. The Canadian field-naturalist. Natural history; Sciences naturelles. 2006 and Holmes: Sexual Dimoki'iiism in Chasmosaurine Ceratopsid 411 Ichrac clillcr in ihc lengths and orientations ol their spin- ous processes. However, analysis of additional Cluis- mosaums material - preferably derived from some yet undiscovered monodominant honebed (Eberth and CJelty 2005) - would be necessary to determine the significance of this variation with regards to sexual dimorphism. The results presented here are therefore only preliminary, pending further investigation of indi- vidual variation in th
. The Canadian field-naturalist. Natural history; Sciences naturelles. 2006 and Holmes: Sexual Dimoki'iiism in Chasmosaurine Ceratopsid 411 Ichrac clillcr in ihc lengths and orientations ol their spin- ous processes. However, analysis of additional Cluis- mosaums material - preferably derived from some yet undiscovered monodominant honebed (Eberth and CJelty 2005) - would be necessary to determine the significance of this variation with regards to sexual dimorphism. The results presented here are therefore only preliminary, pending further investigation of indi- vidual variation in the ceralopsian postcranial skeleton. Finally, previous detailed reviews of the frill mor- phology of either specimen seem to suggest that CMN 2245 and CMN 2280 may, in fact, belong to separate species (C belli and C russelli, respectively), as first put forth by Godfrey and Holmes (1995). This view is further supported by the stratigraphic segregation of the two specimens within the Dinosaur Park Formation of Alberta. Whether the postcranial differences iden- tified here represent interspecific distinctions remains to be demonstrated. Therefore, although there do seem to be a few legitimate differences between the two specimens, the weight of the evidence so far accumu- lated does not support sexual dimorphism as Stern- berg (1927) first suggested it, and there remains little choice but to reject this hypothesis. In the future, sex- ual dimorphism should be attributed to fossil species only when statistical significance and stratigraphic control have been demonstrated. Claims made in the absence of such evidence should be regarded with scepticism. Acknowledgments We would like to thank Gilles Danis, Margaret Feuerstack and Kieran Shepherd for offering access to specimens in their care. Philip Currie and Hans Larsson provided valuable resources and discussion. Andrew Farke, Michael Ryan, and two anonymous reviewers provided constructive criticism on earlier versions of this manus
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