Taxon exclusion mars Mesozoic mammal study

King and Beck 2019
bring us a new phylogenetic analysis restricted to Mesozoic mammals. This represents a massive case of taxon exclusion of basal mammals as demonstrated earlier here, because so many basal mammals are still alive! Think of all the tree shrews, arboreal didelphids, and nearly every little creeping taxon in Glires that nest basal to known Mesozoic mammals. You cannot restrict the taxon list to just those extremely rare Mesozoic mammals.

On the plus side,
King and Beck confirm earlier tree topologies recovered by the large reptile tree (LRT, 1394 taxa) that nest haramiyidans apart from euharamiyidans when they reported, “Tip-dating applied to Mesozoic mammals firmly rejects a monophyletic Allotheria, and strongly supports diphyly of haramiyidans, with the late Triassic Haramiyavia and Thomasia forming a clade with tritylodontids, which is distant from the middle Jurassic euharamiyidans.”

Taxon exclusion
made the authors nest Vintana with euharamiyidans rather than the wombats recovered by the LRT. Other than Vintana, no wombats were included in the King and Beck study—because they are alive. Furthermore, no rodents and aye-ayes were included—because they are alive. So, sans living taxa, King and Beck’s cladogram had no idea where to nest euharamiyidans in the mammal family tree. The wide gamut taxon list of the LRT solves most problems that arise from restricted studies like the King and Beck study.

Figure 4. Mesozoic euthrerians (placentals, in black). Later taxa in light gray. All taxa more primitive than Mesozoic taxa were likely also present in the Jurassic and Cretaceous. None appear after Onychodectes. Madagascar separated from Africa 165-135 mya, deep into the Cretaceous with a population of tenrecs attached. No rafting was necessary. 

Figure 1. Mesozoic euthrerians (placentals, in black). Later taxa in light gray. All taxa more primitive than Mesozoic taxa were likely also present in the Jurassic and Cretaceous. None appear after Onychodectes. Look at all the taxa King and Beck could have added to their analysis!  …and we’re not even looking at the Metatheria and Prototheria here.

More on Mesozoic mammals
here.

References
King B and Beck R 2019. Bayesian Tip-dated Phylogenetics: Topological Effects,
2 Stratigraphic Fit and the Early Evolution of Mammals. PeerJ
doi: http://dx.doi.org/10.1101/533885.

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