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Genes show Neoaves branching before K/Pg extinction



From: Ben Creisler
bcreisler@gmail.com


A new online paper:

Oliver Haddrath and Allan J. Baker (2012)
Multiple nuclear genes and retroposons support vicariance and
dispersal of the palaeognaths, and an Early Cretaceous origin of
modern birds.
Proceedings of the Royal Society B (advance online publication)
doi: 10.1098/rspb.2012.1630
http://rspb.royalsocietypublishing.org/content/early/2012/09/07/rspb.2012.1630.abstract

The origin and timing of the diversification of modern birds remains
controversial, primarily because phylogenetic relationships are
incompletely resolved and uncertainty persists in molecular estimates
of lineage ages. Here, we present a species tree for the major
palaeognath lineages using 27 nuclear genes and 27 archaic retroposon
insertions. We show that rheas are sister to the kiwis, emu and
cassowaries, and confirm ratite paraphyly because tinamous are sister
to moas. Divergence dating using 10 genes with broader taxon sampling,
including emu, cassowary, ostrich, five kiwis, two rheas, three
tinamous, three extinct moas and 15 neognath lineages, suggests that
three vicariant events and possibly two dispersals are required to
explain their historical biogeography. The age of crown group birds
was estimated at 131 Ma (95% highest posterior density 122–138 Ma),
similar to previous molecular estimates. Problems associated with gene
tree discordance and incomplete lineage sorting in birds will require
much larger gene sets to increase species tree accuracy and improve
error in divergence times. The relatively rapid branching within
neoaves pre-dates the extinction of dinosaurs, suggesting that the
genesis of the radiation within this diverse clade of birds was not in
response to the Cretaceous–Paleogene extinction event.