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Progressive Palaeontology 2016 - Oxford: Abstracts and Programme

Year: 2016
Location: Oxford
Hosted By:
Organisied By: Gemma Benevento, Mimi Beckett, Harrie Drage, David Ford, Serjoscha Evers, Dan Delbarre, Andrzej Wolniewicz, César Campuzano, Stephen Pates, Maria Koschowitz, Brooke Johnson, and Fiona Jones
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Abstracts and Programme

Talk abstracts are included here. LT indicates a lightning talk. * indicates the presenting author, whose email address can be found in the delegate list on Page 54 of the: PDF iconAbstract Booklet - 2016.

Session 1

An exceptionally well-preserved skull of a Stanocephalosaurus amenasensis (Capitosauria: Temnospondyli) leads to a new hypothesis on the temnospondyl ear functioning

Thomas Arbez1* and J-Sébastien Steyer1
1Centre de Recherches en Paléobiodiversité et Paléoenvironnements (CR2P), Muséum national d’Histoire naturelle, France

Temnospondyls are a clade of extinct non-amniotic tetrapods, similar to giant salamanders. Like lissamphibians, most of temnospondyls have an amphibious lifestyle, occupying ecosystems such as rivers, lakes and swamps.

The hearing abilities of temnospondyls are an ongoing debate. The temnospondyl stapes is often considered as a middle ear bone, close to the anuran condition and linked with an acoustic function adapted to airborne sound perception. However this bone is sutured with the parasphenoid in several taxa. This peculiar condition questions the traditional acoustic function attributed to the stapes, which could also play a role in the support of a spiracular canal, a conduct allowing to supply in water a hypothetic internal gill cavity. But this hypothesis also has some morphological constraints.

The specimen ZAR05 is an exceptionally well-preserved skull of Stanocephalosaurus.A cranial exploration has been investigated thanks to a micro-CT scan by the AST-RX facility of the Muséum national d’Histoire naturelle. The resulting 3D reconstruction reveals a highly detailed anatomy of columellar cavity and stapes leading to a new hypothesis of the stapes function, as part of a hearing system adapted to underwater sounds perception.

This hypothesis is promising as it explains some peculiar morphological features shared by several temnospondyls and provides an evolutionary scenario which is also compared with that of extant anurans.

Tracking changes in the ecological diversity of Crocodylomorpha through deep geological time

Pedro L. Godoy1*, Richard J. Butler1, Ivan J. Sansom1, James Bendle1 and Roger B. J. Benson2
1University of Birmingham, Birmingham, UK. 2University of Oxford, Oxford, UK.

Crocodylomorpha includes the living crocodylians and all their extinct relatives with similar body plans. Unlike the small number of extant species today (23 species), the fossil diversity of Crocodylomorpha is remarkable. Whereas living forms occupy a limited range of ecological niches, fossil crocodylomorphs are represented by fully marine forms, giant terrestrial preda­tors, bizarre filter-feeders, and even plant-eaters. The main goal of this project is to combine morphological information with environmental data in order to quantitatively investigate how crocodylomorph ecological diversity evolved through time, and which factors drove diversity changes. Among the different methods to assess this disparity is the study of body size and mass evolution, since these features are strongly related to many aspects of animal physiology and ecology. A comprehensive taxonomic sampling across all Crocodylomorpha is important since most evolutionary studies quantifying patterns of morphological radiation are either tem­porally limited, restricted to the origins of modern groups or based on discrete characters. To do so, using the R package GEIGER we fitted four maximum-likelihood models of trait evolution to body size data mapped onto a time calibrated phylogeny, based on a modified version of a recent crocodylomorph supertree. Comparisons of AICc weights obtained for each model demonstrates that the Ornstein-Uhlenbeck (OU) model provided the best fit. The OU is a process which has a constant pull toward an optimum value (in this case 3.23 m). This indicates a constrained pattern of body size evolution around a trait ‘optimum’, suggesting constraints within long-term patterns of crocodylomorph body size evolution.

From fossil record to amphibian conservation

Melanie Tietje1*and Mark-Oliver Rödel1
1Museum für Naturkunde -Leibniz Institute for Evolution and Biodiversity Science, Berlin

An increasing number of publications call for a synergy of palaeobiology and conservation biology, i.e. using the fossil record to increase knowledge on extinction risk. Amphibians are particularly threatened, however there is still uncertainty why some species are threatened and others not. In my PhD research I am investigating the usefulness of the fossil record in amphibian conservation, a fossil record that is often neglected despite amphibians being of great interest in conservational tasks today. We use trait data from fossil and extant amphibians to search links between certain traits and extinction risk of amphibian species. The approach is based on fossils of extinct species, correlating traits and stratigraphic range. Our basic model includes traits that are typically part of IUCN Red List assessments to estimate the conservation status of species, like geographic range. The fossil-based models are then applied on extant species to see how fossil data matches with today’s extinction risk assessments. The amphibian fossil record proves to be of sufficient quality to allow an assessment of extinction risk among amphibians. First results agree with studies usually conducted on fossil invertebrates, underlining the importance of range size and abundance for a species’ survival. Apart from range size and abundance, the type of habitat seems to influence extinction risk in extant amphibians. In this talk, I want to focus on the influence of habitat utilisation on the longevity of species, using the fossil record as a deep time approach.

