No description available.

Eighteen species of Bryozoa are described from the Upper Permian zechstein reef - they are assigned to ten genera in the Orders Fenestrata, Trepostomat and cyclostomata. Emended diagnoses are given at various levels and superspecific taxonomic categories within the Fenestrata are discussed. The examination of type specimens and of a large suite of new material has allowed the limits of intraspecific morphological variability to be defined and has resulted in the synonymising of several species. Three new taxa are described, for which holotypes have been designated :- Ryhopora delicata gen. nov., sp. nov. Acanthocladia magna sp. nov. and Penniretepora waltherinodata subsp. nov. The genera Penniretepora and Kalvariella Are recorded for the first time from the Zechstein reef in N.E. England. Aspects of bryozoan palaeobiology And functional morphology have been inferred at zooid and colony level. A type of ovicell, new in the Fenestrata, is described and is compared with those of the Cheilostomata; the taxonomic significance of this chAracter is assessecl. Patterns of zooid-generated feeding currents are inferred and some correlation of intraspecifically varying zoarial morphology with environment is suggested. The characteristic distribution of Bryozoa in relation to Zechstein reef sub-environments is described. An analysis of species abundance and diversity demonstrates a marked faunal impoverishment in reef-flat communities; new evidence for contemporaneous reef lithification is assessed.

A recently excavated bonebed in the Kerosene Creek Member of the Eocene Rundle Formation has yielded an abundance of crocodilian material. Fossils representing nearly all osteological elements, both cranial and postcranial, have been recovered and described. The described cranial remains are clearly indicative of a new species, Kambara taraina. This new species belongs to the earliest known genus of an endemic Australasian group, the Mekosuchinae, a group which radiated in Australasia during the mid to late Cenozoic and utilized various morphologies to exploit a range of ecologic niches. The early Cenozoic remains poorly known with respect to vertebrates and so this discovery of a new Eocene form is significant, showcasing a large sample of well-preserved material. Cranial material reveals functional divergence among the species of early mekosuchines, reflecting subtle partitioning of feeding strategies. The enlarged insertion area in the caudoventral part of the surangular suggests an increase in adductor mass resulting in a greater bite force. Bite marks in a large chelid plastron, attributable to K. taraina, support this inference. K. taraina is further distinguished from other Kambara species by the possession of a fully interlocking dentition and a decreased number of alveoli. Analysis of the postcranial anatomy suggests an overall generalist crocodilian body plan. However, aspects of the tarsal elements suggest that K. taraina may have been more adept at either terrestrial or shallow water ‘bottom-walking’ locomotion than other generalist aquatic crocodilians. Due to the completeness and size of the sample, description of the Kerosene Creek Member postcranial elements provides a standard reference text for mekosuchine postcranial anatomy, setting a precedent for consideration of postcranial anatomy in a field where little previous work has been done. Functional morphologic analyses of both the cranium and postcranium of K. taraina along with its palaeoenvironmental context suggest that this crocodile fed foraged along the shallow lake margins, operating as an opportunistic ambush predator. Macroscopic and radiographic analyses have revealed pathologic deformities in some elements demonstrating the presence of infection, neoplasm, and fractures that likely resulted from intraspecific fighting in K. taraina. A severely deformed left humerus has been shown to have suffered chronic osteomyelitis, a condition that, although well-documented in the fossil record, has not been previously reported for Australasian fossil crocodiles. A left fibula possesses evidence of neoplastic growth, tentatively attributed to a vascular tumour. The legion is expansile, exhibiting cortical thinning and formed coarse trabeculae in the medullary cavity. This is the first report of neoplasm in a fossil crocodilian from the southern hemisphere, and the first report of a bony vascular tumour in a crocodile. Thorough description of nearly all osteological elements has allowed a comprehensive scoring of K. taraina for cladistic analysis. Preliminary analyses supported the allocation of Mekosuchinae to within Crocodylidae. However, resolution was insufficient to determine taxon relationships within Mekosuchinae and requires a far more thorough analysis. This preliminary analysis demonstrates the inadequacy of current mekosuchine phylogenetics and the necessity for greater attention to be given to the lack of transparency in published cladistic analyses.

