Making a parrot zygodactyl foot: osteology and morphogenesis of the tarsometatarsus in the monk parakeet (Myiopsitta monachus)

CARRIL J,; BARBEITO CG; TAMBUSSI C

ZOOLOGY

ELSEVIER GMBH

Año: 2021

0944-2006

The tarsometatarsus conformation and foot types in birds are unique traits withinvertebrates. We investigate how the tarsometatarsus and the zygodactyl foot areformed during development in the monk parakeet (Myiopsitta monachus). Using bones,whole mount specimens stained for cartilage and bone, and histological sections, wefocus on the osteology and morphogenesis of the tarsometatarsus. We also comparethe tarsometatarsus development between the altricial monk parakeet and theprecocial chicken. The results and conclusions we reached are: (1) the hypotarsus, acharacter of phylogenetic significance, is monocanaliculate in the adult; (2) digit Iretroversion is consequence of the displacement of the articulation site of themetatarsal 1 and its torsion; (3) digit IV retroversion is linked to the development of thetrochlea accesoria; (4) in ovo, the ossification and fusion of the metatarsals begin in themiddle of the shaft and extend cylindrically; and (5) the differences in the developmentof the tarsometatarsus between the monk parakeet and the chicken evidenceheterochronies, probably related with their different types of development.