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Understanding how selective pressures drive morphological change is a central question in evolutionary biology. Feather lice have repeatedly diversified into convergent ecomorphs, based on how they escape from host defenses in different microhabitats. Here, we used nano-computed tomography scan data of 89 specimens of feather lice, belonging to four ecomorph groups to quantify variation of functional traits, including mandibular muscle volume, limb length, and three-dimensional head shape data in these tiny insects. The results suggest that the shape of the head, the proportional volume of the chewing muscles, and the length of the leg segments in feather lice are all strongly associated with specific host-habitats. Further, species that co-occur on hosts have increased rates of morphological evolution, suggesting competition for host space is one of the drivers of morphology. This supports previous work indicating that the phenotypic diversity of feather lice is the result of repeated convergence resulting from resource partitioning, microhabitat specialization, and selection pressures imposed by host defense.

Several species of Cophomantini are known to have an enlarged prepollex, commonly modified as an osseous spine. We surveyed the osteology and myology of the prepollex and associated elements of 94 of the 190 species of Cophomantini, sampling all genera, except Nesorohyla. Two distinct prepollex morphologies were found: a blade-shaped and a spine-shaped morphology. We described the observed variation in 17 discrete characters to study their evolution in the most inclusive phylogenetic hypothesis for Cophomantini. Both morphologies evolved multiple times during the evolutionary history of this clade, but the origin of the spine-shaped distal prepollex in Boana and Bokermannohyla is ambiguous. The articulation of metacarpal II with the prepollex through a medial expansion of the metacarpal proximal epiphysis is a synapomorphy for Boana. The shape of the curve of the spine, and a large post-articular process of the distal prepollex, are synapomorphies for the Boana pulchella group, the latter being homoplastic in the Bokermannohyla martinsi group. Muscle character states associated with the spine-shaped prepollex are plesiomorphic for Cophomantini. We discuss evolution, function, behaviour and sexual dimorphism related to the prepollical elements. A bony spine is associated with fights between males, but forearm hypertrophy could be more related with habitat than with territorial combat.

The cranial anatomy of blindsnakes has been markedly understudied, with the small size and relative rarity of encountering these subterranean reptiles being significant limiting factors. In this article, we re-visit the skull anatomy of the Australian southern blind snake Anilios australis Gray, 1845 using microCT data, and produce the first complete atlas for the cranial anatomy of a representative of this speciose typhlopid genus. The skull is formed by 18 paired and four unpaired elements. We here produce a bone-by-bone description of each element as well as an inner ear endocast for each of two specimens differing in skull size. This approach has revealed the presence of a highly perforated dorsal plate on the septomaxilla-a structure convergent with the cribriform plate of the mammalian ethmoid bone-and a feature previously unknown for typhlopid snakes. This detailed anatomical study will facilitate ongoing taxonomic and systematic studies in the genus Anilios as well as provide comparative data for future studies on blindsnake anatomy more broadly.

Miniaturization has evolved repeatedly in frogs in the moist leaf litter environments of rainforests worldwide. Miniaturized frogs are among the world’s smallest vertebrates and exhibit an array of enigmatic features. One area where miniaturization has predictable consequences is the vestibular system, which acts as a gyroscope, providing sensory information about movement and orientation. We investigated the vestibular system of pumpkin toadlets, Brachycephalus (Anura: Brachycephalidae), a clade of miniaturized frogs from Brazil. The semicircular canals of miniaturized frogs are the smallest recorded for adult vertebrates, resulting in low sensitivity to angular acceleration due to insufficient displacement of endolymph. This translates into a lack of postural control during jumping in Brachycephalus and represents a physical constraint resulting from Poiseuille’s law, which governs movement of fluids within tubes.

Although Conraua goliath is well known as the largest living frog species, the diversity and evolution of the genus Conraua across sub‐Saharan Africa remain poorly understood. We present multilocus phylogenetic analyses of the six currently recognized species that provide insights into divergence times, biogeography, body size evolution and undescribed species. An analysis of divergence times demonstrates that crown‐group Conraua arose some time during the latest Oligocene to mid‐Miocene followed by divergence into major lineages in the mid‐Miocene that may reflect the fragmentation of widespread tropical forests in Africa that began at this time. We find three pairs of sister species, C. crassipes + C. beccarii, C. alleni + C. derooi and C. goliath + C. robusta, each of which diverged during the Miocene. These relationships reject phylogenetic hypotheses based solely on biogeography as the geographically peripheral C. beccarii from north‐eastern Africa is nested within western African species and the Central African species do not form a clade. Our species delimitation analyses provide support for undescribed species in C. alleni, C. beccarii and C. derooi, and possibly C. crassipes, suggesting that the current taxonomy substantially underestimates species diversity. There is no clear directional trend of either increasing or decreasing body size in Conraua and the three largest species do not form a clade. With a robust phylogenetic hypothesis in hand, further field‐based studies are needed to understand the evolution of morphology and life history in this charismatic African anuran clade.

