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ABSTRACT
An unusual fork-tailed coelacanth from the Lower Triassic Sulphur Mountain Formation of British Columbia, Canada, marks the first considerable departure in actinistian body form since the Mississippian Period. Rebellatrix divaricerca, gen. et sp. nov., is unique among coelacanths in its possession of a bifurcated caudal fin, reduced segmentation of fin rays, and fusion of caudal fin elements. Parsimony analysis of a character-taxon matrix of 109 characters and 29 taxa recovered R. divaricerca as sister taxon to Latimerioidei. The family Rebellatricidae is erected to include only R. divaricerca. This novel body shape of the new coelacanth raises questions about the idea that coelacanths were morphologically static following the Mississippian. Rebellatrix divaricerca also emphasizes the morphological diversity of coelacanths during the Early Triassic, a time when species diversity of coelacanths was also highest. The slender, fork-tailed body form suggests fast swimming and an active lifestyle, unique among known fossil and extant coelacanths.
ACKNOWLEDGMENTS
First and foremost, we would like to thank L. Buckley and R. McCrea of the PRPRC who provided the majority of the material for this study and who have made it their goal to preserve British Columbia's natural history. We would also like to thank the Byren, Helm, and Walkley families for their contributions to this paper in finding the holotype on an expedition with the PRPRC. We also thank B. Strilisky, D. Brinkman, M. Newbrey, and A. Neuman for discussions and access to TMP collections. Many thanks are owed to A. M. Murray for use of her microscopy array and A. Lindoe for preparation advice and instruction. We thank M. Skrepnick for his artwork that brought Rebellatrix back to life. Finally, we would like to thank S. McKenzie, M. Mehle, R. Holmes, M. Friedman, G. Clément, and one anonymous reviewer for the helpful critiques and suggestions that greatly improved the manuscript. This research was supported by a University of Alberta teaching assistantship as well as NSERC Discovery Grant A9180 to M.V.H.W.
Handling editor: Matt Friedmann.