Evolutionary Biomechanics of the Dinosaur Jaw Mechanism

James Ormiston1*
1University of Bristol, Bristol

Mechanical advantage (MA) is a useful metric of jaw performance which is easily measured, well-suited to data processing and represents a potential target for selection. This study presents a clade-wide comparison of MA within Dinosauria to identify major trends in the evolution of the jaw mechanism, with a focus on the relevance of phylogeny and dietary preference to MA variation between adductor muscle groups. MA was calculated at three points along the top tooth row for the MAME, MAMP and MPT adductors in 144 taxa. MA values were then placed onto a phylogeny of Dinosauria and subjected to statistical analyses to identify sources of variation between groups and dietary preferences. Phylogenetic signal for MA was also quantified using Pagel’s λ. MA is generally different between ornithischians and saurischians, and between carnivores and herbivores, but herbivores were found to be much more mechanically disparate in PCA plots. This appears to be due to herbivorous saurischians such as diplodocoideans and therizinosaurians diverging from ornithischians in performance space, with the MAME group being responsible for most MA variance. Phylogenetic signal is found to be strong in theropods but less so in ornithopods, with small sample sizes confounding reliable comparisons with other groups. Mechanical divergence of herbivorous saurischians from ornithischians could potentially be interpreted as evidence of anatomical constraints (such as absence of the coronoid process), shifting selection pressure away from saurischian jaw musculature and towards other herbivorous adaptations. Future work would ideally include more marginocephalian and thyreophoran taxa to better optimise statistical comparisons.


LTUnderstanding Elephant Evolution: Still A Formidable Task

Zhang Hanwen1*
1 School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 ITQ, UK

Since its early days, the science of elephant evolution has undergone considerable confusion, as the majority of evolutionary diversity is exclusively confined to the fossil record. A seminal monograph by Vincent Maglio (1973) formed the blueprint of the current consensus, using tra­ditional morphoclines derived from stratigraphic context of the fossils and a priori assumptions about trends of change. On the other hand, cladistic studies have largely focused on broader evolutionary patterns, with emphasis on dental characters obscuring exact species-level interre­lationships, due to prevalence of homoplasy. In particular, convergent evolution of hypsodonty (heightened molar tooth crown) and increase in number of enamel ridges. Recent advancements in understanding early evolution of Eurasian mammoths from China have the potential to pro­vide crucial breakthrough, but the generally confused state of fossil elephant taxonomy from Africa and Asia remains a critical caveat. Therefore, key systematic and palaeobiological ques­tions of early elephant evolution in Africa and their subsequent dispersal to Eurasia must be addressed holistically. A thorough reappraisal of elephant evolution requires a strongly phyloge­netic approach based on an updated cladistic analysis. 164 characters compiled from literature are first examined on modern elephant specimens for logistic repeatability of scoring and in­traspecific variations. Key fossil collections in the museums of Europe, Africa, Asia and North America will be visited to provide a renewed global picture of elephant phylogeny. Preliminary observations of extant and fossil elephants will be presented here.

LTWhat were they thinking? Exploring the potential of neurocranial anatomical studies throughout Ceratopsia.

Claire Bullar1*, Mike Benton1, Qi Zhao2 and Michael Ryan3.
1 School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK 2 Institute of Vertebrate Palaeontology and Palaeoanthropology, Beijing, China 3Cleveland Museum Of Natural History, 1 Wade Oval Dr, Cleveland, OH 44106, United States

The neurocranial anatomy of extinct organisms has intrigued the palaeontological community for years. Since the 19th Century palaeontologists have been examining whether endocasts can provide a good estimate of brain size and morphology and, if so, what this can tell us about the sensory capacity of these long dead organisms. Ceratopsians were one of the most diverse dinosaur clades of the Late Cretaceous and have an outstanding fossil record of basal forms in Asia. Ceratopsian palaeontology currently lacks comprehensive neuroanatomical studies which can illuminate how neurology might predict behaviours that have been suggested by previous research. In this project, we have imaged ceratopsian skulls using high resolution micro-CT scanning to capture small scale internal structures such as cranial nerves and semi-circular canals. These scan stacks are then digitally segmented into brain endocasts and braincase elements using 3D analysis software (Avizo). The first project, described here, investigates changes in neurocranial architecture through ontogeny of one species (Psittacosaurus). This has been a rare chance to acquire detailed 3D information on numerous ontogenetic stages of a single dinosaur species, from hatchling through juvenile to adult, and to link the various allometric and morphometric deviations from isometry to wider function. In further work, the study of this basal form will provide an excellent comparison with more derived neoceratopsians from North America.