Prosymna is a specialized African snake genus lacking close relatives. The evolutionary relationships and history within Prosymna are poorly understood. Here we assembled a multi-gene data set including representatives for 11 of 16 species to investigate the phylogenetic relationships of this group. Our analyses support the monophyly of Prosymna and are congruent with species groups previously recognized on the basis of external morphology. Divergences among extant Prosymna began in the mid-Cenozoic, with the earliest divergence splitting northern from southern lineages. High-resolution computed tomography scans confirm that a specialized skull morphology is found across the genus and was probably present in the common ancestor of Prosymna. This specialization is exemplified by dentition featuring reduced anterior but greatly enlarged, blade-like posterior maxillary teeth and an unusually high degree of fusion of cranial bones. One species, P. visseri, has a hammer-like maxilla unlike that of any other known snake. Evidence for oophagy in Prosymna and the possible roles of morphological specializations in egg-slitting or egg-crushing feeding mechanisms are discussed.

We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site (Myanmar). This new taxon is represented by an articulated skull and the anterior portion of the trunk, including the pectoral girdle and forelimbs. The scleral ossicles and eyelid are also visible, and the specimen exhibits pristine detail of the integument (of both head and body). In a combined molecular and morphological analysis, it was consistently recovered as a scincoid lizard (Scinciformata), as sister toTepexisaurus + Xantusiidae. However, the phylogenetic position of the new taxon should be interpreted with caution as the holotype is an immature individual. We explored the possibility of miscoding ontogenetically variable characters by running alternative analyses in which these characters were scored as missing data for our taxon. With the exception of one tree, in which it was sister to Amphisbaenia, the specimen was recovered as a Pan-xantusiid. Moreover, we cannot rule out the possibility that it represents a separate lineage of uncertain phylogenetic position, as it is the case for many Jurassic and Cretaceous taxa. Nonetheless, this fossil offers a rare opportunity to glimpse the external appearance of one group of lizards during the Early Cretaceous.

Dollo's law of irreversibility states that once a complex structure is lost, it cannot be regained in the same form. Several putative exceptions to Dollo's law have been identified using phylogenetic comparative methods, but the anatomy and development of these traits are often poorly understood. Gastrotheca guentheri is renowned as the only frog with teeth on the lower jaw. Mandibular teeth were lost in the ancestor of frogs more than 200 million years ago and subsequently regained in G. guentheri. Little is known about the teeth in this species despite being a frequent example of trait "re-evolution," leaving open the possibility that it may have mandibular pseudoteeth. We assessed the dental anatomy of G. guentheri using micro-computed tomography and histology and confirmed the longstanding assumption that true mandibular teeth are present. Remarkably, the mandibular teeth of G. guentheri are nearly identical in gross morphology and development to upper jaw teeth in closely related species. The developmental genetics of tooth formation are unknown in this possibly extinct species. Our results suggest that an ancestral odontogenic pathway has been conserved but suppressed in the lower jaw since the origin of frogs, providing a possible mechanism underlying the re-evolution of lost mandibular teeth.

Teeth are present in most clades of vertebrates but have been lost completely several times in actinopterygian fishes and amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.

Squamates exhibit a vast diversity of body plans, which directly determines habitat use and preference. Here the skeleton of the sand-swimmer burrower gymnophthalmid, Calyptommatus leiolepis, is analyzed to investigate how its peculiar fossorial locomotion affects its osteology. Calyptommatus leiolepis is a limb-reduced, short-intermediate tailed lizard. Although there are other studies on its general anatomy, we performed a detailed description of its skeleton. Using high-resolution computer tomography, each bone element within the skeleton was digitally segmented and a detailed description rendered. Anatomical features related to burrowing include the head having a shovel-like snout with a well-developed horizontal soft tissue ridge, nasal cartilages that exclude sand from the nostrils, reduced eyes covered by a brille, lack of forelimbs, extreme reduction of hind limbs, and imbricated scales among others. The genus Calyptommatus has unique features such as a triradiate jugal (with digit-like posterior projections), a reduced pectoral girdle and forelimbs, parasternal processes that interconnect the ribs, and a single digit in the hind limbs. When comparing this species with other gymnophthalmid lizards including, fossorial species, it is clear that Calyptommatus exhibits the highest number of structural modifications within the family. Despite its specialized morphology, it still retains characters that link this genus to other members of Gymnophthalmidae when included in a phylogeny based solely on phenotypic data. Anat Rec, 303:1305-1326, 2020. © 2019 American Association for Anatomy.

