LIMB REDUCTION IN SQUAMATES - IDENTIFICATION OF THE LINEAGES AND DISCUSSION OF THE TRENDS

An attempt is made to identify all squamate lineages having undergone limb reduction in the sense of having lost one or more bones from either the front or rear limb. The limb osteology of the ancestors of these limb reduced lineages is also inferred. On this basis squamates have undergone limb reduction at least 62 times in 53 lineages. Most reductions begin with the loss of a single phalange; however, some may begin with loss of all elements more distal than the mesopodials. Three different patterns of incipient loss occur in the front limb and two in the rear limb. These trends are discussed in the light of the "developmental constraint" and "adaptation" hypotheses.