Underwood's classification of the geckos: a 21st century appreciation

The publication in 1954 of Underwood's ‘On the classification and evolution of geckos’ was the first comprehensive attempt to understand the systematics, evolution and biogeography of this group of lizards. Combining the use of the exploration of novel characters with a global overview of geckos, Underwood erected hypotheses of relationship and patterns of distribution. In the 48 years since that landmark publication much has changed, but much has stayed the same. Underwood's division of geckos into four major clusters is still recognised today, although the sphaerodactyls are now regarded as a group derived from within the gekkonines, and the diplodactylines have been diminished by the removal of several genera and their placement in the gekkonines. The framework that Underwood established has resulted in generic and/or species level phylogenies being generated for the eublepharids, some sphaerodactyls, the carphodactyline diplodactylines and some clusters within the gekkonines. The latter group, because of its size, has remained intractable to detailed systematic analysis at the generic level, although the recognition of many discrete monophyletic clusters within the Gekkonidae (the Gekkoninae of Underwood) holds out the possibility that greater levels of intergeneric resolution are close to realisation. Underwood's initial approach to the systematic analysis of geckos was distinguished by its use of novel characters of the visual system that led to new insights. It is possible that the next breakthrough in higher level systematic analysis of geckos may again come from the exploitation of new character sources. Some examples of these possibilities are discussed.