2006/03/01 by Matthew K. Vickaryous, Brian K. Hall · 1 citation
Earth and Planetary Sciences · Environmental Science · Biochemistry, Genetics and Molecular Biology · #Paleontology and Evolutionary Biology #Ichthyology and Marine Biology #Developmental Biology and Gene Regulation #Amniote #Coracoid #Scapula #Biology #Extant taxon #Anatomy #Pectoral girdle #Evolutionary biology #Vertebrate #Genetics
paper · doi:10.1111/j.1469-7580.2006.00542.x
openalex publication_date 2006/03/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
As in monotreme mammals, the pectoral apparatus of basal (fossil) amniotes includes two coracoid elements, the procoracoid and metacoracoid. Among extant reptiles the metacoracoid has long been assumed lost; this notion is herein challenged. A comprehensive review of data from numerous sources, including the fossil record, experimental embryology, genetic manipulations and an analysis of morphology at the level cell condensations, supports the conclusion that the metacoracoid gives rise to the majority of the reptilian coracoid. By contrast, the reptilian procoracoid remains as a rudiment that is incorporated as a process of the (meta)coracoid and/or the glenoid region of the scapula early during development, prior to skeletogenesis. Application of this integrated approach corroborates and enhances previous work describing the evolution of the pectoral apparatus in mammals. A revised scenario of amniote coracoid evolution is presented emphasizing the importance of considering cell condensations when evaluating the homology of a skeletal complex.