Gracilinanus, Nasua and Ambolestes

Gracilinanus agilis (Gardner and Creighton 1989 This South American gracile mouse opossum nests at the base of the Placentalia 1 clade, so is basal to Nasua and humans. It was separated from the genus Marmosa in 1989. Diet that includes insects, spiders, fruits, termites, beetles and ants, A litter size of up to 15, but usually 7. Females lack a pouch. The young are only attached to the nipples for a short time period and are left in their nests early on in their life.

Nasua nasua (Linneaus 1766) is the extant coatimundi or coati. Here it nests with the Notharctus, as a basalmost primate. Traditionally nested with raccoons (Procyon) Nasua has three molars, all similar, and no carnasial tooth, distinct from all members of the Carnivora in the LRT.

Ambolestes zhoui (Bi et al. 2018, Early Cretaceous, 126 mya; 25cm in length) is is one third the size of the extant opossum, Didelphis. In the LRT nests Ambolestes close to Eomaia, but clloser to Vincelestes.

Bi said in an interview, “Ambolestes zhoui is an early member of the placental lineage. It also carries mixed features both placentals and marsupials”. That is supported by the LRT.

Bi S-B, Zheng X-T, X, Wang X-L, Cignetti N-E, Yang SL and Wible JR 2018. An Early Cretaceous eutherian and the placental/marsupial dichotomy. Nature (advance online publication) DOI: https://doi.org/10.1038/s41586-018-0210-3
https://www.nature.com/articles/s41586-018-0210-3

Gardner AL and Creighton GK 1989. A new generic name for Tate's microtarsus group of South American mouse opossums (Marsupialia: Didelphidae). Proceedings of the Biological Society of Washington 102:3–7.

Linneaus C von 1766. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata. pp. 1–532. Holmiæ. (Salvius)

wiki/Nasua
wiki/Ambolestes
wiki/Gracilinanus