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Statistical analysis of fossil ages supports a Cretaceous origin of placentals

Another rebuttal to the O'Leary et al. paper from last year (which was
extensively discussed on this list -- see

dos Reis M, Donoghue PCJ, Yang Z 2014 Neither phylogenomic nor
palaeontological data support a Palaeogene origin of placental
mammals. Biol Lett 10: 20131003

O'Leary et al. (O'Leary et al. 2013 Science 339, 662-667.
(doi:10.1126/science.1229237)) performed a fossil-only dating analysis
of mammals, concluding that the ancestor of placentals post-dated the
Cretaceous-Palaeogene boundary, contradicting previous
palaeontological and molecular studies that placed the ancestor in the
Cretaceous. They incorrectly used fossil ages as species divergence
times for crown groups, while in fact the former should merely form
minimum-age bounds for the latter. Statistical analyses of the fossil
record have shown that crown groups are significantly older than the
oldest ingroup fossil, so that fossils do not directly reflect the
true ages of clades. Here, we analyse a 20 million nucleotide
genome-scale alignment in conjunction with a probabilistic
interpretation of the fossil ages from O'Leary et al. Our combined
analysis of fossils and molecules demonstrates that Placentalia
originated in the Cretaceous.

David Černý