Habitat is one of the most important factors shaping organismal morphology, but it may vary across life history stages. Ontogenetic shifts in ecology may introduce antagonistic selection that constrains adult phenotype, particularly with ecologically distinct developmental phases such as the free-living, feeding larval stage of many frogs (Lissamphibia: Anura). We test the relative influences of developmental and ecological factors on the diversification of adult skull morphology with a detailed analysis of 15 individual cranial regions across 173 anuran species, representing every extant family. Skull size, adult microhabitat, larval feeding, and ossification timing are all significant factors shaping aspects of cranial evolution in frogs, with late-ossifying elements showing the greatest disparity and fastest evolutionary rates. Size and microhabitat show the strongest effects on cranial shape, and we identify a “large size-wide skull” pattern of anuran, and possibly amphibian, evolutionary allometry. Fossorial and aquatic microhabitats occupy distinct regions of morphospace and display fast evolution and high disparity. Taxa with and without feeding larvae do not notably differ in cranial morphology. However, loss of an actively feeding larval stage is associated with higher evolutionary rates and disparity, suggesting that functional pressures experienced earlier in ontogeny significantly impact adult morphological evolution., The evolution of metamorphic species may be constrained by different ecologies of the larval and adult stages. Here, Bardua et al. show that in frogs, adult ecology is more important than larval ecology for skull evolution, but species that don’t feed as tadpoles evolve faster than those that do.

Scolecophidian snakes have long posed challenges for scholars interested in elucidating their anatomy. The importance, and relative paucity, of high-quality anatomical data pertaining to scolecophidians was brought into sharp focus in the late 20th century as part of a controversy over the phylogeny and ecological origin of snakes. The basal position of scolecophidians in the phylogeny of snakes makes their anatomy, behavior, ecology, and evolution especially important for such considerations. The depauperate fossil record for the group meant that advances in understanding their evolutionary history were necessarily tied to biogeographic distributions and anatomical interpretations of extant taxa. Osteological data, especially data pertaining to the skull and mandible, assumed a dominant role in shaping historical and modern perspectives of the evolution of scolecophidians. Traditional approaches to the exploration of the anatomy of these snakes relied heavily upon serial-sectioned specimens and cleared-and-stained specimens. The application of X-ray computed tomography (CT) to the study of scolecophidians revolutionized our understanding of the osteology of the group, and now, via diffusible iodine-based contrast-enhanced computed tomography (diceCT), is yielding data sets on internal soft anatomical features as well. CT data sets replicate many aspects of traditional anatomical preparations, are readily shared with a global community of scholars, and now are available for unique holotype and other rare specimens. The increasing prevalence and relevance of CT data sets is a strong incentive for the establishment and maintenance of permanent repositories for digital data.

Nonnative species are drivers of global change, affecting biodiversity and burdening society with economic costs. Effective management of an invasion relies on the ability to make accurate predictions about the target species' spread and impact. This requires knowledge of the target species' biology, making taxonomic validation critical. Even so, external morphology is still widely used to determine the species identity of novel invaders. Here, we show that a nonnative pipid frog population in Riverview, Florida, USA, initially identified as African Clawed Frog (Xenopus laevis), is a cryptic invasion of Tropical Clawed Frog (Xenopus tropicalis) and the only known nonnative population of this species. We used DNA sequence data and osteology from high-resolution microcomputed tomography to confirm this identification. Furthermore, we conducted field surveys to delineate the population's invaded range in Florida. We detected the presence of adult X. tropicalis at 22 sites and larvae at a subset of 12 sites, representing an occupied area of approximately 1,630 ha. Differing body size and physiology of these two species of Xenopus suggest considerable differences in their impact, spread, and potential geographic range.

Teeth have been broadly maintained across most clades of vertebrates but have been lost completely at least once in actinopterygian fishes and several times in amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.