LTThe completeness of the tetrapod fossil record

Daniel D. Cashmore1*, Richard J. Butler1 and Roger A. Close1
1School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham

Changes in the quality of the fossil record through time and space can bias our interpretations of tetrapod diversity, ecology, biogeographical patterns and macroevolutionary processes. This project, like recent studies, aims to assess this potential bias by quantifying the completeness of fossil specimens using two main metrics -the Character Completeness Metric (CCM) and the Skeletal Completeness Metric (SCM). CCM quantifies the phylogenetic information contained within a specimen (i.e. the proportion of phylogenetic characters it can be scored for), and SCM quantifies the proportion of a complete skeleton that a specimen preserves. SCM data has been initially compiled for non-avian theropod dinosaurs, and compared to previously generated CCM scores for the same taxa. Each bone of the theropod skeleton was assigned a relative percentage on the basis of 2D modelling of skeletal reconstructions. This allowed the preserved skeletal elements of each specimen to be given a percentage score dependent on the number and completeness of those elements. Data collection for theropods is not yet complete but the average skeletal completeness is around 20-30%. In the future, this project aims to address a number of key questions. Is the marine tetrapod fossil record more complete than the terres­trial? Do species with similar body sizes / ecological preferences share similar levels of fossil completeness? Do changes in fossil completeness through time correlate with major changes in global tetrapod diversity, evolutionary radiations and mass extinctions? Do changes in fossil completeness correlate with estimates of differing fossil record sampling and/or geological bias?

LTHomology issues with the trigeminal nerve foramina in turtles and saurians

Serjoscha W. Evers1* and Roger B. J. Benson1
1University of Oxford, Oxford

The trigeminal (cranial V) nerve of reptiles exits the endocranial cavity through an open­ing on the lateral wall of the braincase -the trigeminal foramen. This foramen is on the laterosphenoid-prootic contact in most archosaurs and lepidosaurs, and is modified to a broad fossa with separate foramina for the trigeminal rami in taxa with an extracranial trigeminal gan­glion. Extant turtles, and most fossil forms, lack an ossified laterosphenoid. Instead, the parietal extends far ventrally, contacting the bony palate and forming the lateral wall of the braincase. The trigeminal foramen of turtles is located at the parietal-pterygoid contact. Topologically, this is at odds with the situation in other reptiles. These differences raise questions about the morphological transformations involved in the origins of the turtle trigeminal foramen, and warrant an assessment of the homology, which might inform the phylogenetic position of turtles among Sauria. New observations on fossil turtles, including the stem-turtle Proganochelys reveal a possible hypothesis for the evolution of the trigeminal nerve foramina in turtles. The trigeminal foramen in turtles transmits the maxillomandibular ramus of the CN V, but not the ophthalmic ramus. In Proganochelys, a medial foramen involving the laterosphenoid, and a laterally placed, dorsally open aperture indicates that an internal trigeminal foramen as present in most other reptiles was secondarily reduced in turtles, and that the trigeminal foramen of turtles is possibly homologous to the maxillomandibular foramen of reptiles with extracranial trigeminal ganglia, such as crocodiles. These observations form the basis for a revision of phylogenetic characters concerning the trigeminal foramen in analyses including turtles and other saurians.

Session 2

Turbulent behaviour: Preservation and survivorship potential of soft-bodied organisms in sediment-density flows

O. Bath Enright1*, N. Minter1, E. J. Sumner2, G. Mángano3 and L. Buatois3
1 School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth. 2 Ocean and Earth Sciences, University of Southampton, National Oceanography Centre, Waterfront Campus, European Way, Southampton. 3 Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, Canada.

A fundamental question in palaeoecology is whether different types of organisms can remain intact during transport and, if alive at the time, could they actually survive such transport? Here I present the results of two annular flume tank experiments designed to determine the effects of turbulent flows on the durability, preservation potential, and survivorship of the polychaete Alitta virens.

The first set of experiments tested the effects of transport duration, grain angularity, and sediment concentration on the damage state caused to freshly euthanized subject. Results show that flow duration and grain angularity are both important factors that had statistically significant effects on the state of damage. However, concentration by itself had no significant effect.

The second set of experiments was conducted to explore the “doomed pioneer” hypothe­sis. This states that organisms living in an oxygenated environment could be caught up in a turbulent flow and transported to an oxygen deficient environment where they are then able to colonize and create trace fossils in anoxic sediment, at least briefly, before eventually expir­ing. This has significant impacts for interpreting trace-fossils in deep-marine settings. Results demonstrated that all polychaetes were capable of surviving turbulent transport over a period of 180 minutes and were also capable of burrowing; however, the time taken to burrow was statistically significantly greater, and the burrowing style differed, compared to those that had not undergone transport.

