Despite being among the largest and most conspicuous geckos across southern and eastern Africa, the toe-padded species of Chondrodactylus have remained one of the most taxonomically difficult groups of African lizards, due chiefly to their overall morphological conservativeness accompanied by high intraspecific variation. Current recognition of taxa is based on recent molecular phylogenetic analyses, but the application of the currently recognized nomina to particular populations has not yet been presented. We present a much-expanded multigene analysis of 234 representatives of the genus Chondrodactylus that supports the recognition of 6 species-level taxa, one without toepads, C. angulifer, as sister to five with pads: C. bibronii, C. turneri, C. laevigatus, C. pulitzerae, and C. fitzsimonsi. In general, the species can be recognized on the basis of the relative size of chin and gular scales, dorsal scalation, and head shape. However, the most widespread species, C. laevigatus is only very subtly distinct from C. turneri, with which it is likely parapatric in East Africa (although western populations of C. laevigatus are unambiguously diagnosable from all other congeners). Intraspecific divergences are high in some of the species. In C. fitzsimonsi there is evidence of shared nuclear haplotypes with C. pulitzerae and potential morphological evidence for hybridization or introgression with C. laevigatus. Chondrodactylus turneri exhibits a mitochondrial gene rearrangement that is unique among all geckos followed by an insertion of roughly 200 base pairs that do not correspond to known sequences. Most Chondrodactylus species are primarily distributed in arid to semiarid southwestern Africa, where as many as 4 species occur in sympatry in northern Namibia. In contrast, C. turneri is limited to the lowlands of the southeast and C. laevigatus follows the “arid-corridor” traversing sub-Saharan Africa southwest to northeast.
INTRODUCTION
Geckos of the genus Chondrodactylus are among the largest and most conspicuous nocturnal lizards in southern Africa. The genus was erected by Peters (1870) to accommodate a large ground-dwelling lizard, C. angulifer, initially found at Hantam, Oorlogsrivier, near the town of Calvinia, in what is now the Northern Cape Province of South Africa. The then-monotypic genus was distinguished by its short digits and absence of adhesive pads, with the toes clad instead by distinctive small pointed scales (Fig. 1 left and inset). The name is derived from the Greek χóνδρoς khóndros, meaning, in this instance, “grain”—in reference to the small grain-like scales under the toes, not cartilage, the more frequent zoological meaning. Chondrodactylus weiri Boulenger, 1887 was described from an unspecified locality in the Kalahari but was quickly relegated to the synonymy of C. angulifer (Boulenger, 1910). No further taxa were allocated to Chondrodactylus until the description of C. angulifer namibensis by Haacke (1976a). Despite a trend in herpetology for several decades to either synonymize or elevate non-nominotypic subspecies (Frost and Hillis, 1990), this taxon has retained its subspecific rank (e.g., Branch, 2014).
Figure 1.
Left pes of Chondrodactylus angulifer (CAS 200011) and right pes of C. bibronii (CAS 266390) illustrating the radically different subdigital ornamentation of the terrestrial type species and the earliest described of the toe-padded members of the genus. Inset shows an enlargement of the spiny subdigital scales that give the genus its name.

Chondrodactylus was subsequently recognized as a member of a proposed evolutionary unit within African geckos, the Pachydactylus group, that also included Pachydactylus Wiegmann, 1834, Colopus Peters, 1869, Rhoptropus Peters, 1869, Elasmodactylus Boulenger, 1895, Palmatogecko Andersson, 1908, and Kaokogecko Steyn and Haacke, 1966 in southern Africa and Tarentola Gray, 1825 and Geckonia Mocquard, 1895 in North Africa, the Mediterranean, and parts of the New World. All of these were united by the putative synapomorphy of hyperphalangy of digit I of both the manūs and pedes (Haacke, 1968, 1976b; Russell, 1972, 1976). Joger (1985), using immunological data, argued that the two geographic units did not comprise a monophyletic group, although morphologically derived phylogenies (e.g., Bauer, 1990; Kluge and Nussbaum, 1995) retrieved them as members of a single clade. Subsequently, Kaokogecko was synonymized with Palmatogecko (Kluge and Nussbaum, 1995) and Geckonia with Tarentola (Carranza et al., 2002). A series of molecular phylogenies (Lamb and Bauer, 2002, 2006; Bauer and Lamb, 2005) assumed Tarentola as an outgroup to the remaining hyperphalangic geckos and established a number of well-supported species groups within Pachydactylus sensu stricto. Lamb and Bauer (2002) confirmed the monophyly of 2 large-bodied clades within Pachydactylus, both of which had been previously recognized on morphological grounds, the P. namaquensis group (Branch et al., 1996), and the P. bibronii group.
More taxonomically inclusive analyses, incorporating Chondrodactylus angulifer (Bauer and Lamb, 2005; Lamb and Bauer, 2006), however, revealed that the P. bibronii group was, in reality, sister to C. angulifer and resulted in the reallocation of its constituent species to an expanded Chondrodactylus, which was recovered as the sister clade to Pachydactylus + Colopus. The same work demonstrated that Palmatogecko was deeply embedded in Pachydactylus, with which it was formally synonymized. With near complete gekkotan sampling at the generic level (Gamble et al., 2008, 2012, 2015), Tarentola has been shown to have evolved hyperphalangy independently of Pachydactylus and its relatives, thus vindicating Joger (1985), and to belong to a trans-Atlantic clade, the Phyllodactylidae (Gamble et al., 2008), which is sister to the Gekkonidae sensu stricto (to which the Pachydactylus group belongs). The most recent phylogeny of the Pachydactylus group (Heinicke et al., 2017), with near taxon-complete sampling at the species level, recovered a topology similar to that of Bauer and Lamb (2005), except that the two species of Colopus, C. wahlbergi and C. kochi, have been subsumed into the P. rangei and P. mariquensis species groups, respectively. Chondrodactylus, now incorporating its highly autapomorphic padless terrestrial type species as sister to a clade of scansorial species (Fig. 1 right), is strongly and unambiguously supported as the immediate sister to Pachydactylus (Heinicke et al., 2017).
Heinicke et al. (2017) included six species of Chondrodactylus in their tree, C. angulifer, C. bibronii, C. pulitzerae, C. fitzsimonsi, P. laevigatus, and P. turneri. However, they provided no explanation for why these nomina were employed. Indeed, standard herpetological species lists for southern Africa in the preceding decades (e.g., Branch, 1998; Griffin, 2000; Alexander and Marais, 2007; Herrmann and Branch, 2013; Bates et al., 2014) would have typically acknowledged only 4 constituent taxa, one variably under 2 different names (C. turneri and C. laevigatus). The senior author of this paper bears responsibility for this disconnect because he and his colleagues used the names consistent with a series of ongoing taxonomic revisions of the group, which, over time, revealed a shifting landscape of more-and-more complete phylogenies, available names, and associated distributions. Although parts of the results of the taxonomic revision of Chondrodactylus have been used in the literature, sometimes extensively, the justification for the recognition of the six species included by Heinicke et al. (2017) has yet to be presented. In addition to creating uncertainties regarding the application of names in the technical literature and for conservation purposes, this situation has also caused confusion in the popular literature (e.g., Schleicher, 2018) and among the online citizen scientist community (e.g., iNaturalist; Reptile Atlas of Africa; Atlasing in Namibia). With this paper we take the opportunity to clarify the application of names to units within the genus and to evaluate both inter- and intraspecific patterns of Chondrodactylus diversity across southern Africa and, to the extent possible, provide morphological markers that may serve to identify specimens of the recognized species in this highly conservative genus.
MATERIALS AND METHODS
Molecular Sampling
Taxon sampling comprises 234 individuals representing all recognized species of Chondrodactylus. The majority of the distributional range of the genus in Angola, Namibia, and South Africa is well-represented, but north central and northeastern populations of Chondrodactylus spp. from Botswana, Zambia, Mozambique, and East Africa are poorly sampled. Zimbabwe is intermediate in this regard. Although this lack of sampling precludes investigating details of population substructure in parts of the continent, our results suggest that our ultimate taxonomic interpretations will be unaffected by the poorer sampling in the east. All samples sequenced, along with locality data, voucher information, and GenBank accession numbers, can be found in Table 1. For some samples represented by partial data, molecular data were used to confirm species identity, but missing data precluded meaningful intraspecific placement. These samples, including 24 represented by RAG1 data only and an additional 7 with limited ND2 data, were included in initial phylogenetic analyses but were ultimately excluded from the final analyses and, thus, are not represented in trees nor are they included in calculations of support values or patristic distances. To root the tree we included 2 outgroup species, Pachydactylus bicolor and Pachydactylus rangei.
Table 1.
Specimens of Chondrodactylus used in the molecular phylogenetic analysis of the genus and their corresponding GenBank numbers. Specimens marked “fragment” in one of the GenBank columns were represented by sequence data adequate to verify species identity but not sufficiently informative for meaningful placement within a species-level clade. These specimens have neither been included in Figure 2 Nor have their sequences been deposited in GenBank. See Materials and Methods for most museum collection abbreviations. Additional museum identifiers are: INBAC = Instituto Nacional da Biodiversidade e Áreas de ConservaÇÃo, Luanda; ISCED = Instituto Superior de CiÊncias de EducaÇÃo da HuÍla, Lubango; LSUMZ = Louisiana Museum of Natural History, Baton Rouge; LUN = LÚrio University, Nampula; NMB = National Museum Bloemfontein; NMZB = Natural History Museum of Zimbabwe, Bulawayo; TNHC = Texas Natural History Collections, University of Texas at Austin; UF = University of Florida, Florida State Museum of Natural History, Gainesville. Collection ID refers to field or tissue numbers: AMB = Aaron M. Bauer; ANG = PEM Angola; DGB = Donald G. Broadley; ESP = Elizabeth Scott Prendini; JB = Jon Boone; JET = James E. Titus-McQuillan; JM = Johan Marais; JVV = Jens V. Vindum; KHH = Koanaka Hills Expedition, Sam Houston State University; KTH = Krystal Tolley; LMH = Vincent Egan; MB, MBUR = Marius Burger; MCZ F, MCZ A, MCZ Z = MCZField series; MDH = Morgan D. Heinz; MH = Michael Cunningham; PEM FN = PEM field number series; WC, WCDNA = Werner Conradie; WRB = William R. Branch . Country abbreviations: ANG = Angola, BOT = Botswana, MOZ = Mozambique, NAM = Namibia, RSA = Republic of South Africa, ZAM = Zambia, ZIM = Zimbabwe.

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Molecular and Phylogenetic Methods
Genomic DNA was isolated from ethanol-preserved tissues via Qiagen DNeasy blood and tissue kit (Valencia, California, USA). We chose to target mitochondrial and nuclear loci that have proven useful in assessing inter- and intraspecific relationships among gekkotans, providing us the opportunity to take advantage of preexisting sequence data. For samples unique to this study, segments of the mitochondrial locus ND2 (NADH dehydrogenase subunit 2; 1,052 base pairs [bp]), and nuclear loci RAG1 (recombination activating gene 1; 1,068 bp) and PDC (Phosducin; 394 bp), were amplified under standard protocols in 25-mL reactions with published and novel primer pairs (see Table 2). Amplified products were visualized on 1.5% agarose gels and purified using AMPure magnetic bead system (Agencourt Bioscience). Sequencing reactions used ABI Prism BigDyeTerminator (Applied Biosystems), and product was purified using Agencourt CleanSeq magnetic bead system (Agencourt Bioscience). Sequencing was carried out on an automated ABI 3730 for electrophoresis, and electropherograms were imported into Geneious 9.0 ( https://www.geneious.com) for assembly and subsequent alignment via MAFFT. We inspected all alignments by eye and made adjustments as needed.
Table 2.
Primers used for PCR amplification and sequencing.