Anolis lizards originated in continental America but have colonized the Greater Antillean islands and recolonized the mainland, resulting in three major groups (Primary and Secondary Mainland and Greater Antillean). The adaptive radiation in the Greater Antilles has famously resulted in the repeated evolution of ecomorphs. Yet, it remains poorly understood to what extent this island radiation differs from diversification on the mainland. Here, we demonstrate that the evolutionary modularity between girdles and limbs is fundamentally different in the Greater Antillean and Primary Mainland Anolis. This is consistent with ecological opportunities on islands driving the adaptive radiation along distinct evolutionary trajectories. However, Greater Antillean Anolis share evolutionary modularity with the group that recolonized the mainland, demonstrating a persistent phylogenetic inertia. A comparison of these two groups support an increased morphological diversity and faster and more variable evolutionary rates on islands. These macroevolutionary trends of the locomotor skeleton in Anolis illustrate that ecological opportunities on islands can have lasting effects on morphological diversification., Both ecological opportunity and phenotypic modularity have been suggested to facilitate adaptive radiations. Feiner et al. show that Anolis lizards evolved a new modularity structure in their island adaptive radiation, but that this modularity did not produce the same extreme diversification when Anolis returned to the mainland.

Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted osseous nares, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed several features inconsistent with its original phylogenetic placement. Here we describe a more complete, specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new interpretation and phylogenetic placement highlights a rare case of convergent evolution rarely seen among reptiles. Our results re-affirm the importance of Myanmar amber in yielding unusual taxa from a forest ecosystem rarely represented in the fossil record.

Ancient amphibians preserved in amber Extant amphibians are represented by three fairly simple morphologies: the mostly hopping frogs and toads, the low-crawling salamanders, and the limbless caecilians. Until the early Pleistocene—and for more than 165 million years—there was another group, the albanerpetontids. We know little about this group because amphibian fossils are poorly preserved, and previous specimens from this group are both rare and mostly badly damaged. Daza et al. describe a set of fossils preserved in amber showing that this group was unusual both in their habitat use (they may been climbers) and their feeding mode, which appears to have been convergent with the ballistic feeding now seen in chameleons (see the Perspective by Wake). Science , this issue p. 687 ; see also p. 654

International audience; Metamorphosis is widespread across the animal kingdom and induces fundamental changes in the morphology, habitat and resources used by an organism during its lifetime. Metamorphic species are likely to experience more dynamic selective pres- sures through ontogeny compared with species with single-phase life cycles, which may drive divergent evolutionary dynamics. Here, we reconstruct the cranial evolution of the salamander using geometric morphometric data from 148 species spanning the order’s full phylogenetic, developmental and ecological diversity. We demonstrate that life cycle influences cranial shape diversity and rate of evolution. Shifts in the rate of cranial evolution are consistently associated with transitions from bipha- sic to either direct-developing or paedomorphic life cycle strategies. Direct-developers exhibit the slowest rates of evolution and the lowest disparity, and paedomorphic species the highest. Species undergoing complete metamorphosis (biphasic and direct-developing) exhibit greater cranial modularity (evolutionary independence among regions) than do paedomorphic species, which undergo differential metamorphosis. Biphasic and direct-developing species also display elevated disparity relative to the evolutionary rate for bones associated with feeding, whereas this is not the case for paedomorphic species. Metamorphosis has profoundly influenced salamander cranial evolution, requiring greater autonomy of cranial elements and facilitating the rapid evolution of regions that are remodelled through ontogeny. Rather than compounding functional con- straints on variation, metamorphosis seems to have promoted the morphological evolution of salamanders over 180 million years, which may explain the ubiquity of this complex life cycle strategy across disparate organisms.

Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted osseous nares, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed several features inconsistent with its original phylogenetic placement. Here we describe a more complete, specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new interpretation and phylogenetic placement highlights a rare case of convergent evolution rarely seen among reptiles. Our results re-affirm the importance of Myanmar amber in yielding unusual taxa from a forest ecosystem rarely represented in the fossil record.

Frogs are a familiar and diverse component of tropical forests around the world. Yet there is little direct evidence from the fossil record for the antiquity of this association. We describe four fossil frog specimens from mid-Cretaceous (~99 mya) amber deposits from Kachin State, Myanmar for which the associated fauna provides rich paleoenvironmental context. Microcomputed tomographic analysis provides detailed three-dimensional anatomy for these small frogs, which is generally unavailable for articulated anurans in the Mesozoic. These crown-group anuran specimens provide the earliest direct evidence for anurans in a wet tropical forest. Based on a distinct combination of skeletal characters, at least one specimen has clear similarities to living alytoid frogs as well as several Mesozoic taxa known from the Jehol Biota in China. Whereas many Mesozoic frogs are from seasonal and mesic paleoenvironments, these fossils provide the earliest direct evidence of anurans in wet tropical forests.

