Figure 1
From: Unusual pectoral apparatus in a predatory dinosaur resolves avian wishbone homology
The alternative hypotheses on the homology of the avian furcula. Comparison between the pectoral apparatus of non-avian reptiles (left) and birds (right). The furcula has been alternatively considered homologous to the clavicles (a–d), the interclavicle (e–h), or as a compound bone including elements from both the clavicles and the interclavicle (i–l). Generalized pectoral apparatus in a non-avian reptile in ventral view (a,e,i) and in left anterolateral view (b,f,j); in the middle, list of the evolutionary changes inferred along the avian stem lineage following the selected hypothesis; generalized pectoral apparatus in a bird (scapula omitted for clarity) in ventral view (c,g,k) and in left lateral view (d,h,l). cl clavicle, co coracoid, fu furcula, ic interclavicle, lr lateral ramus of interclavicle, pr parasternal ramus of interclavicle, sc scapula, st sternum. Drawing by AC.
