A phylogeny of ranid frogs (Anura: Ranoidea: Ranidae), based on a simultaneous analysis of morphological and molecular data

A new genus and species of frog from the Kem Kem (Morocco), the second neobatrachian from Cretaceous Africa

Neobatrachia, a clade representing the majority of extant anuran diversity, is thought to have emerged and diversified during the Cretaceous. Most of the early diversification of neobatrachians occurred in southern Gondwana, especially the regions that are today South America and Africa. Whereas five extinct neobatrachians have been described from the Cretaceous of South America in the last decade, only one is known from Africa. This difference in the known extinct diversity is linked to the lack of well-preserved specimens, understudy of fragmentary remains, and lack of known Cretaceous sites in Africa. Study of fragmentary anuran remains from Africa could allow for the identification of previously unknown neobatrachians, allowing for a better understanding of their early diversification. We reanalysed several previously described anuran specimens from the well-known Kem Kem beds, including using CT-scanning. Through our osteological study, we determined that several cranial bones and vertebrae represent a new hyperossified taxon for which we provide a formal description. Comparison to other hyperossified anurans revealed similarities and affinity of this new taxon with the neobatrachians Beelzebufo (extinct) and Ceratophrys (extant). Phylogenetic analyses supported this affinity, placing the new taxon within Neobatrachia in an unresolved clade of Ceratophryidae. This taxon is the oldest neobatrachian from Africa, and reveals that neobatrachians were already widespread throughout southern Gondwana during the earliest Late Cretaceous.

Hand and foot musculature of Sooglossoidea: synapomorphies, convergences and hind limb digging behaviour in anurans

We describe the hand and foot musculature of the fossorial Indian purple frog, Nasikabatrachus sahyadrensis, and compare it to other members of Sooglossoidea: the Seychellean sooglossid genera Sechellophryne and Sooglossus. Due to the key phylogenetic position of Sooglossoidea, we compare its members with the diversity of Anura and define 52 characters from the hand and foot musculature, among which 26 are novel hypotheses of homology. We found several synapomorphies for Sooglossus, Sooglossidae, Nasikabatrachidae and Sooglossoidea. Additionally, we (1) propose synapomorphies for diverse anuran clades at different taxonomic levels, (2) re-evaluate the identity of some conflicting plantar and palmar muscles in the context of Batrachia and (3) discuss putative adaptations to hind limb digging behaviour resulting from morphological convergences. The lack of a clear pattern of convergences among hind limb digging species suggests the occurrence of a phenomenon of many-to-one mapping from form to function.

Prepollex diversity and evolution in Cophomantini (Anura: Hylidae: Hylinae)

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.

Size, microhabitat, and loss of larval feeding drive cranial diversification in frogs

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.

An integrative phylogenomic approach illuminates the evolutionary history of Old World tree frogs (Anura: Rhacophoridae)

Rhacophoridae are one of the most speciose and ecologically diverse families of amphibians. Resolution of their evolutionary relationships is key to understanding the accumulation of biodiversity, yet previous hypotheses based on Sanger sequencing exhibit much discordance amongst generic relationships. This conflict precludes the making of sound macroevolutionary conclusions. Herein, we conduct the first phylogenomic study using broad-scale sampling and sequences of 352 nuclear DNA loci obtained using anchored hybrid enrichment targeted sequencing. The robust time-calibrated phylogenetic hypothesis clarifies several long-disputed relationships and facilitates the testing of evolutionary hypotheses on spatiotemporal diversification and reproductive modes. The major extant lineages of Rhacophoridae appear to have radiated in mainland Asia, and the spatiotemporal process corresponds with several common accumulations of biodiversity in Asia. Analyses do not detect any case of "Out of Himalaya" in Rhacophoridae. All transitions of reproductive modes appear to have evolved in an ordered, gradual sequence associated with gaining independence of standing water for larval development. The different reproductive modes are phylogenetically conserved and the completion of their transitions appear to have occurred over a period of ~30 Ma, which does not fit a pattern of a rapid burst of diversification. Innovations in reproductive modes associate statistically with the uneven distribution of species-richness between clades, where higher diversification is linked to increased terrestrial modes of reproduction. These results strengthen the hypothesis that breeding innovations drive diversification by providing new opportunities for ecological release and dispersion.

