Evolution of Trophic Systems in Squamates

From lizards to snakes, the trophic system of squamates exhibits at least six major modifications correlated with different feeding strategies. Beginning in lizards, these include 1) shift from tongue to jaws as the primary means of prey capture, accompanied by specialization of the tongue for chenloreception, and 2) increasing skull kineticism. These features continue into snakes along with 3) unilateral jaw displacement during swallowing accompanied by 4) increasing skull kineticism, 5) development of the cervical vertebrae into a lever system for launching the strike, 6) addition of sensory modalities (thermoreception) in some snakes, and in advanced snakes, 7) shift from mechanical to chemical means of predation. Many fundamental features elaborated into the highly kinematic and jaw-based feeding system of snakes actually appear first within lizards. However, the highly kinetic skull of snakes represents not so much an extrapolation of lizard kinesis, as it does a rebuilding, even redesign, of the skull to achieve its high level of kinesis.