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Basal sauropodomorph interrelationships

Ben Creisler

A new online paper:

Claire Peyre de Fabrègues & Ronan Allain and Véronique Barriel (2015)
Root causes of phylogenetic incongruence observed within basal
sauropodomorph interrelationships.
Zoological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/zoj.12290

The relationships among basal sauropodomorphs are controversial.
Results of cladistic analyses vary from a fully paraphyletic
assemblage to a monophyletic core-prosauropod. We apply the
comparative cladistics method to three published cladistic analyses of
sauropodomorph dinosaurs, in order to identify root causes for
differences between phylogenetic results. Except for three taxa
(Saturnalia, Thecodontosaurus, and Efraasia) and one clade
(Gravisauria), the remaining genera are recovered with conflicting
positions. The comparative method is based on indices that allow for
the quantification of the degree of similarity in characters and
character states among analyses. A comparison of primary data,
character selection, and scoring highlights significant discrepancies
in data sets. Our results suggest that one character out of two varies
from one analysis to the other. These are the root causes for the
phylogenetic incongruence observed. The hurdle of the phylogenetic
definition of the clade Sauropoda, which has been defined in four
different ways, is also treated. We concur with several recent papers
following the first node-based definition of Sauropoda.