A New Species of Agriotherium from North America, and Implications for Understanding Transformations in the Metaconid-En
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ORIGINAL PAPER
A New Species of Agriotherium from North America, and Implications for Understanding Transformations in the Metaconid-Entoconid Complex of Bears Qigao Jiangzuo 1,2,3,4
&
John J. Flynn 4
# Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract New material of Agriotherium from the late Hemphillian (~6 Ma) Quiburis Formation in Arizona, North America is reported. These specimens represent a new species, Agriotherium hendeyi, sp. nov., of small size and with a bucco-lingually narrow lower dentition distinguishing it from North American “Agriotherium” schneideri as well as the genotype and other Old World species of Agriotherium. Strikingly, the m1 metaconid-entoconid complex of the new species exhibits a morphologically transitional state between the pattern observed in Indarctos (three cusps) and the typical Agriotherium pattern (two cusps). Together with a review of the variation in A. africanum, a geometric morphometric analysis permits identification and discussion of a proposed transformation pathway from the Indarctos pattern to the Agriotherium pattern. It is shown that the two cusps in the metaconidentoconid complex in Agriotherium correspond to the two entoconids in Indarctos, whereas the ancestral metaconid is reduced or lost in Agriotherium. From a developmental perspective, the metaconid fused to the anterior entoconid as a result of the shortening of the talonid, rather than via replacement of the metaconid by a posterior shift of the entoconid, presumably under selective pressure towards a more typically hypercarnivorous tooth morphology and carnivorous diet. Keywords Agriotherium . Indarctos . Ursidae . Miocene . Hemphillian NALMA . Quiburis Formation . Metaconid-entoconid complex
Abbreviations AMNH American Museum of Natural History, New York, USA AMNH F AM Frick collection (Fossil Mammals), Division of Paleontology, AMNH, USA AMNH M Mammalogy (Vertebrate Zoology) collections, AMNH, USA
IVPP
* Qigao Jiangzuo [email protected]
Hh4 MN
1
Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China
2
CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
4
Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA
L P/p M/m Hh3
Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China Specimens housed in Iziko South African Museum, Cape Town, South Africa upper/lower premolar upper/lower molar Hemphillian3, late Hemphillian North American Land Mammal Age (NALMA) Hemphillian4, latest Hemphillian NALMA Neogene land Mammal Zones of Europe
Introduction The large-sized, geographically widespread, MiocenePleistocene bear Agriotherium and its Miocene relative Indarctos have been known for more than a century. Agriotherium was first established by Wagner (18
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