The complete mitochondrial genome of Pyxicephalus adspersus: high gene rearrangement and phylogenetics of one of the world's largest frogs

The family Pyxicephalidae including two subfamilies (Cacosterninae and Pyxicephalinae) is an ecologically important group of frogs distributed in sub-Saharan Africa. However, its phylogenetic position among the Anura has remained uncertain. The present study determined the complete mitochondrial genome sequence of Pyxicephalus adspersus, the first representative mitochondrial genome from the Pyxicephalinae, and reconstructed the phylogenetic relationships within Ranoidae using 10 mitochondrial protein-coding genes of 59 frog species. The P. adspersus mitochondrial genome showed major gene rearrangement and an exceptionally long length that is not shared with other Ranoidae species. The genome is 24,317 bp in length, and contains 15 protein-coding genes (including extra COX3 and Cyt b genes), four rRNA genes (including extra 12S rRNA and 16S rRNA genes), 29 tRNA genes (including extra tRNALeu (UAG), tRNALeu (UUR), tRNAThr , tRNAPro , tRNAPhe , tRNAVal , tRNAGln genes) and two control regions (CRs). The Dimer-Mitogenome and Tandem duplication and random loss models were used to explain these gene arrangements. Finally, both Bayesian inference and maximum likelihood analyses supported the conclusion that Pyxicephalidae was monophyletic and that Pyxicephalidae was the sister clade of (Petropedetidae + Ptychadenidae).

Sesamoids in tetrapods: the origin of new skeletal morphologies

Along with supernumerary bones, sesamoids, defined as any organized intratendinous/intraligamentous structure, including those composed of fibrocartilage, adjacent to an articulation or joint, have been frequently considered as enigmatic structures associated with the joints of the skeletal system of vertebrates. This review allows us to propose a dynamic model to account for part of skeletal phenotypic diversity: during evolution, sesamoids can become displaced, attaching to and detaching from the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached sesamoids are able to transform into each other, contributing to the phenotypic variability of the tetrapod skeleton. This dynamic model is a new paradigm to delineate the contribution of sesamoids to skeletal diversity. Herein, we first present a historical approach to the study of sesamoids, discussing the genetic versus epigenetic theories of their genesis and growth. Second, we construct a dynamic model. Third, we present a summary of literature on sesamoids of the main groups of tetrapods, including veterinary and human clinical contributions, which are the best-studied aspects of sesamoids in recent decades. Finally, we discuss the identity of certain structures that have been labelled as sesamoids despite insufficient formal testing of homology. We also propose a new definition to help the identification of sesamoids in general. This review is particularly timely, given the recent increasing interest and research activity into the developmental biology and mechanics of sesamoids. With this updated and integrative discussion, we hope to pave the way to improve the understanding of sesamoid biology and evolution.

The Role of Developmental Integration and Historical Contingency in the Origin and Evolution of Cypriniform Trophic Novelties

While functional morphologists have long studied the evolution of anatomical structures, the origin of morphological novelties has received less attention. When such novelties first originate they must become incorporated into an integrated system to be rendered fully functional. Thus, developmental integration is key at the origin of morphological novelties. However, given enough evolutionary time such integration may be broken, allowing for a division of labor that is facilitated by subsequent decoupling of structures. Cypriniformes represent a diverse group of freshwater fishes characterized by several trophic novelties that include: kinethmoid-mediated premaxillary protrusion, a muscular palatal and post-lingual organ, hypertrophied lower pharyngeal jaws that masticate against the base of the neurocranium, novel pharyngeal musculature controlling movement of the hypertrophied lower pharyngeal jaws, and in a few species an incredibly complex epibranchial organ used to aggregate filtered phytoplankton. Here, we use the wealth of such trophic novelties in different cypriniform fishes to present case studies in which developmental integration allowed for the origin of morphological innovations. As proposed in case studies 1 and 2 trophic innovations may be associated with both morphological and lineage diversification. Alternatively, case studies 3 and 4 represent a situation where ecological niche was expanded but with no concomitant increase in species diversity.

