Independent evolution of complex life history adaptations in two families of fishes, live-bearing halfbeaks (zenarchopteridae, beloniformes) and poeciliidae (cyprinodontiformes)

We have previously documented multiple, independent origins of placentas in the fish family Poeciliidae. Here we summarize similar analyses of fishes in the family Zenarchopteridae. This family includes three live-bearing genera. Earlier studies documented the presence of superfetation, or the ability to carry multiple litters of young in different stages of development in the same ovary, in some species in all three genera. There is also one earlier report of matrotrophy, or extensive postfertilization maternal provisioning, in two of these genera. We present detailed life-history data for approximately half of the species in all three genera and combine them with the best available phylogeny to make inferences about the pattern of life-history evolution within this family. Three species of Hemirhamphodon have superfetation but lack matrotrophy. Most species in Nomorhamphus and Dermogenys either lack superfetation and matrotrophy or have both superfetation and matrotrophy. Our phylogenetic analysis shows that matrotrophy may have evolved independently in each genus. In Dermogenys, matrotrophic species produce fewer, larger offspring than nonmatrotrophic species. In Nomorhamphus; matrotrophic species instead produce more and smaller offspring than lecithotrophic species. However, the matrotrophic species in both genera have significantly smaller masses of reproductive tissue relative to their body sizes. All aspects of these results are duplicated in the fish family Poeciliidae. We discuss the possible adaptive significance of matrotrophy in the light of these new results. The two families together present a remarkable opportunity to study the evolution of a complex trait because they contain multiple, independent origins of the trait that often include close relatives that vary in either the presence or absence of the matrotrophy or in the degree to which matrotrophy is developed. These are the raw materials that are required for either an analysis of the adaptive significance of the trait or for studies of the genetic mechanisms that underlie the evolution of the trait.     

Have superfetation and matrotrophy facilitated the evolution of larger offspring in poeciliid fishes?

Superfetation is the ability of females to simultaneously carry multiple broods of embryos, with each brood at a different developmental stage. Matrotrophy is the post‐fertilization maternal provisioning of nutrients to developing embryos throughout gestation. Several studies have demonstrated that, in viviparous fishes, superfetation and matrotrophy have evolved in a correlated way, such that species capable of bearing several simultaneous broods also exhibit advanced degrees of post‐fertilization provisioning. The adaptive value of the concurrent presence of both reproductive modes may be associated with the production of larger newborns, which in turn may result in enhanced offspring fitness. In this study, we tested two hypotheses: (1) species with superfetation and moderate or extensive matrotrophy give birth to larger offspring compared with species without superfetation or matrotrophy; (2) species with higher degrees of superfetation and matrotrophy (i.e. more simultaneous broods and increased amounts of post‐fertilization provisioning) give birth to larger offspring compared with species with relatively low degrees of superfetation and matrotrophy (i.e. fewer simultaneous broods and lesser amounts of post‐fertilization provisioning). Using different phylogenetic comparative methods and data on 44 species of viviparous fishes of the family Poeciliidae, we found a lack of association between offspring size and the combination of superfetation and matrotrophy. Therefore, the concurrent presence of superfetation and moderate or extensive matrotrophy has not facilitated the evolution of larger offspring. In fact, these traits have evolved differently. Superfetation and matrotrophy have accumulated gradual changes that largely can be explained by Brownian motion, whereas offspring size has evolved fluidly, experiencing changes that probably resulted from selective responses to the local conditions.     

Evolutionary innovations of squamate reproductive and developmental biology in the family Chamaeleonidae

The availability of molecular phylogenies has greatly accelerated our understanding of evolutionary innovations in the context of their origin and rate of evolution. Here, we assess the evolution of reproductive mode, developmental rate and body size in a group of squamate reptiles: the chameleons. Oviparity is ancestral and viviparity has evolved at least twice: Bradypodion and members of the Trioceros bitaeniatus clade are viviparous. Viviparous species are medium‐sized as a result of convergence from either small‐sized ancestors or large‐sized ancestors, respectively, but do not differ from oviparous species in clutch size, hatchling size or the trade‐off between clutch and hatchling size. Basal chameleons (Brookesia, Rhampholeon and Rieppeleon) are small‐sized and have developmental rates comparable with those of other lizards. Derived chameleons (Calumma, Chamaeleo, Trioceros and Furcifer) are mostly large‐sized and all have relatively slow developmental rates. Several clades of derived chameleons also exhibit developmental arrest (embryonic diapause or embryonic diapause plus cold torpor) and incubation periods extend to 6–10 months or more. Developmental arrest is associated with dry, highly seasonal climates in which the period favourable for oviposition and hatching is short. Long incubation periods thus ensure that hatching occurs during the favourable season following egg laying. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 656–668.     

