nests as a sister to Procavia, the extant rock hyrax within the Notoungulata. Tiny third incisors, canines and first premolars distinguish this genus, completing the dental arcade. Procavia lacks those teeth.

Mesotherium cristatum (originally 'Typotherium'; Serres 1867; Middle Pleistocene; 1.2m long) was originally considered a typotherid, mesotheriid notoungulate, with rodent-like incisors. Here it nests with Hegetotherium in the LRT. Probably fossorial. Note the deep jugals.

Notostylops murinis (Ameghino 1897, Riggs and Patterson 1935; 75cm in estimated length; Eocene; FMNH-P13319) is widely considered a 'notoungulate' a clade that has been split into several parts in the large reptile tree. Here it nests with Mesotherium, an herbivorous marsupial. The jaws narrowed anteriorly.

Ameghino F 1882. Ungulata, Typotheria, Interatheridae. Catalog de la Prov. de Buenos Aires en la Expedicion Cont. Sud-America. March 1882. Boletino Instituto Geologia Argentino, June 1882. Cont. Conocimenient Mamif. Fosil. Repub. Argentina, in Accd. Nac. Cien., Cordoba 6:474-480. 1889.

Ameghino F 1887. Observaciones generales sobre el orden de mamíferos estinguidos sud-americanos llamados toxodontes (Toxodontia) y sinopsis de los géneros y especies hasta ahora conocidos. Anales del Museo de La Plata 1:1-66.

Ameghino F 1894. Enumeration synoptique des especes de mammifères fossiles des formations éocènes de Patagonie. Boletin de la Academia Nacional de Ciencias en Cordoba (Republica Argentina) 13:259-452.

Ameghino F 1897. Les mamiferes crétacés de l´Argentine. Boletín Instituto Geográfico Argentino 18: 405–521.

Burmeister CV 1888. Relaciónde un viaje a la Gobernaciónde Chubut. Anales del Museo Nacional de Buenos Aires 3:175–252,

Cope ED 1873. Fourth notice of extinct Vertebrata from the Bridger and the Green River Tertiaries. Paleontological Bulletin 17:1–4.

Croft DA 2007. The Middle Miocene (Laventan) Quebrada Honda wildlife, southern Bolivia and a description of ITS Notoungulates. Palaeontology 50(1):277-303.

Riggs ES and Patterson B 1935. Description of some notoungulates from the Casamayor ("Notostylops) beds of Patagonia. Proceedings of the American Philosophical Society 75(2):163-215.

Seoane FD, Cerdeño E 2019. Systematic revision of Hegetotherium and Pachyrukhos (Hegetotheriidae, Notoungulata) and a new phylogenetic analysis of Hegetotheriidae. Journal of Systematic Palaeontology. in press. doi:10.1080/14772019.2018.1545146.

Serres AERA 1867. De l’ostéographie du Mesotherium et de ses affinitiés zoologiques. Comptes Rendus de la Académie des Sciences, Paris 65:6-17, 140-148, 273-278, 429-437, 593-599, 740-748, 841-848.

Stirton RA 1953. A new genus of interatheres from the Miocene of Colombia. University of California Publications in Geological Sciences 29: 265-348.

Serres E 1867. De l’ostéographie du Mesotherium et ses affinités zoologiques. Comptes Rendus de l'Académie des Sciences de Paris: 140-148, t. 65.

Soe AN et al. (6 co-authors) 2017. New remains of Siamotherium pondaungensis (Cetartiodactyla, Hippopotamoidea) from the Eocene of Pondaung, Myanmar: Paleoecologic and phylogenetic implications. Journal of Vertebrate Paleontology 37(1):e1270290https://doi.org/10.1080/02724634.2017.1270290

Spencer WB 1896. Report on the Work of the Horn Scientific Expedition to Central Australia. Four Volumes. London: Dulau and Co.

Suteethorn V, Buffetaut E Helmcke-Ingava Rt JaegerJ-J and Jongkanjanasoontorn Y 1988. Oldest known Tertiary mammals from South-East Asia: Middle Eocene primate and anthracotheres from Thailand. Neues Jahrbuch f€ur Geologie und Palaontologie, Monatshefte 9:563–570.

wiki/Interatherium
wiki/Mesotherium
wiki/Hegetotherium
wiki/Protypotherium
wiki/Miocochilius
wiki/Notostylops
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