Insects that depend on microbial mutualists evolved a variety of organs to transport the microsymbionts while dispersing. The ontogeny and variability of such organs is rarely studied, and the microsymbiont's effects on the animal tissue development remain unknown in most cases. Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae or Platypodinae) and their mutualistic fungi are an ideal system to study the animal-fungus interactions. While the interspecific diversity of their fungus transport organ-mycangia-is well-known, their developmental plasticity has been poorly described. To determine the ontogeny of the mycangium and the influence of the symbiotic fungus on the tissue development, we dissected by hand or scanned with micro-CT the mycangia in various developmental stages in five Xylosandrus ambrosia beetle species that possess a large, mesonotal mycangium: Xylosandrus amputatus, Xylosandrus compactus, Xylosandrus crassiusculus, Xylosandrus discolor, and Xylosandrus germanus. We processed 181 beetle samples from the United States and China. All five species displayed three stages of the mycangium development: (1) young teneral adults had an empty, deflated and cryptic mycangium without fungal mass; (2) in fully mature adults during dispersal, the pro-mesonotal membrane was inflated, and most individuals developed a mycangium mostly filled with the symbiont, though size and symmetry varied; and (3) after successful establishment of their new galleries, most females discharged the bulk of the fungal inoculum and deflated the mycangium. Experimental aposymbiotic individuals demonstrated that the pronotal membrane invaginated independently of the presence of the fungus, but the fungus was required for inflation. Mycangia are more dynamic than previously thought, and their morphological changes correspond to the phases of the symbiosis. Importantly, studies of the fungal symbionts or plant pathogen transmission in ambrosia beetles need to consider which developmental stage to sample. We provide illustrations of the different stages, including microphotography of dissections and micro-CT scans.

Oculudentavis khaungraae was described based on a tiny skull trapped in amber. The slender tapering rostrum with retracted narial openings, large eyes, and short vaulted braincase led to its identification as the smallest avian dinosaur on record, comparable to the smallest living hummingbirds. Despite its bird-like appearance, Oculudentavis showed several features inconsistent with its original phylogenetic placement. Here, we describe a more complete specimen that demonstrates Oculudentavis is actually a bizarre lizard of uncertain position. The new specimen is described as a new species within the genus Oculudentavis. The new interpretation and phylogenetic placement highlight a rare case of convergent evolution in skull proportions but apparently not in morphological characters. Our results re-affirm the importance of Myanmar amber in yielding unusual taxa from a forest ecosystem rarely represented in the fossil record. Fil: Bolet, Arnau. Universitat Autonoma de Barcelona; España Fil: Stanley, Edward L.. Florida Museum Of Natural History; Estados Unidos Fil: Daza, Juan D.. Sam Houston State University; Estados Unidos Fil: Arias Becerra, Joan Salvador. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina Fil: Cernansky, Andrej. Comenius University In Brastislava; Eslovaquia Fil: Vidal García, Marta. University of Calgary. Department of Cell Biology and Anatomy; Canadá Fil: Bauer, Aaron M.. Villanova University; Estados Unidos Fil: Bevitt, Joseph J.. Australian Nuclear Science And Technology Organisation; Australia Fil: Peretti, Adolf. Peretti Museum Foundation; Suiza Fil: Evans, Susan E.. University College London; Estados Unidos

The first amber-embedded fossil representing the lizard family Agamidae, Protodraco monocoli gen. et sp. nov., is described in burmite of the lowermost Cenomanian (ca. 99 Ma; mid-Cretaceous) from northern Myanmar. It is among both the oldest known amber lizards and the oldest fossils of the family. The fossil is a well preserved left hind foot with shank, morphologically similar to basal taxa of modern Southeast Asian agamids. Because of the sparse Cretaceous fossil record it could provide a calibration point for divergence-time analyses and contradicts views that agamids colonized SE Asia during the Paleogene.