There are over 18,500 living species of acanthomorph (spiny-rayed fishes), and they represent half of all living fish species and a third of extant vertebrates. They inhabit countless ecological niches, they are incredibly diverse, and they have developed a number of specialised morphological innovations. The earliest acanthomorphs are known from the Cenomanian, but they were neither diverse not abundant during the Cretaceous period. Following the end-Cretaceous extinction event, the acanthomorphs radiated, and by the Eocene they were anatomically modern. However, our understanding of the relationships between most fossil and living acanthomorphs, and the macroevolutionary processes behind their rise to dominance in the Recent, are poorly known. In this thesis, I aimed to develop our understanding of the evolution of the acanthomorphs by combining palaeontological and neontological data. I undertook three separate projects to accomplish this. First, I studied the anatomy two fossil representatives (†Aipichthys pretiosus and †'Aipichthys' nuchalis) of a primitive acanthomorph lineage, the lampridomorphs. I then placed these taxa in a phylogenetic analysis to reveal the pattern of character evolution leading to the crown-group. Second, I aimed to understand the morpho- logical condition at the base of the acanthomorph tree by studying the relationships between two extinct groups (†Ctenothrissiformes and †Pattersonichthyiformes) that may have branched from the acanthomorph stem. Phylogenetic analyses utilising morphological and molecular data support a stem ctenosquamate placement for these taxa. Third, using a timescaled supertree, I studied the evolution of one of the major acanthomorph innovations, the protrusile upper jaw. The combination of palaeontological and neontological data provided deep insight into the evolution of the acanthomorphs, and allowed for the identification of patterns and processes that could not be identified from studying extant taxa in isolation.

The fossil record yields information on macroevolutionary patterns that remains inaccessible from the study of extant organisms alone, presenting a natural laboratory for us to test hypotheses about the long-term drivers and processes of evolution. Fossil data are therefore increasingly incorporated into evolutionary analyses, both on their own and in combination with neontological data. Phylogeny (an explicit hypothesis of the evolutionary relationships between taxa) can be used as a framework to enable direct comparison of results of comparative methods across many different timescales and taxa, and is now commonly used in investigations of fossil data. This represents an important step towards a unified approach, however, it is not yet fully understood what the effect of using fossil data is on the results of downstream phylogenetic comparative methods, which were originally developed with only living taxa in mind. In this thesis I explore the validity of phylogenetic interpretations of fossil record data. I begin with only taxonomic classification and show that this can in some cases substitute for a cladistically inferred phylogeny in phylogenetic comparative methods, without biasing results. Moving on to scenarios where a timescaled phylogeny is available I investigate the relationship between phylogeny and extinction in the geological past, show that phylogenetic clustering of extinction was common in tetrapods, and present a summary of the ways in which fossil data biases this measurement. Finally, with timescaled phylogenies and a detailed continuous trait dataset available, I interrogate the fossil record of Sauropterygia to uncover the processes of evolutionary change in this highly labile clade. By comparing the results of a suite of phylogenetic comparative methods I demonstrate that neck length evolved through changing vertebral counts rather than somite growth; that the clade experienced a release in evolutionary constraint at the Triassic-Jurassic boundary; and that evidence does not support evolution towards a stationary adaptive peak as a suitable model for phenotypic change in the clade.

