Placentalia 3 basal taxa and their marsupial ancestors to scale

Originally these were all arboreal taxa.
Here in the large reptile tree (LRT, 2340 taxa) placental 3 taxa (Figs 1, 2) are tree-shrews some of which later evolved to become terrestrial shrews, some of which became armored with spines = hedgehogs, some of which developed scales and interlocking plates = glyptodonts. Derived members became echo-locating aquatic taxa = odontocetes. Still others became burrowers = moles.

Some later clade members returned to once again become arboreal = tree sloths and tree anteaters. So here’s another clade with an exotic variety of taxa.

Again, none had canines. Several were toothless. Some = odontocetes phylogenetically reversed their premolars and molars to become canine-like, as in their pre-pelycosaur ancestors.

The original transition
from the marsupial tree shrew Caluromys to placental tree shrews, like Tupaia and Ptilocercus, involved a size decrease (Figs 1, 2). So, phylogenetic miniaturization was once again at play.

The skulls of the placental taxa look more like the skull of the juvenile marsupial (Fig 2).

Prior published cladograms of the Mammalia
did not include enough taxa to recover the four inventions of the placenta. 

Genetic studies do not include fossils. 

The LRT currently needs testing with a similar taxon list. 

This appears to be a novel hypothesis of interrelationships. 
If not please provide a citation so I can promote it here. 

PS
Melin et al 2016 wrote, “Treeshrews [Tupaia tana] and woolly opossums [Caluromys derbianus] are phyletic and/or ecological analogues of ancestral primates, factors that invite study of their opsin genes.”

Animal opsins are molecules that absorb light from the environment for vision..

The LRT does not recover
the clade Euarchonta = Scandentia (treeshrews), Dermoptera (colugos) Plesiadapiforme and the primates (not including bats).

Rather in the LRT Scandentia gives rise to Plesiadapiformes (including multituberculates and rodents and rabbits) in the Placentalia 3 clade, none of which have canines.

Elsewhere on the LRT primates (including colugos and bats) are part of the Placentallia 1 clade, most of which do not lose their canines. Colugos lose the upper canine.

Wortman 1902 was the first to report
the hypothesis of three origins for the placenta, rather than just one, the mistake currently taught in university textbooks and lectures.

References
Melin et al (10 co-authors) 2016. Euarchontan opsin variation brings new focus to primate origins. Molecular Biological Evolution doi: 10.1093/molbev/msv346.
Matthew WD 1906. The Osteology of Sinopa, a Creodont Mammal of the Middle Eocene.
Proc. U. S. Nat. Mus., Vol. XXX, pp. 203-233, pl. XVI.
Wortman JL 1901-1903. Studies of Eocene Mammalia in the Marsh Collection, Peabody Museum. Am. Jour. Sci. 11:333–348.

wiki/Euarchonta

Source: https://pterosaurheresies.wordpress.com/2026/08/20/placentalia-3-basal-taxa-and-their-marsupial-ancestors-to-scale/