Figure 100 from: Sereno P (2012) Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs. ZooKeys 226: 1-225. https://doi.org/10.3897/zookeys.226.2840

Figure 100 - . Bone and keratinous sheath in the upper bill of a parrot. Skull of the budgerigar Melopsittacus undulatus (UCRC R1) with keratinous sheath of upper bill A Lateral view B Magnified anterolateral view. Scale bar equals 1cm in B. Abbreviations: ab attachment platform for bill ama area of muscle attachment b bill sym symphysis.