The mammalian tree is rooted deeply and branched early!
(click for larger image)
All orders are labelled and major lineages are coloured as follows: black, Monotremata; orange, Marsupialia; blue, Afrotheria; yellow, Xenarthra; green, Laurasiatheria; and red, Euarchontoglires. Families that were reconstructed as non-monophyletic are represented multiple times and numbered accordingly. Branch lengths are proportional to time, with the K/T boundary indicated by a black, dashed circle. The scale indicates Myr.
That's the message of a new paper in Nature that compiled sequence data from 4,510 mammalian species (out of 4,554) to assembly that lovely diagram above. Challenging the 'conventional wisdom' that mammalian diversity is the product of an opportunistic radiation of species after the dinosaurs were wiped out at the end of the Cretaceous 65 million years ago, the authors instead identified two broad periods of evolutionary expansion among the mammals: an early event 100-85 million years ago when the extant orders first appeared, and a radiation of modern families in the late Eocene/Miocene. A key point is that there is no change in rates of taxon formation across the Cretaceous/Tertiary (K/T) boundary—mammalian diversity was rich before the dinosaurs disappeared.
Continue reading "Don't blame the dinosaurs" (on Pharyngula)
7 Comments
fnxtr · 29 March 2007
Nice to see taxonomy has a sense of humour. "Tachyglossia"... anteaters, I'm guessing?
Bill Gascoyne · 29 March 2007
John Krehbiel · 29 March 2007
So much for us biologists dogmatically clinging to "darwinism."
Although there is some dissent (considerable actually) in the comments following the article, it is worth noting that 1. the arguments are all based on evidence and 2. there is no name-calling and ad hominem crap.
fnxtr · 30 March 2007
Indeed. The differences of opinion/interpretation are stimulating, which is the whole point.
J-Dog · 30 March 2007
So when did the YEC's and IDers split off from the snakes?
Michael · 30 March 2007
Q: So when did the YEC's and IDers split off from the snakes?
A: Shortly after the Ad-Hominids, since they seems to have inherited most of their traits.
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