Waimanu & avian evolution

[Tim Williams <twilliams_alpha@hotmail.com>]

This was discussed earlier on this list, but this is the official paper...

Kerryn E. Slack, Craig M. Jones, Tatsuro Ando, G. L. (Abby) Harrison, R. 
Ewan Fordyce, Ulfur Arnason and David Penny (2006) Early Penguin Fossils, 
Plus Mitochondrial Genomes, Calibrate Avian Evolution.  Molecular Biology 
and Evolution 23: 1144-1155

Abstract: "Testing models of macroevolution, and especially the sufficiency 
of microevolutionary processes, requires good collaboration between 
molecular biologists and paleontologists. We report such a test for events 
around the Late Cretaceous by describing the earliest penguin fossils, 
analyzing complete mitochondrial genomes from an albatross, a petrel, and a 
loon, and describe the gradual decline of pterosaurs at the same time modern 
birds radiate. The penguin fossils comprise four naturally associated 
skeletons from the New Zealand Waipara Greensand, a Paleocene (early 
Tertiary) formation just above a well-known Cretaceous/Tertiary boundary 
site. The fossils, in a new genus (_Waimanu_), provide a lower estimate of 
61?62 Ma for the divergence between penguins and other birds and thus 
establish a reliable calibration point for avian evolution. Combining fossil 
calibration points, DNA sequences, maximum likelihood, and Bayesian 
analysis, the penguin calibrations imply a radiation of modern (crown group) 
birds in the Late Cretaceous. This includes a conservative estimate that 
modern sea and shorebird lineages diverged at least by the Late Cretaceous 
about 74 ± 3 Ma (Campanian). It is clear that modern birds from at least the 
latest Cretaceous lived at the same time as archaic birds including 
_Hesperornis_, _Ichthyornis_, and the diverse Enantiornithiformes. 
Pterosaurs, which also coexisted with early crown birds, show notable 
changes through the Late Cretaceous. There was a decrease in taxonomic 
diversity, and small- to medium-sized species disappeared well before the 
end of the Cretaceous. A simple reading of the fossil record might suggest 
competitive interactions with birds, but much more needs to be understood 
about pterosaur life histories. Additional fossils and molecular data are 
still required to help understand the role of biotic interactions in the 
evolution of Late Cretaceous birds and thus to test that the mechanisms of 
microevolution are sufficient to explain macroevolution."