Convergence to the tiniest detail: vocal sac structure in torrent-dwelling frogs

Cascades and fast-flowing streams impose severe restrictions on acoustic communication, with loud broadband background noise hampering signal detection and recognition. In this context, diverse behavioural features, such as ultrasound production and visual displays, have arisen in the evolutionary history of torrent-dwelling amphibians. The importance of the vocal sac in multimodal communication is being increasingly recognized, and recently a new vocal sac visual display has been discovered: unilateral inflation of paired vocal sacs. In the diurnal stream-breeding Hylodidae from the Atlantic forest, where it was first described, this behaviour is likely to be enabled by a unique anatomical configuration of the vocal sacs. To assess whether other taxa share this exceptional structure, we surveyed torrent-dwelling species with paired vocal sacs across the anuran tree of life and examined the vocal sac anatomy of exemplar species across 18 families. We found striking anatomical convergence among hylodids and species of the distantly related basal ranid genera Staurois, Huia, Meristogenys and Amolops. Ancestral character state reconstruction identified three new synapomorphies for Ranidae. Furthermore, we surveyed the vocal sac configuration of other anuran species that perform visual displays and report observations on what appears to be unilateral inflation of paired vocal sacs, in Staurois guttatus – an extremely rare behaviour in anurans.

Intrasexually selected weapons

We propose a practical concept that distinguishes the particular kind of weaponry that has evolved to be used in combat between individuals of the same species and sex, which we term intrasexually selected weapons (ISWs). We present a treatise of ISWs in nature, aiming to understand their distinction and evolution from other secondary sex traits, including from 'sexually selected weapons', and from sexually dimorphic and monomorphic weaponry. We focus on the subset of secondary sex traits that are the result of same-sex combat, defined here as ISWs, provide not previously reported evolutionary patterns, and offer hypotheses to answer questions such as: why have only some species evolved weapons to fight for the opposite sex or breeding resources? We examined traits that seem to have evolved as ISWs in the entire animal phylogeny, restricting the classification of ISW to traits that are only present or enlarged in adults of one of the sexes, and are used as weapons during intrasexual fights. Because of the absence of behavioural data and, in many cases, lack of sexually discriminated series from juveniles to adults, we exclude the fossil record from this review. We merge morphological, ontogenetic, and behavioural information, and for the first time thoroughly review the tree of life to identify separate evolution of ISWs. We found that ISWs are only found in bilateral animals, appearing independently in nematodes, various groups of arthropods, and vertebrates. Our review sets a reference point to explore other taxa that we identify with potential ISWs for which behavioural or morphological studies are warranted. We establish that most ISWs come in pairs, are located in or near the head, are endo- or exoskeletal modifications, are overdeveloped structures compared with those found in females, are modified feeding structures and/or locomotor appendages, are most common in terrestrial taxa, are frequently used to guard females, territories, or both, and are also used in signalling displays to deter rivals and/or attract females. We also found that most taxa lack ISWs, that females of only a few species possess better-developed weapons than males, that the cases of independent evolution of ISWs are not evenly distributed across the phylogeny, and that animals possessing the most developed ISWs have non-hunting habits (e.g. herbivores) or are faunivores that prey on very small prey relative to their body size (e.g. insectivores). Bringing together perspectives from studies on a variety of taxa, we conceptualize that there are five ways in which a sexually dimorphic trait, apart from the primary sex traits, can be fixed: sexual selection, fecundity selection, parental role division, differential niche occupation between the sexes, and interference competition. We discuss these trends and the factors involved in the evolution of intrasexually selected weaponry in nature.

