The origin of tetrapods from their fish antecedents , approximately 400 million years ago , was coupled with the origin of terrestrial locomotion and the evolution of supporting limbs .
Polypterus is a member of the basal-most group of ray-finned fish (actinopterygians) and has many plesiomorphic morphologies that are comparable to elpistostegid fishes , which are stem tetrapods .
Polypterus therefore serves as an extant analogue of stem tetrapods , allowing us to examine how developmental plasticity affects the ‘terrestrialization’ of fish .
We measured the developmental plasticity of anatomical and biomechanical responses in Polypterus reared on land .
Here we show the remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods , and we provide insight into stem tetrapod behavioural evolution .
Our results raise the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapods .