Figureȱ 4.ȱ Graphȱ plottingȱ skullȱ max.ȱ widthȱ againstȱ skullȱ totalȱ lengthȱ withoutȱ rhamphothecaȱ forȱ Imperialȱ Woodpecker Campephilus imperialis and Ivory-billed Woodpecker C. principalis, using data from Table 1. in The conundrum of an overlooked skeleton referable to Imperial Woodpecker Campephilus imperialis in the collection of the Natural History Museum at Tring

Figureȱ 4.ȱ Graphȱ plottingȱ skullȱ max.ȱ widthȱ againstȱ skullȱ totalȱ lengthȱ withoutȱ rhamphothecaȱ forȱ Imperialȱ Woodpecker Campephilus imperialis and Ivory-billed Woodpecker C. principalis, using data from Table 1.图4。基于表1所载数据，以无喙鞘头骨总长度为横坐标、头骨最大宽度为纵坐标，绘制帝啄木鸟（Campephilus imperialis）与象牙嘴啄木鸟（C. principalis）的关系图。