Ambrosia beetles and fungi represent an interesting and economically important symbiosis, but the vast majority of ambrosia fungi remain unexplored, hindering research, management of pathogens, and mitigation of invasive species. Beetles in the subtribe Premnobiini are one example of an entire beetle lineage whose fungal symbionts have never been studied. Here, we identify one dominant fungal symbiont of Premnobius cavipennis by using fungus culturing, community sequencing, microtome sectioning and micro-CT scanning of mycangia. Phylogenetic analyses of combined 18S and 28S rDNA and β-tubulin sequences revealed a highly divergent fungal lineage within Ophiostomatales, Afroraffaelea ambrosiae gen. nov. et sp. nov. The newly described fungal lineage represents another origin of the symbiosis within the Kingdom Fungi, adding to our understanding of the geographic ancestry of ambrosia fungi. P. cavipennis possesses pharyngeal mycangia which appear restrictive in fungus selection. This ambrosia beetle-fungus association has remained stable even after invasions into non-native regions.

A recent multilocus molecular phylogeny of the large dragon lizards of the genus Smaug Stanley et al. (2011) recovered a south-eastern clade of two relatively lightly-armoured, geographically-proximate species (Smaug warreni (Boulenger, 1908) and S. barbertonensis (Van Dam, 1921)). Unexpectedly, S. barbertonensis was found to be paraphyletic, with individuals sampled from northern Eswatini (formerly Swaziland) being more closely related to S. warreni than to S. barbertonensis from the type locality of Barberton in Mpumalanga Province, South Africa. Examination of voucher specimens used for the molecular analysis, as well as most other available museum material of the three lineages, indicated that the ‘Eswatini’ lineage—including populations in a small area on the northern Eswatini–Mpumalanga border, and northern KwaZulu–Natal Province in South Africa—was readily distinguishable from S. barbertonensis sensu stricto (and S. warreni) by its unique dorsal, lateral and ventral colour patterns. In order to further assess the taxonomic status of the three populations, a detailed morphological analysis was conducted. Multivariate analyses of scale counts and body dimensions indicated that the ‘Eswatini’ lineage and S. warreni were most similar. In particular, S. barbertonensis differed from the other two lineages by its generally lower numbers of transverse rows of dorsal scales, and a relatively wider head. High resolution Computed Tomography also revealed differences in cranial osteology between specimens from the three lineages. The ‘Eswatini’ lineage is described here as a new species, Smaug swazicus sp. nov., representing the ninth known species of dragon lizard. The new species appears to be near-endemic to Eswatini, with about 90% of its range located there. Our study indicates that S. barbertonensis sensu stricto is therefore a South African endemic restricted to an altitudinal band of about 300 m in the Barberton–Nelspruit–Khandizwe area of eastern Mpumalanga Province, while S. warreni is endemic to the narrow Lebombo Mountain range of South Africa, Eswatini and Mozambique. We present a detailed distribution map for the three species, and a revised diagnostic key to the genus Smaug.

A new species of rupicolous girdled lizard is described from Serra da Neve Inselberg, Namibe Province, southwestern Angola. We sequenced two mitochondrial gene regions (16S and ND2) for the new species and compared these data with those previously published for other Cordylus species. The new species is genetically divergent from the closely related Cordylus machadoi and C. namakuiyus and morphologically distinguished by head scale arrangement, coloration, and osteological characters. Serra da Neve is the second highest peak in Angola and one of the most understudied areas of the country. The discovery of this new species highlights the importance of this inselberg for regional endemism and emphasizes the high conservation importance of the area.

Evolutionary integration (covariation) of traits has long fascinated biologists because of its potential to elucidate factors that have shaped morphological evolution. Studies of tetrapod crania have identified patterns of evolutionary integration that reflect functional or developmental interactions among traits, but no studies to date have sampled widely across the species-rich lissamphibian order Anura (frogs). Frogs exhibit a vast range of cranial morphologies, life history strategies, and ecologies. Here, using high-density morphometrics we capture cranial morphology for 172 anuran species, sampling every extant family. We quantify the pattern of evolutionary modularity in the frog skull and compare patterns in taxa with different life history modes. Evolutionary changes across the anuran cranium are highly modular, with a well-integrated "suspensorium" involved in feeding. This pattern is strikingly similar to that identified for caecilian and salamander crania, suggesting replication of patterns of evolutionary integration across Lissamphibia. Surprisingly, possession of a feeding larval stage has no notable influence on cranial integration across frogs. However, late-ossifying bones exhibit higher integration than early-ossifying bones. Finally, anuran cranial modules show diverse morphological disparities, supporting the hypothesis that modular variation allows mosaic evolution of the cranium, but we find no consistent relationship between degree of within-module integration and disparity.