Comparative Postembryonic Skeletal Ontogeny in Two Sister Lineages of Old World Tree Frogs (Rhacophoridae: Taruga, Polypedates)

Rhacophoridae, a family of morphologically cryptic frogs, with many genetically distinct evolutionary lineages, is understudied with respect to skeletal morphology, life history traits and skeletal ontogeny. Here we analyze two species each from two sister lineages, Taruga and Polypedates, and compare their postembryonic skeletal ontogeny, larval chondrocrania and adult osteology in the context of a well-resolved phylogeny. We further compare these ontogenetic traits with the direct-developing Pseudophilautus silus. For each species, we differentially stained a nearly complete developmental series of tadpoles from early postembryonic stages through metamorphosis to determine the intraspecific and interspecific differences of cranial and postcranial bones. Chondrocrania of the four species differ in 1) size; 2) presence/absence of anterolateral and posterior process; and 3) shape of the suprarostral cartilages. Interspecific variation of ossification sequences is limited during early stages, but conspicuous during later development. Early cranial ossification is typical of other anuran larvae, where the frontoparietal, exoccipital and parasphenoid ossify first. The ossification sequences of the cranial bones vary considerably within the four species. Both species of Taruga show a faster cranial ossification rate than Polypedates. Seven cranial bones form when larvae near metamorphic climax. Ossification of all 18 cranial bones is initiated by larval Gosner stage 46 in T. eques. However, some cranial bone formation is not initiated until after metamorphosis in the other three species. Postcranial sequence does not vary significantly. The comparison of adult osteology highlights two characters, which have not been previously recorded: presence/absence of the parieto-squamosal plates and bifurcated base of the omosternum. This study will provide a starting point for comparative analyses of rhacophorid skeletal ontogeny and facilitate the study of the evolution of ontogenetic repatterning associated with the life history variation in the family.

Evolutionary history of the river frog genus Amietia (Anura: Pyxicephalidae) reveals extensive diversification in Central African highlands

The African river frog genus Amietia is found near rivers and other lentic water sources throughout central, eastern, and southern Africa. Because the genus includes multiple morphologically conservative species, taxonomic studies of river frogs have been relatively limited. We sampled 79 individuals of Amietia from multiple localities in and near the Albertine Rift (AR) of Burundi, Democratic Republic of the Congo, and Uganda. We utilized single-gene (16S) and concatenated (12S, 16S, cyt b and RAG1) gene-tree analyses and coalescent species-tree analyses to construct phylogenetic trees. Two divergence dating approaches were used in BEAST, including secondary calibration points with 12S, 16S, cyt b and RAG1, and a molecular clock with the 12S, 16S, and cyt b genes. All analyses recovered Amietia as monophyletic with strong support, and revealed several well-supported cryptic lineages, which is consistent with other recent phylogeography studies of AR amphibians. Dating estimates were similar, and Amietia diversification is coincident with global cooling and aridification events in the Miocene and Pliocene, respectively. Our results suggest additional taxonomic work is needed to describe multiple new species of AR Amietia, some of which have limited geographic distributions that are likely to be of conservation concern.

Increased androgenic sensitivity in the hind limb muscular system marks the evolution of a derived gestural display

Physical gestures are prominent features of many species' multimodal displays, yet how evolution incorporates body and leg movements into animal signaling repertoires is unclear. Androgenic hormones modulate the production of reproductive signals and sexual motor skills in many vertebrates; therefore, one possibility is that selection for physical signals drives the evolution of androgenic sensitivity in select neuromotor pathways. We examined this issue in the Bornean rock frog (Staurois parvus, family: Ranidae). Males court females and compete with rivals by performing both vocalizations and hind limb gestural signals, called "foot flags." Foot flagging is a derived display that emerged in the ranids after vocal signaling. Here, we show that administration of testosterone (T) increases foot flagging behavior under seminatural conditions. Moreover, using quantitative PCR, we also find that adult male S. parvus maintain a unique androgenic phenotype, in which androgen receptor (AR) in the hind limb musculature is expressed at levels ∼10× greater than in two other anuran species, which do not produce foot flags (Rana pipiens and Xenopus laevis). Finally, because males of all three of these species solicit mates with calls, we accordingly detect no differences in AR expression in the vocal apparatus (larynx) among taxa. The results show that foot flagging is an androgen-dependent gestural signal, and its emergence is associated with increased androgenic sensitivity within the hind limb musculature. Selection for this novel gestural signal may therefore drive the evolution of increased AR expression in key muscles that control signal production to support adaptive motor performance.

