Pseudocheirus peregrinus (Ogilby 1837; ) is the extant ringtail possum. They have grasping feet and hands (with two thumbs) and a prehensile tail, convergent with arboreal didelphids. Cat-sized Pseudocheirus feeds on leaves.

Palaeothentes lemoinei (Ameghino 1887, Forasiepi et al 2014, MPM-PV 3566; Miocene) was considered a prehistoric shrew opossoum (clade: Paucituberculata). Here Palaeothentes nests with Zalambdalastes between Pseudocheirus and Inerteratherium. The skull is 2x wider than tall, the canines are smaller the last premolar is larger with a flat occlusal surface and the nasals split to form a zigzag suture with the frontals.

Zalambdalestes lechei (Gregory & Simpson 1926; Wible et al.2004; Late Cretaceous; 20 cm in length) was considered a eutherian, but not a placental due to the presence of epipubic bones. Here it nests with Palaeothentes. Zalambdalestes was an insect-eating marsupial with long, slender limbs.

Zanycteris paleocenus (Matthew 1917, Burger 2013, Crowell, Wible and Chester 2024; skull length <1cm, Paleocene 61-57my, AMNH 17180) is among the smallest of all mammals and nests with Zalambdalestes in the LRT.

Ameghino F 1887. Enumeracions sistematicad e las especies de mamiferos
fosiles coleccionados por Carlos Ameghino en los terranos eocenos de la Patagonia austral y depositados en el Museo La Plata. Boletin Museo de La Plata, 1:1-26.

Burger BJ 2013. A new species of the archaic primate Zanycteris from the late Paleocene of western Colorado and the phylogenetic position of the family Picrodontidae.PeerJ 1(1):e191

Crowell JW, Wible JR and Chester SGB 2024. Basicranial evidence suggests picrodontid mammals are not stem primates. Biology Letters 20: 20230335.
https://doi.org/10.1098/rsbl.2023.0335

Forasiepi AM, Sánchez-Villagra MR, Schmelzle T,  Ladevèze S and Kay RF 2014. An exceptionally well-preserved skeleton of Palaeothentes from the Early Miocene of Patagonia, Argentina: new insights into the anatomy of extinct paucituberculatan marsupials. Swiss Journal of Palaeontology, 133(1):1-21.

Gervais P and Verreaux J 1842. L'Institut, l'ere Section, Sci., Math, Phys., Nat. :427 p.75

Gregory WK and Simpson GG 1926a. Gregory, W.K., and G.G. Simpson. Cretaceous
mammal skulls from Mongolia. American Museum Novitates 225:1–20.

Gregory WK and Simpson GG 1926b. Gregory, W.K., and G.G. Simpson. Cretaceous
mammal skulls from Mongolia. Nature 118: 698–699.

Kerr J 1792. Animal Kingdom: 198.

Matthew WD 1917. A Paleocene bat. Bulletin of the American Museum of Natural History. 37, 569–571.

Ogilby W 1837. Observations on the opposable power of the thumb in certain mammals, considered as a zoological character; and on the natural affinities which subsist between the Bimana, Quadrumana, and Pedimana. The Magazine of Natural History (Charlesworth) 1: 449-459.

Ramsay EP 1875. Description of a new genus and species of rat kangaroo, allied to the genus Hypsiprymnus, proposed to be called 'Hypsiprymnodon moschatus". Proceedings of the Linnean Society of New South Wales. 1: 33–35.

Wible JR, Novacek MJ and Rougier GW 2004. New data on the skull and dentition in the Mongolian Late Cretaceous eutherian mammal Zalambdalestes. Bulletin of the American Museum of Natural History 281:144pp.

wiki/Musky_rat-kangaroo
wiki/Honey_possum
wiki/Pseudocheirus
wiki/Potorous
wiki/Palaeothentes - not posted yet
wiki/Zalambdalestes
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