Background One goal of evolutionary developmental biology is to understand the role of development in the origin of phenotypic novelty and convergent evolution. Geckos are an ideal system to study this topic, as they are species-rich and exhibit a suite of diverse morphologies-many of which have independently evolved multiple times within geckos. Results We characterized and discretized the embryonic development of Lepidodactylus lugubris-an all-female, parthenogenetic gecko species. We also used soft-tissue μCT to characterize the development of the brain and central nervous system, which is difficult to visualize using traditional microscopy techniques. Additionally, we sequenced and assembled a de novo transcriptome for a late-stage embryo as a resource for generating future developmental tools. Herein, we describe the derived and conserved patterns of L. lugubris development in the context of squamate evolution and development. Conclusions This embryonic staging series, μCT data, and transcriptome together serve as critical enabling resources to study morphological evolution and development, the evolution and development of parthenogenesis, and other questions concerning vertebrate evolution and development in an emerging gecko model.

The Western Ghats (WG) is an escarpment on the west coast of Peninsular India, housing one of the richest assemblages of frogs in the world, with three endemic families. Here, we report the discovery of a new ancient lineage from a high-elevation massif in the Wayanad Plateau of the southern WG. Phylogenetic analysis reveals that the lineage belongs to Natatanura and clusters with Nyctibatrachidae, a family endemic to the WG/Sri Lanka biodiversity hotspot. Based on geographic distribution, unique morphological traits, deep genetic divergence, and phylogenetic position that distinguishes the lineage from the two nyctibatrachid subfamilies Nyctibatrachinae Blommers-Schlösser, 1993 and Lankanectinae Dubois & Ohler, 2001, we erect a new subfamily Astrobatrachinaesubfam. nov.(endemic to the WG, Peninsular India), and describe a new genusAstrobatrachusgen. nov.and species,Astrobatrachus kurichiyanasp. nov.The discovery of this species adds to the list of deeply divergent and monotypic or depauperate lineages with narrow geographic ranges in the southern massifs of the WG. The southern regions of the WG have long been considered geographic and climatic refugia, and this new relict lineage underscores their evolutionary significance. The small range of this species exclusively outside protected areas highlights the significance of reserve forest tracts in the WG in housing evolutionary novelty. This reinforces the need for intensive sampling to uncover new lineages and advance our understanding of the historical biogeography of this ancient landmass.

We report on the first detailed study of the atlas-axis complex in the lizard clade Dibamidae, a family of poorly known fossorial squamates distributed in tropical or subtropical climates. This skeletal bridge is characterized by several features, such as the complete absence of the first intercentrum or the appearance of the first free cervical rib on the axis (usually less developed in Dibamus relative to that in Anelytropsis). Our study shows morphological differences of the atlas-axis complex in the Mexican blind lizard Anelytropsis relative to those of Asian Dibamus, the only two known extant genera of this clade. With regard to taxonomy and phylogenetic topology of the Dibamidae within Squamata, a huge conflict exists between morphology versus molecules. The morphology of the atlas-axis complex is therefore compared with several potential sister clades + Sphenodon. Dibamids share several features with limbless Gekkota, Scincoidea, and Amphisbaenia. The complete absence of the first intercentrum is observed in Rhineura floridana and in Ateuchosaurus chinensis as well, and the free rib associated with the synapophyses of the axis is also present in Acontias meleagris. However, some of these features may result from a limbless, burrowing ecology and thus could represent homoplastic characters. In any case, the morphology of the atlas-axis shows that dibamids share most character states with skinks. Although the atlas-axis complex forms only an additional source of information, this conclusion is consistent with most morphological rather than molecular tree topologies.

A comprehensive, accurate, and revisable alpha taxonomy is crucial for biodiversity studies, but is challenging when data from reference specimens are difficult to collect or observe. However, recent technological advances can overcome some of these challenges. To illustrate this, we used modern approaches to tackle a centuries-old taxonomic enigma presented by Fraser's Clawed Frog, Xenopus fraseri, including whether X. fraseri is different from other species, and if so, where it is situated geographically and phylogenetically. To facilitate these inferences, we used high-resolution techniques to examine morphological variation, and we generated and analyzed complete mitochondrial genome sequences from all Xenopus species, including >150-year-old type specimens. Our results demonstrate that X. fraseri is indeed distinct from other species, firmly place this species within a phylogenetic context, and identify its minimal geographic distribution in northern Ghana and northern Cameroon. These data also permit novel phylogenetic resolution into this intensively studied and biomedically important group. Xenopus fraseri was formerly thought to be a rainforest endemic placed alongside species in the amieti species group; in fact this species occurs in arid habitat on the borderlands of the Sahel, and is the smallest member of the muelleri species group. This study illustrates that the taxonomic enigma of Fraser's frog was a combined consequence of sparse collection records, interspecies conservation and intraspecific polymorphism in external anatomy, and type specimens with unusual morphology.

