A new euharamiyidan, Mirusodens caii (Mammalia: Euharamiyida), from the Jurassic Yanliao Biota and evolution of allotherian mammals Author Mao, Fangyuan Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China & Division of Paleontology, American Museum of Natural History, New York, New York 10024, USA maofangyuan@ivpp.ac.cn Author Li, Zhiheng Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China Author Hooker, Jerry J. Department of Palaeontology, The Natural History Museum, Cromwell Road, London, SW 7 5 BD, United Kingdom Author Meng, Jin Division of Paleontology, American Museum of Natural History, New York, New York 10024, USA & Earth and Environmental Sciences, Graduate Centre, City University of New York, New York, 10016, USA maofangyuan@ivpp.ac.cn text Zoological Journal of the Linnean Society 2023 2023-07-11 199 3 832 859 http://dx.doi.org/10.1093/zoolinnean/zlad050 journal article 10.1093/zoolinnean/zlad050 0024-4082 DDA87133-FF28-41F5-A96B-CDA6A0E74AC5 Genus Mirusodens gen. nov. Type species: Mirusodens caii gen. et sp. nov. Etymology: Mirus , Latin, amazing, remarkable; dens , tooth; in reference to the remarkable tooth morphology of the new genus. Diagnosis: Dental formula I1-C0-P3-M2/i1-c0-p1-m2 (upper/ lower incisor, canine, premolar, and molar); differ from other ‘haramiyidans’ in having the following features: the upper incisor considerably larger than molars and having complex and multiple cusps; three upper premolars identified as P2–P4; P4 having complex roots and a heart-shaped crown with numerous cusps that are regularly arranged in curved rows and decrease in size from outer row toward the basin centre; lower ultimate premolar (p4) twice the length of lower molars and having no distal cusp or heel but having serrations along the mesial half of the crown; upper molars with initial cusp Ax and row Ax; lower molars with cusp b1 that projects mesially from the mesiobuccal base of a1. Remarks: The new genus is dentally distinctive from other ‘haramiyidans’ and other mammaliaforms so that there seems no need to present a differential diagnosis for establishment of the new species. In the description of the dentition, we have a comparison for each set of teeth, which furnishes additional information for species differentiation.