Care must therefore be taken in interpreting both body-and trace-fossil assemblages pre­served in sediment-density flows.

Cambrian microfossils to Cambrian climates: can ‘small shelly fossils’ be used to quantify ancient ocean conditions?

Thomas Hearing1*, Thomas Harvey1, Mark Williams1, Sarah Gabbott1, Philip Wilby2 and Melanie Leng3
1Department of Geology, University of Leicester, Leicester, 2 British Geological Survey, Keyworth 3 NERC Isotope Geosciences Facility, British Geological Survey, Keyworth

The “Cambrian explosion” of animal body and trace fossils across the Neoproterozoic-Phanerozoic transition puzzled Charles Darwin and remains an area of vigorous research. Konservat-Lagerstätten have helped illuminate the biological changes of this ecological revolution, but its environments remain quantitatively poorly constrained. Such quantitative palaeoenvironmental constraints are commonly derived from geochemical proxy data, such as the stable oxygen isotope ratio (δ18O), found in fossil biominerals. Commonly collected from calcareous brachiopod shells and phosphatic conodont elements, δ18O data are used to estimate both water temperatures and the δ18O composition of seawater (often translated into global land ice volume). Unfortunately, euconodonts are not known below uppermost Cambrian strata, and Cambrian carbonate biomin­erals have often undergone severe diagenetic alteration. Cambrian ‘small shelly fossils’ (SSFs) ­the remains of some of the earliest biomineralizing animals -may be an alternative source of this proxy data, but first they must be shown to be robust to diagenetic alteration. We examined the external morphology and internal microstructures of SSFs from the Comley Limestone (Cam­brian Stage 4/5), Shropshire, UK, using optical and scanning electron microscopy. Additionally, we used energy-dispersive X-ray spectroscopy to map the chemistry of selected SSFs. Biological microstructures were dominant, though localised diagenetic microstructures were also observed. Original chemistry is also well preserved in most specimens, with alteration either localised to fractures or discernible by optical microscopy where whole fossils are affected. Carefully se­lected SSFs could therefore be investigated with a view to placing quantitative constraints on the marine environment of the ‘Cambrian explosion’.

Experimental degradation of insects

Nidia Álvarez Armada1*, Maria McNamara1, Stuart Kearns2 and Fiona Gill3
1 School of Biology Earth and Environmental Sciences. University College Cork. 2 School of Earth Sciences. University of Bristol. 3 School of Earth and Environment. University of Leeds.

Coloration plays important ecological and physiological roles in modern insects. Evidence of colour in fossil insects can therefore inform on the original colours of their cuticle and their functions in fossils. Studies on fossil insect colour to date have focussed on structural colours; the fossil record of insect pigments has not been investigated. An understanding of the taphonomy of colour is essential to accurate interpretations of evidence of colour. Here we use an experi­mental approach to understand the taphonomy of pigmentary colours in insects. Untreated and experimentally degraded specimens of extant insects were analysed using light microscopy, mi­crospectrophotometry, scanning electron microscopy (SEM), electron microprobe microanalysis (EPMA) and synchrotron-X-ray fluorescence (XRF), in order to quantify the colour of cuticles during decay and to characterise the trace element signatures. The optical properties of dark coloured regions of the cuticle show minimal alteration during decay; light coloured regions, how­ever, show substantial alteration in both hue and intensity. SEM, EPMA and synchrotron-XRF elemental maps show that sodium, magnesium and calcium are concentrated in dark regions of the cuticle in untreated specimens of all taxa; this elemental zonation is enhanced after decay. Zonation patterns for other elements are more complex, whereby zonation is inverted during decay, or is apparent in only some taxa. These preliminary analyses indicate that spatial dis­tributions of certain trace elements are a widespread marker for melanin in insect cuticles, even after decay, and thus may be a good proxy for melanin-based colour in fossil insects.

Ediacaran Developmental Biology

Frances S. Dunn1*, Alexander G. Liu1 and Philip C. J. Donoghue1
1 The University of Bristol.

The Ediacaran Period, 635-541 million years ago, possesses some of the earliest fossils of com­plex macroscopic organisms. Some of these fossils have been rationalised as members of early animal groups and, thus, may potentially inform the evolution of metazoan axis specification, symmetry making and breaking, and the appearance of a segmented body plan. However, since many Ediacaran organisms cannot be easily reconciled morphologically with modern metazoan clades, multiple alternative interpretations have been proposed, including as algae, fungi, and Xenophyophores. In an attempt to reconcile among competing phylogenetic interpretations of the Ediacaran biota, we have adopted a developmental approach. The few existing develop­mental analyses of Ediacaran macro-organisms invariably conflate developmental pattern with developmental process. We compare growth patterns across populations of three iconic Edi­acaran groups -the rangeomorphs, erniettomorphs and dickinsoniomorphs -revealing hitherto unrecognised ontogenetic characters, such as a basal pre-terminal pole of growth in Charnia masoni. By then considering morphogenetic process in these taxa, we tentatively reassess the phylogenetic position of the Ediacaran macro-organisms. Our findings ally certain members the Ediacaran macro-organisms to the Metazoa, revealing the potential of developmental techniques for study of enigmatic fossil groups.

