Journal of Mammalian Evolution

, Volume 17, Issue 1, pp 21–59 | Cite as

New Observations on the Skull of Pyrotherium (Pyrotheria, Mammalia) and New Phylogenetic Hypotheses on South American Ungulates

  • Guillaume BilletEmail author
Original Paper


The Cenozoic South American endemic pyrotheres, mostly characterized by a bilophodont dentition, are one of the most mysterious ungulates ever known. Even though many specialists have investigated this group, the fascinating question of its origin is still unresolved after more than a century of study. This paper provides a new description of the only known pyrothere skull, that of Pyrotherium from the Deseadan of Patagonia. Detailed comparison of the cranial anatomy indicates strong similarities with the Notoungulata, especially in the auditory region, as already mentioned by some authors. Intriguing similarities are also detected in the anterior dentition of Pyrotherium and the Casamayoran notoungulate Notostylops. These resemblances suggest a unique relationship between Pyrotheria and Notoungulata, specifically between Pyrotheria and Notostylops. These hypotheses are tested through a series of phylogenetic analyses of South American ungulate craniodental anatomy, primarily focusing on Notoungulata and Pyrotheria. These phylogenetic analyses are the first to encompass such a diversity of South American ungulate taxa. When including the bunodont taxon Proticia usually attributed to the Pyrotheria, the strict consensus of the analysis does not present much resolution. When excluding it, the analysis supports the nesting of the pyrotheres within the Notoungulata via an exclusive relationship with Notostylops. This relationship is supported by both cranial and dental anatomy. The analysis also supports the position of Astrapotheria as the sister group of the Notoungulata. It does not support, however, the monophyly of the Litopterna. The clustering of Pyrotheria, Notoungulata, and Astrapotheria supports an isolated evolutionary history of these ungulates in South America similar to that of afrotherian mammals in Africa. These results give rise to new perspectives in research on South American endemic ungulate evolution.


Meridiungulata Notoungulata Phylogeny Anatomy Notostylops 



I am indebted to the following institutions and individuals for access to the specimens that form part of this study and for interesting discussions on notoungulates: Museo Argentino de Ciencias Naturales “Bernadino Rivadavia”, Buenos Aires, Argentina (MACN), Alejandro Kramarz; the Museo de La Plata, La Plata, Argentina (MLP), Marcelo Reguero and Mariano Bond; American Museum of Natural History, New York, US, Judith Galkin and Christopher Norris; Field Museum of Natural History, Chicago, Illinois, US, William Simpson; and Amherst College Museum, Amherst, Massachussets, US, Kate Wellspring. I am especially grateful to Kate Wellspring and ACM staff for kindly facilitating my access to the cumbersome skull of Pyrotherium. I warmly thank Jérémy Anquetin (Université de Rouen, France) for his friendly and invaluable practical help on the phylogenetic analysis and for helpful discussions and advices on the paper. I would also like to thank Jonathan Geisler (Georgia Southern University, US) for helpful discussions on the use of PAUP 4. Thanks are also due to Maëva Orliac (Université de Montpellier II, France), Rodolfo Salas (Museo de Historia Natural, Lima, Peru), Darin A. Croft (Case School of Medicine, Cleveland), Richard L. Cifelli (Oklahoma Museum), Pierre-Olivier Antoine (Université de Toulouse III, France), and Pascal Tassy and Christian de Muizon (Muséum national d’Histoire naturelle, Paris, France) for invaluable comments and discussions on systematics and pyrotheres. I thank also Manuel Martinez and Floréal Solé (Muséum national d’Histoire naturelle, Paris, France) for their friendly and efficient help when searching for articles and photos of specimens. I would also like to thank Javier Gelfo (MLP), John R. Wible (Carnegie Museum) and an anonymous reviewer for their very helpful comments and corrections.


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© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.UMR 5143 (MNHN, CNRS, UPMC), Département histoire de la Terre (CP 38)Muséum national d’Histoire naturelleParisFrance
  2. 2.IPHEP, CNRS UMR 6046, Faculté des Sciences Fondamentales et AppliquéesUniversité de PoitiersPoitiers CedexFrance

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