Back to a single clade Placentalia in the LRT

Previously
and with ~50 fewer MPTs (most parsimonious trees) the large reptile tree recovered three separate origins for placental reproduction (as hypothesized by Wortman 1902).

I am saving that previous matrix and cladogram in case the current experiment in scoring traits requires a return or retreat.

Now
with a few changes to taxon scores in and around Dssacus the transition to a single origin for the placenta is recovered following the mouse-like extant marsupial, Monodelphis domestica. Several taxa are recovered on the placental side of the ledger. See below.

The scientific method requires constant testing and publication,
especially when mistakes/changes arise.

Dissacus zanabazari
(Dissacus zanabazari (Cope 1881; Geisler and McKenna 2007; Early Palaeocene to Early Eocene) was traditionally considered a mesonychid, but here nests with Alcidedorbignya at the base of the Carnivoramorpha, close to Kopidodon at the base of the pre-primates and Pholidocercus at the base of the Xenarthra and Deltatherium at the base of the Pantodonta ALL recently derived from Monodelphis domestica.

So these taxa are all close to the marsupial/plancetal transition.

Click on the links above to see the data, starting with this one,
which shows the skulls all together and to scale.

In unrelated, yet related news…
multituberculates used to nest between Plesidapis and rodents. Now multis arise much earlier among the Marsupialia. Multis are Early Jurassic in origin, so that is now better reflected in the LRT. That makes the many similar traits convergent, rather than homologs with a reversal due to their mobile jaw joint and tooth shapes.

I will reexamine this issue.

This is just one example, more so in mammals, than in any other clade, that changes ‘here’ create unanticipated changes ‘there’ – evidently because this subset of the LRT is overall more fragile than any other vertebrate subset.

It’s still rewarding when overlooked interrelationships like this make themselves known. This one seems to resolve issues, but then I often think that.

References
Cope ED 1881. On some Mammalia of the lowest Eocene beds of New Mexico. Palaeontological Bulletin 33:484-495.
Geisler J and McKenna MC 2007. A new species of mesonychian mammal from the lower Eocene of Mongolia and its phylogenetic relationships. Acta Palaeontologica Polonica 52, 189-212.

wiki/Alcidedorbignya
wiki/Dissacus
wiki/Kopidodon
wiki/Monodelphis
wiki/Pholidocercus