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Abstract
Cricetid rodents have a very high reproductive capacity and usually a short life span, measured in months rather than years. Many of them are also non-gregarious, searching for new resources outside the confines of their present habitat. These features provide cricetid rodents with valuable attributes as agents of historical biology. We describe a new species of cricetid rodent, Paciculus walshi, an Oligocene cricetid rodent in North America; we characterise its enamel microstructure and dental features and review its relationship with other cricetid rodents globally, to place it within the framework of Oligocene historical biology.
Acknowledgements
This study is the initial part of a long range goal of Everett Lindsay and David Whistler to resolve systematic relationships of early evolution of cricetid rodents in North America. We are grateful to Tom Deméré and Kesler Randall of the San Diego Museum of Natural History for the opportunity to study these fossils, to Sam McLeod of the Natural History Museum of Los Angeles County, Jin Meng of the American Museum of Natural History, Josh Samuels and Chris Schierup of the John Day Fossil Beds National Monument, Pat Holroyd of the University of California Museum of Paleontology, Richard Corner of the University of Nebraska State Museum, Amy Henrici of the Carnegie Museum of Natural History, Mary Turner of Yale Peabody Museum, Richard Corner of the University of Nebraska State Museum, Desi Miao of the Kansas Museum of Natural History and Michael Brett-Surman of the Smithsonian Institution for loan of specimens they provided for use in this study. We also wish to thank the following individuals for insight regarding the fossil record and paleontology of small mammals in Asia: Li Chuan-Kuei, Qiu Zhu- Ding, Wang Ban-Yue, Tong Yong-Sheng, Olivier Maridet and Gudrun Daxner-Höck. For review of the manuscript we thank an anonymous reviewer plus excellent reviews by Tom Kelly and Bill Korth whose reviews helped to clarify many of our interpretations. This contribution is dedicated to Yukimitsu Tomida. Yuki is a Champion. Champions understand the tremendous desire, magnitude of hard work and multiple sacrifices that are required to become a winner. When Yuki was collecting fossils in 1984 for his dissertation on small mammal fossils from the Safford and Duncan Basins in Arizona he was driving to Tucson from Safford one evening, after several days of field work, with a load of sediment to screen wash for fossils. Unfortunately, Yuki fell asleep at the wheel, totalled his car and ended up in the hospital with a broken back and numerous bruises. The doctors thought that Yuki would be an invalid for the rest of his life, but also thought Yuki was lucky to have survived this terrible accident. The doctors, however, did not realise the drive, work ethic, and dedication of their patient. Yuki finished his dissertation, with flying colours, in 1985 and few people were aware of the extra stress this accident, in 1984, had placed on Yuki to finish his academic objective. Even now, few people remember Yuki's terrible accident as he has no visible sign of a serious debilitating accident. Yuki's recovery is exemplary of his dedication, work ethic and enthusiasm for his commitment to his profession; this is why we are happy to dedicate this manuscript to the enduring legacy of a trusted colleague, and a dedicated Champion scientist.: This study is the initial part of a long range goal of Everett Lindsay and David Whistler to resolve systematic relationships of early evolution of cricetid rodents in North America. We are grateful to Tom Demeré and Kesler Randall of the San Diego Museum of Natural History for the opportunity to study these fossils, to Sam McLeod of the Los Angeles Museum of Natural History, Jin Meng of the American Museum of Natural History, Josh Samuels and Chris Schierup of the John Day Fossil Beds National Monument, Pat Holroyd of the University of California Museum of Paleontology, Richard Corner of the University of Nebraska State Museum, Amy Henrici of the Carnegie Museum of Natural History, Mary Turner of Yale Peabody Museum, Richard Corner of the University of Nebraska State Museum, Desi Miao of the Kansas Museum of Natural History, and Michael Brett-Surman of the Smithsonian Institution for loan of specimens they provided for use in this study. We also wish to thank the following individuals for insight regarding the fossil record and paleontology of small mammals in Asia: Li Chuan-Kuei, Qiu Zhu- Ding, Wang Ban-Yue, Tong Yong-Sheng, Olivier Maridet and Gudrun Daxner-Höck. For review of the manuscript we thank Tom Kelly.
Disclosure statement
No potential conflict of interest was reported by the authors.