Guaibasaurus candelariensis (Dinosauria, Saurischia) and the early origin of avian-like resting posture

Abstract

Agnolin, F. & Martinelli, A.G., June 2012. Guaibasaurus candelariensis (Dinosauria, Saurischia) and the early origin of avian-like resting posture. Alcheringa 36, 263–267. ISSN 0311-5518.

A specimen of the basal saurisquian Guaibasaurus candelariensis Bonaparte, Ferigolo and Ribeiro (UFRGS-PV-0725-T) from the Faxinal do Soturno locality, Rio Grande do Sul State, Brazil (Caturrita Formation; Late Triassic) lacks any sign of post-mortem transport and burial deformation, and exhibits features (flexed forelimbs, folded hindlimbs under the body and curved neck) that indicate a typical avian-like resting position. The presence in Guaibasaurus of an avian-like resting posture and related physiological implications would extend this unique trait, previously considered restricted to derived maniraptoran theropods, to the base of the Theropoda (or even Saurischia) clade.

Federico Agnolin [[email protected]], Fundación de Historia Natural ‘Félix de Azara’. Departamento de Ciencias Naturales y Antropología, CEBBAD—Universidad Maimónides. Valentín Virasoro 732 (C1405BDB), Buenos Aires, Argentina, and Sección Paleontología de Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Ángel Gallardo 470 (C1405BDB), Buenos Aires, Argentina. Agustín G. Martinelli, Centro Paleontologico de Pesquisas Llewellyn Ivor Price, Museu dos Dinossauros, CCCP-UFTM, BR-262, km 784, Peirópolis, Uberaba, Minas Gerais, Brazil.

Key words:

• Guaibasaurus
• basal Dinosauria
• avian-like resting posture
• homeothermy
• Triassic
• Brazil

Acknowledgements

We thank C. L. Schultz and M. B. Soares (UFRGS) for access to collections under their care. We thank three anonymous reviewers and the Editor S. McLoughlin for comments that improved the manuscript.