To estimate phylogenetic relationships we used IQTree 2 (Minh et al., 2020). To start we analyzed each locus individually using a single representative of each species to investigate among-locus concordance. In addition to the 3 loci forming the core of this study, we also included data from the nuclear gene KIF24 (kinesin family member 24; 592 bp) from the data set of Heinicke et al. (2017). Following this exercise, we concatenated the fully sampled alignments and implemented a concatenated partition-by-locus model (option -q; Chernomor et al., 2016) with preferred substitution models determined by ModelFinder (Kalyaanamoorthy et al., 2017). We estimated branch support using the ultrafast bootstrap (BS) approximation with 1,000 replicates (option -bb 1000; Hoang et al., 2018). Uncorrected pairwise p-distances (mean and range) for the mitochondrial locus ND2 were calculated for ingroup taxa using Geneious 9.0.
Morphology and Species Concept
We use genetic data in combination with morphology in an integrative taxonomic framework (Padial et al., 2010) to apply names to taxa within the genus Chondrodactylus. We adopt the general lineage species concept (de Queiroz, 1999) and recognize species based on a combination of characters suggesting evolutionary independence. Padded members of the genus share a highly conservative morphology and a previous attempt to delimit species within Chondrodactylus by applying a morphometric or statistical approach (Benyr, 1995) did not adequately discriminate among the constituent taxa. As a consequence, for morphological evidence we focused on discrete diagnostic characteristics and grossly observable proportional differences to try to identify features associated with the genetic lineages identified. When possible, we have provided numerical estimates of proportional values, such as head width, but these may vary with sex and age. Head depth, another potentially useful diagnostic trait is even more difficult to meaningfully quantify, as variation due to the position of fixation far exceeds lineage-specific differences.
Note that preserved specimen images have been digitally altered to provide a uniform background and optimize contrast and brightness. Features of the specimens have not been altered.
We examined and confirmed the specific identity of available specimens, including all known primary type material, of toepadbearing Chondrodactylus in the collections of the California Academy of Sciences, San Francisco (CAS); Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts (MCZ); National Museum of Namibia, Windhoek (NMNW); Ditsong National Museum of Natural History, Pretoria (TM); Museum für Naturkunde, Berlin (ZMB); Zoologisches Museum Hamburg (ZMH); Carnegie Museum of Natural History, Pittsburgh (CM); Academy of Natural Sciences of Drexel University, Philadelphia (ANSP); The Natural History Museum, London (NHM, but the older BMNH retained here for continuity with respect to older specimen references); Muséum d'Histoire Naturelle, Genève (MHNG); Musée d'Histoire Naturelle de La Chaux-de-Fonds (MHNC); Zoologische Staatssammlung München (ZSM); Naturhistorisches Museum, Wien (NMW); Museu Regional do Dundo (MD); Port Elizabeth Museum (PEM); Zoologisches Forschungsmuseum Alexander Koenig, Bonn (ZFMK); Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt (SMF); Senckenberg Naturhistorische Sammlungen, Dresden (MTD); Natural History Museum of Los Angeles County (LACM); American Museum of Natural History, New York (AMNH); Iziko South African Museum, Cape Town (SAM); Hungarian Natural History Museum, Budapest (HNHM); McGregor Museum, Kimberley (MMK); and Australian Museum, Sydney (AMS). We also gathered additional museum and other records for mapping purposes. Haacke (1976a) provided a lengthy list of specimens and localities for C. angulifer. In cases of uncertain specific identity, the relevant curators and collections managers were consulted and, when possible, photos or other verification allowing assignment to species were obtained.
Distribution
Chondrodactylus as a whole extends throughout Africa from near the Equator in Kenya through to South Africa, exclusive of near coastal areas of the southwestern Cape (although there is an introduced population in the Kommetjie area of Cape Town; Rose, 1962; Branch, 2014) and the grassland biome that is largely coincident with the Highveld and Drakensberg of South Africa and Lesotho. They are also absent from most of the east coastal regions south of Zululand, KwaZulu-Natal. The records mapped here are not exhaustive, but they provide an adequate picture of the distribution of the members of the genus. When available, decimal latitude/longitude records were used or records were georeferenced as precisely as possible using the WGS84 map datum. Quarter degree square (QDS) records (see Bates et al., 2014) were plotted as points in the center of each QDS grid square, which is adequate for the subcontinental level of mapping used herein.
Distributional data were obtained from South Africa and Swaziland chiefly from Bates et al. (2014), data from Namibia have been gathered by AMB in the course of the preparation of a forthcoming book on the herpetofauna of Namibia (data available from authors). Angolan records include those from Marques et al. (2018) and from a JRS Biodiversity Foundation sponsored project. Records from Zambia, Zimbabwe, Botswana, and Malawi were kindly provided by the late Donald G. Broadley, who had accumulated them as part of the “Reptilia Zambesiaca” project stemming from his doctoral work. This has been supplemented by localities provided by Harith Farooq (Mozambique) and Darren Pietersen (Zambia, Malawi, Mozambique). Records from Kenya were provided by Steven Spawls. These records were augmented by data from GBIF, including photo-vouchered records, and from the literature, particularly Loverdige (1947) and the unpublished thesis of Benyr (1995). Records of C. angulifer were mapped without typically checking identity because the distinctiveness of this taxon effectively precludes misidentification. Records of some padded Chondrodactylus were accepted without examination of the associated vouchers if they derived from areas that support only a single species (e.g., most of South Africa and southeastern Africa north of the Zambezi River).
RESULTS
Molecular Phylogenetics
The final mito-nuclear data set included 3,110 bases, 807 of which were parsimony-informative (ND2–672; RAG1–104; PDC–20; KIF24–11). ModelFinder selected the GTR model for all 4 locus partitions. Individual nuclear markers alone provided little resolution but no strong conflict among loci and were thus combined in a single concatenated analysis. The resultant maximum-likelihood tree of the locus partitioned concatenated alignment (Fig. 2) provides support (BS >95%) for interspecific relationships among Chondrodactylus species, as well as the monophyly of all six recognized taxa (BS 100%). This includes well-supported divergent subclades in C. pulitzerae, C. fitzsimonsi, C. turneri, and C. laevigatus. Patristic distances among these clades, as well as all species, are reported in Table 3.
Figure 2.
Maximum likelihood tree, concatenated and partitioned by locus, of the genus Chondrodactylus, outgroups not shown. Values subtending nodes are ultrafast bootstrap values. (A) Chondrodactylus angulifer, C. bibronii, C. pulitzerae, (B) C. fitzsimonsi, C. turneri, (C) C. laevigatus. Branches are color coded by species with different hues indicating major sublineages within a species.

Table 3.
Uncorrected interspecific and intraspecific patristic distances (as percentages) for the mitochondrial locus ND2 among Chondrodactylus species and populations. mean distance is shown in parentheses alongside ranges. Values were calculated only on the basis of specimens for which ND2 data were substantially complete.

Chondrodactylus is recovered as strongly monophyletic, with C. angulifer as sister to all padded members of the genus (100% BS). Although specimens assignable (based on distribution) to the nominotypical form are monophyletic, they make C. a. namibensis paraphyletic (Fig. 2A). On this basis, and modest intraspecific pairwise genetic distances (Table 3), we tentatively regard the species as monotypic.
Chondrodactylus bibronii was recovered as basal to all other samples of scansorial Chondrodactylus. There is well-supported substructure within C. bibronii, although divergences are relatively shallow, with a general trend of specimens from the northwestern portion of the range (southern Namibia and northern Northern Cape, South Africa) being basal to more easterly and southerly clades (Fig. 2A).
Among remaining members of the genus, C. pulitzerae is sister to its congeners, receiving strong support (100% BS). There are deep divergences within the C. pulitzerae clade, with one well-supported (100% BS) lineage including all specimens from Benguela as well as some individuals from Namibe, Luanda, and Cuanza Norte provinces. Support is also high (98% BS) for the other large group of C. pulitzerae, which includes individuals from Namibe Province in Angola and from the Kunene Region in Namibia (Fig. 2A).
The clade C. laevigatus + C. turneri + C. fitzsimonsi is recovered with 100% bootstrap support, with each species also receiving 100% bootstrap support and the sister group relationship of C. laevigatus and C. turneri receiving 97% bootstrap support (Fig. 2B).
Within Chondrodactylus fitzsimonsi there are 3 relatively deeply divergent clades, all with 100% bootstrap support. One clade is exclusively Angolan. A second chiefly comprises specimens from the western Kunene Region of Namibia, which includes the type locality, and a third includes most specimens from the Erongo Region of Namibia, as far south as the Swakpmund area. However, both Namibian clades include some individuals from the other Namibian region. Specimens from <2 km apart in the Gaias region in the southwestern Kunene Region are represented in both the Kunene and Erongo clades (Fig. 2B).
Chondrodactylus turneri is represented by 2 relatively deeply divergent, well-supported clades, each with little substructure. One of these includes specimens only from Limpopo Province south of the Soutpansberg and the other includes specimens from northernmost Limpopo, as well as from southern and western Zimbabwe and far eastern Botswana (Fig. 2B).
Finally, within C. laevigatus there are 3 subclades, each with 100% bootstrap support. One includes all specimens from the Northern Cape of South Africa as far north as the Khomas Hochland in central Namibia. A second clade includes all material from the Erongo Region northward to the Kunene River and thence northward into Angola and eastward across northeastern Namibia (including the Zambezi Region, formerly known as the Caprivi Strip) and western Botswana. The third subclade is more poorly sampled than the others and includes specimens from northern and eastern Zimbabwe, northern Mozambique, Zambia, and Kenya (Fig. 2C).
Gene Rearrangement
All individuals of C. turneri have a mitochondrial gene rearrangement that is unique among all gekkotans. The region coding for the alanine tRNA (trnA) is replaced by the proline tRNA gene (trnP). Then, following an insertion of roughly 200 base pairs that do not correspond to known sequences, the typical gene order is resumed: trnN, trnC, trnY, and the beginning of the CO1 gene. All C. turneri individuals sequenced for the region following ND2 exhibit the rearrangement. Trees of the phylogeographic portion of this study did not include the tRNAs downstream of ND2, so this rearrangement did not affect topologies or support of the presented trees and may be interpreted as independent verification of the monophyly of C. turneri.
SYSTEMATICS
The pattern of species relationships retrieved here, with large sample sizes, is fully congruent with that previously reported by Heinz (2011) and Heinicke et al. (2017) based on less dense and exemplar-only sampling, respectively.
The scansorial Chondrodactylus (Pachydactylus until 2005) have long been taxonomically problematic because they share a similar body size, color pattern, and habitus (Bauer et al., 1993). They exhibit significant variation in aspects of dorsal scalation, however, ranging from flattened, almost pavement-like dorsal scales, through so-called “button scales,” to strongly keeled or mucronate tubercles, with virtually all possibilities on the spectrum of rugosity expressed. This variation traditionally formed the basis for species recognition within the group (Fischer, 1888; Werner, 1910; FitzSimons, 1938, 1943; Loveridge, 1947).
Benyr (1995), in a seminal but unpublished thesis, dismissed dorsal scalation alone as a diagnostic and, based on broad sampling across the entire distribution of the P. bibronii group (padded Chondrodactylus), instead recognized 3 species on the basis of size of the scales bordering the mental relative to the width of the paravertebral dorsal tubercles: P. bibronii (Smith, 1846), P. laevigatus (Fischer, 1888), and P. fitzsimonsi Loveridge, 1947. Likewise, multivariate analysis of morphometric data could not distinguish among any C. bibronii complex clades recognized here on the basis of eye, head, limb, body, or toe measures (Heinz, 2011), echoing the conclusions of Benyr (1995) and emphasizing the morphological conservatism of this group and the need for molecular data in determining clade boundaries and guiding the search for distinguishing characters.
With the well-established phylogeny supported by the combined mitochondrial and nuclear data presented here, it is now possible to revisit the existing morphological and distributional data for Chondrodactylus and to attempt to identify diagnostic characters consistent with the species-level units we have identified. Previous morphometric approaches have thus far proved inadequate (see above), so we have chosen to focus on discrete characters of potentially diagnostic value. These are based on the examination of approximately 3,000 specimens.
In the accounts that follow a partial chresonymy is provided for each species. This includes all newly proposed names and the first occurrence of new combinations.
Chondrodactylus Peters, 1870
Homodactylus Gray, 1864:59 (non Homodactylus Fitzinger, 1843 = Gerrhosauridae). Type species: Homodactylus turneri Gray, 1864, by monotypy.
Chondrodactylus Peters, 1870:110. Type species: Chondrodactylus angulifer Peters, 1870 by monotypy.
Content. Chondrodactylus angulifer Peters, 1870, C. bibronii (Smith, 1846), C. turneri (Gray, 1864), C. laevigatus (Fischer, 1888), C. pulitzerae (Schmidt, 1933), C. fitzsimonsi (Loveridge, 1947).
Although Bauer and Lamb (2005) transferred Pachydactylus bibronii group taxa to Chondrodactylus, they did not provide a revised diagnosis for the significantly expanded genus. We take the opportunity to do so here.
Diagnosis. Large sized gekkonid geckos (adult snout-to-vent length [SVL] typically >75 mm) with or without adhesive toepads. Manus and pes with hyperdactyly of digit I; phalangeal formulae (3-3-4-5-3 manus, 3-3-4-5-4 pes). Head large, body robust, tail short (63.2% SVL; Haacke 1976a) to moderate (110% SVL) in length. Claws minute or absent. Precloacal and femoral pores absent in both males and females. Dorsum gray to brown or reddish/ orange-brown, usually banded, although this pattern may be weak or the bands disrupted. Venter immaculate white. All species are typically sexually dichromatic with males exhibiting distinct white spots, particularly in the shoulder region (these may be absent in some C. angulifer; Haacke, 1976a), as first noted by Schmidt (1933) for C. pulitzerae.
Distribution. Chondrodactylus has a broad distribution in sub-Saharan Africa, occupying desert, semidesert, savanna, woodland, and other habitats from southern South Africa, northward through Namibia, Botswana, Zimbabwe, and Mozambique, to southern and western Angola, and thence eastward to southern and eastern Zambia, Malawi, Tanzania, and southern Kenya. A controversial record from Rwanda is considered to be in error (see C. laevigatus species account). Within this broad area members of the genus are absent only from the extreme coastal south of the Eastern and Western Cape provinces and higher elevations and grassland areas in Lesotho and adjacent parts of South Africa. Sparse and scattered records at the periphery of the range result in an imprecise knowledge of distribution at the northern margins of the distribution.
Comments. Homodactylus Gray, 1864, with H. turneri its type species by monotypy, would have temporal priority over Chondrodactylus Peters, 1870 when turneri and angulifer are included in the same genus. However, Gray's generic name is a junior homonym of Homodactylus Fitzinger, 1843 (Gerrhosauridae), with Caitia africanus Gray, 1838 = Tetradactylus africanus (Gray, 1838) as its type species by original designation.
Chondrodactylus angulifer Peters, 1870
Figure 3.
Chondrodactylus angulifer Peters, 1870: Monatsb. Akad. Wiss. Berlin 1870:111, pl., fig. 1. Lectotype: ZMB 6750 (formerly ZMB 6750A; collector H. Meyer), designated by Bauer and Günther (1991). Paralectotypes: ZMB 90588–89 (formerly 6750B and 6750C). ZMB 6749, also a paralectotype, could not be located (F. Tillack, in litt., 7 June 2021) and an additional specimen in Zoological Institute, Russian Academy of Sciences, Saint Petersburg (ZISP) 2632 is also a member of the type series. Type locality: “Hantam, Oorlogsrivier, S. W. Africa” [= Calvinia, Northern Cape Province, South Africa].
Chondrodactylus weiri Boulenger, 1887:340. Type locality: “Kalahari Desert.” Holotype: BMNH 1946.8.23.58 (formerly BMNH 87.3.15.1; collector J.J. Weir).
Chondrodactylus angulifer angulifer Haacke (1976a:54, pls. 4, 5–top, 6–right, 7–left, 8–bottom).
Chondrodactylus angulifer namibensis Haacke, 1976a: Ann. Transvaal Mus. 30(5):64, pls. 5 (bottom), 6 (left), 7 (right), 8 (top). Holotoype: TM 32632 (collector W.D. Haacke). Type locality: “Amichab (= Anigab) Mountain, Namib Park, central Namib Desert, South West Africa (±23°11′S, 15°30′E. Altitude about 1,000 m).” See Mashinini and Mahlangu (2013) for data on paratypes.
Diagnosis. A large Chondrodactylus (SVL to ≥113 mm; Haacke 1976a). This taxon is unambiguously distinguishable from all of its congeners by the absence of adhesive toepads under all digits. Its short, stubby, digits, as well as plantar surfaces, appear puffy and bear raised spiny scales (Fig. 1 inset), which appear to be one type of pedal specialization for movement in loose sand (see Bauer and Russell, 1991). Distal 2 phalanges of each digit greatly reduced in size and recurved. Digits of manus clawless. Body cylindrical, tail cylindrical, not depressed. Head large, deep, rounded; eyes large (Fig. 3). Extrabrillar “fringe” above eye prominent. Dorsum and flanks covered with rows of low, pointed, though non-keeled tubercles. Original tail shorter than body length (63.2–80.5% SVL; Haacke, 1976a), distinctly verticillate. Dorsal pattern more-or-less uniform, speckled, or weakly to strongly banded and may be predominantly brownish, reddish, burnt orange or pale cream. Consistent pattern elements include a dark saddle across the shoulders and white to cream lines from the snout, through the dorsal part of the eye to the upper temporal region (Fig. 3). Iris bronze to coppery. See Haacke (1976a) for a detailed description of the species and variation in pattern.
Distribution. Chondrodactylus angulifer occupies most of arid and semiarid western southern Africa (Fig. 4, top), mostly in areas within the 300 mm isohyet (Haacke, 1976a). In South Africa it occurs west of 24°E throughout most of the Northern Cape Province, and in adjacent regions of the Western Cape Province (although not south of the Cape Fold Mountains), as well as the far west of the Eastern Cape (Branch, 2014). It reaches its southernmost point near Touwsrivier (Haacke, 1976a). In Botswana it is known only from the southwestern corner of the country and in Namibia it occurs broadly south of the Tropic of Capricorn, but north of the lower Kuiseb River it occurs chiefly in the far west of the country (Haacke, 1976a). A significant range extension of the species into the Omaheke Region of Namibia has been documented since the previous revision of the species. Its northernmost occurrence has been recorded near Orupembe in the Kunene Region (Haacke, 1976a).
Comments. The name Chondrodactylus a. namibensis was previously applied to populations north of the Kuiseb River as well as for coastal or near coastal populations as far south as northern Namaqualand. The occurrence of specimens ostensibly attributable to both C. a. angulifer and C. a. namibensis in near sympatry in the Sperrgebiet (Branch, 1994) and in the Richtersveld (Bauer and Branch, “2001” 2003), as well as “intermediate populations” in and around the Richtersveld (Haacke, 1976a), suggests that the two named forms may reflect variation, primarily in color pattern, along a steep west-to-east cline in the driest regions of the distribution. Our genetic sampling showed no evidence of a clear divergence between the nominal subspecies. We here regard C. angulifer as a monotypic species, but caution that a much more deeply and broadly sampled phylogeographic study is needed to adequately assess genetic variation across the vast distribution of this taxon. In particular, we lack genetic material from the Kgalagadi region. Although C. weiri Boulenger, 1887 continued to be recognized by Sternfeld (1911) for animals from this area, all authors since have accepted Boulenger's (1910) synonymization with C. angulifer and morphological data (Haacke, 1976a) have not suggested noteworthy variation.
Figure 3.
Chondrodactylus angulifer life photos. (A) Sesriem, Hardap Region, Namibia; –24.48529°, 15.79713°; (B) Springbok, Namaqualand, Northern Cape Province, South Africa; (C) Witsand Reserve, Northern Cape Province, South Africa, –28.568368°, 22.493221°; (D) Gaias, Kunene Region, Namibia. Based on distribution, D would be a typical C. a. namibensis and the remaining specimens would represent the nominate form. The characteristic white spots, especially on the shoulder, identify males (B, C). Photo credits: (A) Randall Babb; (B, D) Johan Marais; (C) Ryan van Huyssteen.

