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Placental mammal relationships clarified

By jlynch on April 10, 2006.

A just-published paper in PLoS Biology has thrown some light on the relationship between placental mammals. The authors used retroposed elements, and by scanning more than 160,000 chromosomal loci and selecting from only phylogenetically informative retroposons, they recovered 28 clear, independent monophyly markers that they feel conclusively verify the earliest divergences in placental mammalian evolution.

Below the fold, I provide a copy of their derived phylogeny, but a few things are worth noting:

  • Eutheria are divided into Xenarthra, Afrotheria & Boreotheria, with the Xenarthra - sloths and armadillos - being the first clade to branch off.
  • Boreotheria are themselves comprised of Supraprimates (which also include rodents and tree shrews) and Laurasiatheria (insectivores, artiodactyls, cetacea & carnivores).
  • Within the latter group, the Cetartiodactyls and carnivores are closely related - nicely backing up the whale fossil record.
  • A whole bunch of these groups - Afrotheria, Boreotheria, Supraprimates, Laurasiatheria, and Cetartiodactyls, didn't exist as taxa when I was in grad school!

The paper is Kriegs JO, Churakov G, Kiefmann M, Jordan U, Brosius J, et al. (2006) Retroposed Elements as Archives for the Evolutionary History of Placental Mammals. PLoS Biol 4(4): e91 and there is a commentary here. Of course, it is important to remember that any nested pattern we see is due to the designer's wisdom in creating the approximately 100 original "kinds" (which are, we will remember, at the family level).

i-b953ef063537af1a7b9bbf20a88b4b96-10.1371_journal.pbio.0040091.g002-M.jpg

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evolution

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By Bruce Thompson (not verified) on 10 Apr 2006 #permalink

Did the golden mole retain the cloaca from our marsupial ancestor? Or did it evolve later? In what way is it the same as the marsupial cloaca? In what way is it different? Which genes govern cloaca in golden moles? Are they different than the genes that govern cloacal development in marsupials.