Seeing into the Carboniferous: eyes of Tullimonstrum gregarium (Mazon Creek, Carboniferous) reveal a vertebrate affinity

Thomas Clements1*, Andrei Dolocan2, Peter Martin3,4, Mark A. Purnell1, Jakob Vinther3,5, and Sarah E. Gabbott1
1Department of Geology, University of Leicester, Leicester, LE1 7RH, UK; 2Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA 3School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK 4Interface Analysis Centre, HH Wills Physics Laboratory, University of Bristol, Bristol, BS8 1TQ, UK 5School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK

Tullimonstrum gregarium is an iconic soft-bodied fossil from the Carboniferous Mazon Creek Lagerstätte (Illinois). Despite a large number of specimens and distinct anatomy, various anal­yses over the last five decades have failed to determine the phylogenetic affinities of the “Tully Monster”, and although it has been allied to such disparate phyla as the Mollusca, Annelida or Chordata, it remains enigmatic. The phylogenetic affinities of Tullimonstrum have defied confi­dent systematic placement because none of its preserved anatomy provides unequivocal evidence of homology, without which comparative analysis fails. Here we show that the eyes of Tullimon­strum possess ultrastructural details indicating homology with vertebrate eyes. Anatomical anal­ysis using scanning electron microscopy reveals that the eyes of Tullimonstrum preserve a retina defined by a thick sheet comprising distinct layers of spheroidal and cylindrical melanosomes. Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and multivariate statistics pro­vide further evidence that these microbodies are melanosomes, confirming the discovery of the oldest pigment in the fossil record. A range of animals have melanin in their eyes, but the posses­sion of melanosomes of two distinct morphologies arranged in layers, forming retinal pigmented epithelium (RPE), is a vertebrate synapomorphy. Our analysis indicates that in addition to ev­idence of colour patterning, ecology and thermoregulation, fossil melanosomes can also carry a phylogenetic signal. Identification in Tullimonstrum of spheroidal and cylindrical melanosomes, forming the remains of RPE, indicates that it is a vertebrate; considering its body parts in this new light suggests it was an anatomically unusual member of total group Vertebrata.


LTMicrovertebrates from the Hell Creek Formation of South Dakota, USA

Elspeth Wallace1*
1University of Manchester, Manchester

Microvertebrate fossil assemblages are present within the Hell Creek Formation (South Dakota, USA) preserving a wealth of different fauna including mammals, amphibians and birds. Such fossils provide key insights into the palaeoecology of the latest extent of the Mesozoic. Microvertebrate fossil assemblages have been identified from new sites within the Hell Creek Formation, forming the basis for this study. The aims of this investigation are to understand the processes of preservation relating to these assemblages and to describe the recovered mi­crovertebrates for the first time. With this new information, the palaeoecology of the South Dakotan part of the Formation will be reconstructed. Meticulous stratigraphic logging was un­dertaken during fieldwork to investigate the preservation of the accumulations. This shed light on the palaeoenvironment present at the time of deposition and elucidated the taphonomic bias associated with the accumulations. It was shown that microvertebrate accumulations are the re­sult of deposition as a precursor and/or conclusion to flooding events. Palaeoecological research was undertaken at the AMNH (New York) where fossils were identified to the lowest taxonomic level possible and an understanding of the organism?s lifestyle gained before an ecological pyra­mid was recreated. Future research will include comparison of these results to those of other researchers to develop a better understanding of the processes and palaeoecology of the Hell Creek Formation as a whole. This study will provide an insight into the enigmatic environment present during the last days of the dinosaurs and illuminate a complex, dynamic ecosystem lost in time.

LTExceptional preservation of trilobite moulting behaviour from the Emu Bay Shale, South Australia

Harriet B. Drage1,2,*, James D. Holmes3, Diego García-Bellido3 and Allison C. Daley1,2
1Department of Zoology, University of Oxford, South Parks Road, Oxford, OX13PS 2Oxford University Museum of Natural History, Parks Road, Oxford, OX13PW 3The University of Adelaide, North Terrace, Adelaide, South Australia, Australia 4South Australian Museum, North Terrace, Adelaide, South Australia, Australia

Exoskeleton moulting behaviour is uniquely variable in trilobites with respect to other Arthropoda. In-situ preserved assemblages of shed trilobite exoskeleton sclerites from the Cam­brian Stage 2 Emu Bay Shale (EBS), South Australia, record unparalleled detailed behavioural information for moulting events. This exceptional preservation results from a lack of disruptive abiotic and biotic processes (currents, bioturbation), and rapid burial.

