Osteology and phylogeny of a new species of Araripesuchus (Crocodyliformes: Mesoeucrocodylia) from the Late Cretaceous
of Madagascar

Abstract

A new species of Araripesuchus present in the Maevarano Formation of Madagascar is described. The taxon is known from at least five individuals, including a nearly complete animal, three partial skulls and associated post-cranial remains, as well as disarticulated post-cranial elements. This large sample, coupled with CT-scans, allows a detailed description of its morphology. The new form shares a number of derived characters with Araripesuchus gomesii and Araripesuchus patagonicus, but is distinguished from them by the presence of four autapomorphies. Additionally, the new form lacks a number of derived features present in A. gomesii and A. patagonicus.

Phylogenetic relationships of Araripesuchus are evaluated using a parsimony analysis including 29 mesoeucrocodylian taxa. In all of the most parsimonious trees the new taxon is recovered as sister group to A. gomesii+A. patagonicus. Araripesuchus is diagnosed by five unambiguous synapomorphies and forms a clade with the Malagasy crocodyliform Mahajangasuchus insignis and peirosaurids. This group is depicted as more closely related to neosuchians than to notosuchians. When Araripesuchus wegeneri is included in the analysis, it is recovered as a member of the Araripesuchus clade. Although, its position in the clade is unresolved and character support is weak, this finding supports A. wegeneri as a valid species of Araripesuchus.

Keywords:

• Crocodyliformes
• osteology
• Araripesuchus
• Late Cretaceous
• Madagascar
• Maevarano formation

Acknowledgements

This work could not have been accomplished without the help of numerous individuals. To them, I am deeply indebted. As this work represents a large part of my Masters thesis, foremost among these people is my supervisor, Christopher Brochu. I am also grateful to the other members of my committee—Jonathan Adrain and Greg Buckley.

For access to collections and various undescribed material, I am indebted to and would like to thank Jorge Calvo and L. Salgado (Museo de Geología y Paleontología de la Universidad Nacional del Comahue); Mark Norell, Diego Pol and John Maisey (American Museum of Natural History); Fernando Novas, Sebastian Apesteguía and Alejandro Kramarz (Museo Argentino de Ciencias Naturales, Buenos Aires); F. L. de Broin (MNHN) W. Simpson and A. Resetar (Field Museum); and Paul Sereno (University of Chicago).

With apologies to those inadvertently left from this list, I am grateful for conversations, correspondence, and/or general assistance from James Clark, Diego Pol, Mark Norell, David Krause, Matt Carrano, Scott Sampson, Paul Upchurch, Cathy Forster, Chris Bell, Pete Makovicky, Jorge Calvo, Sebastian Apesteguia, John Callery, Paul Sereno, Jessica Maisano, Rich Ketchem, Matt Colbert, Carl Brett, Glenn Storrs, Colin Sumrall, Lindsay James, Nathan Smith and numerous individuals from the University of Iowa Paleontology and Systematics Discussion Group. Carrie Leonard took the vast majority of the photographs used within, while Mick Ellison filled in for a number of my oversights. Luci Betti Nash skillfully illustrated the reconstruction of the skull and Carolyn McKee-Freese graciously provided the life reconstruction. Gareth Dyke and two anonymous reviewers provided helpful comments. Any mistakes or errors remain my own.

Financial support for this research was provided by the Evolving Earth Foundation, The Paleontological Society, University of Iowa Student Government, and the University of Iowa Department of Geoscience Littlefield Fund.