Cronopio dentiacutus (Rougier et al. 2011, early Late Cretaceous, 98 mya; MPCA PV 454 and others; 2 cm est. skull length) was originally described as a dryolestid mammal. Tradtionally and here dryolestids nest outside of the Theria, basal to Didelphis. Here Cronopio nests with Acristatherium. This shrew-like mammal had a long rostrum and extraordinary saber-tooth canines. In dorsal and palatal view the rostrum was pinched then expanded.

Acristatherium yanensis (Hu et al., 2010; early Cretaceous (Aptian), 125 mya, IVPP V15004) was originally described as a tiny eutherian mammal. By contrast, in the large reptile tree Acristatherium nests with Cronopio, a taxon not originally tested. Both have a flattened cranium without a crest.

Caenolestes fuliginosus (originally Hyracodon fuliginosus Tomes 1863) is the original shrew-opossum, the one that gave its name to the clade Caenolestidae.

Rhyncholestes raphanurus (Osgood, 1924; long-nosed shrew-opossum, Chilean shrew opossum, extant; snout-vent length 20cm), nests in the large reptile tree with Caenolestes and Acristotherium. Rhyncholestes lacks a marsupium = pouch.

Tarsipes rostratus (Gervais & Verreaux 1842; Beck, Voss and Jansa 2022, up to 8.5cm snout-vent length + up to 10cm) is the extant and nocturnal honey possum, a tiny nectar eater related to Rhyncholestes (above). The tiny teeth are reduced to cones and widely spaced. Gestation lasts for 28 days, with two to four young being produced. At birth, they are the smallest of any mammal, weighing 0.005 g. Pouch development takes 60 days. When the babies emerge they are left in a sheltered area, but within days start to cling to the mother during her travels.

Bradshaw D and Bradshaw F 2012. The physiology of the honey possum, Tarsipes rostratus, a small marsupial with a suite of highly specialised characters: a review. J Comp Physiol 182(4):469-89. doi: 10.1007/s00360-011-0632-9.

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

Hu Y-M, Meng J, Li C-K and Wang YQ 2016. New basal eutherian mammal from the Early Cretaceous Jehol biota, Liaoning, China. Proceedings of the Royal Society B.
doi:10.1098/rspb.2009.0203 Published online

Osgood WH 1921. A monographic study of the American marsupial, Caenolestes. Field Museum of Natural History, Zoological series 14:1–156.

Osgood WH 1924. Field Mus. Nat. Hist. Publ., Zool. Ser. 14:170.

Rougier GW, Apesteguía S and Gaetano LC 2011. Highly specialized mammalian skulls from the Late Cretaceous of South America. Nature. 479: 98–102.

Tomes PZS 1863. A small marsupial from Ecuador, named Hyracodon fuliginosus. Proceedings of the Zoological Society, London: 50–51.

wiki/Cronopio
wiki/Acristatherium
wiki/Caenolestes
wiki/Rhyncholestes
Paucituberculata
wiki/Honey_possum