The evolutionary origins of animal phyla are intimately linked with the Cambrian explosion, a period of radical ecological and evolutionary innovation that begins approximately 540 Mya and continues for some 20 million years, during which most major animal groups appear. Lophotrochozoa, a major group of protostome animals that includes molluscs, annelids and brachiopods, represent a significant component of the oldest known fossil records of biomineralised animals, as disclosed by the enigmatic ‘small shelly fossil’ faunas of the early Cambrian. Determining the affinities of these scleritome taxa is highly informative for examining Cambrian evolutionary patterns, since many are supposed stem-group Lophotrochozoa. The main focus of this thesis pertained to the stem-group of the Brachiopoda, a highly diverse and important clade of suspension feeding animals in the Palaeozoic era, which are still extant but with only with a fraction of past diversity. Major findings include adding support for tommotiid affinity as stem-group lophophorates. Determining morphological character homologies vital to reconstructing the brachiopod stem-group was achieved by comparing Cambrian Lagerstätten with the widespread biomineralised record of Cambrian stem-brachiopods and small shelly fossils. Polarising character changes associated with the putative transition from scleritome organisms to crown-group brachiopods was furthered by the description of an enigmatic agglutinated tubular lophophorate Yuganotheca elegans from the Chengjiang Lagerstätte, China, which possesses an unusual combination of phoronid, brachiopod and tommotiid characters. These efforts were furthered by the use of X-ray tomographic techniques that revealed novel anatomical features, including exceptionally preserved setae in the tommotiid Micrina. The evidence for a common origin of columnar brachiopod shell structures in the tommotiids is suggested and critically examined. Enigmatic and problematic early and middle Cambrian lophotrochozoans are newly described or re-described in light of new evidence, namely: the stem-brachiopod Mickwitzia occidens Walcott from the Indian Springs Lagerstätte, Nevada; a putative stem-group entoproct Cotyledion tylodes Luo and Hu from Chengjiang, China; a new enigmatic family of rhynchonelliform brachiopods exemplified by the newly described Tomteluva perturbata from the Stephen Formation, Canada; and the tommotiid Micrina etheridgei (Tate) from the Flinders Ranges, South Australia. Cladistic analyses of fossil morphological data supports a monophyletic Brachiopoda.

Predation is a key factor in evolutionary dynamics. It disrupts the potential of fossilisation in prey items and is poorly recorded in the fossil record; failed predation in conical marine gastropods is recorded in scars. Quantifying the scar distribution and collection and taphonomic biases present in the fossil record of the gastropod Neptunea contraria, of the Red Crag Formation, Gelasian, Pleistocene, UK is necessary to approach this dynamic. Neptunea contraria is highly abundant in the Red Crag Formation which is easily accessed. The size and scarring on a large number (450+) of individuals was collected, recorded and measured from pre-existing and new material. The size distribution of Neptunea contraria is non-normal and is enriched in larger individuals, the scar distribution – expected to be Poisson – is not so. Taphonomic and Collection bias had a large influence over the size and scar distributions of Neptunea contraria. Material from the same localities shows very different size distributions. The lack of Poisson distribution suggests different rates of unsuccessful predation over life history of Neptunea contraria, assuming the data is valid. / Predation anses vara en viktig faktor inom ekologi och evolution men till vilken grad har effekterna av predation förändrats genom geologisk tid? Det centrala fokuset i denna studie ligger i att frambringa en förståelse av både population- och predationsfördelningen bland marina snäckor av arten Neptunea contraria av Pleistocen ålder från Red Crag-formationen, East Anglia, Storbritannien.Framgångsrik predation resulterar i förstörelsen av snigeln och dess livshistoria registreras i deras skal. Misslyckad predation bevaras i skalen bland individer som överlevt genom ärrbildningar. Det finns ett okänt samband mellan misslyckad och framgångsrik predation.Samlingen av fossilt material från Sedgwick-museet i Cambridge, Storbritannien, ligger till grund för denna studie. Detta material är ofullständigt (d.v.s. material saknas) och noterbart fragmenterat vilket orsakats av nedbrytande processer, därav tafonomi. Denna studie belyser flertalet källor som ger upphov till ett ofullständigt fossilt register, därav processer direkt relaterade till fossilisering och antropogen insamling. Genom att jämföra flertalet uppsättningar av fossilt material som insamlats av olika personer så kan graden av bias i förhållande till insamlingen undersökas. Resultatet av denna studie visar att samlingen av fossila sniglar som för närvarande finns på Sedgwick-museet är ofullständig. Detta är ett tillstånd som uppkommit delvis på grund av inkomplett insamling.Fördelningen av ärr orsakade av misslyckad predation förväntades följa en poissonfördelning. Denna förutsägelse motsägs sannerligen av nuvarande data. Troligtvis har detta förorsakats av en låg ”miss-lyckad predationsfrekvens”, vilket antyder att graden av predation inte är konstant.Sniglar av en större storlek saknar ärr på den övre delen av sina skal, vilket tyder på att frekvensen av misslyckad predation var låg i de juvenila stadierna. (

The origin of many lophotrochozoan groups can be traced to “small shelly fossil” (SSF) faunas of the Early Cambrian. Antarctica is a key region of study, due to the continent’s known close geographical proximity to well-studied Australian and Indian basins in in the Cambrian. Few studies have focused on this region however, due to a paucity of data. Re-examination of camenellan sclerites from the Early Cambrian Shackleton Limestone of the Churchill Mountains of Antarctica has revealed a previously unidentified species of Dailyatia in the formation, co-occurring alongside previously described Dailyatia odyssei Evans and Rowell, 1990, as in the Arrowie Basin of Australia. Re-examination of material previously described as Kennardia sp. A and Kennardia sp. B has indicated that these taxa can likely be synonymized as a second species of Dailyatia. Dailyatia sclerites were also found in the temporally equivalent “Schneider Hills Limestone” formation, which cropsout in the Argentina Range of Antarctica. These specimens appear to belongto a third species of Dailyatia, suggesting that the spatial distribution of tommotiids in the Early Cambrian was more complex than previously recognized, and that the group may be useful in future biostratigraphic studies. A study ofthe Middle Cambrian (Drumian Stage) Nelson Limestone Formation of the Neptune Range, Antarctica has revealed a moderately diverse brachiopod and trilobite fauna. The brachiopods have strong faunal links to taxa from South Australia and India, as well as other parts of the Antarctic province, fitting independent strong evidence for a united East Gondwanan region in the Middle Cambrian. An unidentified camenellan tommotiid sclerite is also described from the Nelson Limestone. This extends the worldwide temporal range of the tommotiid clade into the Drumian Stage, and suggests that more basal members of the brachiopod stem-group survived to form part of a more diverse Middle Cambrian fauna.

No description available.

