Figure 4.

Overview of terminology describing ossified structural elements of the songbird syrinx. Alternative nomenclatures of previous authors [16,18,19,28,43,52,72,73,106,123-129]. The system that we adopt in this study is a combination of terminologies proposed by Häcker [129], Chamberlain and colleagues [125], and Warner [126]. Note in particular the approach proposed by Ames [19], which emphasizes the microstructure of individual syringeal bones that make up the tympanum. Abbreviations as listed in Table 1.