Meeting Abstract
Iguanomorpha is a speciose clade including chameleons, agamas, basilisks, anoles, and iguanas, among others. The iguanomorph fossil record includes some extinct clades (e.g., Gobiguania and Priscagamidae) and numerous other fossil species. Inclusion of fossil iguanomorphs has been conspicuously spotty in recent morphological and combined-evidence analyses. The possible iguanian Bharatagama (Triassic) is absent from published analyses despite being the only putative pre-Cretaceous (K) iguanian. A recent morphological study suggested that Gobiguania is non-holophyletic, but failed to include the anchor taxon for that clade—one of only five well-preserved taxa used to establish it. I sought to test the phylogenetic relationships of Iguanomorpha by including those fossils mentioned above and others critical for reconstructing ancestral morphologies (e.g., Afairiguana, Lapitiguana, Geiseltaliellus). Using my own iguanomorph data matrix (169 species and 1318 morphological characters) as a starting point, I mimicked taxon and character samplings of earlier studies. These analyses recovered topologies similar to the ones recovered in the studies they mimicked. By contrast, analyses of my full data set recover a holophyletic Gobiguania, Isodontosaurus (K) as the basalmost member of the agama-chameleon clade, and find Arretosaurus (Eocene) to be the sister taxon to Priscagama (K). Priscagamidae and Gobiguania are basal (non-iguanian) iguanomorph clades. Bharatagama is united with Pleurosaurus (Rhynchocephalia) based on the presence of a robust dentary coronoid process and procumbent anterior dentition; it is not an iguanian. These relationships persist when published molecular data were used to perform a combined evidence analysis. In addition to offering a novel phylogenetic hypothesis, these findings further emphasize the importance of historical data offered by fossils in any phylogenetic study, even one based on combined morphological and molecular data.