From Clinging to Digging: The Postembryonic Skeletal Ontogeny of the Indian Purple Frog, Nasikabatrachus sahyadrensis (Anura: Nasikabatrachidae)

The Indian Purple frog, Nasikabatrachus sahyadrensis, occupies a basal phylogenetic position among neobatrachian anurans and has a very unusual life history. Tadpoles have a large ventral oral sucker, which they use to cling to rocks in torrents, whereas metamorphs possess adaptations for life underground. The developmental changes that underlie these shifts in habits and habitats, and especially the internal remodeling of the cranial and postcranial skeleton, are unknown. Using a nearly complete metamorphic series from free-living larva to metamorph, we describe the postembryonic skeletal ontogeny of this ancient and unique monotypic lineage. The torrent-dwelling larva possesses a dorsoventrally flattened body and a head with tiny dorsal eyes, robust lower and upper jaw cartilages, well-developed trabecular horns, and a definable gap between the trabecular horns and the tip of the snout. Unlike tadpoles of many other frogs, those of Nasikabatrachus retain larval mouthparts into late metamorphic stages. This unusual feature enables the larvae to maintain their clinging habit until near the end of metamorphosis. The subsequent ontogenetic shift from clinging to digging is correlated with rapid morphological changes and behavioral modifications. Metamorphs are equipped with a shortened tibiafibula and ossified prehallical elements, which likely facilitate initial digging using the hind limbs. Subsequently, the frogs may shift to headfirst burrowing by using the wedge-shaped skull, anteriorly positioned pectoral girdle, well-developed humeral crests and spatula-shaped forelimbs. The transition from an aquatic life in torrents to a terrestrial life underground entails dramatic changes in skeletal morphology and function that represent an extreme in metamorphic remodeling. Our analysis enhances the scope for detailed comparative studies across anurans, a group renowned for the diversity of its life history strategies.

The phylogenetic position and diversity of the enigmatic mongrel frog Nothophryne Poynton, 1963 (Amphibia, Anura)

The phylogenetic relationships of the African mongrel frog genus Nothophryne are poorly understood. We provide the first molecular assessment of the phylogenetic position of, and diversity within, this monotypic genus from across its range-the Afromontane regions of Malawi and Mozambique. Our analysis using a two-tiered phylogenetic approach allowed us to place the genus in Pyxicephalidae. Within the family, Nothophryne grouped with Tomopterna, a hypothesis judged significantly better than alternative hypotheses proposed based on morphology. Our analyses of populations across the range of Nothophryne suggest the presence of several cryptic species, at least one species per mountain. Formal recognition of these species is pending but there is a major conservation concern for these narrowly distributed populations in an area impacted by major habitat change. The phylogenetic tree of pyxicephalids is used to examine evolution of life history, ancestral habitat, and biogeography of this group.

Phylogenetic relationships of †Luisiella feruglioi (Bordas) and the recognition of a new clade of freshwater teleosts from the Jurassic of Gondwana

BACKGROUND

Teleosts constitute more than 99 % of living actinopterygian fishes and fossil teleosts have been studied for about two centuries. However, a general consensus on the definition of Teleostei and the relationships among the major teleostean clades has not been achieved. Our current ideas on the origin and early diversification of teleosts are mainly based on well-known Mesozoic marine taxa, whereas the taxonomy and phylogenetic relationships of many Jurassic continental teleosts are still poorly understood despite their importance to shed light on the early evolutionary history of this group. Here, we explore the phylogenetic relationships of the Late Jurassic (Oxfordian - Tithonian) freshwater †Luisiella feruglioi from Patagonia, in a comprehensive parsimony analysis after a thorough revision of characters from previous phylogenetic studies on Mesozoic teleosts.

