A supertree of early tetrapods

Marcello Ruta, Jonathan E. Jeffery, Michael I. Coates

Abstract

A genus–level supertree for early tetrapods is built using a matrix representation of 50 source trees. The analysis of all combined trees delivers a long–stemmed topology in which most taxonomic groups are assigned to the tetrapod stem. A second analysis, which excludes source trees superseded by more comprehensive studies, supports a deep phylogenetic split between lissamphibian and amniote total groups. Instances of spurious groups are rare in both analyses. The results of the pruned second analysis are mostly comparable with those of a recent, character–based and large–scale phylogeny of Palaeozoic tetrapods. Outstanding areas of disagreement include the branching sequence of lepospondyls and the content of the amniote crown group, in particular the placement of diadectomorphs as stem diapsids. Supertrees are unsurpassed in their ability to summarize relationship patterns from multiple independent topologies. Therefore, they might be used as a simple test of the degree of corroboration of nodes in the contributory analyses. However, we urge caution in using them as a replacement for character–based cladograms and for inferring macroevolutionary patterns.