1 Biology Department, Villanova University, Villanova PA, USA; 2 Zoologisches Forschungsmuseum A. Koenig, Bonn, Germany A reconsideration of Sphaerodactylus dommeli Böhme, 1984 (Squamata: Gekkota: Sphaerodactylidae), a Miocene lizard in amber J UAN D. DAZA 1 ,AARON M. BAUER 1 ,PHILIPP WAGNER 1,2 and WOLFGANG BÖHME 2 Abstract The Miocene gecko in amber, Sphaerodactylus dommeli, is one of the best-preserved fossil gekkotan species; nonetheless, its identity has been ques- tioned and it has been insinuated to be an iguanian referable to the mega-diverse genus Anolis. In this paper, we provide digital X‐rays and new osteo- logical evidence that include 11 characters that reaffirms its placement within the infraorder Gekkota and eight characters that specifically place this fossil within the species-rich genus Sphaerodactylus, in which it was originally described. This contribution seeks to eliminate remaining scepticism about the generic allocation of this species, and to provide a reliable calibration point for ongoing research in squamate phylogenetics, especially for biogeographical studies and molecular dating inference. This contribution also reviews many diagnostic characters for the two genera in question, which is critical for the correct identification of amber-embedded specimens representing the rich Hispaniolan lizard paleocommunity. Key words: Fossil – Anolis – digital X‐rays – osteology – anatomy – Domincan Republic Introduction Sphaerodactylus dommeli Böhme, 1984 was described based on two specimens from the amber deposits of Hispaniola (Domini- can Republic, La Toca Mine). These specimens, together with Yantarogekko balticus, include the best-preserved amber-embed- ded geckos reported in the literature (Böhme 1984; Poinar 1992; Bauer et al. 2005). Sphaerodactylus dommeli, S. ciguapa (Daza and Bauer 2012), and at least three more specimens (Schlee 1990; Kluge 1995; Grimaldi 1996; Grimaldi et al. 2000) repre- sent the oldest records of the extant genus Sphaerodactylus, otherwise only known before the Holocene from disarticulated material from the late Pleistocene of Puerto Rico (Pregill 1981). These amber-preserved species document the presence of Sph- aerodactylus in the Greater Antilles between 15 and 20 MYA (Grimaldi 1995; Iturralde-Vinent and MacPhee 1996), during or before an important stage of Caribbean tectonics, the formation of the Mona Passage, which resulted in the separation of His- paniola and Puerto Rico (Iturralde-Vinent and MacPhee 1996; MacPhee et al. 2003). Sphaerodactylus fossils dated based on Dominican amber age estimations (Lambert et al. 1985; Grimaldi 1995; Iturralde-Vinent and MacPhee 1996) have been used as calibration points in recent molecular studies (Gamble et al. 2008a,b; Gamble et al. 2011a; Nielsen et al. 2011; Heinicke et al. 2011) and have pro- vided comparisons for estimates of rates of evolution based on other data (Hass and Hedges 1991; Hedges et al. 1991; Hedges 1996). Indeed, S. dommeli is particularly critical in this regard, as there are few fossil-based calibration points within the Gekkota (Lee et al. 2009a; Oliver and Bauer 2011). The few putative gekkotans from the Mesozoic are of uncertain phylo- genetic affinity (Alifanov 1989; Borsuk-Białynicka 1990; Arnold and Poinar 2008) as is the Early Eocene gecko Yantarogekko balticus (Bauer et al. 2005). Likewise, most other Tertiary gekkotans are known from fragmentary remains and cannot be reliably situated in the gekkotan phylogeny. Miocene remains of geckos from St. Bathans, New Zealand have been used as cali- bration points (Lee et al. 2009a), but these are attributable to the Diplodactylidae, a family of Australo-Pacific geckos that is highly divergent from the Gekkonoidea, the clade to which approximately 85% of extant geckos belong. Likewise, Pygopus hortulanus from Riversleigh, Australia has been used for calibra- tion (Jennings et al. 2003; Oliver et al. 2007; Smith et al. 2007; Gamble et al. 2008b), but in this particular case, there are some discrepancies on the estimated divergence dates, in part attributed to the uncertainty of the fossil’s phylogenetic position (Lee et al. 2009b). Aside from Sphaerodactylus in Dominican amber, the only fossil calibration point within the Gekkonoidea is provided by specimens of the sphaerodactylid Euleptes from the Miocene of Central Europe (Müller 2001; Müller and Mödden 2001; Augé 2005; Čerňanský and Bauer 2010). Given the significance of S. dommeli for understanding the evolution of geckos, it is necessary to address scepticism in the literature regarding its familial allocation. The specimens of S. dommeli exhibit a truly gekkotan habitus and, as was men- tioned in the original description, both specimens have the dis- tinctive asymmetric claw sheath of Sphaerodactylus (Böhme 1984; see also Parker 1926; Vanzolini 1957; Peters and Donoso- Barros 1970; Schwartz 1973; Kluge 1995; Gamble et al. 2011b). Nonetheless, its assignment to the genus Sphaerodactylus has been questioned and it has been suggested that its general habi- tus (proportions of limbs, shape of head) is consistent with an anoline lizard (Frost in Kluge 1995). It has additionally been rec- ommended that the type material of ‘Sphaerodactylus’ dommeli must be re-examined in order to correctly reclassify the species (Kluge 1995). This uncertainty has been repeated in several sub- sequent publications (MacPhee and Iturralde-Vinent 1995; de Queiroz et al. 1998; Pregill 1999). De Queiroz et al. (1998), based on published photographs of S. dommeli (Böhme 1984; Schlee 1990), determined that the distal position of the toe pads of the holotype was inconsistent with this specimen being an anole, but they did not comment on the paratype, because the toe pads were not clearly visible on the photographs available to them, leaving open the possibility that at least the paratype of S. dommeli might not be a gecko. In this paper, we review skeletal characters in the holotype and external morphology of the paratype of S. dommeli to pro- vide evidence that refutes its identification as an Anolis (Kluge 1995). In order to verify the taxonomic allocation of S. dommeli, Corresponding author: Juan D. Daza (juand.daza@gmail.com) Contributing authors: Aaron M. Bauer (aaron.bauer@villanova.edu), Philipp Wagner (philipp.wagner.zfmk@uni-bonn.de), Wolfgang Böhme (w.boehme.zfmk@uni-bonn.de) Subsequent to the acceptance of this paper, we obtained high resolution X-ray computed tomography imagery for the paratype of Sphaerodactylus dommeli that confirms that it is correctly allocated to genus. Details of its osteology will be reported elsewhere. J Zoolog Syst Evol Res (2013) 51(1), 55--63 Accepted on 22 August 2012 © 2012 Blackwell Verlag GmbH J Zoolog Syst Evol Res doi: 10.1111/jzs.12001