Figure 4.
Distribution of Chondrodatylus angulifer (top) and C. bibronii (bottom). In this and following maps, localities from which sequenced specimens were derived are indicated by a white ring around the locality dot and type localities are indicated by a star. For C. angulifer the type localities of the nominate form (in South Africa) and C. a. nambiensis (in central Namibia) are indicated. The type locality of C. weiri is too vague to plot. The type locality plotted for C. bibronii is that of Pachydactylus stellatus.

Toepad-bearing Chondrodactylus
All remaining species of Chondrodactylus retain the plesiomorphic condition (for the Pachydactylus group sensu Bauer and Lamb 2005) of adhesive scansorial pads under all of the digits (Fig. 1 right). The species are highly conservative with respect to most aspects of external morphology. All are large members of the broader Pachydactylus group with robust, somewhat depressed bodies and large subtriangular heads (Fig. 5). The dorsum bears longitudinal rows of enlarged scales or tubercles, which range from completely flattened and juxtaposed to raised and strongly keeled to mucronate (Fig. 6). The dorsal pattern is mostly stereotypic; all have a predominantly brownish to grayish dorsum with variably developed transverse bands or markings that are a darker brown to blackish that may be bordered or marked with cream to bright white tubercles. In adult males there are bright white markings that are typically larger and more conspicuous on the shoulder region and nape than elsewhere. Hatchlings and juveniles have bolder patterns than adults and scale features, like keels and mucrones, are poorly developed in younger animals.
Figure 5.
Comparative dorsal views of heads of adult Chondrodactylus spp. (A) C. bibronii (CAS 223900), 99.2 km N of Helmringhausen, Hardap Region, Namibia; (B) C. pulitzerae (CAS 254790), Iona National Park, Namibe Province, Angola; (C) C. fitzsimonsi (CAS 175392), 49.2 km N of Cape Cross Rd., Erongo Region, Namibia; (D) C. turneri (CAS 266390), Farm Harmony, Hoedspruit District, Limpopo Province, South Africa; (E) C. laevigatus—western clade (CAS 266423), Farm Garub, Karas Region, Namibia; (F) C. laevigatus—Kgaligadi clade (MCZ Z37838), Ghanzi, Ghanzi District, Botswana; (G) C. laevigatus—eastern clade (CAS 266396), Elim Mission, Manicaland, Zimbabwe; (H) C. laevigatus—“Vulkangegiet” [Rwanda, see comments in text] (ZMB 24300). Images standardized to similar size for ease of comparison. Photos (A–G) A.M. Bauer, (H) Frank Tillack (ZMB).

Figure 6.
Comparative dorsal scalation of Chondrodactylus spp. (A) Close up of a single strongly mucronate upper flank tubercle of Chondrodactylus bibronii (CAS 223900); dorsal scalation in the shoulder and thoracic region, centered on the vertebral midline: (B) C. bibronii (CAS 223900), 99.2 km N of Helmringhausen, Hardap Region, Namibia; (C) C. fitzsimonsi (CAS 266381), near Virei, Namibe Province, Angola; (D) C. pulitzerae (CAS 223916), 4 km N of Sesfontein, Kunene Region, Namibia; (E) C. turneri (CAS 266390), Farm Harmony, Hoedspruit District, Limpopo Province, South Africa; (F) C. laevigatus—eastern clade (CAS 266396), Elim Mission, Manicaland, Zimbabwe; (G) C. laevigatus—Kgaligadi clade (MCZ Z37838), Ghanzi, Ghanzi District, Botswana; (H) C. laevigatus—western clade (CAS 266423), Farm Garub, Karas Region, Namibia. Images standardized to similar size for ease of comparison. Photos A.M. Bauer.

Early attempts to make sense of the various names applied to members of the “Pachydactylus bibronii” complex were largely unsuccessful and most earlier workers lumped all specimens from across southern Africa into a single, highly variable C. bibronii (e.g., Roux, 1907). Despite the ubiquity of these geckos in most of southern Africa, material from Namibia was very poorly represented in museum collections prior to the German colonial period commencing in 1884 and Central and East African material remained scarce until well into the 20th century. Werner (1910) and Parker (1936), amongst others, attempted to interpret the taxonomy of the group in light of the growing number of specimens available, but their interpretations relied too heavily on dorsal scalation and resulted in decades of confusion. Indeed, Schmidt (1933), Parker (1936), FitzSimons (1943), Loveridge (1947), and Mertens (1955) all found the distribution and allocation of names within this group to be difficult. Parker (1936) devised a method of species delimitation that was largely followed by FitzSimons (1943), Loveridge (1947), and Mertens (1955); but, in reality, this resulted in all four authors thoroughly confounding P. bibronii, P. turneri, and P. laevigatus. Indeed, FitzSimons (1943:109) stated “in South Africa at least, turneri appears to preponderate in the West, while eastwards bibronii is the dominant form”—precisely the opposite of the actual situation. He (FitzSimons, 1946:360) clarified that he regarded turneri as “the more heavily keeled variety” of P. bibronii. The work of Benyr (1995) summarized the features reported for each species by all previous authors and identified 3 character states pertaining to the size of the scales bordering the mental relative to the size of the paravertebral dorsal tubercles (Fig. 7). In over 25 years of field and museum work, we have found this character to be reliable for distinguishing C. bibronii and C. fitzsimonsi from all other taxa, but C. laevigatus, C. pulitzerae, and C. turneri share the same (intermediate) character state.
Figure 7.
Comparative chin and gular region of (A) Chondrodactylus bibronii (CAS 223900), 99.2 km N of Helmringhausen, Hardap Region, Namibia; (B) C. turneri (CAS 266390), Farm Harmony, Hoedspruit District, Limpopo Province, South Africa; and (C) C. fitzsimonsi (CAS 266381), near Virei, Namibe Province, Angola. Images standardized to similar size for ease of comparison. Photos A.M. Bauer.

