Citation: Ed. Grogan et R. Lund, Debeerius ellefseni (fam. nov., gen. nov., spec. nov.), an autodiastylic chondrichthyan from the Mississippian Bear Gulch Limestone of Montana (USA),the relationships of the chondrichthyes, and comments on gnathostome evolution, J MORPH, 243(3), 2000, pp. 219-245