2015/05/14 by João Francisco Botelho, Daniel Smith‐Paredes, Sergio Soto‐Acuña +3 · 3 citations
Earth and Planetary Sciences · Environmental Science · #Paleontology and Evolutionary Biology #Turtle Biology and Conservation #Avian ecology and behavior
paper · pdf · doi:10.1038/srep09840
openalex publication_date 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
Most birds have an opposable digit 1 (hallux) allowing the foot to grasp, which evolved from the non-opposable hallux of early theropod dinosaurs. An important morphological difference with early theropods is the twisting of the long axis of its metatarsal. Here, we show how embryonic musculature and the onset of its activity are required for twisting of metatarsal 1 (Mt1) and retroversion of the hallux. Pharmacologically paralyzed embryos do not fully retrovert the hallux and have a straight Mt1 shaft, phenocopying the morphology of early tetanuran dinosaurs. Molecular markers of cartilage maturation and ossification show that differentiation of Mt1 is significantly delayed compared to Mt2-4. We hypothesize on how delayed maturation may have increased plasticity, facilitating muscular twisting. Our experimental results emphasize the importance of embryonic muscular activity in the evolutionary origin of a crucial adaptation.