Chondrodactylus bibronii (Smith, 1846)
Figures 5A, 6A,B, 7A, 8, 9, 10.
Tarentola bibronii Smith, 1846: Illustr. Zool. S. Afr. Pl. L, fig. 1 and 2 accompanying unnumbered text pages. Lectotytpe: BMNH 1946.8.26.20 (collector Andrew Smith) here designated (see Comments below). Paralectotypes: BMNH 1946.8.26.21–28 (collector Andrew Smith). Type locality: “Southern Africa,” here restricted to Southern Africa (South Africa or Namibia) south of –26.4°S and west of 26.4°E.
Pachydactylus bibronii Smith (1849: unpaginated index and errata slip).
Homodactylus bibronii (part) Gray (1865:612).
Pachydactylus bibroni (part) Boulenger (1910:460).
Pachydactylus bibronii var. stellatus Werner, 1910:309. Lectotype: NMW 17995:4 (collector Leonhard Schultze, 1903–1905; from the collection of Franz Werner) here designated (see Comments below). Type locality: “Groß-Namaland,” [= Great Namaqualand] Namibia. On the basis of the lectotype locality, the type locality is here restricted to “Bethanien” [Karas Region, Namibia]. Paralectotypes: See Comments below.
Pachydactylus stellatus Hewitt (1911:43).
Pachydactylus bibroni stellatus Hewitt (1927:401).
Pachydactylus bibronii bibronii (part) FitzSimons (1935a:527).
Pachydactylus bibronii stellatus FitzSimons (1935a:528).
Pachydactylus bibronii turneri (part) Parker (1936:129).
Pachydactylus bibronii var. turneri (part) FitzSimons (1943:109).
Chondrodactylus bibronii Bauer and Lamb (2005:117).
Diagnosis. A large Chondrodactylus (SVL to 108 mm, TM 18185) bearing prominent subdigital lamellae. Body very robust, somewhat depressed, habitus most similar to C. turneri among its congeners. Head large, subtriangular, both wide and high, area behind orbits squarish, with nearly parallel lateral sides (Fig. 5A), in contrast to the wide rectangular parietal table of C. fitzsimonsi and more rounded shape of other congeners; snout short and rounded with a shallow midline concavity. Canthus rostralis moderately well-developed, scales on snout and canthal region smooth, domed, equal to or larger than those on parietal region but smaller than those on occiput, which are heterogeneous, strongly keeled and stellate, with prominent striae radiating from the central keel. Circumauricular scales prominent and strongly keeled to mucronate. Scales between posterior rim of orbit and ear greatly enlarged, oblong, with prominent keels. Chin and gular scales minute and granular (Fig. 7A), approximately 5 contained within half the diameter of a paravertebral dorsal tubercle. Dorsal tubercles large, round, and very strongly keeled or mucronate (Fig. 6B), largest in paravertebral position just posterior of midbody, becoming mucronate on flanks (Fig. 6A) and in lumbar region; tubercles in 14–16 longitudinal rows (several shorter rows continue onto the flanks, but only near the midbody), tubercles within a single row usually separated by granular scales from each other, but tubercles of adjacent longitudinal rows often in touch with one another. Vertebral midline covered by a series of small keeled tubercles alternating with even smaller smooth scales, each several times the size of intertubercular granules (Fig. 6B). Scales on dorsal surfaces of thighs, shanks, upper arms, and forearms mucronate. Tail approximately equal to or slightly greater than SVL, strongly verticillate, each whorl at tail-base bearing 6–8 enlarged, raised mucronate tubercles; tubercles per whorl decreasing distally. Across the body as a whole, the scalation of C. bibronii is typically more heavily sculptured than in its congeners giving it a distinctly rugose appearance that contrasts strongly with the button-scaled morphology of western clade C. laevigatus, the only toe-padded congener with which it is sympatric.
Dorsal coloration usually light to mid-brown or grayish with moderately well-developed to bold dark brown dorsal crossbars, especially dark on the nape and shoulders. Basic pattern similar to congeners with nape, shoulder, mid-body, mid-abdomen, and hip bands, which may appear as wide bands, each becoming paler anteriorly or as a series of chevrons or zigzag lines formed only by the darker posterior border of each band. Bright white markings, when present, typically immediately posterior to dark bands. Tail banded, with 7–8 dark bands fading ventrolaterally (Fig. 9). Iris bronze to coppery.
Distribution. Chondrodactylus bibronii has a temperate distribution, occurring from the southern Eastern and Western Cape Provinces of South Africa, northward through most of the Northern Cape and the far western Free State, as well as sporadically along the western periphery of North West Province. In Namibia it occurs south of the Kuiseb River, although it is absent from the southern sand sea except for some rocky isolates. It enters extreme southwestern Botswana along the Nossob River and near the junction of the Nossob and Molopo River (Fig. 4, bottom). It is broadly sympatric and even syntopic with C. laevigatus in southern Namibia (Methuen and Hewitt, 1914) and the Richtersveld of the far northern Northern Cape (Bauer and Branch, “2001” 2003). Although its range approaches that of C. turneri in North West Province, South Africa, there are no known examples of sympatry or parapatry.
Comments. The syntypes of Tarentola bibronii Smith, 1846 are without specific locality. Although the majority of Smith's period in South Africa (1821–1837) was spent within the bounds of the then Cape Colony, which would have harbored only C. bibronii, his expedition to Namaqualand in 1828 would have brought him into the extreme southern limits of the range of C. laevigatus. In 1831 on his expedition to Natal, he reached Zululand and Delagoa Bay at the southern limit of C. turneri and on his expedition to the interior of South Africa (1834–1835) any northeastern localities visited after departing Kuruman (Kirby, 1965) would have all been in the range of C. turneri. Boulenger (1885) listed Smith's types but did not provide the precise number of specimens present. At the time of Boulenger's writing Pachydactylus laevigatus had not yet been described and Homodactylus turneri was regarded by him as a synonym of Tarentola bibronii. Later, FitzSimons (1937) reported on the status of Smith's type material in London and Edinburgh. As of 1935 he recorded 9 surviving specimens in the type series. Following World War II these were reregistered as BMNH 1946.8.26.20–28, and these specimens were examined by one of us (AMB) in 2016. As reported by FitzSimons (1937), of the 9 specimens 5 are adult, 1 is a subadult, and 3 are juveniles. FitzSimons found one of the adults to be a good match for the larger animal in Smith's (1846) plate L, fig. 1 and considered it “quite probably the type.” However, FitzSimons did not indicate which specimen this was, nor did he, or any previous or subsequent author formally designate a lectotype for the taxon (Uetz et al., 2019).
Smith's (1846) illustration shows an adult and a juvenile. The latter is not rendered in sufficient detail to determine much. The adult, however, clearly has strongly keeled tubercles, a feature not found in Namaqualand C. laevigatus. The written description, while relatively detailed, is insufficient to unambiguously distinguish C. bibronii from C. turneri, although the reference to the chin and gular scales as “minute” is certainly consistent with the former species. Smith's illustrated adult has an original tail. This characterizes only 2 of the adult syntypes, BMNH 1946.8.26.20 and BMNH 1946.8.26.22. Both Specimens unambiguously exhibit the diagnostic minute chin and gular scales of C. bibronii. In contrast, the other members of the type series are referable to C. turneri. Given that the syntype series is composite, we here designate a lectotype to stabilize the established use of the name Chondrodactylus bibronii for the primarily western South African species. BMNH 1946.8.26.20 is in good condition (Fig. 9), with the original tail broken, but present with the specimen. BMNH 1946.8.26.22 is in poor to fair condition with the tail still attached, but with the body discolored and the skin somewhat pulpy with the tubercles mostly flattened. It is likely that the latter specimen is that figured by Smith because the tail of the former is distinctive in its prominent tubercles, whereas that illustrated is more typical and similar to BMNH 1946.8.26.22. Given the somewhat deteriorated state of the other specimen, we here select BMNH 1946.8.26.20 as the lectotype of Tarentola bibronii. Although it is highly likely that the specimen was collected within the confines of the Cape Colony as it existed in Smith's time, the possibility that it was collected beyond the bounds of the colony remains, and there even exists the possibility that it was collected outside of the present Republic of South Africa because Smith's journey to Namaqualand crossed the Orange (Gariep) River into extreme southern Namibia. Thus, it is possible to restrict the type locality only slightly from the original “Southern Africa” to Southern Africa (South Africa or Namibia) south of –26.4°S and west of 26.4°E.
Werner (1910) described Pachydactylus bibronii var. stellatus as a subspecies from Great Namaqualand, southern Namibia, recognizing it as distinct from both P. laevigatus and the nominotypical form. Parker (1936) subsequently synonymized P. b. stellatus with P. turneri based on their shared widespread stellate tubercles. Parker assigned Namibian material from 4 localities to P. turneri. In fact, 3 of these (Otjosongombe, Otavifontein, and Lake Otjikoto) represent a clade of C. laevigatus that is characterized by particularly spinose scalation (see C. laevigatus species account), whereas the fourth, Maltahöhe, supports some of the most northerly populations of C. bibronii (Fig. 7A). Indeed, all southern Namibian Chondrodactylus that have stellate tubercles anywhere on the body are, in fact, referable to C. bibronii. Thus, Werner's (1910) types from Great Namaqualand are also C. bibronii and the synonymization of P. stellatus with P. turneri by Parker (1936) and followed by FitzSimons (1943) and Loveridge (1947) was in error. This name is here allocated to the synonymy of C. bibronii (Smith, 1846). This has been confirmed by examination of NMW 17995.4 (Gemel et al., 2019), which is unambiguously referable to this species (Fig. 10). In order prevent future instability should another member of the original syntype series be found to be referable to C. laevigatus, we here designate NMW 17995.4 as the lectotype of Pachydactylus bibronii stellatus. The identification of some of Franz Werner's type material can be difficult because he was not based at a museum himself, and largely described material housed in a diversity of collections (other than that in Vienna, from which he was barred until 1919; see Adler, 1989) or material from his own large private collection, portions of which were sold to institutions around the world. Delisle et al. (2013, 2016) listed BMNH 1923.3.16.7 (collector Leonhard Schultze) and NMW 17995:1–2 as syntypes. However, the BMNH registers indicate no specimen with the registration number listed and no corresponding specimen could be located among either the type or non-type material in London (P. Campbell, pers. comm. 1 June 2021). The solution seems to be that 23.3.16.7 was the Werner collection number associated with NMW 17995:3 and 17995:4. NMW 17995:1, 17995:2, and 17995:3 were all collected by Schltze and at least the last two came from the Werner collection, but only 17995:4 is listed as part of the type series by Gemel et al. (2019). It is certainly possible that these additional specimens, all of which bear only the locality “Deutsch SW-Afrika,” may be paralectotypes.
The chin scale/paravertebral dorsal tubercle ratio is sufficient to unambiguously identify specimens to Chondrodactylus bibronii. Intraspecific divergences in C. bibronii are particularly shallow, with no evidence of taxonomically relevant variation. Benyr (1995) illustrated examples of variation in the species and we illustrate the very minor variation seen across the range of the species (Fig. 8).
Figure 8.
Representative Chondrodactylus bibronii life photos. (A) Gochas, Hardap Region, Namibia; (B) Springbok, Namaqualand, Northern Cape Province, South Africa; (C) Southern Sperrgebiet, Karas Region, Namibia, –27.90622, 15.90694; (D) Vicinity of Prince Albert, Western Cape, South Africa. Photo credits: (A–C) Johan Marais; (D) Tyrone Ping.

Figure 9.
Lectotype of Tarentola bibronii Smith, 1846 (BMNH 1946.8.26.20), here designated, part of a composite type series, including both C. bibronii and C. turneri. (Top): entire specimen with broken original tail and scale bar (20 mm). Photograph A.M. Bauer. (Bottom): enlargement of head and trunk to show details of dorsal scalation. Photograph Patrick Campbell © The Trustees of the Natural History Museum, London. Differences in color reflect different lighting conditions.

Figure 10.
Lectotype of Pachydactylus stellatus Werner, 1910 (NMW 17995:4), here designated, from Bethanien, Karas Region, Namibia. Photo Georg Gassner (NMW).

Chondrodactylus fitzsimonsi (Loveridge, 1947)
Figures 5C, 6C, 7C, 11.
Pachydactylus laevigatus Schmidt (1933:5, pl. I, second from left).
Pachydactylus laeviegatus tessellatus FitzSimons, 1938:172, fig. 6. Holotype: TM 17202 (collector V. F. M. FitzSimons). Type locality: “Kamanyab” [= Kamanjab], Kunene Region] Namibia. See Mashinini and Mahlangu (2013) for additional data on the type series.
Pachydactylus laevigatus laevigatus (part) FitzSimons (1943:109).
Pachydactylus laevigatus fitzsimonsi Loveridge, 1947:400. Nomen substitutum (see below).
Pachydactylus fitzsimonsi Benyr (1995:50); Branch (1998:255).
Chondrodactylus fitzsimonsi Bauer and Lamb (2005:117).
Diagnosis. A moderate-sized Chondrodactylus (SVL to ≥89.3 mm SVL; CAS 176273; Bauer et al., 1993) bearing prominent subdigital lamellae. Body robust, somewhat depressed; head large, triangular, very broad across adductor musculature and angle of jaws (approximately as broad as long), snout moderately elongate, rounded (Fig. 5C), canthus rostralis relatively prominent, interorbital region weakly concave. Crown of head wide, flat; parietal table rectangular. Chin and gular scales enlarged, juxtaposed, either rounded or polygonal, a row of 5 chin scales approximately twice the width of a paravertebral dorsal tubercle (Fig. 7C). Dorsal head scales large, flattened (chiefly in midline) weakly domed (laterally), never keeled, larger on loreal region than on crown, largest above ears and across occiput. Anterior margin of ear bearing 3–4 enlarged conical tubercles. No discrete rows of enlarged dorsal tubercles. Dorsal scales large, heterogeneous in size, flat, and juxtaposed, rounded to polygonal, in some cases forming a virtual pavement of juxtaposed scales; interstitial granules absent or rare in northern specimens. Dorsal scales rounded, slightly raised but flat-topped in southern populations, never bearing a keel or mucro; interstitial granules often present (Fig. 6C). Scales on thighs flattened to weakly conical, smooth, not keeled or mucronate. Tail weakly (Fig. 11C) to strongly (Fig. 11D) verticillate, each whorl at tail-base bearing six enlarged conical (dorsal) to mucronate (lateral) tubercles, less prominent than in congeners; tubercles per whorl decreasing distally.
Dorsal coloration either dark, with almost black cross-barring or pale, oatmeal-colored with darker dorsal markings. Typically with a dark band on nape ventrolaterally coalescent (or nearly so) with a wide band across shoulders, the space between enclosing a lighter brown area. Additional broad bands at midbody, above mid-abdomen, and across hips, posterior border of each band darkest, anterior border from bold to diffuse, intermediate area paler; in some specimens only the dark posterior borders of these markings remain in adults. Small dark spots present or absent within pale spaces between body bands. White scales, when present, adjacent to darkest posterior borders of dorsal bands. Tail with alternating light and dark bands. Light bands more- or-less uniform; dark bands with bold anterior and especially posterior borders and fading to intermediate brown centrally. Approximately 7–8 dark bands on original tails. Pale lines from nostril through eye and on to upper temporal region less pronounced and more diffuse than in congeners. Iris bronze to coppery.
Distribution. Chondrodactylus fitzsimonsi is restricted to the western regions of northern Namibia and adjacent southern Angola (Fig. 12, right). In Namibe Province, Angola it is found south of Moçâmedes (formerly Namibe) to the Namibian border in Iona National Park (Ceríaco et al., 2016; Marques et al., 2018) with a single record from Ongueria, just above the escarpment in Huíla Province (Laurent, 1964). The distribution commonly reported for the species (e.g., Branch, 1998) extends southward in the Kunene Region of Namibia at least as far as the Grootberg Pass and the type locality at Kamanjab. A phenotypically distinctive morph has a far western distribution extending from the northern Kaokoveld southward to the west of the Brandberg and thence to Henties Bay in the Erongo Region. The species is absent from the northern Namib dunefields and in much of its range is associated with boulder landscapes.
Comments. Pachydactylus laevigatus fitzsimonsi Loveridge, 1947 was proposed to replace the name P. l. tessellatus FitzSimons, 1938, which was preoccupied by P. tessellatus (Werner, 1910), which is currently regarded as a synonym of Pachydactylus capensis (Smith, 1846). Schmidt's (1933) plate image of “P. laevigatus” from Pico Azevedo reveals that his specimens were, in fact, C. fitzsimonsi, and we have subsequently confirmed this through examination of the relevant specimen (CM 5621). Benyr (1995) treated C. fitzsimonsi as a full species in his unpublished thesis, and this was followed by Branch (1998) and subsequent authors. The identification of C. fitzsimonsi has generally been nonproblematic because of its restricted range and highly distinctive morphology.
There is deep divergence within C. fitzsimonsi. A chiefly Erongo Region clade from near the Brandberg and in near coastal regions north of Henties Bay is sister to remaining populations. This includes specimens from Gaias Spring in the southwestern Kunene Region, adjacent to the Brandberg. A more widely distributed clade (the chiefly Kunene subclade) occurs in near sympatry with the Erongo clade (within 2 km of each other near Gaias) but extends northward to the Angolan border and inland to the top of the escarpment. A single sequenced specimen from Henties Bay falling within this subclade may represent a translocated specimen. Chondrodactylus fitzsimonsi from the area of Gaias are morphologically identical regardless of clade membership and differ from specimens from the type locality and other more inland and northerly areas (see Fig. 11). The morphological and genetic variation within C. fitzsimonsi will be the subject of a subsequent study. The most common nuclear haplotype of C. fitzsimonsi is shared by both morphs of the species; however, 2 C. fitzsimonsi haplotypes found in the southwest of the distribution are close to haplotypes of C. pulitzerae (Heinz, 2011). Along the western edge of the species' distribution occasional specimens with head shapes and dorsal scalation intermediate between C. fitzsimonsi and either C. pulitzerae or C. laevigatus, with which they may be sympatric or even syntopic, are encountered.
Figure 11.
Chondrodactylus fitzsimonsi life photos. (A) Northern Kaokoveld, Kunene Region, Namibia; (B) Gaias, Kunene Region, Namibia; (C) Virei, Namibe Province, Angola, –16.09130, 12.83568; (D) Virei, Namibe Province, Angola, –16.09130, 12.83568. Photo credits: (A–B) Johan Marais; (C–D) Ishan Agarwal. (A) Illustrates the typical darker and bolder pattern of northern and inland populations, whereas (B) shows the paler “oatmeal-colored” pattern typical of the western, near-desert populations.

