Phascogale tapoatafa (type Didelphis pincillata Shaw 1800, originally Vivera tapoatafa Meyer 1793, Fig 1) are traditional dasyurid Australian marsupials. Their common names are wambengers and mousesacks. In the LRT Phascogale does not nest with other dasyurids. In the LRT Phascogale is now the basal-most extant marsupial.

Phascogale lacks a pouch, as in the traditional genus Monodelphis, represented in the LRT by three species. None of these four taxa are related to one another in the LRT = they don't nest together and apart from other marsupials in a pouch-less clade. Pouches disappeared by convergence. Even so, marsupial bones are present.

Nocturnal and arboreal Phascogale (16–27 cm svl) nests at the base of the marsupial clade that produced Early Cretaceous Eomaia and Early Jurassic multituberculates, along with extant rodents, kangaroos and marsupial moles. Flat-skulled Late Cretaceous Asiatherium is a proximal ancestor close to the Late Triassic origin of the marsupial clade. So this is a very long-lived arboreal taxon, going back 200 million years, despite its self-limited ability to reproduce. Males die soon after mating during their first year of life. Females generally produce only one litter of six pups during three years of life.

Eomaia scansoria (Ji et al. 2002) Barremian, Early Cretaceous ~125 mya, ~10 cm in length) was originally considered a basal eutherian mammal, but not a placental mammal. Here it nests as a basal marsupial.

Distinct from Didelphis the mandible of Eomaia had a larger canine and three fewer molars. The coronoid process was tall without any posterior process. The molars were more asymmetrical in shape, with taller cusps.

The slender scapula included a central ridge and the coracoid was greatly reduced and invisible in lateral view. The shoulder joint was ventrally oriented, indicating a parasagittal motion for the forelimbs to finally match the hind limbs. The humerus and radius/ulna were more gracile and elongated.

The pelvis was relatively smaller with fewer protruding processes. The fibula was more gracile. The metatarsals were more nearly subequal as were all the non-ungual phalanges.

Cokotherium jiufotangensis (Ji et al. 2002) Barremian, Early Cretaceous ~125 mya, ~10 cm in length) is a sister to Eomaia in the LRT. This µCT scan helps one understand the more nebulous data on Eomaia.

Ji et al 2002. The earliest known eutherian mammal, Nature 416:816-822.

Meyer FAA 1793. Systematisch-summarische Uebersicht der neuesten zoologischen Entdeckungen in Neuholland und Afrika. Leipzig, Dykischen: 1–178 + 6 unnum. index.

Shaw G 1800. Descriptions of the Mus Bursarius and Tubularia Magnifica; from drawings communicated by Major-General Thomas Davies - Transactions of the Linnean Society of London 5: 227-229, Tab. 8-9. London.

Temminck CJ 1824. Monogr. Mamm. vol.1 p.23, 56.

Wang H-B, Hoffmann S, Wang D-C, Wang Y-Q. 2022. A new mammal from the Lower Cretaceous Jehol Biota and implications for eutherian evolution. Phil. Trans. R. Soc. B 377: 20210042. https://doi.org/10.1098/rstb.2021.0042

wiki/Phascogale
wiki/Eomaia
wiki/Cokotherium