La transition Crétacé inférieur-Crétacé supérieur (environ 100 millions d'années) marque une période cruciale pour l'évolution de certaines plantes à graines. Elle correspond à la rapide radiation des plantes à fleurs et à la réorganisation écologique des Angiospermes et des conifères. Cependant, notre connaissance des plantes à graines durant le Crétacé moyen et en Laurasie reste encore très partielle. Pendant la dernière décennie, la microtomographie synchrotron s'est avérée une technique d'imagerie très performante pour l'étude les structures internes de divers fossiles. Jusqu'à maintenant, les applications de cette technique n'ont été que très limitées en paléobotanique. C'est dans ce contexte que cette thèse s'est intéressée : (1) au développement de nouvelles approches d'imagerie par tomographie, utiles en paléobotanique, et sur différents types de préservation ; (2) à l'utilisation de ces nouvelles approches pour compléter notre connaissance de la morpho-anatomie, la systématique, la diversité, et l'écologie des plantes à graines laurasiatiques du Crétacé moyen. Ainsi, un peu plus d'une centaine de spécimens (e.g. inflorescences, fleurs, fruits, et grains de pollen d'Angiospermes ; cônes and axes feuillés de conifères) provenant de gisements paléontologiques français ont été étudiés par tomographie synchrotron. Pour la première fois, de nombreuses fleurs très diversifiées sont décrites dans les dépôts cénomaniens de Charente-Maritime et du Gard (Ouest et Sud-Est de la France). Dans certains cas, toutes les unités florales du périanthe, de l'androcée, et du gynécée sont préservées. Un nouveau protocole combinant microtomographie par contraste de phase de propagation et nano-holotomographie a été développé pour étudier des petits spécimens isolés tels que des fleurs préservées sous forme de fusain ou de lignite (taille de voxel proche de 50 nm). Les données tomographiques permettent de les décrire de la morphologie générale à la paroi des grains de pollen, in situ, dans les étamines. Ces fleurs sont majoritairement attribuées à des Lauraceae et des Platanaceae. De plus, des nodules siliceux, opaques, denses, et contenant des inclusions végétales sont ici signalés dans les dépôts cénomaniens de Charente-Maritime. Ils contiennent d'abondants restes de conifères. Ils sont préservés sous forme de perminéralisation siliceuse et en trois dimensions. Ce travail propose un protocole tomographique multi-échelles, haute résolution et haute énergie, utile à l'étude d'inclusions végétales contenues à l'intérieur de nodules rocheux de grande dimension. Le conifère Glenrosa est décrit pour la première fois, de la morphologie générale des structures végétatives et reproductives à l'histologie. Ce travail soutient que pendant le Cénomanien, les environnements les plus ouverts sur la mer étaient dominés par les conifères alors que les milieux littoraux plus internes et protégés montraient quant à eux des flores à dominante angiospermienne. / The Lower Cretaceous-Upper Cretaceous transition (about 100 million years ago) stands as a crucial period for the evolution of some seed plants. It consists of the brutal radiation of flowering plants and an ecological reorganisation of Angiosperms and conifers. However, our knowledge of mid-Cretaceous Laurasian seed plants remains partial. During the last decade, synchrotron microtomography has successfully been employed for non-destructively imaging inner structures of various types of fossil remains. To date, the applications of this technique in palaeobotany are still limited. This thesis focuses on: (1) developing new tomographic imaging approaches at the European Synchrotron Radiation Facility (ESRF, Grenoble, France), relevant to palaeobotany, and especially for investigating various kinds of plant preservations; (2) applying these approaches to improve our knowledge about the morpho-anatomy, the systematics, the diversity, and the ecology of Laurasian seed plants during the mid-Cretaceous. Hundreds of unique or rare mid-Cretaceous fossil plant specimens (e.g. inflorescences, flowers, fruits, and pollen grains of Angiosperms; cones and leafy axes of conifers) from French Cretaceous deposits were imaged and investigated using several new synchrotron tomographic protocols. For the first time, abundant and diverse fossil flowers are described from the Cenomanian deposits of Charente-Maritime and Gard (western and southeastern France, respectively). In some cases, all floral units of the perianth, the androecium, and the gynoecium are preserved. A new tomographic approach combining propagation phase contrast X-ray microtomography and nano-holotomography was developed to image those small and isolated plant specimens such as charcoalified/lignitized fossil flowers (up to 50 nm of voxel size). This allows the description of fossil flowers, from their gross morphology to the micromorphology of the exine of in situ pollen grains inside stamens. They are mainly and unambiguously ascribed to Lauraceae and Platanaceae. In addition, large, opaque and dense silica-rich flint nodules containing plant inclusions are reported from the Cenomanian deposits of Charente-Maritime. They contain abundant hidden conifer. These Cenomanian conifers are exceptionally well-preserved in three dimensions and consist of siliceous permineralisation. We propose a multiscale, high resolution and high energy tomographic protocol useful for the study of plant inclusions contained inside large rocky nodules. We study the partially unexplored extinct conifer Glenrosa, from the gross morphology to the histology of its vegetative and reproductive structures. This work supports that during the Cenomanian and in coastal areas, on the one hand, palaeoenvironments which were highly influenced by marine inputs were probably dominated by conifers. On the other hand, innermost and protected palaeoenvironments showed Angiosperm-dominated floras.