The extensive collections of Estaingia bilobata and Redlichia takooensis moult assemblages housed in the South Australian Museum were surveyed, and a number of specimens displaying the full observable range of variation in moulting chosen for closer examination. Moulting behaviour was interpreted for each of these specimens. Results were contrasted to moulting behaviours described for the extremely common two other extremely common trilobite species from other localities also with exceptional fossil preservation (Ogygopsis klotzi from Burgess Shale in British Columbia, and Elrathia kingii from Wheeler Shale in Utah).

Observations and inferences made on moulting behaviour were much more detailed from the EBS in comparison to species from the other localities. At the EBS, very rare moulting events (such as disarticulation of the entire cephalon) requiring unusual patterns of movement are dis­cernable. These are not preserved in other localities with greater transportation of disarticulated sclerites. These observations suggest that trilobite moulting is more variable than expected, and flexible within a single species even during their early evolution. Further work will involve quan­tifying the proportion of each of the moult assemblages for the extensive populations of EBS trilobites.

LTMeiofaunal burrowing at the Cambrian-Precambrian boundary

Luke Parry1,2, Daniel Condon3, Russell Garwood4, Duncan McIlroy5, Paulo Boggiani5 and Alexander G. Liu2
1Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK. 2School of Earth Sciences, University of Bristol, Life Sciences Building, 24, Tyndall Avenue, Bristol, BS8 1TQ, U.K. 3British Geological Survey, Nicker Hill, Keyworth, Nottinghamshire, NG12 5GG, U.K. 4Department of Earth Sciences, Memorial University of Newfoundland, Alexander Murray Building, 300 Prince Philip Drive, St. John’s, NL, A1B 3X5, Canada. 5 Instituto de Geociências, Universidade de São Paulo, Rua do lago 562, São Paulo, SP, Brazil.

Macroscopic animals are first represented as both body and trace fossils in the latest Edi­acaran Period, with diversification of the metazoan crown group phyla occurring across the Ediacaran-Cambrian boundary. Despite the emerging consensus on the origin of macroscopic animals, the origin of the meiofauna -a polyphyletic assemblage of animals that includes both phyla known from the macrofauna and clades that are wholly restricted to the interstitial realm -remains poorly constrained, due to the low preservation potential of both their body and ichno­fossils. We describe a new exceptionally preserved ichnofauna from the Neoproterozoic-Cambrian Corumbá Group of central western Brazil. The burrows are preserved in three dimensions by infills iron oxide (originally pyrite) framboids, making them amenable to 3D reconstruction using CT scanning. The ichnofossils consist of meandering trails with sub-horizontal to shallow-vertical trajectories, exhibiting rare dichotomous branching and sinusoidal movement. The traces reach an observed minimum diameter of 50µm and are sub-circular in cross section, indicating a likely small-bodied, vermiform trace maker. The moderately dense ichnofabric is largely con­fined to discrete sedimentary horizons, and reveals micro-bioturbation by meiofaunal organisms not normally visible in the conventional trace fossil record. U-Pb TIMS dating of associated tuff horizons constrain the age of these ichnofossils to slightly younger than 541Ma, approximately coeval with the Ediacaran-Cambrian boundary. Sediment reworking by meiofaunal organisms is otherwise only known back to the Triassic, confirming a hidden history of meiofaunal animals from the Fortunian onwards.

Session 3

Macroevolution of parareptiles

Armin Elsler1*, Michael J. Benton1, Marcello Ruta2 and Alex Dunhill3
1 University of Bristol, Bristol, * 2 University of Lincoln, Lincoln 3 University of Leeds, Leeds

Parareptilia is an enigmatic clade of early tetrapods that was previously regarded as being related to modern turtles. Molecular and relatively recent morphological analyses reject such a relationship, making parareptiles an extinct group known from the latest Carboniferous to the latest Triassic. Despite being diverse in terms of ecology, morphology and body size, Parareptilia have been largely neglected in recent macroevolutionary analyses.

Here we present new data on the diversity and body size evolution of parareptiles. A database containing information on different proxies for body size, diet and stratigraphic range (at sub­stage level) of clade members was assembled. A biodiversity estimate based on raw taxic richness shows several alternating drops and peaks during the Palaeozoic. A phylogenetic diversity es­timate, based on an informal supertree of all known species of Parareptilia, depicts a slightly different picture with a more gradual increase in biodiversity over time. Both diversity curves show that the overall number of species wasn’t much affected by the end-Permian mass extinc­tion. Biodiversity reached a peak in the Induan and plummeted rapidly afterwards, staying relatively low throughout the Triassic.

Femur length was chosen as a proxy for body size and various likelihood models of continuous character evolution were fitted to the dataset. Preliminary analyses indicate that an OU model fits the data best, followed by a trend model.

This study is part of a larger project trying to shed light on the evolution of body size of all early tetrapods.

Investigating the decline of the Synapsida across the Permo-Triassic extinction and early Mesozoic using mandibular morphometrics

Suresh Singh1, Tom Stubbs2, Armin Elsler3 and Mike Benton4
1 University of Bristol, Bristol. 2 University of Bristol, Bristol. 3 University of Bristol, Bristol. 4 University of Bristol, Bristol.

The decline of non-mammalian synapsids in the early Mesozoic was a key moment in evolu­tionary history that fostered the rise of the dinosaurs. Synapsids experienced great taxonomic and ecological success through the early Permian to the middle Triassic, and were the predom­inant terrestrial vertebrates. Despite being severely impacted by the Permo-Triassic extinction event, surviving clades (Anomodontia and Eutheriodontia) were quick to recover. Nonetheless, synapsid diversity fell through the late Triassic. The circumstances surrounding the turnover from synapsid to diapsid prevalence within the Triassic remain uncertain, though it is tradition­ally attributed to competitive exclusion by the emerging archosaurs. Conversely recent studies suggest the turnover resulted from independent intrinsic factors, and was ultimately a passive process. Here we use mandibular landmark data collected from 152 genera and geometric mor­phometric methods to chart synapsid mandibular disparity and morphospace evolution through the late Permian to the early Jurassic. By studying functional anatomy linked closely to feeding, we discern possible patterns of trophic ecology, which is a key influence on evolution and a signif­icant area of contemporary interspecific competition. Our results provide an eco-morphological perspective to non-mammalian synapsid macroevolution from their peak in the late Permian to their decline in the late Triassic, and provide some support to aspects of the competitive exclusion narrative. This study illustrates how investigations of macroevolution benefit from consideration of morphological, as well as traditional taxonomic approaches.

Dynamics of dental evolution in ornithopod dinosaurs

Edward Strickson1, Albert Prieto-Márquez1, Michael J. Benton1 and Thomas L. Stubbs1
1 School of Earth Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.

Ornithopods were key herbivorous dinosaurs in Mesozoic terrestrial ecosystems, with a va­riety of tooth morphologies. Several clades, especially the ’duck-billed’ hadrosaurids, became hugely diverse and abundant almost worldwide. Yet their evolutionary dynamics have been disputed, particularly whether they diversified in response to events in plant evolution. Here we focus on their remarkable dietary adaptations, using tooth and jaw characters to examine changes in dental disparity and evolutionary rate. Ornithopods explored different areas of dental morphospace throughout their evolution, showing a long-term expansion. There were four major evolutionary rate increases, the first among basal iguanodontians in the Middle-Late Jurassic, and the three others among the Hadrosauridae, above and below the split of their two major clades, in the middle of the Late Cretaceous. These evolutionary bursts do not correspond to times of plant diversification, including the radiation of the flowering plants, and suggest that dental innovation was a major driver in ornithopod evolution.

Quantitative virtual histology: visualising the microstructure of avian bone using high-resolution and high-throughput synchrotron-based computed tomography

Katherine Williams1*, Gareth Dyke2, Neil Gostling1, Richard O. C. Oreffo1 and Philipp Schneider1
1 University of Southampton, Southampton, UK 2 University of Debrecen, Debrecen, Hungary

Accurate estimation of ontogenetic age in fossils is crucial for understanding taxonomy and evolutionary patterns in extinct animals but, in birds, robust ageing remains to be established. Histological study provides a promising approach, since bone microstructure is known to vary with both age and tissue deposition rate. However, to date, most histological studies have been qualitative, 2D, and tested in only a limited range of extant species. Our aim is to use minimally destructive 3D imaging to quantify the relationship between ontogenetic age and microstructural bone features in living birds, to accurately estimate age in avian fossils.

Our approach centres on using synchrotron-based computed tomography (SR CT) to image cortical bone in growth series of two extant bird species (duck and quail). From these 3D data sets, we describe cortical bone microstructure through quantitative morphometry down to cellular scales, including measures such as canal volume density or mean osteocyte lacuna volume.

Preliminary results show that SR CT imaging of modern avian bone allows for high spatial resolution and provides sufficient contrast required to accurately assess cortical bone microstruc­ture in 3D for quantitative virtual histology. In contrast, lab-based micro-CT measurements of the same bones, did not provide a high-throughput approach at sufficient contrast-to-noise and signal-to-noise ratio for reliable virtual histology.

As next steps, we are including a phylogenetically and functionally broader sample base for our virtual histology approach, which will be applied to fossil material to estimate ontogenetic age and growth rate in fossil birds.

