INCLUDING GONDWANIC ANKYLLOPOEXIAN DINOSAURS IN THE PHYLOGENY, A NECESSARY STEP FOR UNDERSTANDING THEIR PALEOBIOGEOGRAPHY

GUILLERMO SALINAS; RUBÉN JUÁREZ VALIERI; LUCAS FIORELLI; JORGE CALVO

Trelew

Jornada; XXIII Jornadas Argentinas de Paleontología de Vertebrados; 2007

Museo Paleontológico Egidio Feruglio

A common problem with global paleobiogeographic models of ankylopollexian ornithopods (a node-based taxon defined by Camptosaurus + Parasaurolophus) is the use of phylogenies lacking global sampling, because they include just one or two Gondwanan taxa. Our working group is carrying on the simultaneous study of several Argentinean forms, traditionally considered hadrosaurs. In this work a new phylogenetic analysis of Ankylopollexia is presented. The results are novel due to the inclusion of a great quantity of characters (247) and taxa (35). Five of these are Gondwananic and are the focus of the present research. The strict consensus tree highlights the following points: Lurdusaurus and Lanzhousaurus are found as basal taxa within Styracosterna (all taxa closer to Parasaurolophus, but than Camptosaurus), and outside of the node-based taxon Hadrosauriformes (node defined by Iguanodon + Parasaurolophus). Ouranosaurus is recognized as a basal Hadrosauroidea. Secernosaurus, in turn, occupies an unnamed polytomyc with Eolambia, Protohadros and more derived hadrosaurs (Bactrosaurus + Parasaurolophus). Lastly, the node-based taxon Hadrosauridae (Telmatosaurus + Parasaurolophus) is formed by «Claosaurus + (Telmatosaurus + the Salitral Moreno "Lambeosaurinae") + ("Kritosaurus" australis + Euhadrosauria)). This basal dichotomy is novel, and it outlines important paleobiogeographic implications. The Gondwanan forms present a topology of successive sister taxa with respect to derived hadrosaurs; therefore, it produces either multiple dispersal events or a widespread biogeographic distribution for Styracosterna through the Cretaceous. Euhadrosauria is not found in Gondwana, in contrast to the traditional dispersion model showing that South American hadrosaurs arrived from North America during the Campanian.