Our timescale reveals that rates of molecular evolution vary across genes and among taxa through time, thereby refuting the widely used mitogenomic or cytochrome b molecular clock in birds. Moreover, the 5-Myr divergence time assumed between 2 genera of geese (Branta and Anser) to originally calibrate the standard mitochondrial clock rate of 0.01 substitutions per site per lineage per Myr (s/s/l/Myr) in birds was shown to be underestimated by about 9.5 Myr.
Major ouch time!
It's embarrassing that anyone used this as late as 2006. (It has recently been refuted, I think in the latest paper on the phylogeny of Neornithes.)
We found no support for the hypothesis that the molecular clock in birds "ticks" according to a constant rate of substitution per unit of mass-specific metabolic energy rather than per unit of time, as recently suggested.
What a pity.
Indeed.
Our analysis advances knowledge of rates of DNA evolution across birds and other vertebrates and will, therefore, aid comparative biology studies that seek to infer the origin and timing of major adaptive shifts in vertebrates.
A nice way of putting what a biomedical researcher seeking major founding would without doubt have called "...will revolutionize our understanding of..."
Where's the revolution?
Instead, let me doubt the dates. A Permian date for the basal divergence of the crown of Archosauria is suspect. An Early Cretaceous date for the basal divergence of Neornithes is highly suspect. And so on... I've recently done some molecular dating; some programs let you fiddle with several parameters that can greatly influence the results, others seem to have them inbuilt and inalterable...
This is an interesting paper in this context: