Whip it into shape: Revision of the Demansia psammophis (Schlegel, 1837) complex (Squamata: Elapidae), with a description of a new species from central Australia

The genus Demansia Günther is the most diverse genus of Australian terrestrial elapids. A phylogenetic framework for the familiar but problematic taxa D. psammophis and D. reticulata (Gray) has been long overdue to ascertain interspecific relationships and resolve unclear taxonomic issues. Here we present an integrated molecular phylogenetic and morphological analyses to review species delineation, resulting in confirmation that both D. psammophis and D. reticulata are full species and that some populations referred to D. r. cupreiceps Storr are not distinguishable from more typical D. reticulata. We also find the widespread central Australian population (treated by most authors as part of cupreiceps) to be specifically distinct. We redescribe D. psammophis and D. reticulata to clarify morphological and geographical boundaries and describe D. cyanochasma sp. nov. based on a combination of molecular genetic markers, details of colour and pattern, adult total length and a few morphometric attributes. We also designate a lectotype for D. psammophis from the original syntype series and comment on the necessity for further taxonomic refinement of this distinctive group.

A giant armoured skink from Australia expands lizard morphospace and the scope of the Pleistocene extinctions

There are more species of lizards and snakes (squamates) alive today than any other order of land vertebrates, yet their fossil record has been poorly documented compared with other groups. Here, we describe a gigantic Pleistocene skink from Australia based on extensive material that includes much of the skull and postcranial skeleton, and spans ontogenetic stages from neonate to adult. Tiliqua frangens substantially expands the known ecomorphological diversity of squamates. At approximately 2.4 kg, it was more than double the mass of any living skink, with an exceptionally broad, deep skull, squat limbs and heavy, ornamented body armour. It probably filled the armoured herbivore niche that land tortoises (testudinids), absent from Australia, occupy on other continents. Tiliqua frangens and other giant Plio-Pleistocene skinks suggest that small-bodied groups that dominate vertebrate biodiversity might have lost their largest and often most morphologically extreme representatives in the Late Pleistocene, expanding the scope of these extinctions.

Ontogenetic allometry underlies trophic diversity in sea turtles (Chelonioidea)

Despite only comprising seven species, extant sea turtles (Cheloniidae and Dermochelyidae) display great ecological diversity, with most species inhabiting a unique dietary niche as adults. This adult diversity is remarkable given that all species share the same dietary niche as juveniles. These ontogenetic shifts in diet, as well as a dramatic increase in body size, make sea turtles an excellent group to examine how morphological diversity arises by allometric processes and life habit specialisation. Using three-dimensional geometric morphometrics, we characterise ontogenetic allometry in the skulls of all seven species and evaluate variation in the context of phylogenetic history and diet. Among the sample, the olive ridley (Lepidochelys olivacea) has a seemingly average sea turtle skull shape and generalised diet, whereas the green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) show different extremes of snout shape associated with their modes of food gathering (grazing vs. grasping, respectively). Our ontogenetic findings corroborate previous suggestions that the skull of the leatherback (Dermochelys coriacea) is paedomorphic, having similar skull proportions to hatchlings of other sea turtle species and retaining a hatchling-like diet of relatively soft bodied organisms. The flatback sea turtle (Natator depressus) shows a similar but less extreme pattern. By contrast, the loggerhead sea turtle (Caretta caretta) shows a peramorphic signal associated with increased jaw muscle volumes that allow predation on hard shelled prey. The Kemp’s ridley (Lepidochelys kempii) has a peramorphic skull shape compared to its sister species the olive ridley, and a diet that includes harder prey items such as crabs. We suggest that diet may be a significant factor in driving skull shape differences among species. Although the small number of species limits statistical power, differences among skull shape, size, and diet are consistent with the hypothesis that shifts in allometric trajectory facilitated diversification in skull shape as observed in an increasing number of vertebrate groups.

Plicidentine and the repeated origins of snake venom fangs

Snake fangs are an iconic exemplar of a complex adaptation, but despite striking developmental and morphological similarities, they probably evolved independently in several lineages of venomous snakes. How snakes could, uniquely among vertebrates, repeatedly evolve their complex venom delivery apparatus is an intriguing question. Here we shed light on the repeated evolution of snake venom fangs using histology, high-resolution computed tomography (microCT) and biomechanical modelling. Our examination of venomous and non-venomous species reveals that most snakes have dentine infoldings at the bases of their teeth, known as plicidentine, and that in venomous species, one of these infoldings was repurposed to form a longitudinal groove for venom delivery. Like plicidentine, venom grooves originate from infoldings of the developing dental epithelium prior to the formation of the tooth hard tissues. Derivation of the venom groove from a large plicidentine fold that develops early in tooth ontogeny reveals how snake venom fangs could originate repeatedly through the co-option of a pre-existing dental feature even without close association to a venom duct. We also show that, contrary to previous assumptions, dentine infoldings do not improve compression or bending resistance of snake teeth during biting; plicidentine may instead have a role in tooth attachment.

Redescription of the skull of the Australian flatback sea turtle, Natator depressus, provides new morphological evidence for phylogenetic relationships among sea turtles (Chelonioidea)

Chelonioidea (sea turtles) are a group where available morphological evidence for crown-group relationships are incongruent with those established using molecular data. However, morphological surveys of crown-group taxa tend to focus on a recurring subset of the extant species. The Australian flatback sea turtle, Natator depressus, is often excluded from comparisons and it is the most poorly known of the seven extant species of Chelonioidea. Previous descriptions of its skull morphology are limited and conflict. Here we describe three skulls of adult N. depressus and re-examine the phylogenetic relationships according to morphological character data. Using X-ray micro Computed Tomography we describe internal structures of the braincase and identify new phylogenetically informative characters not previously reported. Phylogenetic analysis using a Bayesian approach strongly supports a sister-group relationship between Chelonia mydas and N. depressus, a topology that was not supported by previous analyses of morphological data but one that matches the topology supported by analysis of molecular data. Our results highlight the general need to sample the morphological anatomy of crown-group taxa more thoroughly before concluding that morphological and molecular evidence are incongruous.

What's under the hood? Phylogeny and taxonomy of the snake genera Parasuta Worrell and Suta Worrell (Squamata: Elapidae), with a description of a new species from the Pilbara, Western Australia

Despite decades of phylogenetic studies, the generic and species-level relationships of some Australian elapid snakes remain problematic. The morphologically conservative genus Parasuta comprises small nocturnal snakes with a particularly obfuscated taxonomic history. Here we provide a molecular phylogenetic analysis of all currently recognised species including members of the sister genus Suta and provide new morphological data that lead to a taxonomic revision of generic and species boundaries. We failed to find support for monophyly of Parasuta or Suta, instead supporting previous evidence that these two genera should be combined. Our species-level investigations revise the boundaries between P. gouldii (Gray) and P. spectabilis (Krefft) resulting in recognition that both P. spectabilis bushi (Storr) and P. spectabilis nullarbor (Storr) are conspecific with P. gouldii. We also find the Pilbara population of P. monachus (Storr) to be specifically distinct. As a consequence of this information, we synonymise Parasuta with its senior synonym Suta, redescribe S. gouldii, S. monachus and S. spectabilis to clarify morphological and geographical boundaries and describe S. gaikhorstorum sp. nov., which differs from all other described Suta species, including the geographically proximate and similar-looking S. monachus, by a combination of molecular genetic markers, morphometric attributes, details of colouration and scalation. The recognition of S. gaikhorstorum sp. nov. adds to the growing list of the many endemic reptiles from this exceptionally diverse biotic region. We also designate a lectotype for S. spectabilis from the original syntype series, highlight a distinctive population from the Great Victoria Desert in Western Australia and comment on further unresolved issues regarding the relationships between S. dwyeri (Worrell) and S. nigriceps (Gȕnther).

Reproductive phenotype predicts adult bite-force performance in sex-reversed dragons (Pogona vitticeps)

Sex-related differences in morphology and behavior are well documented, but the relative contributions of genes and environment to these traits are less well understood. Species that undergo sex reversal, such as the central bearded dragon (Pogona vitticeps), offer an opportunity to better understand sexually dimorphic traits because sexual phenotypes can exist on different chromosomal backgrounds. Reproductively female dragons with a discordant sex chromosome complement (sex reversed), at least as juveniles, exhibit traits in common with males (e.g., longer tails and greater boldness). However, the impact of sex reversal on sexually dimorphic traits in adult dragons is unknown. Here, we investigate the effect of sex reversal on bite-force performance, which may be important in resource acquisition (e.g., mates and/or food). We measured body size, head size, and bite force of the three sexual phenotypes in a colony of captive animals. Among adults, we found that males (ZZm) bite more forcefully than either chromosomally concordant females (ZWf) or sex-reversed females (ZZf), and this difference is associated with having relatively larger head dimensions. Therefore, adult sex-reversed females, despite apparently exhibiting male traits as juveniles, do not develop the larger head and enhanced bite force of adult male bearded dragons. This pattern is further illustrated in the full sample by a lack of positive allometry of bite force in sex-reversed females that is observed in males. The results reveal a close association between reproductive phenotype and bite force performance, regardless of sex chromosome complement.

Recognition of reptile predator scent is innate in an endangered lizard species

Chemical cues can alert prey to the presence of predators before the predator is within visual proximity. Recognition of a predator’s scent is therefore an important component of predator awareness. We presented predator and control scents to wild, wild-born captive, and predator-naive captive-born pygmy bluetongue lizards to determine (1) whether lizards respond to reptile chemical cues differently from controls, (2) whether captive lizards respond more strongly to a known predator than to other predatory reptiles, (3) whether captive-born lizards recognise predators innately, whether captive-born lizards have reduced predator recognition compared with wild lizards and whether time spent in captivity reduces responses to predators, and (4) whether the avoidance response to predator detection differs between naive and experienced lizards. There was no significant difference in the number of tongue flicks to predator scent among wild, wild-born and captive-born lizards, suggesting that predator detection is innate in the pygmy bluetongue lizard and time in captivity did not reduce predator recognition. The number of tongue flicks directed towards brown snake scent was significantly higher than that to the novel and water controls for all lizard origins. Lizards of all origins continued to bask in the presence of predator scents, suggesting that chemical cues alone may be insufficient to instigate an avoidance response and other cues may be required.

The morphological diversity of the quadrate bone in squamate reptiles as revealed by high-resolution computed tomography and geometric morphometrics

We examined the morphological diversity of the quadrate bone in squamate reptiles (i.e. lizards, snakes, amphisbaenians). The quadrate is the principal splanchnocranial element involved in suspending the lower jaw from the skull, and its shape is of particular interest because it is potentially affected by several factors, such as phylogenetic history, allometry, ecology, skull kinesis and hearing capabilities (e.g. presence or absence of a tympanic ear). Due to its complexity, the quadrate bone is also considered one of the most diagnostic elements in fragmentary fossil taxa. We describe quadrates from 38 species spread across all major squamate clades, using qualitative and quantitative (e.g. geometric morphometrics) methods. We test for possible correlations between shape variation and factors such as phylogeny, size, ecology and presence/absence of a tympanum. Our results show that the shape of the quadrate is highly evolutionarily plastic, with very little of the diversity explained by phylogenetic history. Size variation (allometric scaling) is similarly unable to explain much shape diversity in the squamate quadrate. Ecology (terrestrial/fossorial/aquatic) and presence of a tympanic ear are more significant, but together explain only about 20% of the diversity observed. Other unexplored and more analytically complex factors, such as skull biomechanics, likely play additional major roles in shaping the quadrates of lizards and snakes.

The homologies and evolutionary reduction of the pelvis and hindlimbs in snakes, with the first report of ossified pelvic vestiges in an anomalepidid (Liotyphlops beui)

We report the first example of ossified pelvic vestiges in an anomalepidid snake, Liotyplophs beui, and provide a review of the diversity of limb and pelvic elements within Serpentes. We trace the evolution, homology and reduction of the pelvic elements and hindlimbs from the oldest known snakes through to living forms. Evolutionary analysis of the pelvic and limb data shows that the most recent common ancestor of all living snakes (Serpentes) most probably retained all three pelvic elements and rudimentary hindlimbs (femoral spurs). Subsequently, there have been multiple losses of ossified pelvic and hindlimb elements and regaining of ossified pelvic elements. Reduction of the pelvis has followed different routes in the two primary groups of living snakes (scolecophidians and alethinophidians). The single remaining rod-like element in some scolecophidians is the ischium, whereas the single remaining rod-like element in many basal alethinophidians is the pubis. Notably, many basal alethinophidians share a distinctive configuration of cloacal spur (claw), femur and a sizeable pubis, which is likely to be related functionally to the widespread use of the hindlimbs in mating and courtship, rather than the usual representation of the bones as non-functional vestiges.

Novel vascular plexus in the head of a sea snake (Elapidae, Hydrophiinae) revealed by high-resolution computed tomography and histology

Novel phenotypes are often linked to major ecological transitions during evolution. Here, we describe for the first time an unusual network of large blood vessels in the head of the sea snake Hydrophis cyanocinctus. MicroCT imaging and histology reveal an intricate modified cephalic vascular network (MCVN) that underlies a broad area of skin between the snout and the roof of the head. It is mostly composed of large veins and sinuses and converges posterodorsally into a large vein (sometimes paired) that penetrates the skull through the parietal bone. Endocranially, this blood vessel leads into the dorsal cerebral sinus, and from there, a pair of large veins depart ventrally to enter the brain. We compare the condition observed in H. cyanocinctus with that of other elapids and discuss the possible functions of this unusual vascular network. Sea snakes have low oxygen partial pressure in their arterial blood that facilitates cutaneous respiration, potentially limiting the availability of oxygen to the brain. We conclude that this novel vascular structure draining directly to the brain is a further elaboration of the sea snakes' cutaneous respiratory anatomy, the most likely function of which is to provide the brain with an additional supply of oxygen.

Heterochronic Shifts Mediate Ecomorphological Convergence in Skull Shape of Microcephalic Sea Snakes

Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.

Changes in ontogenetic patterns facilitate diversification in skull shape of Australian agamid lizards

BACKGROUND

Morphological diversity among closely related animals can be the result of differing growth patterns. The Australian radiation of agamid lizards (Amphibolurinae) exhibits great ecological and morphological diversity, which they have achieved on a continent-wide scale, in a relatively short period of time (30 million years). Amphibolurines therefore make an ideal study group for examining ontogenetic allometry. We used two-dimensional landmark-based geometric morphometric methods to characterise the postnatal growth patterns in cranial shape of 18 species of amphibolurine lizards and investigate the associations between cranial morphology, and life habit and phylogeny.

RESULTS

For most amphibolurine species, juveniles share a similar cranial phenotype, but by adulthood crania are more disparate in shape and occupy different sub-spaces of the total shape space. To achieve this disparity, crania do not follow a common post-natal growth pattern; there are differences among species in both the direction and magnitude of change in morphospace. We found that these growth patterns among the amphibolurines are significantly associated with ecological life habits. The clade Ctenophorus includes species that undergo small magnitudes of shape change during growth. They have dorsoventrally deep, blunt-snouted skulls (associated with terrestrial lifestyles), and also dorsoventrally shallow skulls (associated with saxicolous lifestyles). The sister clade to Ctenophorus, which includes the bearded dragon (Pogona), frill-neck lizard (Chlamydosaurus), and long-nosed dragon (Gowidon), exhibit broad and robust post-orbital regions and differing snout lengths (mainly associated with scansorial lifestyles).

CONCLUSIONS

Australian agamids show great variability in the timing of development and divergence of growth trajectories which results in a diversity of adult cranial shapes. Phylogenetic signal in cranial morphology appears to be largely overwritten by signals that reflect life habit. This knowledge about growth patterns and skull shape diversity in agamid lizards will be valuable for placing phylogenetic, functional and ecological studies in a morphological context.

Diversification across biomes in a continental lizard radiation

Ecological opportunity is a powerful driver of evolutionary diversification, and predicts rapid lineage and phenotypic diversification following colonization of competitor-free habitats. Alternatively, topographic or environmental heterogeneity could be key to generating and sustaining diversity. We explore these hypotheses in a widespread lineage of Australian lizards: the Gehyra variegata group. This clade occurs across two biomes: the Australian monsoonal tropics (AMT), where it overlaps a separate, larger bodied clade of Gehyra and is largely restricted to rocks; and in the larger Australian arid zone (AAZ) where it has no congeners and occupies trees and rocks. New phylogenomic data and coalescent analyses of AAZ taxa resolve lineages and their relationships and reveal high diversity in the western AAZ (Pilbara region). The AMT and AAZ radiations represent separate radiations with no difference in speciation rates. Most taxa occur on rocks, with small geographic ranges relative to widespread generalist taxa across the vast central AAZ. Rock-dwelling and generalist taxa differ morphologically, but only the lineage-poor central AAZ taxa have accelerated evolution. This accords with increasing evidence that lineage and morphological diversity are poorly correlated, and suggests environmental heterogeneity and refugial dynamics have been more important than ecological release in elevating lineage diversity.

Palaeoecological inferences for the fossil Australian snakes Yurlunggur and Wonambi (Serpentes, Madtsoiidae)

Madtsoiids are among the most basal snakes, with a fossil record dating back to the Upper Cretaceous (Cenomanian). Most representatives went extinct by the end of the Eocene, but some survived in Australia until the Late Cenozoic. Yurlunggur and Wonambi are two of these late forms, and also the best-known madtsoiids to date. A better understanding of the anatomy and palaeoecology of these taxa may shed light on the evolution and extinction of this poorly known group of snakes and on early snake evolution in general. A digital endocast of the inner ear of Yurlunggur was compared to those of 81 species of snakes and lizards with known ecological preferences using three-dimensional geometric morphometrics. The inner ear of Yurlunggur most closely resembles both that of certain semiaquatic snakes and that of some semifossorial snakes. Other cranial and postcranial features of this snake support the semifossorial interpretation. While the digital endocast of the inner ear of Wonambi is too incomplete to be included in a geometric morphometrics study, its preserved morphology is very different from that of Yurlunggur and suggests a more generalist ecology. Osteology, palaeoclimatic data and the palaeobiogeographic distribution of these two snakes are all consistent with these inferred ecological differences.

The morphology of the inner ear of squamate reptiles and its bearing on the origin of snakes

The inner ear morphology of 80 snake and lizard species, representative of a range of ecologies, is here analysed and compared to that of the fossil stem snake Dinilysia patagonica, using three-dimensional geometric morphometrics. Inner ear morphology is linked to phylogeny (we find here a strong phylogenetic signal in the data that can complicate ecological correlations), but also correlated with ecology, with Dinilysia resembling certain semi-fossorial forms (Xenopeltis and Cylindrophis), consistent with previous reports. We here also find striking resemblances between Dinilysia and some semi-aquatic snakes, such as Myron (Caenophidia, Homalopsidae). Therefore, the inner ear morphology of Dinilysia is consistent with semi-aquatic as well as semi-fossorial habits: the most similar forms are either semi-fossorial burrowers with a strong affinity to water (Xenopeltis and Cylindrophis) or amphibious, intertidal forms which shelter in burrows (Myron). Notably, Dinilysia does not cluster as closely with snakes with exclusively terrestrial or obligate burrowing habits (e.g. scolecophidians and uropeltids). Moreover, despite the above similarities, Dinilysia also occupies a totally unique morphospace, raising issues with linking it with any particular ecological category.

Patterns of postnatal ontogeny of the skull and lower jaw of snakes as revealed by micro-CT scan data and three-dimensional geometric morphometrics

We compared the head skeleton (skull and lower jaw) of juvenile and adult specimens of five snake species [Anilios (=Ramphotyphlops) bicolor, Cylindrophis ruffus, Aspidites melanocephalus, Acrochordus arafurae, and Notechis scutatus] and two lizard outgroups (Ctenophorus decresii, Varanus gilleni). All major ontogenetic changes observed were documented both qualitatively and quantitatively. Qualitative comparisons were based on high-resolution micro-CT scanning of the specimens, and detailed quantitative analyses were performed using three-dimensional geometric morphometrics. Two sets of landmarks were used, one for accurate representation of the intraspecific transformations of each skull and jaw configuration, and the other for comparison between taxa. Our results document the ontogenetic elaboration of crests and processes for muscle attachment (especially for cervical and adductor muscles); negative allometry in the braincase of all taxa; approximately isometric growth of the snout of all taxa except Varanus and Anilios (positively allometric); and positive allometry in the quadrates of the macrostomatan snakes Aspidites, Acrochordus and Notechis, but also, surprisingly, in the iguanian lizard Ctenophorus. Ontogenetic trajectories from principal component analysis provide evidence for paedomorphosis in Anilios and peramorphosis in Acrochordus. Some primitive (lizard-like) features are described for the first time in the juvenile Cylindrophis. Two distinct developmental trajectories for the achievement of the macrostomatan (large-gaped) condition in adult snakes are documented, driven either by positive allometry of supratemporal and quadrate (in pythons), or of quadrate alone (in sampled caenophidians); this is consistent with hypothesised homoplasy in this adaptive complex. Certain traits (e.g. shape of coronoid process, marginal tooth counts) are more stable throughout postnatal ontogeny than others (e.g. basisphenoid keel), with implications for their reliability as phylogenetic characters.

Photographic identification of individuals of a free-ranging, small terrestrial vertebrate

Recognition of individuals within an animal population is central to a range of estimates about population structure and dynamics. However, traditional methods of distinguishing individuals, by some form of physical marking, often rely on capture and handling which may affect aspects of normal behavior. Photographic identification has been used as a less‐invasive alternative, but limitations in both manual and computer‐automated recognition of individuals are particularly problematic for smaller taxa (<500 g). In this study, we explored the use of photographic identification for individuals of a free‐ranging, small terrestrial reptile using (a) independent observers, and (b) automated matching with the Interactive Individual Identification System (I³S Pattern) computer algorithm. We tested the technique on individuals of an Australian skink in the Egernia group, Slater's skink Liopholis slateri, whose natural history and varied scale markings make it a potentially suitable candidate for photo‐identification. From ‘photographic captures’ of skink head profiles, we designed a multi‐choice key based on alternate character states and tested the abilities of observers — with or without experience in wildlife survey — to identify individuals using categorized test photos. We also used the I³S Pattern algorithm to match the same set of test photos against a database of 30 individuals. Experienced observers identified a significantly higher proportion of photos correctly (74%) than those with no experience (63%) while the I³S software correctly matched 67% as the first ranked match and 83% of images in the top five ranks. This study is one of the first to investigate photo identification with a free‐ranging small vertebrate. The method demonstrated here has the potential to be applied to the developing field of camera‐traps for wildlife survey and thus a wide range of survey and monitoring applications.

Bony skull development in the Argus monitor (Squamata, Varanidae, Varanus panoptes) with comments on developmental timing and adult anatomy

Varanids represent one of the most charismatic squamate clades and include the largest living lizards; however, little is known about their embryonic development and what it might reveal about the origin of their derived anatomy. In the present study, we describe external organogenesis and skull formation of Varanus panoptes in great detail. We compared timing of ossification with the patterns seen in other squamates, using three major hypotheses of squamate interrelationship as phylogenetic templates, and were able to detect heterochronic patterns in ossification that are associated with adult anatomy in each phylogeny. However, we refrain from preferring one topology given the current lack of congruence between molecular and morphological data sets. The rule of thumb that early appearance of developmental characters is correlated to larger prominence in adults is critically discussed and we conclude that such simple correlations are the exception rather than the rule. The entanglement of developmental processes detected herein highlights the non-independent formation of adult characters that are usually treated as independent in phylogenetic studies, which may bias the output of such studies. Our comprehensive descriptions of embryonic development may serve as a resource for future studies integrating the complex processes of embryogenesis into broad-scale phylogenetic analyses that are likely to show that change in embryonic timing is one of the major sources of morphological diversification.

Taxonomic revision of the Australian arid zone lizards Gehyra variegata and G. montium (Squamata, Gekkonidae) with description of three new species

The taxonomy of central Australian populations of geckos of the genus Gehyra has been uncertain since chromosomal studies carried out in the 1970s and 1980s revealed considerable heterogeneity and apparently independent patterns of morphological and karyotypic diversity. Following detailed molecular genetic studies, species boundaries in this complex have become clearer and we here re-set the boundaries of the three named species involved, G. variegata (Duméril & Bibron, 1836), G. montium Storr, 1982, and G. nana King, 1982, and describe three new species. Two of the new species, G. moritzi and G. pulingka, include populations formerly assigned to either G. montium or G. nana Storr, 1982, while the third, G. versicolor, includes all of the eastern Australian populations formerly assigned to G. variegata.

Tikiguania and the antiquity of squamate reptiles (lizards and snakes)

Tikiguania estesi is widely accepted to be the earliest member of Squamata, the reptile group that includes lizards and snakes. It is based on a lower jaw from the Late Triassic of India, described as a primitive lizard related to agamids and chamaeleons. However, Tikiguania is almost indistinguishable from living agamids; a combined phylogenetic analysis of morphological and molecular data places it with draconines, a prominent component of the modern Asian herpetofauna. It is unlikely that living agamids have retained the Tikiguania morphotype unchanged for over 216 Myr; it is much more conceivable that Tikiguania is a Quaternary or Late Tertiary agamid that was preserved in sediments derived from the Triassic beds that have a broad superficial exposure. This removes the only fossil evidence for lizards in the Triassic. Studies that have employed Tikiguana for evolutionary, biogeographical and molecular dating inferences need to be reassessed.

Corrigendum to: Phylogenetic relationships in the lizard genus Diplodactylus Gray and resurrection of Lucasium Wermuth (Gekkota, Diplodactylidae)

Diplodactylid geckos offer a model system for investigating the biogeographic history of Australia and adaptive radiations in the arid zone, but there is considerable uncertainty in the systematics of several key genera. We used sequence data from mitochondrial DNA to carry out a comprehensive analysis of phylogenetic relationships of geckos in the genus Diplodactylus. Parsimony and Bayesian analyses were highly concordant and allocated all species to one of two monophyletic clades, one comprising the species placed in the vittatus and conspicillatus species groups, the other comprising species placed in the stenodactylus and steindachneri species groups, plus D. byrnei, formerly in the vittatus group. The distinctness of these two clades is supported by external morphology of the digits, body and limb proportions, and osteology of the bones in the orbital region, and we use these characters to formally define the two clades as genera. We revive and expand the genus Lucasium for D. byrnei, D. steindachneri and the stenodactylus group, with the other species staying in a redefined Diplodactylus. The monotypic Rhynchoedura is distinct from Lucasium, although the Bayesian mtDNA analysis (but not parsimony) gives some support for a sister-group relationship between Lucasium and Rhynchoedura. Molecular data suggest that each of these clades represents a distinct radiation into semiarid and arid terrestrial habitats during the mid-Tertiary, well before the hypothesised Pliocene onset of major aridification.

Miocene skinks and geckos reveal long-term conservatism of New Zealand's lizard fauna

The New Zealand (NZ) lizard fossil record is currently limited to late Quaternary remains of modern taxa. The St Bathans Fauna (early Miocene, southern South Island) extends this record to 19-16 million years ago (Myr ago). Skull and postcranial elements are similar to extant Oligosoma (Lygosominae) skinks and Hoplodactylus (Diplodactylinae) geckos. There is no evidence of other squamate groups. These fossils, along with coeval sphenodontines, demonstrate a long conservative history for the NZ lepidosaurian fauna, provide new molecular clock calibrations and contradict inferences of a very recent (less than 8 Myr ago) arrival of skinks in NZ.

Cryptic diversity in vertebrates: molecular data double estimates of species diversity in a radiation of Australian lizards (Diplodactylus, Gekkota)

A major problem for biodiversity conservation and management is that a significant portion of species diversity remains undocumented (the 'taxonomic impediment'). This problem is widely acknowledged to be dire among invertebrates and in developing countries; here, we demonstrate that it can be acute even in conspicuous animals (reptiles) and in developed nations (Australia). A survey of mtDNA, allozyme and chromosomal variation in the Australian gecko, genus Diplodactylus, increases overall species diversity estimates from 13 to 29. Four nominal species each actually represent multi-species complexes; three of these species complexes are not even monophyletic. The high proportion of cryptic species discovered emphasizes the importance of continuing detailed assessments of species diversity, even in apparently well-known taxa from industrialized countries.

Rapid and repeated limb loss in a clade of scincid lizards

Background

The Australian scincid clade Lerista provides perhaps the best available model for studying limb reduction in squamates (lizards and snakes), comprising more than 75 species displaying a remarkable variety of digit configurations, from pentadactyl to entirely limbless conditions. We investigated the pattern and rate of limb reduction and loss in Lerista, employing a comprehensive phylogeny inferred from nucleotide sequences for a nuclear intron and six mitochondrial genes.

Results

The inferred phylogeny reveals extraordinary evolutionary mutability of limb morphology in Lerista. Ancestral state reconstructions indicate at least ten independent reductions in the number of digits from a pentadactyl condition, with a further seven reductions proceeding independently from a tetradactyl condition derived from one of these reductions. Four independent losses of all digits are inferred, three from pentadactyl or tetradactyl conditions. These conclusions are not substantially affected by uncertainty in assumed rates of character state transition or the phylogeny. An estimated age of 13.4 million years for Lerista entails that limb reduction has occurred not only repeatedly, but also very rapidly. At the highest rate, complete loss of digits from a pentadactyl condition is estimated to have occurred within 3.6 million years.

Conclusion

The exceptionally high frequency and rate of limb reduction inferred for Lerista emphasise the potential for rapid and substantial alteration of body form in squamates. An absence of compelling evidence for reversals of digit loss contrasts with a recent proposal that digits have been regained in some species of the gymnophthalmid clade Bachia, possibly reflecting an influence of differing environmental and genetic contexts on the evolution of limb morphology in these clades. Future study of the genetic, developmental, and ecological bases of limb reduction and loss in Lerista promises the elucidation of not only this phenomenon in squamates, but also the dramatic evolutionary transformations of body form that have produced the extraordinary diversity of multicellular organisms.

Evolution and maintenance of colour pattern polymorphism in Liopholis (Squamata:Scincidae)

We examined the evolution and maintenance of colour pattern polymorphism in an Australian lineage of scincid lizards, the genus Liopholis. Liopholis comprises 11 species, with representatives in both the temperate zone and arid zone. Specimens from all major Australian museums were examined to characterise colour pattern polymorphism within Liopholis, and investigate geographic variation in the relative abundance of morphs within polymorphic species. We used a previously published phylogeny for Liopholis to investigate the evolution and maintenance of colour pattern polymorphism within the group. Five species were found to exhibit colour pattern polymorphism (L. margaretae margaretae Storr, L. m. personata Storr, L. montana Donnellan et al., L. multiscutata Mitchell & Behrndt, L. pulchra Werner, L. whitii Lacépède), with six species being monomorphic (L. guthega Donnellan et al., L. inornata Rosén, L. kintorei Stirling & Zietz, L. modesta Storr, L. slateri Storr, L. striata Sternfeld). Three colour morphs occur in L. whitii, with the relative abundance of each varying significantly among latitudes. The patterned morph is most common, while the incidence of the plain-back morph decreases at latitudes higher than 35°S. The L. whitii patternless morph occurs only within a narrow latitudinal band (34–38°S). In L. multiscutata, the relative abundance of the patterned (~89–93%) and patternless morph (~7–11%) is consistent across regions, except for the Nullarbor Plain region where the patternless morph is more common (~39%). Our analyses suggest a single origin of colour pattern polymorphism in Liopholis, followed by the subsequent loss of polymorphism on four occasions. The secondary loss of polymorphism might be associated with climate or habitat, possibly as the result of shifts into the arid zone or alpine regions of Australia. This study provides the necessary framework for future studies of colour pattern polymorphism in Liopholis.

Injuries to lizards: conservation implications for the endangered pygmy bluetongue lizard (Tiliqua adelaidensis)

Understanding the potential threats of predation can play a crucial role in conservation management of threatened species. We investigated the frequency of sublethal injuries to live individuals of the endangered pygmy bluetongue lizard (Tiliqua adelaidensis). We found that there was no significant difference in the frequency of injury between males and females. However, there was a significant difference in injury frequency between adults and subadult animals and also between two close, but isolated, populations of pygmy bluetongue lizards. These data can be used, with caution, to understand the predation risks in natural populations of this species. They also suggest that predation would be a significant hazard that must be considered in any translocation program that is considered for this species.

An arid-adapted middle Pleistocene vertebrate fauna from south-central Australia

How well the ecology, zoogeography and evolution of modern biotas is understood depends substantially on knowledge of the Pleistocene. Australia has one of the most distinctive, but least understood, Pleistocene faunas. Records from the western half of the continent are especially rare. Here we report on a diverse and exceptionally well preserved middle Pleistocene vertebrate assemblage from caves beneath the arid, treeless Nullarbor plain of south-central Australia. Many taxa are represented by whole skeletons, which together serve as a template for identifying fragmentary, hitherto indeterminate, remains collected previously from Pleistocene sites across southern Australia. A remarkable eight of the 23 Nullarbor kangaroos are new, including two tree-kangaroos. The diverse herbivore assemblage implies substantially greater floristic diversity than that of the modern shrub steppe, but all other faunal and stable-isotope data indicate that the climate was very similar to today. Because the 21 Nullarbor species that did not survive the Pleistocene were well adapted to dry conditions, climate change (specifically, increased aridity) is unlikely to have been significant in their extinction.

Phylogenetic relationships in the lizard genus Diplodactylus Gray and resurrection of Lucasium Wermuth (Gekkota, Diplodactylidae)

Diplodactylid geckos offer a model system for investigating the biogeographic history of Australia and adaptive radiations in the arid zone, but there is considerable uncertainty in the systematics of several key genera. We used sequence data from mitochondrial DNA to carry out a comprehensive analysis of phylogenetic relationships of geckos in the genus Diplodactylus. Parsimony and Bayesian analyses were highly concordant and allocated all species to one of two monophyletic clades, one comprising the species placed in the vittatus and conspicillatus species groups, the other comprising species placed in the stenodactylus and steindachneri species groups, plus D. byrnei, formerly in the vittatus group. The distinctness of these two clades is supported by external morphology of the digits, body and limb proportions, and osteology of the bones in the orbital region, and we use these characters to formally define the two clades as genera. We revive and expand the genus Lucasium for D. byrnei, D. steindachneri and the stenodactylus group, with the other species staying in a redefined Diplodactylus. The monotypic Rhynchoedura is distinct from Lucasium, although the Bayesian mtDNA analysis (but not parsimony) gives some support for a sister-group relationship between Lucasium and Rhynchoedura. Molecular data suggest that each of these clades represents a distinct radiation into semiarid and arid terrestrial habitats during the mid-Tertiary, well before the hypothesised Pliocene onset of major aridification.

The Harderian gland of two species of skink (Tiliqua rugosa and Hemiergis decresiensis): a discussion of the significance of lymphatic tissue in the squamate Harderian gland

The Harderian gland is an orbital structure ubiquitous in reptiles. Numerous functions have been ascribed to this gland, including osmoregulation, chemoreception, and immunity. The anatomical, histological, histochemical, and ultrastructural characteristics of the Harderian gland of two species of skink, Tiliqua rugosa (Gray, 1825) and Hemiergis decresiensis (Cuvier, 1829), were examined. Mucous and serous secretory cells were observed in both species. In T. rugosa, mucous cells are located in a small anterior region, while serous cells occupy most of the gland. In contrast, the Harderian gland of H. decresiensis contains mainly serous cells, with a few anteriorly located mucous cells. In both species, the serous granules exhibit internal compartmentalization. There is no evidence of either lipid secretions or salt secreting cells. However, there were either a few plasma cells (H. decresiensis) or several lymphatic aggregations (T. rugosa) in the serous portion of the gland. The presence of such lymphatic tissue may suggest a role in either the head-associated lymphatic tissue (HALT) system or the eye-associated lymphatic tissue (EALT). The difference between these two is based upon terminology, the consolidation of which would allow meaningful comparative analyses. The presence of lymphatic tissue implies that the Harderian gland could play a role in ocular immunity.

A phylogenetic analysis of Pseudonaja (Hydrophiinae, Elapidae, Serpentes) based on mitochondrial DNA sequences

A phylogenetic analysis of mitochondrial ND4 and adjacent tRNA sequences for a geographically extensive series of specimens reveals nine major clades within Pseudonaja, of which six are largely coincident with nominal taxa (P. affinis, P. guttata, P. inframacula, P. ingrami, P. modesta, and P. textilis). The remaining three clades are composed of specimens presently referred to P. nuchalis. Two of these clades correspond with the "Darwin" and "Southern" morphs of previous authors, while the third clade incorporates the "Orange with black head" and "Pale head, grey nape" morphs. We are unable to confirm the presence of consistent karyotypic differences between "Orange with black head" and "Pale head, grey nape" specimens, however, P. inframacula, P. textilis, and P. nuchalis "Darwin" are found to exhibit distinctive karyotypes, as previously reported. These results, in conjunction with additional observations of karyotpic and morphological variation, are consistent with nine historically-independent lineages (i.e., species) within Pseudonaja. There is strong support for a clade composed of P. affinis, P. inframacula, P. ingrami, P. textilis, and the three P. nuchalis lineages, and for the relationships (P. inframacula, P. nuchalis "Southern") and (P. nuchalis "Darwin", P. nuchalis "Orange with black head"--"Pale head, grey nape" ).

Substantial genetic substructuring in southeastern and alpine Australia revealed by molecular phylogeography of the Egernia whitii (Lacertilia: Scincidae) species group

Palaeoclimatic events and biogeographical processes since the mid-Tertiary are believed to have strongly influenced the evolution and distribution of the terrestrial vertebrate fauna of southeastern Australia. We examined the phylogeography of the temperate-adapted members of the Egernia whitii species group, a group of skinks that comprise both widespread low- to mid-elevation (E. whitii) and montane-restricted species (Egernia guthega, Egernia montana), in order to obtain important insights into the influence of past biogeographical processes on the herpetofauna of southeastern Australia. Sequence data were obtained from all six temperate-adapted species within the E. whitii species group, and specifically from across the distributional ranges of E. whitii, E. guthega and E. montana. We targeted a fragment of the ND4 mitochondrial gene (696 bp) and analysed the data using maximum likelihood and Bayesian methods. Our data reveal a deep phylogeographical break in the east Gippsland region of Victoria between 'northern' (Queensland, New South Wales, Australian Capital Territory) and 'southern' (Victoria, Tasmania, South Australia) populations of E. whitii. This divergence appears to have occurred during the late Miocene-Pliocene, with the Gippsland basin possibly forming a geographical barrier to dispersal. Substantial structuring within both the 'northern' and the 'southern' clades is consistent with the effects of Plio-Pleistocene glacial-interglacial cycles. Pleistocene glacial cycles also appear to have shaped the phylogeographical patterns observed in the alpine species, E. guthega and E. montana. We used our results to examine the biogeographical process that led to the origin and subsequent diversification of the lowland and alpine herpetofauna of southeastern Australia.

Molecular phylogeography and systematics of the arid-zone members of the Egernia whitii (Lacertilia: Scincidae) species group

We assembled a molecular phylogeny for the arid-zone members of the Egernia whitii species group to test Pianka's [Zoogeography and speciation of Australian desert lizards: an ecological perspective, Copeia (1972) 127-145] hypothesis that habitat specificity to the three major arid-zone vegetation communities is the primary cause of lizard speciation within the arid interior of Australia. This hypothesis predicts that species should exhibit phylogeographic structuring concordant with the major arid-zone vegetation types. Sequence data were obtained from four of the five arid-zone members of the E. whitii species group, and from across the ranges of the ecologically generalized E. inornata and E. multiscutata and the more specialized E. striata. We targeted a fragment (696 base pair (bp)) of the mitochondrial genome comprising the 3' half of the ND4 gene. We analysed the data using parsimony, maximum likelihood and Bayesian methods. Our phylogeny confirms the monophyly of the arid-zone members of the species group, although the phylogenetic relationships among species were not fully resolved. Although our topology does not support the recognition of the existing subspecies within E. multiscutata, there is a substantial phylogeographic break between South Australian/Victorian (Clade 1) and Western Australian (Clade 2) populations. We found considerable phylogeographic structure within E. inornata, with six major clades identified. However, these clades were not concordant with the distribution of habitat types in the arid-zone. Phylogeographic structure was also observed in the more specialized E. striata, although our analysis revealed close phylogenetic affinities between the sympatric species E. striata and E. kintorei. Shimodaira-Hasegawa topology tests were equivocal in regard to whether the phylogeographic structure within E. striata was in accordance with Pianka's predictions. Although our data failed to provide strong support for the suggestion that ecological and habitat factors are responsible for the diversification of arid-zone lizards, most E. inornata and E. striata populations had similar habitats, indicating that adaptation to particular habitats may have some role in the speciation of lizards in the Australian arid-zone.

The Australian scincid lizard Menetia greyii: a new instance of widespread vertebrate parthenogenesis

Molecular data derived from allozymes and mitochondrial nucleotide sequences, in combination with karyotypes, sex ratios, and inheritance data, have revealed the widespread Australian lizard Menetia greyii to be a complex of sexual and triploid unisexual taxa. Three sexual species, three presumed parthenogenetic lineages, and one animal of uncertain status were detected amongst 145 animals examined from south-central Australia, an area representing less than one-seventh of the total distribution of the complex. Parthenogenesis appears to have originated via interspecific hybridization, although presumed sexual ancestors could only be identified in two cases. The allozyme and mtDNA data reveal the presence of many distinct clones within the presumed parthenogenetic lineages. This new instance of vertebrate parthenogenesis is a first for the Scincidae and only the second definitive case of unisexuality in an indigenous Australian vertebrate.

The Harderian gland of two species of snakes: Pseudonaja textilis (Elapidae) and Thamnophis sirtalis (Colubridae)

The reptilian Harderian gland is a poorly understood cephalic structure. Despite the recent assertion that in snakes it may function as part of the vomeronasal system, the Harderian gland has been described in few snake species. In this study we examined the gross anatomy, histology, and ultrastructure of the Harderian gland of two different advanced snake species (Colubroidea): Pseudonaja textilis (Elapidae) and Thamnophis sirtalis (Colubridae). In both species the Harderian gland is a large serous gland whose secretions pass directly into the vomeronasal organ via the nasolacrimal duct. Contrary to previous publications, the Harderian gland in both species studied possesses a specific duct system lined by mucous cells. However, the Harderian glands of these two species differ in shape, the histochemical nature of these mucous secretions, and the ultrastructure of the serous granules. In conclusion, though the Harderian glands of snakes are remarkably conserved morphologically, there is some interspecific variation.

Use of burrows by the endangered pygmy blue-tongue lizard, Tiliqua adelaidensis (Scincidae)

The pygmy blue-tongue lizard, Tiliqua adelaidensis, had been considered extinct until its recent rediscovery near Burra in the mid-north of South Australia. The lizards apparently rely on spider burrows with a single entrance as refuge sites. In this paper we describe observations from all-day video recordings of the entrances of burrows occupied by lizards on 31 days across the spring and early summer of 1996. The lizards spent most of each day either retreated down the burrow or basking at the burrow entrance. Early in the season, when temperatures were cooler, lizards spent more of each day basking, and more of their basking time fully emerged from the burrow, than later in the season. Results are consistent with the hypothesis that the lizards thermoregulate by moving in and out of the burrow. Lizards also fed by making short excursions from the burrow, often to catch passing invertebrate prey, although they also fed on flowers early in spring. Later in the season lizards were more likely to vacate their burrows for longer times, or to move away from their burrows, and mating activity was observed when males approached burrows occupied by females. The observations suggest that pygmy blue-tongue lizards rely heavily on burrows for many activities, and that any conservation management scheme for this endangered species will rely on maintaining an adequate supply of burrows.