Figure 12.
Distribution of Chondrodatylus pulitzerae (left) and C. fitzsimonsi (right). Stars represent the type localities of Pachydactylus bibronii pulitzerae (purple) and P. laevigatus tessellatus (rose).

Chondrodactylus pulitzerae (Schmidt, 1933)
Figures 5B, 6D, 13.
Homodactylus bibroni Bocage (1867a:220).
Pachydactylus bibronii (part) Boulenger (1885:201).
Pachydactylus bibroni (part) Boulenger (1910:460).
Pachydactylus bibronii pulitzeræ Schmidt (1933:6, pl. 1, far left). Holotype: CM 5619 (collectors R. and L. Boulton). Type locality: “Pico Azevedo,” Namibe Province, Angola (McCoy and Richmond, 1966). The 2 paratypes are FMNH 18478 [formerly CM 5620] (Marx, 1958) and MCZ R39728 [formerly CM 5622] (Barbour and Loveridge, 1946).
Pachydactylus bibroni pulitzerae Parker (1936:129).
Pachydactylus laeviegatus laeviagatus (part) Loveridge (1947:398).
Pachydactylus bibronii pulitzerae (part) Loveridge (1947:403).
Pachydactylus bibronii turneri (part) Loveridge (1947:405).
Pachydactylus laevigatus pulitzerae Benyr (1995:50).
Pachydactylus turneri (part) Branch (1998:254).
Pachydactylus turneri pulitzerae Bauer (“1999” 2000:56).
Chondrodactylus pulitzerae Heinz (2011:55), Ceríaco et al. (2014:670).
Chondrodactylus cf. pulitzerae (part) Conradie et al. (2016:24).
Diagnosis. A large Chondrodactylus (to ≥102.2 mm SVL; PEM R21610) bearing prominent subdigital lamellae. Body robust and somewhat depressed. Head large and triangular, not as broad as long (usually <90% broad as long), inflection at ear relatively angular when viewed from above, snout more pointed than in congeners, elongate, canthus rostralis relatively well-developed, loreal region somewhat inflated, interorbital region strongly concave. Scales from parietal region forward small (smallest medially), smooth to weakly keeled, contrasting strongly with the very large stellate scales on the occiput and nape. Unlike congeners, most dorsal head scales, except those of snout, are separated from one another by minute granules (Fig. 5B). Enlarged tubercles of nape becoming more conical to mucronate laterally. Prominent spiny tubercles over ears. Chin and gular scales small and granular, approximately 5 chin scales contained within the diameter of a single paravertebral dorsal tubercle. Dorsal tubercles large, oval, and weakly to strongly keeled, usually separated by smaller granular scales, becoming conical to mucronate on flanks. A “naked” mid-vertebral line, at least on the occiput, nape and shoulders, although often extending well down the trunk or to the tail base, several granular scale rows wide and appearing at a distance as a pale mid-vertebral stripe (Fig. 6D). This may be clearly evident along the entire trunk (Fig. 13A), or part thereof (Fig. 13B, C) or may be relatively subtle (Fig. 13D) but is always present. A similar “naked” area, although always limited to the nape is present in some C. turneri. 16–18 regular to irregular longitudinal rows of relatively flattened, smooth to keeled, but rarely stellate, oval to rounded, dorsal tubercles. Trunk tubercles almost always separated from one another in all directions by small granules. Tubercles on dorsum of thigh very large, flattened to weakly inflated, becoming keeled or mucronate on shank. Tail distinctly verticillate, each whorl at tail-base bearing 6–8 enlarged, though not strongly projecting, keeled or conical (dorsal) to strongly mucronate (lateral) tubercles; tubercles per whorl decreasing distally.
Dorsal coloration usually buff to light brown with indistinct to moderately well-developed reddish-brown to dark brown dorsal crossbars, especially anteriorly. Basic pattern similar to congeners, with nape, shoulder, mid-body, mid-abdomen, and hip bands. White tubercles, when present, typically immediately posterior of dark bands. Pale interspaces in between darker bands may form a regular pattern of oval markings connected by the pale middorsal granular line (Fig. 13A). Thick pale line from snout to dorsal portion of eye generally distinct and bordered above and below by thinner dark lines. Tail banded, with 8–9 dark bands fading laterally; boundaries between pale and dark bands usually marked by complete or incomplete dark brown edges; some darker bands may be reduced to middorsal blotches.
Distribution. The species is known from southwestern and western Angola as far north as Capanda in Malanje Province (Ceríaco et al., 2014) and Luanda and Cacuaco, Luanda Province (Ceríaco et al., 2017; Marques et al., 2018; Fig. 12, left). Both the Capanda record and one from Huambo Province are above the Angolan Escarpment. Loveridge (1947) followed by Mertens (1955, 1971) tentatively assigned material (e.g., MCZ R43401) from the Erongo Mountains in Namibia to this taxon, although he suggested they might alternatively represent an undescribed species. In fact, only C. laevigatus occurs in this region. Ceríaco et al. (2016) noted the presence of C. pulitzerae in far northwestern Namibia but did not provide details. It occurs from the border at the Kunene River south as far as Sesfontein (entire Namibian distribution in the Kunene Region) with a single locality further south at “10 km N of the Hunkab River” (but unknown where along the river, TM 52910–11). Throughout most of its range in Namibia it is sympatric with C. laevigatus and C. fitzsimonsi, although its easternmost occurrences in both Angola and Namibia are out of the range of the latter species.
Comments. Prior to its description by Schmidt (1933), specimens referable to this taxon were assigned to P. bibronii (Bocage, 1867a, b, 1887a, b, 1895; Boulenger, 1885; Mertens, 1926), based on overall similarity and the presence of mostly strongly keeled or mucronate scales across the dorsum. Parker (1936) and later authors (Mertens, 1937, 1938; Barbour and Loveridge, 1946; Loveridge, 1947; Hellmich, 1957a, b; Marx, 1958; Laurent, 1964) accepted Schmidt's trinomial and regarded P. b. pulitzerae as an Angolan endemic (but see comments about Erongo populations above), although Monard (1937) used only the binomen C. bibronii and Loveridge (1947) used not only Schmidt's name but also P. l. laevigatus and P. b. turneri in referring to some Angolan specimens. Pachydactylus bibronii pulitzerae was subsequently referred to by Mertens (1955, 1971) and Wermuth (1965) but otherwise the name then went largely unused in the published literature for 5 decades. It was regarded as a valid subspecies of P. laevigatus by Benyr (1995) and as a full species of Chondrodactylus by Heinz (2011) in their respective unpublished theses. Ceríaco et al. (2014) first used C. pulitzerae as a specifically valid name on the basis of Heinz's (2011) molecular data, and it has since been used consistently (e.g., Ceríaco et al., 2016, 2017; Conradie et al., 2016; Heinicke et al., 2017; Marques et al., 2018; Branch et al., 2019).
Specimens genetically sampled fall into a more northern clade, extending northward of the Giraul River in Namibe Province, Angola, and a southern clade occurring southward into Namibia. The genetic identity of a specimen from Quiçama (CAS 263109) with one from Cambambe (PEM R21611), 150 km distant, and their high similarity to specimens from northern Namibe, approximately 450 km away, along with the sporadic distribution of C. pulitzerae north of Lobito, raises the possibility that some northern records may represent introductions, although Bocage (1895) stated that the species (as Pachydactylus bibronii) was common south of the Kwanza River. More extensive sampling is needed both north and east of Namibe Province to determine whether the range is contiguous and whether there is genetic substructure consistent with geography.
Figure 13.
Chondrodactylus pulitzerae life photos. (A) Rocky outcrop near Virei, Namibe Province, Angola, –16.05543, 12.82340; (B) Chimalavera, Benguela Province, Angola; (C) 22 km west of Caraculo, Namibe Province, Angola, –15.01558, 12.55503; (D) Quiçama National Park, Luanda Province, Angola. Photo credits: (A) Ishan Agarwal; (B) Luis M.P. Ceríaco, (C) Johan Marais; (D) John Cavagnaro.

