Tree shrews and Early Cretaceous ancestors linked and segregated
The mammal subset
of the large reptile tree (LRT, 2336 taxa) has been difficult to resolve: There have been 340 days of revising scores as of today, with no end in sight.
All well worth the effort. I am learning as I go.
Today, a breakthrough – maybe.
Figure 1. Extant tree shrews, Tupaia and Ptilocercus, appear to have undergone their own evolution from Early Cretaceous pre-marsupials like Anebodon and Origolestes through marsupials like Dromiciops and Glironia, to their present placental selves, by convergence with three other lineages that produced placental taxa.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg?w=95″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg?w=323″ class=”size-full wp-image-92005″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg” alt=”Figure 1. Extant tree shrews, Tupaia and Ptilocercus, appear to have undergone their own evolution from Early Cretaceous pre-marsupials like Anebodon and Origolestes through marsupials like Dromiciops and Glironia, to their present placental selves, by convergence with three other lineages that produced placental taxa.” width=”584″ height=”1849″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg?w=584&h=1849 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg?w=47&h=150 47w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg?w=95&h=300 95w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/03/tree-shrew-evolution.588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Extant tree shrews, Tupaia and Ptilocercus, appear to have undergone their own evolution from Early Cretaceous pre-marsupials like Anebodon and Origolestes through marsupials like Dromiciops and Glironia, to their present placental selves, by convergence with three other lineages that produced placental taxa.
Tree shrews, traditional order Scandentia,
include extant placentals Tupaia and Ptilocercus (Fig 1). Similar, but marsupial, are extant Dromiciops and Glironia (Fig 1). Also similar, are pre-marsupial Early Cretaceous Anebodon and Origolestes (Fig 1).
From now on these six taxa are boxed together in the LRT, seemingly following their own path with an evolution of reproduction modes and skull traits convergent with other taxa tested in the LRT.
For instance,
Ptilocercus and Tupaia developed a postorbital bar and U-shaped wrist joint that usually linked them to another arboreal clade, the primates. Dromiciops developed palatal vacuities otherwise found in some marsupials by convergence. The Cretaceous taxa, Anebodon and Origolestes, have a slot shape in the posterior mandible that links them to the earliest mammals and their proximal outgroup kin, this time by homology.
Neither Dromciops nor Glironia have a pouch.
Note the premaxillary teeth
in Ptilocercus and Tupaia. Such teeth are not found in primates.
This might be an erroneous hypothesis,
but I wanted to share it with you, for whatever value it has. The scientific method was followed here. Errors are part of the process of experimentation. Not all pan out.
On the other hand, this may be a solution.
I will trash this web post
with an explanation if and when a more parsimonious solution presents itself.
References
wiki/Convergent_evolution
Source: https://pterosaurheresies.wordpress.com/2025/03/17/tree-shrews-and-early-cretaceous-ancestors-linked-and-segregated/
