Matching phylogenies to stratigraphy

[Guy Leahy <xrciseguy@sbcglobal.net>]

Syst Biol. 2006 Jun;55(3):512-21.   
Uncertainty in the age of fossils and the
stratigraphic fit to phylogenies.

Pol D, Norell MA. 
CONICET, Museo Paleontologico Egidio Feruglio, Av.
Fontana 140, Trelew 9100, Chubut, Argentina.
dpol@mef.org.ar

The ages of first appearance of fossil taxa in the
stratigraphic record are inherently associated to an
interval of error or uncertainty, rather than being
precise point estimates. Contrasting this temporal
information with topologies of phylogenetic
relationships is relevant to many aspects of
evolutionary studies. Several indices have been
proposed to compare the ages of first appearance of
fossil taxa and phylogenies. For computing most of
these indices, the ages of first appearance of fossil
taxa are currently used as point estimates, ignoring
their associated errors or uncertainties. The effect
of age uncertainty on measures of stratigraphic fit to
phylogenies is explored here for two indices based on
the extension of ghost lineages (MSM* and GER). A
solution based on randomization of the ages of
terminal taxa is implemented, resulting in a range of
possible values for measures of stratigraphic fit to
phylogenies, rather than in a precise but arbitrary
stratigraphic fit value. Sample cases show that
ignoring the age uncertainty of fossil taxa can
produce misleading results when comparing the
stratigraphic fit of competing phylogenetic
hypotheses. Empirical test cases of alternative
phylogenies of two dinosaur groups are analyzed
through the randomization procedure proposed here.