Chondrodactylus turneri (Gray, 1864)
Figures 5D, 6E, 7B, 14, 15.
Homodactylus turneri Gray, 1864: Proc. Zool. Soc. London 1864:59, pl. 9, fig. 2. Lectotype: BMNH 1946.8.26.7 (collector J. Kirk), here designated (see Comments below). Paralectotypes: BMNH 1946.8.26.8, 64.1.9.10–13, 64.1.9.15 (collector J. Kirk). Type locality: “southeastern Africa,” (restricted to “Tette” [=Tete], Mozambique fide Loveridge 1947:405; see Comments below).
Pachydactylus Bibronii (part) Peters (1865:457).
Homodactylus bibronii (part) Gray (1865:612).
Pachydactylus bibronii bibronii (part) FitzSimons (1935b:336).
Pachydactylus bibronii turneri (part) Parker (1936:129).
Pachydactylus bibronii var. turneri (part) FitzSimons (1943:109).
Pachydactylus bibronii turneri (part) Loveridge (1947:405).
Pachydactylus laevigatus turneri Benyr (1995:50)
Pachydactylus turneri Branch (1998:254).
Pachydactylus turneri turneri Griffin (2003:30).
Chondrodactylus turneri Bauer and Lamb (2005:117).
Diagnosis. A moderately sized Chondrodactylus (to ≥95 mm SVL, MCZ R190407) bearing prominent subdigital lamellae. Body robust and somewhat depressed. Head large, relatively deep, and subtriangular, nearly as broad as long, inflection at ear gently curved when viewed from above (contrasting with C. pulitzerae), snout typically shorter and broader than in congeners, canthus rostralis moderately developed more variable than in congeners; loreal region moderately to strongly inflated, interorbital region flattened to weakly concave. Tubercles on occipital region very large and keeled to stellate, becoming smaller on the crown and interorbital region and slightly larger again on the dorsum of the snout; interorbital and especially snout scales distinctly domed, most bearing weakly defined keels. Most anterior dorsal head tubercles in contact with one another, whereas tubercles of the occiput and nape usually well-separated from one another by tiny granules (Fig. 5D). Tubercles around ear heterogeneous, generally less massive than in other congeners. Chin and gular scales small and granular, becoming progressively smaller postero-medially (Fig. 7B), approximately 5 chin scales contained within the diameter of a single paravertebral dorsal tubercle. Dorsal tubercles large, oval to rounded, strongly keeled, variably bearing small peripheral pustules or short to long radiating ridges in a stellate pattern, becoming smaller and more conical to mucronate on flanks. Trunk tubercles usually well-separated by smaller granular scales, forming 14–18, usually very regular longitudinal rows of enlarged tubercles (Fig. 14). In addition, mid-vertebral line with much smaller, rounded, keeled tubercles separated from one another by alternating pairs of paravertrebral keeled tubercles intermediate in size between the tubercles of the mid-dorsal and more lateral tubercle rows (Fig. 6E). Tubercles on dorsum and postaxial surface of thigh and shank large, somewhat flattened, keeled or stellate. Scales on upper arm non-tuberculate, imbricating, becoming tubercular on forearm, keeled to mucronate, but much smaller than tubercles of shank. Tail distinctly verticillate, each whorl at tail-base bearing six (eight close to tail base) enlarged, though not strongly projecting, keeled or conical (dorsal) to strongly mucronate (lateral) tubercles; tubercles per whorl decreasing to 4 then 2 on distal portion of tail.
Dorsal coloration buff to light to medium brown, sometimes with reddish or grayish tones with indistinct to moderately well-developed dark brown to almost black dorsal crossbars, especially prominent anteriorly. Basic pattern similar to congeners, with nape, shoulder, mid-body, mid-abdomen, and hip bands. White tubercles, when present, typically immediately posterior to or within dark bands. Tail banded, boldly or obscured, with 8–10 dark bands fading laterally; boundaries between pale and dark bands usually marked by complete or incomplete dark brown edges; some darker bands may be reduced to middorsal blotches.
Additionally, C. turneri exhibits a genetic autapomorphy—a rearrangement of the genes coding for transfer RNAs downstream of ND2 (see Discussion), which is not only unique among its congeners, but also among all gekkotans.
Distribution. Chondrodactylus turneri occupies most of the southeastern margin of the distribution of the genus (Fig. 16). Its range in South Africa and Eswatini (formerly Swaziland) has been presented by Branch (2014; only records east of 25°E apply to this species, others are actually C. laevigatus). It occurs in northern KwaZulu-Natal (i.e., Zululand), central and eastern Eswatini, throughout most of Mpumalanga and Limpopo (except parts of Sekhukuneland), in northern Gauteng and in northeastern North West Province. In Botswana C. turneri occurs along the southeast margins of the country and in Zimbabwe it occupies the southern and central parts of the country. Nearly all Chondrodactylus records in southern Mozambique are also likely referable to this species, although this is based on biogeographic grounds and weak support from morphology. The precise dividing line between C. laevigatus and C. turneri in Zimbabwe and central and northern Mozambique remains unclear but, based on morphology and limited genetic sampling, the division in the former country may roughly correspond to the division between the Zambezi and Limpopo drainages.
Sampling in Mozambique is uneven and genetic material is derived only from Nampula in the north of the country. Specimens from throughout the northern provinces of Niassa, Cabo Delgado, and Nampula provinces all appear to be C. laevigatus. Specimens from south of Beira are conspecific with those in Masvingo and southern Manicaland in Zimbabwe and with those in the South African lowveld (i.e., C. turneri). This is supported by the relatively contiguous lowland habitat and, to the extent possible, in the absence of unambiguous diagnostic features, by morphology. Specimens from the type locality of Homodactylus turneri Gray, 1864 at Tete and from lowland localities downstream of there are also almost certainly referable to this species. However, specimens from closer to Cahora Bassa in western Tete Province and from northern portions of Manhica and Sofala provinces are problematic. Geographically, they lie between C. laevigatus from the Vumbas in Zimbabwe (genetically confirmed) to the southwest and Malawi (morphologically determined) and northern Mozambique to the northeast. However, the Zambezi Valley provides a low-elevation riparian corridor deep into the inland of Tete Province, with Tete itself lying at only 140 m. Elevation may explain some aspect of the distribution boundary between C. laevigatus and C. turneri, but it is clearly not the sole factor because C. laevigatus occurs at quite low elevations in some places, whereas C. turneri is present in Bulawayo and the Waterberg Massif of Limpopo, both >1,000 m in elevation.
Comments. The published type locality for C. turneri (Gray, 1864) is “SouthEastern Africa,” interpreted to be Tette (=Tete), Mozambique by Loveridge (1947) and entered as such in the British Museum of Natural History (now The Natural History Museum, London) re-registration catalogue. In fact, Gray (1864) explicitly listed Tette (now Tete) as a locality for only some of the specimens collected by Kirk. The rest of the specimens, including Homodactylus turneri, are associated only with the general locality “South-Eastern Africa,” which could be anywhere within the area visited by John Kirk on the Zambezi Expedition during the period 1858–1863. Although Kirk spent a good deal of time at Tete and in the Shire Highlands in what is today Malawi, he also collected specimens below Tete on the Lower Zambezi, including near Sena (Senna) and the mouth of the Shire River. In addition, during the early period of the expedition, Kirk was stationed in the Zambezi Delta and on numerous occasions during the expedition he returned to the river mouth. Other biological specimens returned by Kirk have the localities Quellimane (now Quelimane) and Gorongoza (Günther, 1864; Hill, 1922; Dritsas, 2005). When locality data were available for Kirk's material, he apparently did provide it to the scientists who were working with the material (Dritsas, 2005). The absence of a specific locality suggests that either the specimens represented something widespread in the area covered by Kirk's journeys or that the data were not recorded or were subsequently lost. It must also be remembered that Kirk's primary natural history interest was in botany (Hill, 1922), so it is perhaps not surprising that herpetological material, largely collected incidentally to plants, might not be as carefully recorded. Based on a lack of explicit locality data accompanying the syntypes of H. turneri, we think it likely that the type series of H. turneri may have originated from multiple sites in the lower Zambezi Valley.
All 7 syntypes of Homodactylus turneri are in good condition, nonetheless, their specific identity is still difficult to establish with certainty. All appear to be referable to Chondrodactylus turneri as recognized here on the basis of ≥1 morphological traits; however, there is overlap with C. laevigatus in each of these traits. Given the extreme similarity of these two congeners and the uncertainty surrounding their precise distributional limits (as well as the extent of the area from which the types were collected), we consider it prudent to select a lectotype to stabilize the current use of the name C. turneri. We here designate BMNH 1946.8.26.7 (Fig. 15) as the lectotype of Homodactylus turneri on the basis that it is characterized by the greatest number of C. turneri features, specifically, head deep, snout short and broad, lores inflated, and relatively extensive exposed granular skin on occiput, nape, and anterior midline of the back.
This species was synonymized with Pachydactylus bibronii by Peters (1865) and, for the majority of the period since, it has remained in the synonymy of this species (see synonymies of FitzSimons, 1943 and Loveridge, 1947). Gray (1865) himself, noted that he had somehow overlooked Smith's (1846) description and illustration of Tarentola bibronii and sank H. turneri into its synonymy; however, he retained the generic name Homodactylus, believing the species to be generically distinct. Gray (1865) further acknowledged that Peters, who had examined Smith's types, had pointed out the synonymy. Loveridge (1947), largely following Parker (1936) and FitzSimons (1943), recognized it as a subspecies of C. bibronii but included P. bibronii stellatus in its synonymy and his concept of the taxon included specimens from Angola and Namibia currently allocated to C. laevigatus as well as true C. bibronii from the Free State and Northern Cape provinces of South Africa. Benyr (1995), however, identified a reliable scale character (the size of the anterior chin scales relative to the paravertebral dorsal tubercles) that unambiguously separated P. bibronii from what he considered to be P. laevigatus, with 3 subspecies, the nominotypical form in the Northern Cape and western Namibia, P. l. pulitzerae in Angola, and P. l. turneri in the east. Benyr (1995), however, had overlooked that Homodactylus turneri Gray, 1864 had priority over Pachydactylus laevigatus Fischer, 1888 and thus, as corrected by Branch (1998) and discussed by Lamb and Bauer (2002), the taxon names became P. t. turneri, P. t. pulitzerae, and P. t. laevigatus. Since the transfer of the P. bibronii group to Chondrodactylus the majority of the literature on Southern African reptiles has applied the name C. turneri to scansorial Chondrodactylus (other than C. bibronii) distributed from Kenya to South Africa (e.g., Branch, 2014).
The genetic distinctiveness of C. laevigatus from C. turneri sensu stricto was demonstrated by Heinz (2011) in his unpublished thesis; however, the two names were not used in the published literature as specifically valid to refer to different taxa until several years later (see C. laevigatus account), although without explicit justification. Phenotypically, C. laevigatus from the east of its range strongly resembles C. turneri; thus, unambiguous identification of specimens from areas of parapatry, from Botswana and Zimbabwe through East Africa, can be difficult, especially in the case of juveniles.
Figure 14.
Chondrodactylus turneri life photos. (A) Tete, Tete Province, Mozambique. (B) Gaza, Gaza Province, Mozambique. (C) Lephalale, Limpopo Province, South Africa. (D) Steelpoort, Limpopo Province, South Africa. (E) Alldays, Limpopo Province, South Africa. Photo credits: (A–C) Luke and Ursula Verburgt (Enviro-Insight); (D–E) Johan Marais.

Figure 15.
Lectotype of Homodactylus turneri Gray, 1864 (BMNH 1946.8.26.7), here designated, from Tete, Tete Province, Mozambique. Photograph by A.M. Bauer © The Trustees of the Natural History Museum, London.

Figure 16.
Distribution of Chondrodactylus turneri (green) and C. laevigatus (brown). Scattered genetic samples in the east of the range of C. laevigatus provide an indication of the approximate southern boundary of the species east of 20°E. Split green/brown symbols indicate specimens from near the boundary zone between the two taxa that have not been genotyped and which were examined prior to the “discovery” of relevant diagnostic features, or which have not been examined by the authors. Stars represent the type localities of Homodactylus turneri (green) and Pachydactylus laevigatus (brown).