Co‐evolution of the premaxilla and jaw protrusion in cichlid fishes (Heroine: Cichlidae)

The ability of Perciform fishes to protrude their jaw has likely been critical to the trophic diversification of this group, which includes approximately 20% of all vertebrates. The length of the ascending process of the premaxilla is thought to influence the maximum extent that cichlids and other Perciforms protrude their oral jaw. Using a combination of morphometrics, kinematics, and new phylogenetic hypotheses for 20 Heroine cichlid species, we tested the evolutionary relationship between the length of the premaxillary ascending process and maximum jaw protrusion. In this clade, the length of the ascending process of the premaxilla ranged from 11.6–32.7% with respect to standard length whereas maximum jaw protrusion ranged from 3.5–23.4% with respect to standard length. The evolutionary relationships among the Heroine cichlids obtained from the genetic partitions cytochrome b, S7, and RAG1 showed limited concordance. However, correlations between the length of the ascending process and maximum jaw protrusion were highly significant when examined as independent contrasts using all three topologies. Evolutionary change in the length of the ascending process of the premaxilla is likely critical for determining the amount of jaw protrusion in Perciform groups such as cichlid fishes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 619–629.     

Revision and cladistic analysis of the jumping spider genus Onomastus (Araneae: Salticidae)

The jumping spider genus Onomastus Simon, 1900 is revised. Four new species: Onomastus indra sp. nov. , Onomastus kaharian sp. nov. , Onomastus pethiyagodai sp. nov. , and Onomastus rattotensis sp. nov. are described. Parsimony analysis of 26 morphological characters supported the monophyly of Onomastus. Lyssomanes is sister to Onomastus. Onomastus separates into two clades: the widespread South‐East Asia clade and the South Asia clade. The South Asia clade is restricted to the Sri Lanka–Western Ghats biodiversity hotspot. Species of the South Asia clade appear to be spot endemics, highly in danger of extinction because of habitat loss and climate change. Male palps are complex and species‐specific, suggesting rapid divergent evolution. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 711–745.     

Evaluating hypotheses on the origin and diversification of the ringneck snake Diadophis punctatus (Colubridae: Dipsadinae)

Close affinities recognized between taxa in Mexico and the contiguous USA have led to a variety of biogeographical scenarios. One such hypothesis suggests that species that occur in both countries have an origin in central Mexico followed by dispersal into the USA. This study expands upon previous phylogeographical work of the ringneck snake Diadophis punctatus by incorporating new data from previously unsampled areas appropriate to critically assess hypotheses regarding a Mexican origin for this species. Maximum likelihood and maximum parsimony analyses inferred a derived position for the lineage from southern Mexico with constraint tests for alternate evolutionary hypotheses resulting in significantly worse likelihood values. Ancestral area reconstructions inferred an origin for D. punctatus in the south‐eastern USA followed by a south‐east to north‐east then westward directionality of historical migration. The position within the phylogeny and date estimate for the south‐western + Mexico clade suggests a recent invasion into central Mexico with expansion into the Nearctic/Neotropic transition zone. The extensive lineage diversity inferred from the mtDNA suggests that the genus is a complex of cryptic species whose conservational status should be re‐evaluated on both the national and regional levels. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 629–640.     

The evolution of conspicuous facultative mimicry in octopuses: an example of secondary adaptation?

The ‘Mimic Octopus’Thaumoctopus mimicus Norman & Hochberg, 2005 exhibits a conspicuous primary defence mechanism (high‐contrast colour pattern during ‘flatfish swimming’) that may involve facultative imperfect mimicry of conspicuous and/or inconspicuous models, both toxic and non‐toxic (Soleidae and Bothidae). Here, we examine relationships between behavioural and morphological elements of conspicuous flatfish swimming in extant octopodids (Cephalopoda: Octopodidae), and reconstructed ancestral states, to examine potential influences on the evolution of this rare defence mechanism. We address the order of trait distribution to explore whether conspicuous flatfish swimming may be an exaptation that usurps a previously evolved form of locomotion for a new purpose. Contrary to our predictions, based on the relationships we examined, flatfish swimming appears to have evolved concurrently with extremely long arms, in a clade of sand‐dwelling species. The conspicuous body colour pattern displayed by swimming T. mimicus may represent a secondary adaptation potentially allowing for mimicry of a toxic sole, improved disruptive coloration, and/or aposematic coloration. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 68–77.     

Higher and lower‐level relationships of the deep‐sea fish order Alepocephaliformes (Teleostei: Otocephala) inferred from whole mitogenome sequences

Fishes of the order Alepocephaliformes, slickheads and tubeshoulders, constitute a group of deep‐sea fishes poorly known in respect to most areas of their biology and systematics. Morphological studies have found alepocephaliform fishes to display a mosaic of synapomorphic and symplesiomorphic characters, resulting in great difficulties when attempting to resolve intra‐ and interrelationships. Molecular data recently added to the confusion by removing Alepocephaliformes from the Euteleostei and placed them as incertae sedis within the Otocephala. In the present study we attempt to further clarify relationships of Alepocephaliformes by adding newly determined whole mitogenome sequences from 19 alepocephaliforms in order to address 1) phylogenetic position of Alepocephaliformes within the Otocephala; and 2) intrarelationships of Alepocephaliformes. The present study includes 96 taxa of which 30 are alepocephaliforms and unambiguously aligned sequences were subjected to partitioned maximum likelihood and Bayesian analyses. Results from the present study support Alepocephaliformes as a genetically distinct otocephalan order as sister clade to Ostariophysi (mostly freshwater fishes comprising Gonorynchiformes, Cypriniformes, Characiformes, Siluriformes and Gymnotiformes). The disputed family Bathylaconidae was found to be an artificial assemblage of the two genera Bathylaco and Herwigia, with the former as the sister group of the family Alepocephalidae and the latter nested within Alepocephalidae. Platytroctidae was found to be monophyletic as sister clade to the rest of Alepocephaliformes. Previously unrecognized clades within the family Alepocephalidae are presented and a clade comprising Alepocephalus, Conocara and Leptoderma was recovered as the most derived. As long as the current classification is being followed, the genera Alepocephalus, Bathytroctes, Conocara and Narcetes were all found non‐monophyletic. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 923–936.     

How to become a yucca moth: minimal trait evolution needed to establish the obligate pollination mutualism

The origins of obligate pollination mutualisms, such as the classic yucca–yucca moth association, appear to require extensive trait evolution and specialization. To understand the extent to which traits truly evolved as part of establishing the mutualistic relationship, rather than being pre‐adaptations, we used an expanded phylogenetic estimate with improved sampling of deeply‐diverged groups to perform the first formal reconstruction of trait evolution in pollinating yucca moths and their nonpollinating relatives. Our analysis demonstrates that key life‐history traits of yucca moths, including larval feeding in the floral ovary and the associated specialized cutting ovipositor, as well as colonization of woody monocots in xeric habitats, may have been established before the obligate mutualism with yuccas. Given these pre‐existing traits, novel traits in the mutualist moths are limited to the active pollination behaviours and the tentacular appendages that facilitate pollen collection and deposition. These results suggest that a highly specialized obligate mutualism was built on the foundation of pre‐existing interactions between early Prodoxidae and their host plants, and arose with minimal trait evolution. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 847–855.     

Once a land of big wild rivers: specialism is context‐dependent for riparian snails (Pulmonata: Valloniidae) in central Europe

Specialist species may be perceived as such because of their narrow ecological requirements, but this may be context‐dependent. The genus Vallonia (Gastropoda Pulmonata: Valloniidae) includes widespread generalist species and also two specialists endemic to Central Europe: Vallonia suevica, restricted to warm, wet meadows and riverbanks subject to seasonal flooding; and Vallonia declivis, living only in wet to humid meadows, riverbanks, and reedbeds. Both have experienced dramatic declines; as is the case with many land snails, their global conservation status has been underestimated: these species are Critically Endangered. Other congenerics are probably dispersed by birds. In contrast, the distributions of these meadow specialists appear to be the outcome of their strictly riparian habitat coupled with dispersal by fish. Thus, they have tracked drainage changes through the Pleistocene from their origin in the floodplain uplands of the Danube biodiversity hotspot in the Pliocene. Natural dispersal mechanisms have been disrupted, and riparian and river ecosystems have been destroyed throughout Europe. This has led big‐river specialist molluscs and their associated fishes to the brink of extinction. The notion of specialism thus depends on the ecological context; it is useful to stress their non‐invasive character, current restriction to scarce habitats, and evolution under quite different conditions. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.     

Global stingless bee phylogeny supports ancient divergence,vicariance, and long distance dispersal

Stingless bees (Meliponini) are one of only two highly eusocial bees, the other being the well studied honey bee (Apini). Unlike Apini, with only 11 species in the single genus Apis, stingless bees are a large and diverse taxon comprising some 60 genera, many of which are poorly known. This is the first attempt to infer a phylogeny of the group that includes the world fauna and extensive molecular data. Understanding the evolutionary relationships of these bees would provide a basis for behavioural studies within an evolutionary framework, illuminating the origins of complex social behaviour, such as the employment of dance and sound to communicate the location of food or shelter. In addition to a global phylogeny, we also provide estimates of divergence times and ancestral biogeograhic distributions of the major groups. Bayesian and maximum likelihood analyses strongly support a principal division of Meliponini into Old and New World groups, with the Afrotropical+Indo‐Malay/Australian clades comprising the sister group to the large Neotropical clade. The meliponine crown clade is inferred to be of late Gondwanan origin (approximately 80 Mya), undergoing radiations in the Afrotropical and Indo‐Malayan/Australasian regions, approximately 50–60 Mya. In the New World, major diversifications occurred approximately 30–40 Mya. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 206–232.     

Molecular systematics of flyingfishes (Teleostei: Exocoetidae): evolution in the epipelagic zone

The flyingfish family Exocoetidae is a diverse group of marine fishes that are widespread and abundant in tropical and subtropical seas. Flyingfishes are epipelagic specialists that are easily distinguished by their enlarged fins, which are used for gliding leaps over the surface of the water. Although phylogenetic hypotheses have been proposed for flyingfish genera based on morphology, no comprehensive molecular studies have been performed. In the present study, we describe a species‐level molecular phylogeny for the family Exocoetidae, based on data from the mitochondrial cytochrome b gene (1137 bp) and the nuclear RAG2 gene (882 bp). We find strong support for previous morphology‐based phylogenetic hypotheses, as well as the monophyly of most currently accepted flyingfish genera. However, the most diverse genus Cheilopogon is not monophyletic. Using our novel flyingfish topology, we examine previously proposed hypotheses for the origin and evolution of gliding. The results support the progressive transition from two‐wing to four‐wing gliding. We also use phylogenetic approaches to test the macroecological effects of two life history characters (e.g. egg buoyancy and habitat) on species range size in flyingfishes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 161–174.     

Biogeography of the grasses (Poaceae): a phylogenetic approach to reveal evolutionary history in geographical space and geological time

The grasses (Poaceae) are the fifth most diverse family of angiosperms, including 800 genera and more than 10 000 species. Few phylogenetic studies have tried to investigate palaeo‐biogeographical and palaeo‐ecological scenarios that may have led to present‐day distribution and diversity of grasses at the family level. We produced a dated phylogenetic tree based on combined plastid DNA sequences and a comprehensive sample of Poaceae. Furthermore, we produced an additional tree using a supermatrix of morphological and molecular data that included all 800 grass genera so that ancestral biogeography and ecological habitats could be inferred. We used a likelihood‐based method, which allows the estimation of ancestral polymorphism in both biogeographical and ecological analyses for large data sets. The origin of Poaceae was retrieved as African and shade adapted. The crown node of the BEP + PACCMAD clade was dated at 57 Mya, in the early Eocene. Grasses dispersed to all continents by approximately 60 million years after their Gondwanan origin in the late Cretaceous. PACCMAD taxa adapted to open habitats as early as the late Eocene, a date consistent with recent phytolith fossil data for North America. C₄ photosynthesis first originated in Africa, at least for Chloridoideae in the Eocene at c. 30 Mya. The BEP clade members adapted to open habitats later than PACCMAD members; this was inferred to occur in Eurasia in the Oligocene. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 543–557.     

Molecular phylogenetic relationships and the coevolution of placentotrophy and superfetation in Poecilia (Poeciliidae: Cyprinodontiformes)

Members of Poeciliidae are used as model organisms for experimental studies on natural and sexual selection, and comparative studies of life-history evolution. The latter have demonstrated multiple origins of both superfetation and placentotrophy within Poeciliidae. Most recently, placentotrophy has been described in five species of Poecilia (Pamphorichthys), but only one of these (P.hasemani) shows evidence of superfetation. Here, we use a molecular phylogeny based on concatenated nuclear and mitochondrial gene sequences to test hypotheses of correlated evolution between superfetation and placentotrophy in Poecilia. Taxon sampling included all species in the subgenera Micropoecilia and Pamphorichthys for which the presence or absence of placentotrophy and superfetation have been determined, as well as representatives of all other Poecilia subgenera (Acanthophacelus, Limia, Mollienesia, Poecilia, Pseudolimia). Phylogenetic analyses were performed with maximum parsimony, maximum likelihood, and Bayesian methods; ancestral states for life-history characters were reconstructed with parsimony and SIMMAP; correlation analyses were performed with SIMMAP; and divergence times were estimated using a relaxed molecular clock. All subgenera in Poecilia were recovered as monophyletic. The basal split in Poecilia is between P. (Acanthophacelus)+P. (Micropoecilia) and the other five subgenera. In the latter clade, P. (Poecilia) is the sister-group to the remaining four subgenera. Within P. (Pamphorichthys), all analyses with the combined data set recovered P. (Pamphorichthys) araguaiensis as the sister taxon to P. (Pamphorichthys) hollandi, and P. (Pamphorichthys) scalpridens as the sister taxon to P. (Pamphorichthys) minor. P. (Pamphorichthys) hasemani was either the sister taxon to P. (Pamphorichthys) hollandi+P. (Pamphorichthys) minor (maximum likelihood, Bayesian) or the sister taxon to all other Pamphorichthys species (maximum parsimony). Ancestral state reconstructions suggest that placentotrophy and superfetation evolved on the same branch in P. (Micropoecilia), whereas placentotrophy evolved before superfetation in P. (Pamphorichthys). SIMMAP analyses indicate a statistically significant association between placentotrophy and superfetation. Within P. (Micropoecilia) both placentotrophy and superfetation evolved in ≤4 million years. Within P. (Pamphorichthys), superfetation evolved in ≤9 million years on the P. (Pamphorichthys) hasemani branch, and placentotrophy evolved in ≤10 million years in the common ancestor of this subgenus.     

The anatomy of the basal ornithischian dinosaur Eocursor parvus from the lower Elliot Formation (Late Triassic) of South Africa

Ornithischia is a morphologically and taxonomically diverse clade of dinosaurs that originated during the Late Triassic and were the dominant large‐bodied herbivores in many Cretaceous ecosystems. The early evolution of ornithischian dinosaurs is poorly understood, as a result in part of a paucity of fossil specimens, particularly during the Triassic. The most complete Triassic ornithischian dinosaur yet discovered is Eocursor parvus from the lower Elliot Formation (Late Triassic: Norian–Rhaetian) of Free State, South Africa, represented by a partial skull and relatively complete postcranial skeleton. Here, the anatomy of Eocursor is described in detail for the first time, and detailed comparisons are provided to other basal ornithischian taxa. Eocursor is a small‐bodied taxon (approximately 1 m in length) that possesses a plesiomorphic dentition consisting of unworn leaf‐shaped crowns, a proportionally large manus with similarities to heterodontosaurids, a pelvis that contains an intriguing mix of plesiomorphic and derived character states, and elongate distal hindlimbs suggesting well‐developed cursorial ability. The ontogenetic status of the holotype material is uncertain. Eocursor may represent the sister taxon to Genasauria, the clade that includes most of ornithischian diversity, although this phylogenetic position is partially dependent upon the uncertain phylogenetic position of the enigmatic and controversial clade Heterodontosauridae. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 648–684.     

An osteology‐based appraisal of the phylogeny and evolution of kangaroos and wallabies (Macropodidae: Marsupialia)

Macropodids are the most diverse group of marsupial herbivores ever to have evolved. They have been the subject of more phylogenetic studies than any other marsupial family, yet relationships of several key clades remain uncertain. Two important problem areas have been the position of the merrnine (Lagostrophus fasciatus) and the phylogenetic proximity of tree‐kangaroos and rock‐wallabies. Our osteological analysis revealed strong support for a plesiomorphic clade ( Lagostrophinae subfam. nov. ) containing Lagostrophus and Troposodon, which is likely to have originated in the early Miocene. The extinct short‐faced kangaroos (Sthenurinae) emerged in the middle Miocene as the sister lineage to a clade containing all other living kangaroos and wallabies (Macropodinae). New Guinea forest wallabies ( Dorcopsini trib. nov. ) are the most plesiomorphic macropodines; the other two main lineages include tree‐kangaroos and rock‐wallabies (Dendrolagini), and ‘true’ kangaroos and wallabies (Macropodini). These phylogenetic outcomes are broadly consistent with the results of recent molecular studies, although conflicts remain over the relative positions of some macropodins (e.g. Setonix, Onychogalea, and Wallabia). Given the presence of derived dendrolagins and macropodins in early Pliocene localities, it is probable that most macropodine genera originated in the late Miocene. Key functional–adaptive trajectories within the craniodental and locomotory systems of the dominant macropodid lineages represent varying responses to the spread of drier, open habitats following the Miocene Climatic Optimum. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 954–987.     

The female reproductive unit of Ephedra (Gnetales): comparative morphology and evolutionary perspectives

Morphological variation in Ephedra (Gnetales) is limited and confusing from an evolutionary perspective, with parallelisms and intraspecific variation. However, recent analyses of molecular data provide a phylogenetic framework for investigations of morphological traits, albeit with few informative characters in the investigated gene regions. We document morphological, anatomical and histological variation patterns in the female reproductive unit and test the hypothesis that some Early Cretaceous fossils, which share synapomorphies with Ephedra, are members of the extant clade. Results indicate that some morphological features are evolutionarily informative although intraspecific variation is evident. Histology and anatomy of cone bracts and seed envelopes show clade‐specific variation patterns. There is little evidence for an inclusion of the Cretaceous fossils in the extant clade. Rather, a hypothesized general pattern of reduction of the vasculature in the ephedran seed envelope, probably from four vascular bundles in the fossils, to ancestrally three in the living clade, and later to two, is consistent with phylogenetic and temporal analyses, which indicate that extant diversity evolved after the Cretaceous–Tertiary boundary. Notwithstanding striking similarities between living and Cretaceous Ephedra, available data indicate that the Mesozoic diversity went almost entirely extinct in the late Cretaceous causing a bottleneck effect in Ephedra, still reflected today by an extraordinarily low level of genetic and structural diversity. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 163 , 387–430.     

Placental structures and their association with matrotrophy and superfetation in poeciliid fishes

Both matrotrophy, the maternal provisioning of nutrients to developing embryos after fertilization, and superfetation, the simultaneous presence of two or more groups of embryos at different stages of development, occur at varying degrees among species of the fish family Poeciliidae. However, it is still unclear if these two reproductive modes depend on the presence of relatively complex placentas. We describe the ultrastructure of the maternal follicular placenta of 11 poeciliid fishes using electron microscopy. In addition, we quantified six ultrastructure characteristics that reflect the degree of complexity (number of vesicles, area of vesicles, number of microvilli, microvilli length, thickness of the maternal follicle and follicular area). Using phylogenetic comparative methods, we evaluated the relationship between degree of matrotrophy and placental characteristics. We also analysed the potential effect of the presence of superfetation on placental complexity. We found a positive relationship between the degree of matrotrophy and follicular area, number of microvilli and number and area of vesicles. Similarly, follicular area and number of microvilli were larger in species with superfetation than in those without superfetation. We conclude that high degrees of matrotrophy and superfetation are associated with placental characteristics that increase the efficiency of nutrient transfer between mother and embryos.     

The petrosal and inner ear of the Late Jurassic cladotherian mammal Dryolestes leiriensis and implications for ear evolution in therian mammals

Dryolestes leiriensis is a Late Jurassic fossil mammal of the dryolestoid superfamily in the cladotherian clade that includes the extant marsupials and placentals. We used high resolution micro‐computed tomography (µCT) scanning and digital reconstruction of the virtual endocast of the inner ear to show that its cochlear canal is coiled through 270°, and has a cribriform plate with the spiral cochlear nerve foramina between the internal acoustic meatus and the cochlear bony labyrinth. The cochlear canal has the primary bony lamina for the basilar membrane with a partially formed (or partially preserved) canal for the cochlear spiral ganglion. These structures, in their fully developed condition, form the modiolus (the bony spiral structure) of the fully coiled cochlea in extant marsupial and placental mammals. The CT data show that the secondary bony lamina is present, although less developed than in another dryolestoid Henkelotherium and in the prototribosphenidan Vincelestes. The presence of the primary bony lamina with spiral ganglion canal suggests a dense and finely distributed cochlear nerve innervation of the hair cells for improved resolution of sound frequencies. The primary, and very probably also the secondary, bony laminae are correlated with a more rigid support for the basilar membrane and a narrower width of this membrane, both of which are key soft‐tissue characteristics for more sensitive hearing for higher frequency sound. All these cochlear features originated prior to the full coiling of the therian mammal cochlea beyond one full turn, suggesting that the adaptation to hearing a wider range of sound frequencies, especially higher frequencies with refined resolution, has an ancient evolutionary origin no later than the Late Jurassic in therian evolution. The petrosal of Dryolestes has added several features that are not preserved in the petrosal of Henkelotherium. The petrosal characters of dryolestoid mammals are essentially the same as those of Vincelestes, helping to corroborate the synapomorphies of the cladotherian clade in neural, vascular, and other petrosal characteristics. The petrosal characteristics of Dryolestes and Henkelotherium together represent the ancestral morphotype of the cladotherian clade (Dryolestoidea + Vincelestes + extant Theria) from which the extant therian mammals evolved their ear region characteristics. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 433–463.     

Global phylogeny of Hadrosauridae (Dinosauria: Ornithopoda) using parsimony and Bayesian methods

The late Cretaceous hadrosaurids were the most specialized and diverse clade of ornithopod dinosaurs. Parsimony and Bayesian methods were implemented to elucidate the phylogenetic relationships of all hadrosaurid species. Traditional and geometric morphometrics were applied to discover patterns of variation containing phylogenetic information. In total, 286 phylogenetically informative characters (196 cranial and 90 postcranial) were defined and documented: the most extensive character data set ever constructed for hadrosaurid dinosaurs. Of these, 136 characters were used for the first time in phylogenetic analysis of these ornithopods, and 93 were modified from those of other authors. Parsimony and the Bayesian analysis (using the Mk model without the gamma parameter) confirmed the split of hadrosaurids into Saurolophinae and Lambeosaurinae. Saurolophines included a major clade composed of the Prosaurolophus–Saurolophus and the Kritosaurus–Gryposaurus–Secernosaurus subclades. Edmontosaurus and Shantungosaurus were recovered outside the major clade of saurolophines. The Brachylophosaurus clade was recovered as the most basal clade of saurolophines in the parsimony analysis, whereas following the Bayesian analysis it was recovered as the sister clade to the Kritosaurus–Gryposaurus–Secernosaurus clade. These two analyses resulted in a Lambeosaurinae composed of a succession of Eurasian sister taxa to two major clades: the Parasaurolophus clade and the Hypacrosaurs altispinus–Corythosaurus clade. In contrast, the Bayesian analysis using the Mk model with the gamma parameter included, resulted in an unbalanced hadrosauroid tree, with a paraphyletic Saurolophinae, and with the Prosaurolophus clade, Edmontosaurus, and Shantungosaurus as successively closer sister taxa to Lambeosaurinae. Based on the strict reduced consensus tree derived from the parsimony analysis, Hadrosauridae was redefined as the clade stemming from the most recent common ancestor of Hadrosaurus foulkii and Parasaurolophus walkeri. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 435–502.