. The Canadian field-naturalist. Natural history; Sciences naturelles. <%. The Canadian Field-Naturalist ^AR 0^ 2008 Volume 120, Number 4 October-DecVA^^i^^^^ ^rv A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia) Jordan C. Mallon'-^ and Robert B. Holmes^-'* 'Department of Earth Sciences, Carleton University, Ottawa, Ontario KIS 5B6 Canada; e-mail: ^Research Division, Palaeobiology, Canadian Museum of Nature, Box 3443, Station D, Ottawa, Ontario KIP 6P4 Canada ^Current address: Faculty
. The Canadian field-naturalist. Natural history; Sciences naturelles. <%. The Canadian Field-Naturalist ^AR 0^ 2008 Volume 120, Number 4 October-DecVA^^i^^^^ ^rv A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia) Jordan C. Mallon'-^ and Robert B. Holmes^-'* 'Department of Earth Sciences, Carleton University, Ottawa, Ontario KIS 5B6 Canada; e-mail: ^Research Division, Palaeobiology, Canadian Museum of Nature, Box 3443, Station D, Ottawa, Ontario KIP 6P4 Canada ^Current address: Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive, Calgary, Alberta T2N 4Ni Canada; e-mail: "•Current address: Department of Biological Sciences, University of Alberta, CW 405 Biological Sciences Building, Edmonton, Alberta T6G 2E9 Canada; e-mail: holmes I Mallon, Jordan C, and Robert B. Holmes. 2006. A reevaluation of sexual dimorphism in the postcranium of the chasmosaurine ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia). Canadian Field-Naturalist 120(4): 403^12. The sexual dimorphism attributed to Chasmosaurus belli by Sternberg (1927) is revisited and reevaluated. A reexamination of the two specimens originally considered by Sternberg reveals that they are less complete than first suggested, with only a moderate amount of overiapping material between them. Only a few of the postcranial elements (humeri, sternal plates, and presacral vertebrae) show evidence of dimorphism, the significance of which is either doubtful or equivocal. Instead of repre- senting sexual dimorphs, it is likely that the two specimens belong to separate species, C. belli and C. russelli. as evidenced by their distinct frill morphologies and by their stratigraphic segregation within the Dinosaur Park Formation of Alberta. These findings emphasize the need to remain sceptical about claims advocating sexual dimorphism in the fossil record
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