A new specimen of Guaibasaurus candelariensis (basal Saurischia) from the Late Triassic Caturrita Formation of southern Brazil

Abstract

The comparison of the anatomy of a second incomplete skeleton of Guaibasaurus candelariensis to that of basal Saurischia suggests that the origin of the “Prosauropoda” was from unknown basal saurischians, after separating from theropods (except herrerasaurids). Guaibasaurus and Saturnalia are part of this early dichotomy, and they bear mixed characters-states of basal theropods and “prosauropods” type. The Late Triassic age of both Guaibasaurus and Saturnalia (the latter is older) predates the ‘dominance’ of basal sauropodomorphs as well as the appearance of the basal theropod Zupaysaurus, both recorded from the upper Los Colorados Formation of Argentina.

Keywords:

• Guaibasaurus
• basal Saurischia
• Caturrita Formation
• Late Triassic
• Brazil

Acknowledgements

We acknowledge the National Geographic Society for financial support to the 2002 palaeontological field work in the Late Triassic localities in southern Brazil, to the Instituto de Geociências, Universidade Federal de Rio Grande do Sul (Brazil) and Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (Argentina), for facilities to develop this research; to Dr. F. Novas for critical reading of a previous manuscript; and to the reviewer Drs. K. Padian and M. Langer for idiomatic and conceptual critics which improved the manuscript.