RESULTS

We retrieved †Luisiella feruglioi as the sister taxon of the Late Jurassic †Cavenderichthys talbragarensis, both taxa in turn forming a monophyletic group with the Early Cretaceous †Leptolepis koonwarri. This new so far exclusively Gondwanan freshwater teleost clade, named †Luisiellidae fam. nov. herein, is placed outside crown Teleostei, as a member of the stem-group immediately above the level of †Leptolepis coryphaenoides. In addition, we did not retrieve the Late Jurassic †Varasichthyidae as a member of †Crossognathiformes. The position of †Crossognathiformes within Teleocephala is confirmed whereas †Varasichthyidae is placed on the stem.

CONCLUSIONS

The general morphology of luisiellids is that of basal, stem Teleocephala; however, most of their synapomorphies have evolved independently in teleocephalans. Similarly, the resemblance between varasichthyids and crossognathiforms might be due to parallel evolution. In accordance to most teleostean phylogenies, our analysis shows that a major morphological change occurred along the stem line and are currently recorded at the level of †Leptolepis coryphaenoides. A stem-based total clade Teleostei has been accepted for this work.

Systematics and biogeography of the Hylarana frog (Anura: Ranidae) radiation across tropical Australasia, Southeast Asia, and Africa

We present an inclusive molecular phylogeny for Hylarana across its global distribution, utilizing two mitochondrial and four nuclear gene regions for 69 of the 97 currently described species. We use phylogenetic methods to test monophyly of Hylarana, determine relationships among ten putative subgenera, identify major clades, reconstruct biogeographic history, and estimate continental dispersal dates. Results support Hylarana as a monophyletic group originating approximately 26.9MYA and comprising eight clades that partly correspond to currently described subgenera plus two new groups. The African and Australasian species each form clades embedded within a paraphyletic Southeast Asian group. We estimate that Africa and Australasia were colonized by Hylarana s.l. from SE Asia approximately 18.7 and 10.8MYA, respectively. Biogeographic reconstructions also support three separate colonization events in India from Southeast Asia. Examination of museum specimens identified morphological characters useful for delineating subgenera and species. We herein elevate all supported subgenera to genus rank and formally describe two new genera to produce a revised taxonomy congruent with our new phylogenetic and biogeographic findings.

Evolutionary relationships of the critically endangered frog Ericabatrachus baleensis Largen, 1991 with notes on incorporating previously unsampled taxa into large-scale phylogenetic analyses

BACKGROUND

The phylogenetic relationships of many taxa remain poorly known because of a lack of appropriate data and/or analyses. Despite substantial recent advances, amphibian phylogeny remains poorly resolved in many instances. The phylogenetic relationships of the Ethiopian endemic monotypic genus Ericabatrachus has been addressed thus far only with phenotypic data and remains contentious.

RESULTS

We obtained fresh samples of the now rare and Critically Endangered Ericabatrachus baleensis and generated DNA sequences for two mitochondrial and four nuclear genes. Analyses of these new data using de novo and constrained-tree phylogenetic reconstructions strongly support a close relationship between Ericabatrachus and Petropedetes, and allow us to reject previously proposed alternative hypotheses of a close relationship with cacosternines or Phrynobatrachus.

CONCLUSIONS

We discuss the implications of our results for the taxonomy, biogeography and conservation of E. baleensis, and suggest a two-tiered approach to the inclusion and analyses of new data in order to assess the phylogenetic relationships of previously unsampled taxa. Such approaches will be important in the future given the increasing availability of relevant mega-alignments and potential framework phylogenies.

The first endemic West African vertebrate family - a new anuran family highlighting the uniqueness of the Upper Guinean biodiversity hotspot

BACKGROUND

Higher-level systematics in amphibians is relatively stable. However, recent phylogenetic studies of African torrent-frogs have uncovered high divergence in these phenotypically and ecologically similar frogs, in particular between West African torrent-frogs versus Central (Petropedetes) and East African (Arthroleptides and Ericabatrachus) lineages. Because of the considerable molecular divergence, and external morphology of the single West African torrent-frog species a new genus was erected (Odontobatrachus). In this study we aim to clarify the systematic position of West African torrent-frogs (Odontobatrachus). We determine the relationships of torrent-frogs using a multi-locus, nuclear and mitochondrial, dataset and include genera of all African and Asian ranoid families. Using micro-tomographic scanning we examine osteology and external morphological features of West African torrent-frogs to compare them with other ranoids.