The limbless skink Ophiomorus punctatissimus is a cryptozoic species found in the Peloponnese region of Greece and on the Greek island Kythira. To provide the first thorough description of the cranial and postcranial osteology of this species, both disarticulated specimens and X-ray computed tomographies of wet-preserved specimens were examined in detail. Resulting from this, an anatomical atlas of this species is provided. Two separate considerations, an evolutionary and an ecomorphological one, are made based on the observed adaptations related to limb loss in this skink. The structure of the girdles shows a particular pattern of reduction: whereas the pelvic girdle is mostly vestigial, the pectoral girdle is instead well developed, with all the elements typical of limbed lizards except for the actual limbs. This led us to hypothesize an asynchronous pattern of limb reduction during the evolution of this species, in which the hindlimbs regressed earlier than the forelimbs. Furthermore, considerations based on overall body morphology, osteology and the structure of the inner ear led to the recognition of this species as a burrowing ecomorph. In contrast to the morphology normally displayed in this ecomorph, O. punctatissimus is characterized by the retention of autotomic vertebrae in its tail. This is consistent with the habitats in which it lives, where active burrowing would be difficult because of the hard, rocky terrain. Instead, this skink hides among rocks on the surface and is, therefore, subject to greater predation risk.

Although our inventory of Earth’s biodiversity remains incomplete, we still require analyses using the Tree of Life to understand evolutionary and ecological patterns. Because incomplete sampling may bias our inferences, we must evaluate how future additions of newly discovered species might impact analyses performed today. We describe an approach that uses taxonomic history and phylogenetic trees to characterize the impact of past species discoveries on phylogenetic knowledge using patterns of branch-length variation, tree shape, and phylogenetic diversity. This provides a framework for assessing the relative completeness of taxonomic knowledge of lineages within a phylogeny. To demonstrate this approach, we use recent large phylogenies for amphibians, reptiles, flowering plants, and invertebrates. Well-known clades exhibit a decline in the mean and range of branch lengths that are added each year as new species are described. With increased taxonomic knowledge over time, deep lineages of well-known clades become known such that most recently described new species are added close to the tips of the tree, reflecting changing tree shape over the course of taxonomic history. The same analyses reveal other clades to be candidates for future discoveries that could dramatically impact our phylogenetic knowledge. Our work reveals that species are often added non-randomly to the phylogeny over multiyear time-scales in a predictable pattern of taxonomic maturation. Our results suggest that we can make informed predictions about how new species will be added across the phylogeny of a given clade, thus providing a framework for accommodating unsampled undescribed species in evolutionary analyses.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae) rely on a symbiosis with fungi for their nutrition. Symbiotic fungi are preserved and transported in specialized storage structures called mycangia. Although pivotal in the symbiosis, mycangia have been notoriously difficult to study, given their minute size and membranous structure. We compared the application of novel visualization methods for the study of mycangia, namely micro-computed tomography (micro-CT) and laser ablation tomography (LATscan) with traditional paraffin sectioning. Micro-CT scanning has shown the greatest promise in new organ discovery, while sectioning remains the only method with sufficient resolution for cellular visualization. All three common types of mycangia (oral, mesonotal, and pronotal) were successfully visualized and presented for different species of ambrosia beetles: Ambrosiodmus minor (Stebbing) 1909, Euplatypus compositus (Say) 1823, Premnobius cavipennis Eichhoff 1878, Scolytoplatypus raja Blandford 1893, Xylosandrus crassiusculus (Motschulsky) 1866 and X. amputatus (Blandford) 1894. A reconstruction of the mycangium and the surrounding musculature in X. amputatus is also presented. The advantages of micro-CT compared to the previously commonly used microtome sectioning include the easy visualization and recording of three-dimensional structures, their position in reference to other internal structures, the ability to distinguish natural aberrations from technical artifacts, and the unprecedented visualizations of the anatomic context of mycangia enabled by the integrated software.