Chironectes minimus (von Zimmermann 1780, 30 cm snout to rump, 36cm tail) is the extant water opossum. This sole aquatic marsupial has a water-proof pouch with a unique sphincter for access. And it nests in the LRT as the proximal outgroup taxa to the Eutheria, although the aquatic niche and webbed feet are autapomorphies not retained in descendant taxa among the placental mammals. These traits have had the entire Cretaceous and Cenozoic to develop after that phylogenetic split. Both males and females have a pouch.

Kopidodon macrognathus (originally Cryptopithecus macrognathus Wittich 1902; Weitzel 1933/4; Tobien 1969; Naturmuseum Senckenberg; 115cm total length; middle Eocene, 47 mya) is traditionally considered, "a squirrel-like mammal with large canines." Here it nests with water opossums like Chironectes. The Messel fossil shows it had long hair and a bushy tail. There were 26-29 presacral vertebrae + 3 sacrals. The foreclaws were taller than wide (similar to arboreal mammals) and larger than the hind claws. The feet were plantigrade. The limbs were heavily muscled and designed for slow movement. The tail vertebrae diminished posteriorly to tiny elongate bones. Stomach contents include fruit and seeds.

Traditionally considered a member of the Cimolesta, this is an invalid, paraphyletic clade. Likewise considered a member of the Pantolesta, this is likewise an invalid, paraphyletic clade in the LRT. Likewise considered a member of the Paroxyclaenidae.

Gobiohyus orientalis (Matthew and Granger 1925, Coombs and Coombs 1977) was considered a member of the Helohyidae and Artiodactyla. Here it nests between Kopidodon and Palaeosinopa.

Clemens WA and von Koenigswald W 1993. A new skeleton of Kopidodon macrognathus from the Middle Eocene of Messel and the relationship of paroxyclaenids and pantolestids based on postcranial evidence. Kaupia 3, 1993, S. 57–73.

Coombs MC and Coombs WP Jr. 1977. Dentition of Gobiohyus and a Reevaluation of the Helohyidae (Artiodactyla). Journal of Mammalogy58(3): 291-308.

Matthew WD and Granger W 1925. New mammals from the Irdin Manha Eocene of Mongolia. American Museum Novitates 198:1-10.

Orliac MJ, Argot C and Gilissen E 2012. Digital Cranial Endocast of Hyopsodus (Mammalia, “Condylarthra”): A Case of Paleogene Terrestrial Echolocation? PlosOne v.7(2); 2012PMC3277592

Rose KD and von Koenigswald W 2005. An exceptionally complete skeleton of Palaeosinopa (Mammalia, Cimolesta, Pantolestidae) from the Green River Formation, and other postcranial elements of the Pantolestidae from the Eocene of Wyoming (USA): Palaeontographica Abteilung A 273: 55–96.

Tobien H 1969. Kopidodon (Condylarthra, Mammalia) aus dem Mitteleozän (Lutetium) von Messel bei Darmstadt (Hessen). Notizblätter der hessischen Landesanstalt für Bodenforschung 97, 1969, S. 7–37.

Weitzel K 1933. Kopidodon macrognathus Wittich, ein Raubtier aus dem Mitteleozän von Messel. Notizblätter des Vereins für Erdkunde der hessischen geologischen Landesanstalt Darmstadt 14, 1933, S. 81–88

Wittich E 1898 1902. ein Raubtier aus dem Mitteleozän von Messel. Notizblatt des Vereins für. Erdkunde zu Darmstadt (5)14: 81-88.

Zimmerman EAWv 1780. Geographische Geschichte der Menschen, und der algemein verbreiteten Vierfüssigen Thiere. Zweiter Band. Leipzig: Wenganschen Buchhandlung 2:6.

wiki/Water_opossum_Chironectes
wiki/Gobiohyus - not yet posted
wiki/Kopidodon