Sminthopsis crassicaudata (Gould 1844; 6-9 cm long with 5-7cm tail, Australia) is the extant fat-tailed dunnart, a mouse-like insectivorous carnivorous marsupial with an open pouch. The lifespan is less than 2 years. This genus prefers extreme, semi-arid environments. Daily torpor enables this niche. Prepubes are present. This taxon gave rise to Macroscelides a placental, convergent with other placentals.

Macroscelides proboscideus (Shaw 1800, 10-30cm) is the extant round-eared elephant shrew or sengi. It is not a sister to Scutisorex, the hero shrew, nor related to Rhynchocyon another traditional sengi. Macroscelides is not related to elephants either, contra Wikipedia. The cranium is expanded with acoustic space on this nocturnal desert dweller. Diet includes insects, shoots and roots. The limbs are long and slender, making it one of the fastest small mammals.

Ningaui pilbara (Archer 1975, extant, Australia. 4.5 to 5.8cm + a longer tail) is among the smallest of all mammals of all time. In the LRT Ningaui is a phylogenetically miniaturized descendant of Sminthopsis, transitional to extant placental tree shrews AND the Petaurus clade of marsupials that include sugar gliders, marsupial lions and wombats. Note the tiny canine tooth (orange). Males are larger than females. Litters of 4 to 6 pouch young are produced. Lifespan rarely over a year. The skull is shorter than 1cm in length. This taxon was originally named Ningaui. See citation below.