FIGURE 2.

The relationship between the endocast structures and the brain regions. The brain section images have been scaled up relative to the scale bar according to the specimen's calculated shrinkage value. (a) A thionin‐stained axial section of the brain of a ruffed grouse (Bonasa umbellus, RUGR 344) sectioned by A. Iwaniuk's laboratory. The hyperpallium is outlined in red on the left hemisphere. (b) A lateral view of the endocast of a ruffed grouse (AMNH Birds SKEL 21616) showing the location of the Wulst and optic lobe. The position along the brain's rostrocaudal axis from which the slices shown in (a) and (c) would have been extracted are indicated by a dotted line with the appropriate letter. (c) A thionin‐stained axial section of the brain of a ruffed grouse sectioned by A. Iwaniuk's laboratory. The optic tectum is outlined in red on the left side. Abbreviations: H, hyperpallium; OL, optic lobe; OT, optic tectum; W, Wulst. Scale bar = 5 mm