Chondrodactylus laevigatus (Fischer, 1888)
Figures 5F, G, H, 6E, F, G, H, 17, 18, 19.
Pachydactylus capensis Peters (1854:615). [previously included in the synonymy of C. turneri, e.g., Loveridge (1947)].
Platydactylus (Pachydactylus) Bibronii Peters (1862:15). [previously included in the synonymy of C. turneri, e.g., Loveridge (1947)].
Pachydactylus Bibronii Peters (1869:139).
Pachydactylus laevigatus Fischer, 1888:15, pl. 2, fig. 3. Syntypes: BMNH 1946.8.26.1–2 (formerly BMNH 89.12.16.9–10; collector J. Steingröver). Type locality: “bei Aus und auf dem Wege nach Bethanien” [= near Aus and on the way to Bethanien], Karas Region, Namibia.
Pachydactylus bibroni laevigatus Methuen and Hewitt (1914:129, fig. 14).
Pachydactylus stellatus Schmidt (1933:5).
Pachydactylus bibronii laevigatus FitzSimons (1935a:527).
Pachydactylus bibronii bibronii (part) FitzSimons (1935b:336).
Pachydactylus laevigatus laevigatus FitzSimons (1938:172).
Pachydactylus bibronii turneri (part) Parker (1936:129).
Pachydactylus bibronii pulitzerae (part) Loveridge (1947:403).
Pachydactylus bibronii pulitzerae Hellmich (1957b:49)
Pachydactylus turneri (part) Branch (1998:254).
Pachydactylus turneri laevigatus Griffin (2003:30).
Chondrodactylus turneri (part) Bauer and Lamb (2005:117)
Chondrodactylus turneri laevigatus Bauer et al. (2006:90).
Chondrodactylus cf. pulitzerae (part) Conradie et al. (2016:24).
Chondrodactylus laevigatus Ceríaco et al. (2014:670).
Diagnosis. A large Chondrodactylus (to ≥100 mm SVL, MCZ R190191) bearing prominent subdigital lamellae. Body robust and somewhat depressed. Head large, relatively depressed, and subtriangular, not as broad as long but proportionally wider across adductor region than C. pulitzerae; inflection at ear gently curved when viewed from above, snout somewhat longer and more acuminate than in C. turneri, canthus rostralis moderately developed, loreal region weakly to moderately inflated, interorbital region flattened to weakly concave or with a narrow furrow. Tubercles on occiput and posterior half of crown large very large and keeled to stellate, becoming smaller on the anterior crown and interorbital region and slightly larger again on the dorsum of the snout; interorbital and especially snout scales flattened or domed, keelless or with only weakly defined keels. Most anterior dorsal head tubercles in contact with one another, whereas tubercles of the crown and nape may be separated from one another by tiny granules (Fig. 5E–H), although typically not as widely spaces as in C. turneri. Tubercles anterior and dorsal to ear heterogeneous, generally large and bearing a prominent longitudinal keel. Chin and gular scales small and granular, becoming progressively smaller postero-medially (condition similar to Fig. 7B), approximately 5 chin scales contained within the diameter of a single paravertebral dorsal tubercle. Dorsal tubercles large, oval to rounded, from unkeeled to strongly keeled, if strongly keeled then variably bearing small peripheral radiating ridges, although not as strongly stellate as in C. bibronii, becoming smaller and more conical on flanks. Trunk tubercles usually well-separated by smaller granular scales, forming 14–20 (usually 18 in the western clade, 14 in the eastern clade, and 16–18 in the Kgaligadi clade), slightly irregular to very regular longitudinal rows of enlarged tubercles (Fig. 17). In addition, mid-vertebral line with a mixture of granules and smaller, rounded, unkeeled to moderately keeled tubercles (single or in pairs; Fig. 6F–H). Tubercles on dorsum and postaxial surface of thigh and shank large, somewhat flattened, to keeled or mucronate. Scales on upper arm non-tuberculate, flattened, imbricating, becoming tubercular on forearm, conical to mucronate, but smaller and less prominent than tubercles of shank. Tail distinctly verticillate, each whorl at tail-base bearing 6 (8 close to tail base) enlarged, keeled (proximal whorls) or conical to strongly mucronate tubercles; tubercles per whorl decreasing to 4 then 2 on distal portion of tail.
Dorsal coloration buff to light to medium brown, sometimes with reddish or grayish tones with indistinct to well-developed dark brown to almost black dorsal crossbars, especially prominent anteriorly. Basic pattern similar to congeners, with nape, shoulder, mid-body, mid-abdomen, and hip bands. White tubercles, when present, typically immediately posterior to or within dark bands. Tail banded, boldly or obscured, with 8–10 dark bands fading laterally; boundaries between pale and dark bands usually marked by complete or incomplete dark brown edges; some darker bands may be reduced to middorsal blotches.
Variation. Individuals of the western clade of C. laevigatus are highly distinctive and easily distinguished from all other congeners, including members of the “Kgaligadi” and Eastern clades. They are generally more depressed overall (Fig. 17A–B) and have the characteristic button-scale type tubercles, which are typically raised but not, or only weakly, keeled. This clade extends from the southernmost limits of the species to the Otjozondjupa Region of northcentral Namibia. The “Kgaligadi” clade extends northward from the Otjozondjupa and Erongo regions to southern Angola and eastward through the Caprivi Strip and northern Kgaligadi, and the Eastern clade continues from western Zimbabwe and central Zambia to East Africa. We could identify no diagnostic characters distinguishing members of these two clades from one another. Members of these clades usually have the dorsal tubercles more strongly keeled or conical (Fig. 17D) and often bearing transverse stria or having a stellate pattern of keels on at least some scales (particularly on the occiput and nape). Especially strongly keeled specimens of the “Kgaligadi” clade occur in populations near Uis, Takauasa (e.g., NMNW 210), and in the Grootfontein/Tsumeb region of northern Namibia (Fig. 17E). The Eastern clade, likewise, expresses a spectrum of rugosities from moderate to extensive (Figs. 17E, F, H, G and Fig. 18 in order of increasingly large and strongly textured tubercles). The Western clade button-scaled geckos, which share much of their range with the very rugose C. bibronii may be exhibiting character displacement in areas of sympatry. The greatest difficulty in the identification of Chondrodactylus species from each other is distinguishing the “Kgaligadi” and Eastern clade C. laevigatus from C. turneri. This is especially difficult in the broad area from central Zimbabwe to central Mozambique in which they likely occur in parapatry or potentially even sympatry (unverified).
Distribution. Chondrodactylus laevigatus has by far the broadest range of any member of the genus (Fig. 16). Its distribution in South Africa has been documented (as C. turneri [part]) by Branch (2014) and is limited to northern portions of the Northern Cape Province from near Springbok, east along the Orange River as far as Upington, with scattered records near the Molopo and Nossob rivers in the Mier Kalahari and Steinkopf in Namaqualand. It is probably more-or-less continuously distributed throughout this area except for sandy areas that offer no suitable refuge sites, but is most frequently encountered from Lekkersing northward to the Namibian border and in rocky areas along the south shore of the Orange River, where it is syntopic with C. bibronii (Methuen and Hewitt, 1914), even occupying refuges beneath the same rock slabs (Bauer and Branch, “2001” 2003). Virtually the whole of Namibia is occupied by C. laevigatus, with the exception of the Namib sand seas and portions of the Kalahari that are devoid of rocks and trees. Nonetheless, isolated rocky outcrops surrounded by sand for many kilometers may support populations of C. laevigatus. Verified records in Angola are few (Marques et al., 2018) but include records in Cunene (Monard, 1937), Huíla (Baptista et al., 2019; Butler et al., 2019) and Cuando Cubango (Conradie et al., 2016 [as C. cf. pulitzerae]) provinces, all above the Angolan escarpment. It is likely distributed widely across the southern Angolan Plateau, although the verified records are too few to estimate its northern limits. A record by Schmidt (1933) from Pico Azevedo in the lowlands of Namibe is referable to C. fitzsimonsi (Marques et al., 2018); however, we here report several records in coastal Namibe Province (Table 1).
To the east of Namibia and Angola, the distribution of C. laevigatus is less precisely known. It occurs throughout suitable habitats in western and northern Botswana, western and northern Zimbabwe, through Zambia and diagonally northeastward as far as southern Kenya. No examples of sympatry with C. turneri are known with certainty, but its ability to co-occur with C. bibronii and C. fitzsimonsi suggests that this may be possible, perhaps in regions of central Zimbabwe or along the course of the Zambezi River in Mozambique. The eastward extension of C. laevigatus roughly follows the Zambezi Valley and in Zambia is mostly bracketed by the Zambezi and Luangwa rivers (Simbotwe and Mubamba, 1993). Sampling in central Mozambique is poor, but existing records suggest that lowland records south of the Pungwe River are C. turneri, whereas those north of the Ligonha River are C. laevigatus. The distribution of C. laevigatus in Tanzania and Kenya appears to be disjunct and scattered (Loveridge, 1928, 1947, 1951, 1955, 1957a). This may be an artifact of collection effort or bias or it may reflect limited suitable habitats, or perhaps competition with large-bodied Hemidactylus spp. and Elasmodactylus spp.
An isolated record of a Chondrodactylus sp. from Rwanda has often been reported or plotted, albeit with some speculation (de Witte, 1941; Loveridge, 1947, 1957b; Spawls et al., 2006, 2018) and stems from a report by Sternfeld (1912) based on a specimen from the “Vulkangebiet.” The single specimen, ZMB 24330 (Fig. 18), was collected by Reinhard Houy on the 1911 expedition led by Hans Heinrich Josef Meyer to the area between Lake Kivu and Lake Victoria (Meyer, 1913). The Museum für Naturkunde catalogue entry for the specimen lists only “Dt. Ost Afrika.” Vulkangegiet, the published locality, is more specific but still vague, referring to the area to the northeast of Lake Kivu, in northern Rwanda and adjacent Nord-Kivu Province, Democratic Republic of Congo. This record has never been verified by additional vouchers or by records with specific localities and the species has not been mentioned in more recent regional literature (e.g., Laurent, 1956). In the absence of confirmation of the occurrence of Chondrodactylus in the region and in light of the unlikely disjunction from the otherwise more-or-less contiguous distribution of the genus, we regard this record as dubious and consider both the Democratic Republic of Congo and Rwanda to be outside of the range of the genus. ZMB 24330 is typical of Chondrodactylus laevigatus from East Africa (see below) and the expedition would have passed through the known range of this species from Kilamatinde to Morogo in east-central Tanzania on its way back to the coast. The mid-sized chin scales (Fig. 18B) and slightly concave snout profile (Fig. 18C) are characteristic of C. laevigatus in general, whereas the very large body tubercles (Fig. 18A) are typical of the East African clade specifically.
The exact patterns of distribution of C. turneri and C. laevigatus in Zimbabwe, central Mozambique, and southernmost Malawi are uncertain. The characters used herein to distinguish eastern (highly tuberculate) laevigatus from turneri were not yet determined more than a decade ago when this project began. Thus, some specimens were examined before what ultimately proved to be the most diagnostically valuable characters were identified. Further, not all specimens for which we have locality data (i.e., are plotted in Fig. 16) have been examined by us. This applies particularly to specimens from the Natural History Museum of Zimbabwe. From genotyped individuals, we know that C. laevigatus extends across northern Zimbabwe from Lake Kariba to the former Elim Mission in the Vumba Mountains, whereas C. turneri occurs from Bulawayo east to southern Masvingo and Manicaland provinces. Chondrodactylus laevigatus likely occupies the higher elevations throughout the Eastern Highlands of Zimbabwe, but we are currently unsure of the allocation of the populations of the Zimbabwean Midlands. Likewise, we are uncertain where a switch to (or an area of sympatry with) C. turneri might occur between the Chimanimani Mountains and the adjacent lowlands. Likewise, the identity of populations between the lower end of Lake Kariba and the vicinity of Tete and between the Lower Zambezi and the Shire Highlands of Malawi remains uncertain.
Comments. The description of Pachydactylus laevigatus was by J.G. Fischer, who was the volunteer in charge of the herpetological collections of the Hamburg Museum at the time (Adler, 2007). Fischer (1888) mentioned only 2 specimens of this species received from Steingröver, one of which was illustrated. When Fischer died the following year, his collection was purchased by the British Museum from “Madame Fischer.” The collection included a number of other Namibian specimens corresponding to material cited in the same paper. Fischer's (1888) illustration of the dorsum of one of his syntypes matches exactly the color pattern of BMNH 1946.12.26.1 (Fig. 19), as does its regenerated tail and size (89 mm SVL), confirming its identity as a type. Details of the second specimen also correspond well to BMNH 1946.12.26.2. Both syntypes are unambiguously assignable to the same taxon and cannot be mistaken for any other congener.
The type locality of Pachydactylus laevigatus Fischer, 1888 lies within the distribution of the southwestern clade and members of this clade are easily diagnosable on morphological grounds, being characterized by the button-scaled morphology, with tubercular keels and mucrones lacking. In both remaining subclades, body scalation is more heterogeneous and some populations are characterized by an extremely acuminate tuberculation, similar to that of C. turneri (see above). Given the lack of ambiguity regarding the identity of the syntypes and the fact that no syntypes are unaccounted for, there is no compelling reason to designate a lectotype in this instance.
Prior to the description of P. laevigatus, specimens of this species were referred to P. bibronii (e.g., Boulenger, 1885). As the specific epithet implies, typical C. laevigatus are characterized by their relatively smooth (so-called “button-scaled”) tubercles, which easily distinguish them from C. bibronii, which have much more strongly keeled or mucronate tubercles. However, although this scale morphology is typical in the western half of Namibia and in adjacent areas of South Africa, the phenotype of C. laevigatus becomes decidedly more “bibronii-like” from the Namibian Kalahari, Kavango, and Zambezi Regions eastwards. As a consequence, eastern P. laevigatus until 1995 had frequently been assigned to P. bibronii. Benyr (1995), however, identified a reliable scale character (the size of the gular scales relative to the paravertebral dorsal tubercles) that unambiguously separated P. bibronii from what he considered to be P. laevigatus, with 3 subspecies—the nominotypical form in the Northern Cape and western Namibia, P. l. pulitzerae in Angola, and P. l. turneri in the east of the subcontinent. Benyr (1995), however, had overlooked that Homodactylus turneri Gray, 1864 had temporal priority over Pachydactylus laevigatus Fischer, 1888. Branch (1998), however, who was cognizant of this, recognized a monotypic P. turneri for all geckos in the P. bibronii group exclusive of P. bibronii itself and the distinctive C. fitzsimonsi from northwestern Namibia. Although Branch (1998) provided no justification for the resurrection of P. turneri, the rationale was subsequently explained by Lamb and Bauer (2002), and the taxon names subsequently recognized in light of Benyr's (1995) work were P. t. turneri, P. t. pulitzerae, and P. t. laevigatus. Most subsequent authors did not use trinomials; therefore, the name Pachydactylus turneri (and, after 2005, Chondrodactylus turneri) was widely applied sensu Branch (1998) until the genetic distinctiveness of C. laevigatus and C. pulitzerae from C. turneri sensu stricto was explicitly demonstrated by Heinz (2011) in his unpublished thesis. However, C. turneri and C. laevigatus were not recognized in their current sense in the published systematic literature until Ceríaco et al. (2014) and later Heinicke et al. (2017), although again without explicit justification. Marques et al. (2018) likewise used C. laevigatus as specifically distinct from C. turneri, citing the unpublished phylogeny of Heinz (2011).
Heinz (2011) reported shared nuclear haplotypes amongst individuals from across Namibia, indicating gene flow across the various morphotypes of C. laevigatus. Likewise, he found similar haplotypes represented in northeastern Zimbabwean Chondrodactylus that we here interpret as C. laevigatus, whereas these haplotypes differed markedly from those in southeastern Zimbabwe and eastern South Africa, all of which also share a rearrangement in ND2 and are here interpreted as C. turneri. In part because of these shared haplotypes, we choose to recognize C. laevigatus as a single species. However, an argument could be made for its subdivision into 3 putative species, based on the deep mitochondrial divergence between the main subclades and their strong support (BS 100%). Under such a scenario C. laevigatus sensu stricto, the western clade, would be easily diagnosable, but the difficulties of distinguishing the more eastern forms from C. turneri would still remain.
Figure 17.
Chondrodactylus laevigatus life photos. (A) Augrabies Falls National Park, Northern Cape Province, South Africa; (B) Kobos, Hardap Region, Namibia; (C) Otavi Highlands, Otjosondjupa Region, Namibia, –19.32511, 18.39078; (D) Shamvura Lodge, Kavango Region, Namibia; (E) Cuamba Town, Niassa Province, Mozambique; (F) Near Nsanje, Nsanje District, Southern Region, Malawi; (G) Near Mtera Reservoir, Dodoma/Iringa Regions, Tanzania; (H) West of Magadi, Kajiado County, Kenya. A and B represent the Western clade, C and D represent the “Kgaligadi” clade, and E––H represent the Eastern clade. Photo credits: (A) Luke Kemp; (B–D) Johann Marais; (E) Daniel M. Portik; (F–G) Colin Tilbury; (H) Steven Spawls.

Figure 18.
ZMB 24330, a specimen originally reported as Pachydactylus bibronii from the “Vulkangebiet” of East Africa by Sternfeld (1912). No further specimens from this area (modern Rwanda) have been reported and it is likely that that this specimen, which is typical of East African C. laevigatus in its large body scales (A), mid-sized chin scales (B), and slightly concave snout in profile (C) was collected on the return trip to the coast through central Tanzania.

Figure 19.
Syntype of Pachydactylus laevigatus Fischer, 1888 (BMNH 1946.12.26.1), from the western Karas Region, Namibia. Photograph by A.M. Bauer © The Trustees of the Natural History Museum, London.

