More news on tree shrews: not related to primates

Those two conical premaxillary teeth
in tree shrews, like extant Ptilocercus (Figs 1, 2) and Tupaia, now have an origin from another extant SE Asian taxon: the shrew-mole, Uropsilus (Fig 2), which shares several homologous traits, particularly in the dentition.

Citations linking these three taxa seem to be lacking on Google.
So today’s post may represent a novel hypothesis of interrelationships.

Both tree shrews are now in the arboreal and terrestrial clade
of Labidolemur, Anagale, hedgehogs, apatemyids and ?marsupial lions, like Thylacoleo.

According to Wikipedia –Treeshrew –
“As fellow members of Euarchonta, treeshrews are closely related to primates,” 

This seems logical on many grounds, however…

The large reptile tree (LRT, 2336 taxa) no longer supports that hypothesis of interrelationships.

“Taxonomists continue to refine the treeshrews’ relations to primates and to other closely related clades. Molecular phylogenetic studies have suggested that the treeshrews, with the primates and the flying lemurs (colugos), belong to the grandorder Euarchonta. According to this classification, the Euarchonta are sister to the Glires (lagomorphs and rodents), and the two groups are combined into the superorder Euarchontoglires.

In the LRT flying lemurs are lemurs = primates. So are bats.

“Several other arrangements of these orders have been proposed in the past, and the above tree is only a well-favored proposal. Although it is known that Scandentia is one of the most basal euarchontoglire clades, the exact phylogenetic position is not yet considered resolved:”

Hopefully this novel interrelationship will be tested soon by academics using trait studies. Deep time gene studies fail too often. Gene studies failed this time, too.

The Labidolemur clade
precedes Rodentia (including Multituberculata) in the LRT. This clade had a separate origin of the placenta, apart from Primates (including bats). Today’s academic taxonomists don’t recognize more than one origin for the placenta (Wortman 1902) in mammals.

The loss of the upper canine
in Ptilocercus (Fig 1) along with the reduction to two conical premaxillary teeth are traits not shared with primates, but does have a precursor homolog in Uropsilus (Fig 1). The other teeth share and one-to-one correspondence in size and shape. Plesiadapis is also a primate-like (by convergence) member of the Labidolemur clade in the LRT. Several clade members, other than tree shrews, are also arboreal.

Uropsilus lacks the postorbital bar and arboreal niche
that Ptilocercus and primates developed by convergence. The LRT took a long time overcoming that development, which affects at least five LRT scores.

Labidolemur kayi
(Silcox et al. 2010, Late Paleocene) is an ancestor of Apatemys in the LRT.

Uropsilus scoricipes 
(Milne-Edwards 1871; Hoffmann 1984, central China) is the extant shrew-mole, long considered the link between shrews and moles.

Tupaia chinensis
(Raffles 1821) extant, was derived from a sister to Ptilocercus.

Ptilocercus lowii
(pen-tailed tree shrew, extant, Le Gros-Clark 1926) nests among other tree dwelling placentals (= Scandentia) close to Tupaia.

In the early days of the LRT
with far fewer tested taxa, Ptilocercus and Tupaia nested basal to rodents. That postorbital ring was not recognized as convergent until now. Learning continues every day.

References
Blainville HMD 1838. Recherches sur l’anciennete des Mammiferes insectivores a la
surface de la terre; précéddées de l’histoirc de la science a ce sujet, des principes de leur classification et de leur distribution géographique actuelle. Comptes Rendus Hebdomadaires de Séances de I’Académie des Sciences, 6:738–744.
Le Gros-Clark WE 1926.On the Anatomy of the Pen-tailed Tree-Shrew (Ptilocercus lowii.) Proceedings of the Zoological Society of London 96: 1179-1309.
DOI – 10.1111/j.1096-3642.1926.tb02241.x
Milne-Edwards  H 1871. Descriptions of new species, in footnotes, pp. 92-93 In David, A., Journal d’un voyage en Mongolia et en Chine fait en 1866-68. Nouv. Arch. Mus. d’Hist. Nat. Paris, 7 (Bull.): 75-100.
Raffles TS 1821. Descriptive Catalogue of a Zoological Collection made on account of the Honourable East India Company, in the Island of Sumatra and its Vicinity, under the Direction of Sir Thomas Stamford Raffles, Lieutenant-Governor of Fort Marlborough; with additional Notices illustrative of the Natural History of those Countries. The Transactions of the Linnean Society of London (Linnean Society of London) XIII: 239–340.

wiki/Ptilocercus
wiki/Uropsilus
wiki/Tupaia
wiki/Treeshrew
wiki/Labidolemur – not yet posted

Source: https://pterosaurheresies.wordpress.com/2025/03/18/more-news-on-tree-shrews-not-related-to-primates/