Hoxful Monsters

The Australian scincid clade Lerista provides an excellent model for studying limb reduction in squamates (lizards and snakes).These Small lizards are a commonly found in Australian continent and nearly 75 different species are available.

Species of Lerista show a very high variability in limbs -ranging from pentadactyl to complete loss of limbs.Recent work published in BMC Evolutionary Biology Journal (Open access) demonstrate that several species of these Lizards have rapidly evolved an elongate, limbless body form.Mark Hutchinson’s lab lead by Adam Skinner had investigated the pattern and rate of limb reduction and loss in Lerista, employing a comprehensive phylogeny inferred from nucleotide sequences for a nuclear intron and six mitochondrial genes.

The reason for loss of limbs in these lizards is believed to be thier habitat ,which happens to be sand and they spend most of time swimming through soil;”limbs are not only unnecessary for this, but may actually be a hindrance”.

The results of phylogeny(Which was done to investigate the pattern and rate of limb reduction ) revealed that evolution of a snake-like body form has occurred not only repeatedly but also very rapidly and without any evidence of reversals.

“At the highest rate, complete loss of digits from a pentadactyl condition is estimated to have occurred within 3.6 million years”. Compared to similarly dramatic evolutionary changes in other animals, this is blisteringly fast.–Adam Skinner

Citation and Image Credit:

Adam Skinner, Michael S Y Lee and Mark N Hutchinson

Rapid and repeated limb loss in a clade of scincid lizards.

BMC Evolutionary Biology 2008, 8:310doi:10.1186/1471-2148-8-310