Altriciality and the Evolution of Toe Orientation in Birds

摘要: Specialized morphologies of bird feet have evolvedseveraltimesindependentlyasdifferentgroupshave become zygodactyl, semi-zygodactyl, heterodactyl, pam- prodactyl or syndactyl. Birds also convergently evolved similar modes development, in a spectrum that goes from precocial to altricial. Using the new context pro- vided by recent molecular phylogenies, we compared evolution foot morphology and development among extant avian families. Variations arrangement toes with respect anisodactyl ancestral condition occurred only altricial groups. Those groups repre- sent four independent events super-altriciality many transformations toe arrangements (at least three one pamprodactyl group, several syndactyl). We pose delayed skeletal maturation due altriciality facilitates epigenetic influence embryonic muscular activity over developing toes, allowing for repeated evolu- tion innovations their morphology.