RESULTS

Our analyses reveal Petropedetidae (Arthroleptides, Ericabatrachus, Petropedetes) as the sister taxon of the Pyxicephalidae. The phylogenetic position of Odontobatrachus is clearly outside Petropedetidae, and not closely related to any other ranoid family. According to our time-tree estimation Odontobatrachus has been separated from other frog lineages since the Cretaceous (90.1 Ma; confidence interval: 84.2-97.1 Ma). Along with this molecular evidence, osteological and external diagnostic characters recognize West African torrent-frogs as distinct from other ranoids and provide strong support for the necessity of the recognition of a new family of frogs. This is the only endemic vertebrate family occurring in the Upper Guinea biodiversity hotspot.

CONCLUSION

Based on molecular and morphological distinctiveness, the West African torrent-frog Odontobatrachus natator is allocated to a newly described anuran family. The discovery of an endemic vertebrate family in West Africa highlights the Upper Guinean forests as an outstanding, but highly endangered biodiversity hotspot.

New material of Beelzebufo, a hyperossified frog (Amphibia: Anura) from the late cretaceous of Madagascar

The extant anuran fauna of Madagascar is exceptionally rich and almost completely endemic. In recent years, many new species have been described and understanding of the history and relationships of this fauna has been greatly advanced by molecular studies, but very little is known of the fossil history of frogs on the island. Beelzebufo ampinga, the first named pre-Holocene frog from Madagascar, was described in 2008 on the basis of numerous disarticulated cranial and postcranial elements from the Upper Cretaceous (Maastrichtian) Maevarano Formation of Madagascar. These specimens documented the presence of a hyperossified taxon that differed strikingly from extant Malagasy frogs in its large size and heavy coarse cranial exostosis. Here we describe and analyse new, articulated, and more complete material of the skull, vertebral column, and hind limb, as well as additional isolated elements discovered since 2008. μCT scans allow a detailed understanding of both internal and external morphology and permit a more accurate reconstruction. The new material shows Beelzebufo to have been even more bizarre than originally interpreted, with large posterolateral skull flanges and sculptured vertebral spine tables. The apparent absence of a tympanic membrane, the strong cranial exostosis, and vertebral morphology suggest it may have burrowed during seasonally arid conditions, which have been interpreted for the Maevarano Formation from independent sedimentological and taphonomic evidence. New phylogenetic analyses, incorporating both morphological and molecular data, continue to place Beelzebufo with hyloid rather than ranoid frogs. Within Hyloidea, Beelzebufo still groups with the South American Ceratophryidae thus continuing to pose difficulties with both biogeographic interpretations and prior molecular divergence dates.

Understanding of the impact of chemicals on amphibians: a meta-analytic review

Many studies have assessed the impact of different pollutants on amphibians across a variety of experimental venues (laboratory, mesocosm, and enclosure conditions). Past reviews, using vote-counting methods, have described pollution as one of the major threats faced by amphibians. However, vote-counting methods lack strong statistical power, do not permit one to determine the magnitudes of effects, and do not compare responses among predefined groups. To address these challenges, we conducted a meta-analysis of experimental studies that measured the effects of different chemical pollutants (nitrogenous and phosphorous compounds, pesticides, road deicers, heavy metals, and other wastewater contaminants) at environmentally relevant concentrations on amphibian survival, mass, time to hatching, time to metamorphosis, and frequency of abnormalities. The overall effect size of pollutant exposure was a medium decrease in amphibian survival and mass and a large increase in abnormality frequency. This translates to a 14.3% decrease in survival, a 7.5% decrease in mass, and a 535% increase in abnormality frequency across all studies. In contrast, we found no overall effect of pollutants on time to hatching and time to metamorphosis. We also found that effect sizes differed among experimental venues and among types of pollutants, but we only detected weak differences among amphibian families. These results suggest that variation in sensitivity to contaminants is generally independent of phylogeny. Some publication bias (i.e., selective reporting) was detected, but only for mass and the interaction effect size among stressors. We conclude that the overall impact of pollution on amphibians is moderately to largely negative. This implies that pollutants at environmentally relevant concentrations pose an important threat to amphibians and may play a role in their present global decline.

