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I'm asking this question as a cat owner. I've seen a figure like 94 MA for the most recent ancestor of both cats and humans (this from, I guess, molecular clock arguments), and it kind of lines up with the geologic timescale of the Atlantic ocean opening up south to north. Moreover, Laurasiatheria literally means "beasts from Laurasia", and Boreoeutheria is "true northern beasts".

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  • $\begingroup$ I'm starting to think I'm asking this question in the wrong community. Maybe geology is closer to home? $\endgroup$ Commented Feb 21 at 16:19
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    $\begingroup$ I disagree, this is the right site for phylogeny questions. $\endgroup$
    – bob1
    Commented Feb 21 at 19:56

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It would seem the answer is "No" at the current understanding of this issue.

You should understand that this is a very complex topic, which is based on both molecular (i.e. DNA sequences or protein sequences derived from DNA or by protein sequencing) and morphology. These are both hamstrung to some extent by the lack of mammalian fossils from this period to confirm any tree, but there are a fair number of early mammalian fossils for this period in particularly in North America but also from Eurasia. Most of the implied phylogeny analyses have been done using DNA from existing species and these results don't always agree depending on which sequences are used. To quote one paper from 20081, where segments are the different DNA sequences they analyzed:

Laurasiatheria was generally not well resolved in any of our analyses, and orders within Laurasiatheria did not have a consistent relationship among the different segments.

It would seem that the Laurasiatheria2 and the Euarchontoglires3 are fairly widely supported as "real" clades, both based on DNA sequences, but there is some dispute as to whether Boreoeutheria is real, with some saying yes, others no.

A 2007 paper from Wildman et al., 20074, had this to say:

The mode of diversification between Laurasiatheria and Euarchontoglires remains murky, and it is unclear whether this was primarily because of vicariance between North America and Eurasia, some other vicariant event, or dispersal.

I found a paper by Springer et al. from 2011, which seems to be the current authority on the question, and is free to read on PubMed Central (see last link in reference; it might also be free to read at the DOI link, which takes you to the publication in the Philosophical Transactions journal)5. In the section titled Placental Biogeography, they state (with my emphasis), that Eurasia, not North America is the likely origin:

The remaining placental orders are placed in Laurasiatheria (Eulipotyphla, Chiroptera, Perissodactyla, Cetartiodactyla, Carnivora, Pholidota) and Euarchontoglires (Primates, Dermoptera, Scandentia, Rodentia, Lagomorpha). With the exception of bats, these orders have first fossil occurrences that are exclusively Laurasian. Our reconstructions provide support for Eurasia, but not North America, as the ancestral area for these clades...

...Further, the fossil record suggests that Eutheria were dominant in Eurasia throughout the Cretaceous, but were absent from North America through much of the Late Cretaceous and only attained appreciable diversity there during the last approximately 10 Myr of the period

More recent papers seem to take this information as understood and I can't see any more recent papers that dispute it.

Refs:

  1. Prasad AB, Allard MW; NISC Comparative Sequencing Program; Green ED. Confirming the phylogeny of mammals by use of large comparative sequence data sets. Mol Biol Evol. 2008 Sep;25(9):1795-808. doi: https://doi.org/10.1093/molbev/msn104. Epub 2008 May 2. PMID: 18453548; PMCID: PMC2515873.

  2. Waddell PJ, Okada N, Hasegawa M. Towards resolving the interordinal relationships of placental mammals. Syst Biol. 1999 Mar;48(1):1-5. PMID: 12078634.

  3. Murphy WJ, Eizirik E, Johnson WE, Zhang YP, Ryder OA, O'Brien SJ. Molecular phylogenetics and the origins of placental mammals. Nature. 2001 Feb 1;409(6820):614-8. doi: https://doi.org/10.1038/35054550. PMID: 11214319.

  4. Wildman DE, Uddin M, Opazo JC, Liu G, Lefort V, Guindon S, Gascuel O, Grossman LI, Romero R, Goodman M. Genomics, biogeography, and the diversification of placental mammals. Proc Natl Acad Sci U S A. 2007 Sep 4;104(36):14395-400. doi: https://doi.org/10.1073/pnas.0704342104. Epub 2007 Aug 29. PMID: 17728403; PMCID: PMC1958817.

  5. Springer MS, Meredith RW, Janecka JE, Murphy WJ. The historical biogeography of Mammalia. Philos Trans R Soc Lond B Biol Sci. 2011 Sep 12;366(1577):2478-502. doi: https://doi.org/10.1098/rstb.2011.0023. PMID: 21807730; PMCID: PMC3138613.

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    $\begingroup$ Hat's off to you! This is an amazing answer to what was basically a shower thought of mine. Thanks! $\endgroup$ Commented Apr 28 at 0:37
  • $\begingroup$ @EmanuelLandeholm No problem, I'm a total nerd so learning things outside of my sphere of expertise and putting my search skills to use is always fun. $\endgroup$
    – bob1
    Commented Apr 28 at 0:57

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