Journal of Mammalian Evolution

, Volume 26, Issue 4, pp 447–478 | Cite as

Reigitherium (Meridiolestida, Mesungulatoidea) an Enigmatic Late Cretaceous Mammal from Patagonia, Argentina: Morphology, Affinities, and Dental Evolution

  • Tony Harper
  • Ana Parras
  • Guillermo W. RougierEmail author
Original Paper


New dental and dentary fossils collected in the Upper Cretaceous La Colonia Formation in central Patagonia provide new evidence on the morphology, feeding ecology, and relationships of the enigmatic mammal Reigitherium. The newly discovered specimens described here include elements of the upper dentition and several partial dentaries, elucidating fundamental questions of serial homology and postcanine dental formula (four premolars and three molars). This new evidence supports a nested position of Reigitherium within the advanced meridiolestidan clade Mesungulatoidea. Apomorphic features of the upper and lower molariform elements include intense enamel crenulation circumscribed within the primary trigon and trigonid, elevated cingulids, and the neomorphic appearance of cusps/cuspulids, all of which increase overall crown complexity. A Dental Topography Analysis comparing Reigitherium and its sister taxon Peligrotherium to Cretaceous and Cenozoic therians demonstrates functional similarity between the mesungulatoids and South American marsupial taxa that succeed them in the small-to medium-sized herbivore niche during the Paleocene. Previous taxonomic attributions of Reigitherium are discussed and comparisons with other meridiolestidans highlight the remarkable radiation of this group in the Cretaceous of South America.


Reigitherium Meridiolestida Dental complexity Mesozoic Mammalia 



We would like to thank Dr. Rubén Cúneo, Leandro Canessa, and other personnel of the Museo Paleontológico Egidio Feruglio, Chubut, Argentina for years of support. We are additionally grateful to David Archibald and Ken Rose for their deep insight into mammalian evolution and access to the therian comparative specimens used here, and Patrick Luckett for helpful comments on dental homology and proofreading early drafts of the manuscript. Tim Phelps and the other faculty at Johns Hopkins University Department of Art as Applied to Medicine provided expert input and guidance to TH in the production of illustrations, and Justin Gladman and Doug Boyer at Duke University’s Shared Materials and Instrumentation Facility (SMIF) graciously contributed access and assistance with the high quality imaging required for the description of small enigmatic mammalian fossils, for which we are also very grateful. We would also like to thank Dr. Alejandro Karmarz for access to the collections of Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina, and intellectual and material support through the years. Finally, we thank Rosío B. Vera for her diligent assistance in picking through La Colonia sediments. This research was supported by NSF via the DEB 0946430 and DEB 1068089 grants (to GWR), USA, and by the RAICES program (PICT-2016-3682), Agencia de Investigación Cientifica, CONICET, Argentina.

Supplementary material

10914_2018_9437_MOESM1_ESM.pdf (49 kb)
Online Resource 1 Tables listing new La Colonia specimens described in text, and the therian comparative sample used in the reported Dental Topography Analysis (DTA) (PDF 48 kb)
10914_2018_9437_MOESM2_ESM.nex (7 kb)
Online Resource 2 Character matrix used in Maximum Parsimony and Bayesian analyses described in text (NEX 6 kb)


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Authors and Affiliations

  • Tony Harper
    • 1
  • Ana Parras
    • 2
  • Guillermo W. Rougier
    • 3
    Email author
  1. 1.Center for Functional Anatomy and EvolutionJohns Hopkins UniversityBaltimoreUSA
  2. 2.INCITAP (CONICET-UNLPam), Facultad de Ciencias Exactas y NaturalesUniversidad Nacional de La PampaSanta RosaArgentina
  3. 3.Department of Anatomical Sciences and NeurobiologyUniversity of LouisvilleLouisvilleUSA

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