Structural diversity of nuptial pads in Phyllomedusinae (Amphibia: Anura: Hylidae)

We studied the morphological variation of the nuptial pads using light microscopy and scanning electron microscopy (SEM) in 26 species of phyllomedusines (Anura: Hylidae), representing the five currently recognized genera. All phyllomedusines have single nuptial pads with dark colored epidermal projections (EPs). Spine-shaped EPs occur in Cruziohyla calcarifer, Phrynomedusa appendiculata and in one species of Phasmahyla. The other species have roundish EPs. The density of the EPs on the pad is variable. Species in the Phyllomedusa hypochondrialis Group have EPs with a density that varies between 764 ± 58/mm(2) and 923 ± 160/mm(2). In all other studied species (including the Phyllomedusa burmeisteri and Phyllomedusa perinesos groups, Phyllomedusa camba, Phyllomedusa boliviana, Phyllomedusa sauvagii, Phyllomedusa bicolor, and Phyllomedusa tomopterna) the density of EPs varies between 108 ± 20/mm(2) and 552 ± 97/mm(2). Pores were observed with SEM in C. calcarifer, Agalychnis lemur, Agalychnis moreletii, but its presence is confirmed through histological sections on several other species. Its visibility using SEM seems to be related with the level of separation between adjacent EPs. The pores in the four studied species of Agalychnis are shown with SEM and histological sections to have a characteristic epidermal rim, that is absent in the otherphyllomedusines. Unlike most previous reports on breeding glands, those of phyllomedusines are alcian blue positive, indicating the presence of acidic mucosubstances on its secretions.

Evolution and plasticity of anuran larval development in response to desiccation. A comparative analysis

Anurans breed in a variety of aquatic habitats with contrasting levels of desiccation risk, which may result in selection for faster development during larval stages. Previous studies suggest that species in ephemeral ponds reduce their developmental times to minimize desiccation risks, although it is not clear how variation in desiccation risk affects developmental strategies in different species. Employing a comparative phylogenetic approach including data from published and unpublished studies encompassing 62 observations across 30 species, we tested if species breeding in ephemeral ponds (High risk) develop faster than those from permanent ponds (Low risk) and/or show increased developmental plasticity in response to drying conditions. Our analyses support shorter developmental times in High risk, primarily by decreasing body mass at metamorphosis. Plasticity in developmental times was small and did not differ between groups. However, accelerated development in High risk species generally resulted in reduced sizes at metamorphosis, while some Low risk species were able compensate this effect by increasing mean growth rates. Taken together, our results suggest that plastic responses in species breeding in ephemeral ponds are constrained by a general trade-off between development and growth rates.

Concealed weapons: erectile claws in African frogs

Vertebrate claws are used in a variety of important behaviours and are typically composed of a keratinous sheath overlying the terminal phalanx of a digit. Keratinous claws, however, are rare in living amphibians; their microstructure and other features indicate that they probably originated independently from those in amniotes. Here we show that certain African frogs have a different type of claw, used in defence, that is unique in design among living vertebrates and lacks a keratinous covering. These frogs have sectorial terminal phalanges on their hind feet that become functional by cutting through the skin. In the resting state, the phalanx is subdermal and attached to a distal bony nodule, a neomorphic skeletal element, via collagen-rich connective tissue. When erected, the claw breaks free from the nodule and pierces the ventral skin. The nodule, suspended by a sheath attached to the terminal phalanx and supported by collagenous connections to the dermis, remains fixed in place. While superficially resembling the shape of claws in other tetrapods, these are the only vertebrate claws known to pierce their way to functionality.