GATESY, J.E.: The Influence of Fossils on the Stability of Phylogenetic Relationships among Extant Taxa: A Preliminary Empirical Assessment in the Age of Genomics

The addition of extinct taxa into a phylogenetic analysis can have three consequences for the stability of relationships among extant taxa. The fossils can: 1) stabilize a grouping of extant taxa, 2) have no impact on a group�s stability, or 3) destabilize a grouping of extant taxa. If the fossils sufficiently destabilize relationships among extant taxa, a tree topology can be overturned by the paleontological evidence. Because fossils are generally very incomplete, in terms of total characters that can be sampled, some systematists have argued that fossils should rarely overturn phylogenies based on extant taxa only. This generalization might hold in the age of genomics where multiple genetic loci, thousands of informative characters, can be sequenced from extant taxa but not from extinct taxa. Here, I make a preliminary empirical assessment of the influence of fossils on tree stability for various subclades of Amniota (�reptiles,� mammals, and birds), and determine whether extinct taxa generally solidify character support for relationships among extant taxa.