Key to the Species of Chondrodactylus
1a. Digits short, without adhesive toepads (Fig. 1 left) C. angulifer
1b. All digits with toepads bearing broad adhesive lamellae (Fig. 1 right) 2
2a. Chin and gular scales large, a row of 5 chin scales approximately twice the width of a paravertebral dorsal tubercle (Fig. 7C); head strongly triangular, about as wide as long (Fig. 5C); dorsal scales flat or weakly raised but never keeled (Fig. 6C) C. fitzsimonsi
2b. Chin and gular scales small, ≥5 chin scales contained within the width of a single paravertebral tubercle (Fig. 7 and B) 3
3a. Chin and gular scales minute and granular, approximately 5 chin granules contained in half the width of a paravertebral tubercle (Fig. 7A); dorsal tubercles large, always strongly keeled and/or mucronate (Fig. 6B) C. bibronii
3b. Chin and gular scales small and granular, approximately 5 chin granules contained in the width of a single paravertebral tubercle (Figs. 7B, 18B); dorsal tuberculation variable (Figs. 6D–H) 4
4a. Head relatively narrow (usually <90% broad as long), snout acuminate; large stellate tubercles on nape and occiput contrasting with smaller, less rugose scales on crown and snout (Fig. 5B); dorsal midline on at least nape and shoulders “naked”—without small tubercles, often giving the appearance of a white vertebral stripe (Fig. 6D) C. pulitzerae
4b. Head wider (>90% broad as long), snout broader, less acuminate (Figs. 5D–H); anterior middorsum without “naked” stripe, at least some tubercular scales in dorsal midline (Figs. 6E–H) 5
5a. Head and body somewhat depressed (Figs. 17A–B); dorsum with distinctly raised, but keelless or very weakly keeled tubercles (Fig. 6H) C. laevigatus (part—Western Clade)
5b. Head and body not depressed; dorsal tubercles strongly keeled to stellate (Figs. 6E–G) 6
6a. Head deep; snout short and broad, head approximately as wide as deep, lores moderately to strongly inflated (Fig. 5D); snout deep (less steeply sloped; Fig. 14) and slope of snout sometimes with a slight convexity when viewed in profile; relatively extensive exposed granular skin on occiput, nape, and anterior midline of the back; [Southeastern Africa, east of 25°E, southern Zimbabwe and Mozambique lowlands and lower Zambezi River Valley] C. turneri
6b. Head of intermediate depth; snout of moderate length, broad, lores weakly to moderately inflated (Figs. 5F–H, 18C); snout less deep and slope of snout sometimes with a slight concavity when viewed in profile; exposed granular skin on occiput, nape, and anterior midline of the back not extensive; [Southern Africa, west of 25°E, upper and middle Zambezi Valley, Zimbabwe Highlands, Zambia, Malawi (exclusive of the lower Shire Valley), Mozambique north of the Ligonha River through eastern Tanzania to southern Kenya] C. laevigatus (Kgaligadi and Eastern Clades)
DISCUSSION
Chondrodactylus geckos are the largest and among the most frequently encountered geckos in Southern Africa, where they are often seen in and around human dwellings (Cott, 1934; FitzSimons, 1943; Loveridge, 1947). They share a convoluted taxonomic history complicated by sympatry across comparatively broad ranges with limited morphological differentiation despite deep genetic divergences (Fig. 2, Table 3). Our genetic data clearly support the recognition of six deeply divergent clades, which we here recognize as species. The pattern of relationships we found among these six species is congruent with that reported by Heinicke et al. (2017) based on just a single representative each. Our much deeper sampling, however, has revealed previously unreported patterns of intraspecific variation.
Divergence within each of the species is relatively deep, up to 17% intraspecific divergence in ND2, with interspecific divergences of approximately 30% between Chondrodactylus angulifer and all its congeners and 13–24% between the toe-padded species (Table 3). These values are high with respect to intrageneric divergences in some other gekkotans, but similar to divergences seen among Pachydactylus species (e.g., Bauer et al., 2002; Heinicke et al., 2017). However, unlike Pachydactylus and most other geckos, Chondrodactylus spp. are large-bodied habitat-generalists, occupying either large areas of more-or-less contiguous sandy terrestrial environments (C. angulifer) or almost any type of rocky, vegetative or anthropogenic climbing surfaces (toe-padded species; Heinz, 2011). The vagility of the constituent climbing species is attested to by their occurrence in small patches of rock, isolated by kilometers by open sand (Haacke, 1975; pers. obs., A.M. Bauer) and by their propensity for inadvertent translocation (see C. pulitzerae and C. laevigatus accounts), whereas their adaptability is shown by the ability of most species to survive and flourish in and around human habitation (Rose, 1962; Branch, 2014). On first principles, these attributes would appear to promote genetic connectivity across geographic distance and decrease the rate of speciation. Heinicke et al. (2017) verified this within the broader Pachydactylus clade to which Chondrodactylus belongs, showing that diversification rates increased only in lineages combining small size (associated with low vagility) and habitat specialization. Such taxa typically also have small distributional ranges (Dynesius and Jansson, 2000). Consequently, Chondrodactylus, as well as Elasmodactylus and the large-bodied Pachydactylus namaquensis group (Branch et al., 1996), are relatively species-poor in comparison with small-bodied clades, within which individual species specialize on particular substrate types (Bauer, 1999 “2000”, 2010; Branch et al., 2011).
Large pairwise distances among Chondrodactylus species correspond to deep interspecific splits, with divergence dates estimated by Heinicke et al. (2017) falling between the mid-Oligocene for the split between the padless C. angulifer and padded relatives to the late Miocene for the split between C. turneri and C. laevigatus. Miocene speciation events may have been influenced by climatic and habitat turnover through this period (Porknoy et al., 2015) as historic pulses of aridity in southern Africa led to the repeated contraction, expansion, and shifting movement of the borders of the Kalahari and Namib deserts (van Zinderen Bakker, 1975; Lancaster, 1981; Stokes et al., 1997; Goudie, 1999). This pattern has been proposed to have contributed to speciation in chameleons (Tolley et al., 2008). With the expansion of the Namib and Kalahari and the development of the “arid corridor” connecting the southwest to the Horn of Africa (Wagner, 2010) C. laevigatus likely also expanded its range. Ties between the southwest and Horn have been noted in birds (Winterbottom, 1967), plants (Verdcourt,1969; de Winter, 1971; Jürgens, 1997), mammals (Lorenzen et al., 2006; Montgelard and Matthee, 2012), amphibians (Poynton, 1995) and scorpions (Prendini, 2005), as well as in snakes (Wüster et al., 2007) and other lizards (Wagner, 2010; Kissling et al., 2016; Freitas et al., 2018; Wagner et al., 2018). However, biogeographic expansions via the arid corridor among disparate groups are not necessarily temporally congruent, because it is likely that such a corridor has been intermittently “open” and “closed.” This repeated isolation and secondary contact may also have contributed to the diversification of this group and close relatives like Pachydactylus.
Of course, any interpretation of diversification rates is dependent on the knowledge base for the constituent taxa. Is it possible that the genus Chondrodactylus is, in fact, more species-rich than we acknowledge? Are they undercounted? Toe-padded Chondrodactylus are conspicuous wherever they occur and, with the exception of C. fitzsimonsi, are commonly commensal, at least under some circumstances. Although the possibility of localized undocumented endemism exists, we are aware of only a single population that we suspect to represent an additional valid species. This is a dwarf Chondrodactylus, apparently endemic to inselbergs in the southern Namib dune sea (Haacke, 1975) and it will be described elsewhere. Given the relatively deep genetic divergences within some of the species recognized herein, others might consider the elevation of major subclades to species rank. However, identifying diagnostic features of these less-inclusive units may be difficult and shared nuclear haplotypes (Heinz, 2011) argue against further splitting.
Nonetheless, further investigation is warranted, particularly in C. pulitzerae, in which the deepest divergences are seen (although unaccompanied by obvious morphological differences), and in C. laevigatus, which exhibits, by far, the greatest phenotypic diversity across its range. We identified 3 major subclades within C. laevigatus. One of these, the western clade, from which the type specimens derive, is morphologically distinctive, exhibiting the button-scaled tuberculation with little variation across most of its range in the Northern Cape and southern and central Namibia. However, to the north and east, C. laevigatus becomes much more spiny or rugose, with the dorsal pholidosis resembling that of C. bibronii or C. turneri. This difference may reflect character displacement, because C. laevigatus is especially smooth-scaled when it is sympatric with C. bibronii, but becomes spinier when it occurs by itself (Figs. 6, 17). Alternatively, tubercle size and scale number may be related to environmental variables. It has been demonstrated in a diversity of lizards that body scale size and, reciprocally, number may vary with hydric conditions as a means to reduce water loss in xeric environments (e.g., Thorpe and Baez, 1987, 1993; Malhotra and Thorpe, 1997; Calsbeek et al., 2006). By and large, smaller tubercles and more exposed granules are typical of C. laevigatus in the most arid portions of its distribution in the south and west of its distribution, whereas the Kgadigadi and East African clades occupy areas of higher rainfall and exhibit larger tubercles. This runs counter to the predicted trend, but this exception in desert geckos has been previously noted (Calsbeek et al., 2006). Certainly a quantitative assessment of scalation variation and its possible association with environmental variables is warranted, though beyond the scope of the present study.
How robust the 3 subclades of C. laevigatus are remains uncertain. Although our genetic sampling covers a large area, more fine-scale sampling is needed, especially in East Africa. Further sampling may reveal whether, in fact, there are 3 discrete subclades, or if these lose clear support with collections from intervening areas. Most importantly, further sampling in the east, particularly in the Midlands of Zimbabwe, in Tete and other central provinces of Mozambique, and in southern Malawi, will help to more unambiguously determine the range limits of both C. laevigatus and C. turneri. As discussed in the accounts for these two species, the morphological differences between the two in these areas are subtle at best. Our estimations of the species ranges (Fig. 16) are based on the sparse genetic sampling east of about 25°E and largely on the gestalt of preserved specimens, informed by the examination of many hundreds of individuals. More for simplicity than any reflection of reality, we have assumed that these two species occur in allopatry or parapatry, but intensive sampling in critical regions could reveal otherwise because it is clear from the situation in the west of the continent that toe-padded Chondrodactylus can occur in broad sympatry and even syntopy.
Two species are of particular interest genetically. Chondrodactylus turneri is characterized by a mitochondrial genome rearrangement. Such rearrangements are known from most major vertebrate taxa, including gekkotans (Kumazawa et al., 2014), probably arising via a “duplication-random loss” model (Moritz et al., 1987; Boore, 2000; San Mauro et al., 2006). Rearrangement is strongly associated with the loss of the origin of light-strand replication (between -trnaN and -trnaC) among vertebrates including squamate reptiles (Macey et al., 2005), suggesting this loss is a precursor to rearrangement (Macey et al., 1997, 1998). A complete sequence of the rearranged genome of C. turneri is highly desirable to determine the location of the alanine tRNA, as well as to determine whether the inserted proline tRNA is a duplicate. The 200 base-pair insert following trnP is likely a copy of a portion of the mitochondrial control region, the section immediately adjacent in the typical vertebrate mitochondrial genome. Five other rearrangements, duplications, and/or deletions within gekkotans include two in the genus Uroplatus, rearrangements within the genera Tropiocolotes and Stenodacylus (Kumazawa et al., 2014), and duplications in Heteronotia (Fujita et al., 2007).
Chondrodactylus fitzsimonsi is also of interest because some individuals share nuclear genes with C. pulitzerae and specimens appearing to show a phenotype intermediate between fitzsimonsi and laevigatus are known from inland of the Skeleton Coast of northern Namibia. Circumstantial evidence suggests that hybridization may occur along the edge of the Namib, or perhaps that there has been past introgression. Increased sampling of individuals and more nuclear markers should be able to distinguish between current hybridization and past introgression or a possible combination of the two (Twyford and Ennos, 2012).
Four species of Chondrodactylus (C. angulifer, C. fitzsimonsi, C. laevigatus, C. pulitzerae) can occur in sympatry in northwestern Namibia. This area corresponds to the Kaokoveld–Damaraland center of diversity and endemism, noted in plants (Jürgens, 1991, 1997; Craven and Vorster, 2006) and scorpions (Prendini, 2005) as well as reptiles (Simmons et al., 1998), including the speciose “northwestern group” of Pachydactylus geckos (Bauer and Lamb, 2005; Bauer, 2010). The region's rugged topology and complex geology, as well as its position bordering the arid lowlands and the more mesic mopane transition zone upland, are thought to contribute to high levels of diversity and endemism (Irish, 2002; Prendini, 2005), and in this instance may facilitate the co-occurrence of multiple congeners that seem to share very similar niche parameters. The significant overlap of the ranges of Chondrodactylus spp. in southwestern Africa indicates that features such as the Kunene River in the north and the Orange (Gariep) River in the south do not seem to represent significant barriers to most of the regional herpetofauna (Simmons et al., 1998; Bauer et al., 2006). Although they tend to be extremely common lizards where found, there are few reports on the natural history or ecology (beyond isolated reports of predators and prey, see e.g., Cott, 1934; FitzSimons, 1943; Loveridge, 1947) of members of the genus. With little ecological data to draw from, it is difficult to determine how species remain discrete from one another in sympatry, or even syntopy (FitzSimons, 1938; Bauer and Branch, “2001” 2003). Chondrodactylus bibronii have been noted to display gregarious aggregation behavior, with multiple full-grown adults of both sexes found in the same rock crevices (FitzSimons, 1943; Branch, 1998; Meyer and Mouton 2007). Though a study as to whether this aggregation is induced by limited availability of optimal shelters or whether it is the result of mutual conspecific attraction was inconclusive (Meyer and Mouton 2007), these observations suggest behavioral cues may mediate interactions, hinting at the possibility that behavioral isolation may be reinforcing species-level boundaries. These limited ecological insights highlight how much more there is to learn about Chondrodactylus and Africa's herpetofauna in general.
ACKNOWLEDGMENTS
Animals were collected under permits to the corresponding author from the relevant conservation authorities in their respective countries of origin over a 30-year period. Additional tissues were kindly provided by Mirko Barts, Marius Burger, Johan Marais, Krystal Tolley (South African National Biodiversity Institute), the late John Visser, and the late Bill Branch (Port Elizabeth Museum). Specimens were examined in the collections of the institutions listed in Materials and Methods. The curators and collection managers of these institutions are thanked for their generous hospitality and access to material in their care. Jens Vindum, Lauren Scheinberg, and Erica Ely (CAS); James Hanken and José Rosado (MCZ); Frank Tillack, Rainer Günther, and Mark-Oliver Rödel (ZMB); Shiela Broadley and the late Don Broadley (Natural History Museum of Zimbabwe); Patrick Campbell and Jeff Streicher (NHM); Werner Conrade and the late Bill Branch (PEM); and Lauretta Mahlengu and Lemy Mahinini (TM) rendered particular assistance. We thank Georg Gassner and Silke Schweiger (NMW), Frank Tillack (ZMB), Johan Marais, Luke and Ursula Verburgt (Enviro-Insight), Colin Tilbury, Steve Spawls, Luke Kemp, Daniel M. Portik, and Tyrone Ping for providing critical photos and Patrick Cambell (BMNH) for his assistance in checking and photographing critical type material. Andrei Barabanov kindly provided information regarding the ZISP paralectotype of Chondrodactylus angulifer, and Gregory Watkins-Colwell (Yale Peabody Museum of Natural History) also helped during the gestation of this manuscript.
Morgan Heinz particularly thanks Riaana Marais, Belinda Burger, Shiela Broadley, Bernard Mupangapanga, Cathy Sharp, and Liz Scott for support and friendship in South Africa and Zimbabwe, and Nicole Rocha, Lauren Adderly, Juan Daza, Philipp Wagner, and Rick Jahn for their friendship and mentorship in the lab. Matthew Heinicke and Sayantan Biswas assisted in initial data collection and analysis.
This work was supported by National Science Foundation grants DEB 0515909 and DEB 0844523 to AMB, the Philadelphia chapter of the Association for Women in Science, the Villanova University Office of Graduate Studies, and by the Villanova University Department of Biology.