Uncertainty in the age of fossils and the stratigraphic fit to phylogenies

POL, D.; NORELL, M.A.

SYSTEMATIC BIOLOGY

Taylor and Francis Co., Ltd.

Lugar: Lawrence; Año: 2006 vol. 55 p. 512 - 521

1063-5157

Several measures have been proposed for measuring the fit between stratigraphic information and phylogenetic trees that including fossil taxa. In empirical analyses of stratigraphic fit to phylogenies, the uncertainty in the age of fossil terminal taxa is not currently considered. Usually, the age of appearance of fossil taxa is taken as the midpoint of the chronostratigraphic temporal range to which the sediments are referred. Such an approach can produce misleading results since the age difference of two fossil taxa is always disregarded if they are referred to the same chronostratigraphic unit, but counted if they belong to different units. Although this may seem desirable, if two fossil taxa lived during the same chronostratigraphic unit, in absence of further evidence, their real age difference could be as large as the temporal length of the chronostratigraphic unit or as small as zero. In contrast, if two fossil taxa lived during two contiguous chronostratigraphic units, in absence of further evidence, their real age difference could be as large as the temporal length of both chronostratigraphic units or could approach zero.The problem of age uncertainty in stratigraphic fit measures is explored here and a possible solution that incorporates uncertainties in age assignment for fossil taxa is proposed for the calculation of the GER and MSM*.