Locomotion and paleoclimate explain the re-evolution of quadrupedal body form in Brachymeles lizards

Evolutionary reversals, including re-evolution of lost structures, are
commonly found in phylogenetic studies. However, we lack an understanding
of how these reversals happen mechanistically. A snake-like body form has
evolved many times in vertebrates, and occasionally, a quadrupedal form
has re-evolved, including in Brachymeles lizards. We use body form and
locomotion data for species ranging from snake-like to quadrupedal to
address how a quadrupedal form could re-evolve. We show that large,
quadrupedal species are faster at burying and surface locomotion than
snake-like species, indicating a lack of expected performance trade-off.
Species with limbs use them while burying, suggesting that limbs are
useful for burying in wet, packed substrates. Paleoclimatological data
suggest that Brachymeles originally evolved a snake-like form under a
drier climate likely with soil in which it was easier to dig. The
quadrupedal clade evolved as the climate became humid, where limbs and
large size facilitated fossorial locomotion in packed soils.