Class Reptilia (reptiles) has had a famous history in terms of evolutionary change through time. Reptilia is home to lizards, crocodiles, snakes, turtles, and even dinosaurs! If dinosaurs weren’t exciting enough, researchers have recently been interested in the multiple instances of limb-loss among reptiles. The most notable taxonomic group within Reptilia to evolve leglessness are snakes. However, they are joined but several taxa of lizards, including glass lizards, blind skinks, and worm lizards, to also evolve the loss of limbs.
In this lesson, we will introduce the large themes of evolution by natural selection and convergent evolution by using limb loss in scaled lizards (order Squamata) as a case study. Students will be presented with scenarios differing in environmental conditions to see what selective pressures may result in evolving leglessness, based on the prevailing evolutionary hypotheses. Additionally, students will be presented with a simplified phylogenetic tree of squamates and asked to determine whether leglessness was evolved convergently or not. After the lesson, students will hopefully understand the selective pressures that brought about leglessness in scaled lizards and be able to determine the different legless lizard taxa evolved leglessness convergently or not.