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Bull. not. Hist. Mux. Loud. (Zool.) 68(2): 113-121 



Issued 28 November 2002 



Underwood's classification of the geckos: a 21 st 

 century appreciation 



ANTHONY P. RUSSELL 



Department of Biological Sciences, University of Calgary; 2500 University Drive N.W., Calgary, Alberta, 

 Canada, T2N 1N4. email: anissell@ucalgary.ca 



AARON M. BAUER 



Biology Department, Villanova University, 800 Lancaster Avenue, Villanova, Pennsylvania 19085-1699, USA 



SYNOPSIS. The publication in 1 954 of Underwood's 'On the classification and evolution of geckos' was the first comprehensive 

 attempt to understand the systematica, 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. 



INTRODUCTION 



'[We] would like to make a distinction between how [Dr. Underwood! 

 thought about the classification of [gekkotans] and what he thought, 

 since in [our] view how a man thinks is far more important than what 

 he thinks ... [we] suggest that how [Underwood] thought about 

 classification survives untarnished to this day. Does what he thought 

 about it bear critical scrutiny nearly fifty years later?' With these 

 words (bracketed modifications aside) Garth Underwood (1971a) 

 began his A Modern Appreciation of Camp's ''Classification of the 

 Lizards.'' Nearly 50 years after its publication we here consider 

 Underwood's classification of the Gekkota, its central position in the 

 study of these lizards, its influence on subsequent work in the field 

 and how its conclusions have been modified over the intervening 

 decades. This work was Underwood's first substantial contribution 

 to squamate evolution, preceding other major contributions to the 

 systematics of pygopods (Underwood, 1957) and snakes 

 (Underwood, 1967) and establishing the way he was to think about 

 and employ character analysis in approaches to what had previously 

 been regarded as rather intractable problems. 



Garth Underwood was interested in both the theory and practice 

 of systematics and also in the evolutionary morphology of the 

 organisms that he chose as the subjects of his systematic analyses. 

 He was bold in embracing novel sources of data for his systematic 

 analyses, put forward hypotheses of relationship in the hopes that 

 they would be scrutinised and evaluated by others, and frequently 

 returned to systematic problems that he had already published some 

 years earlier to bring fresh insights and approaches. Specimens 

 always figured prominently as a primary source of inspiration and 

 new data. 



A comparison of the lizard families recognised by Boulenger 

 ( 1885), Camp (1923), and most modern workers (e.g., Macey e tal., 

 1997; Harris et al, 1999) reveals almost no discrepancies. The 

 gekkotan lizards, however, are an exception. Until the middle of the 

 20"' century, lizard systematists variously recognised the 

 Eublepharidae and Uroplatidae as entities distinct from the 

 Gekkonidae. Different classificatory schemes reflected not only 

 different interpretations of characters, but alternative views of the 

 systematic meaning of novel morphologies. For most of the time 

 after the description of the first gecko genera by Laurenti (1768), 

 gecko systematics was dominated by alpha systematic treatments 

 and the allocation of newly discovered species to an ever growing 

 number of genera, defined chiefly by externally discernible digital 

 features. This reliance on digital characters as almost the sole 

 determinant of affinity resulted in the widespread recognition of 

 composite genera constituted by digitally convergent taxa. Further, 

 the focus on foot structure did little to resolve higher order relation- 

 ships among gekkotans, as the digital characters then recognised 

 suggested many discrete clusterings of species, but provided few 

 putative links between them. 



Garth Underwood was led to the topic of gecko classification, 

 which he ( 1954:469) characterised as 'far from stable', through his 

 research on the reptilian eye. His earlier work on retinal morphology 

 (Underwood 1951a) and pupil shape (Underwood 1951b) had both 

 highlighted the distinctiveness of the gecko eye and suggested that 

 ophthamological characters could be of use in the resolution of 

 higher order relationships among the many gecko genera. 

 Underwood's optimism that the eye could provide useful characters 

 was bolstered by the then recent work of Bellairs (1948), who had 

 conclusively demonstrated that the true eyelids of the eublepharid 

 geckos were primitive to the derived condition of a well-developed 



© The Natural History Museum. 2002 



