Figure 4. Comparison of the frontal bones of Wilsonium, Amyzon and Plesiomyxocyprinus. A, frontal of Wilsonium brevipinne from the Eocene Allenby Formation, Blakeburn Mine, British Columbia, Canada, UALVP 12610; B, frontal of Plesiomyxocyprinus arratiae from the Eocene Huadian Formation, Huadian, Jilin, China, IVPP V 15711.29 (images modified from Liu & Chang 2009, fig. 2a, b); C, frontal of Amyzon aggregatum from the Eocene of Horsefly, British Columbia, Canada, UALVP 32931. A, B, dorsal view; C, medial view. Anterior is to the top. Abbreviations: fpf, fronto-parietal fontanelle; obp, orbital process of frontal; on, orbital notch of frontal. Scale bars = 5 mm.