LTMultidisciplinary methodological study on the origin of tissue-specific uv luminescence emission on well preserved vertebrate fossils

Maurizio Sansonetti1
1Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum, Università di Bologna, Bologna, Italy

UV photoluminescence is an extended tool in paleontology, used to highlight morphologies, to recognized artifacts and to discriminate tissues. During restoring phase at the Museo Geo­logico Giovanni Capellini (MGGC), Bologna, UV light was used to find fragments of harmed by falling’s fossils during the earthquake of 2012. Right that time it has been noticed that Bolca’s specimens show an unexpected photoluminescence emission for each well preserved soft-tissues. As well known from museographic study, MGGC fishes of Bolca’s collection are historical speci­mens, they had been prepared attractively to be sold easily by the owners of the pit to collectors and scientists since the XVII century. As historical goods, the sampling on MGGC Bolca’s specimens is usually not allowed, and in light of that value it has been decided to study the origin of this Tissue-specific UV photoluminescence Emission proceeding by a multidisciplinary approach. Several approaches has already been used to deeply understand the triggers of this phenomenon: UV photoluminescence in historical fossil specimens could have origins in vari­ous causes identified in (1)artifacts, (2)preserved autofluorescent compounds from (2a)original organs or from (2b)other biological activities, (3)different mineral compositions, and/or (4)flu­orophores in part per billion into the crystal lattice. Palaeontological interpretation for each deduced from bibliography potential triggers, or overlay of more than one of them, will help to recognize the evidence of a exact common event that had could happened between life of the specimens and exposition of its fossil, stepping through decomposition processes, digging, preparation... Not only paleontology disciplines are involved, but also biology, microbiology, thanatology, taphonomy, museography, history, chemistry of cultural heritage.

Multidisciplinary investigation is then the most suitable approach to deeply understand the phenomenon of Tissue-specific UV Luminescence in vertebrate fossil from historical collection.

LTInvestigating Siliceous Microfossils using Imaging Flow Cytometry

Ellen MacDonald1*, Kate Hendry1 and Paul Halloran2
1 University of Bristol, Bristol, U.K. 2 University of Exeter, Exeter, U.K.

Diatoms are used extensively in investigations of past climate reconstruction pollution, pro­ductivity and silicon cycling. Traditional methods of diatom identification involve time consum­ing slide production and counting. This study is the first to test the capabilities of Imaging Flow Cytometry to capture the diversity of microfossils in a sediment sample. Imaging Flow Cytometry is commonly used in cell biology as a means to quantify fluorescence and automati­cally image cell types. An ImageStream X Mk II flow cytometer was used to process a cultured sample of the diatom Phaeodactylum tricornutum and Holocene sediment samples from Edward VIII Gulf, East Antarctica. An automatic identification method was developed using IDEAS software to automatically group images into 7 final classifications. In a test population of 163 focused diatom images the accuracy of identification was 86%. In batches of 100, 000 images this accuracy dropped to an average of 52.5% over 11 core depths. Automatic identification of diatoms is much more successful in cultured samples. Colonial and solitary morphotypes of P. tricornutum were identified to an accuracy of over 90% in sample sizes of 100, 000 images. Sedi­ment sample images were dominated by fragments, unidentifiable particulate matter and diatom girdle bands. The lack of usable images in each data set limited the identification abilities of the IDEAS software. Future work would investigate improved methods of cleaning and isolating diatoms in the core sediments.

LTInferring the diets of pterosaurs and extant analogues using quantitative 3D textural analysis of tooth microwear

Jordan Bestwick1*, David Unwin1 and Mark Purnell1
1 University of Leicester, Leicester

Pterosaurs (Pterosauria) were a successful group of Mesozoic flying reptiles that success­fully persisted for 150 million years. The diets of pterosaurs have been debated and a range of hypotheses have been proposed, including insectivory, piscivory and carnivory. Most of these hypotheses are founded on similarities between the tooth morphologies of pterosaurs and ex­tant organisms. This approach assumes that tooth form and function are correlated with diet, which is not always the case. An alternative method involves quantitative analysis of the 3D sub-micron scale textures of worn tooth surfaces -dental microwear texture analysis. Microwear is produced during feeding as abrading food items alter tooth surface textures. Material prop­erties of food create different microwear characteristics; in general harder items create rougher surfaces. 3D textural analysis of microwear has never been applied to pterosaurs. This study will determine whether microwear patterns can be detected in pterosaur teeth, and the extent to which microwear textures differ between pterosaur taxa with putatively different diets. An important component in this process is to validate pterosaur microwear by examining microwear textures of extant analogues with known diets to provide comparative data sets. Prospective analogues include bats (Chiroptera) and crocodilians (Crocodylia), as species within each clade have insectivorous, piscivorous and/or carnivorous diets. This study will test the hypothesis that microwear textures in extant analogues vary according to diet, and that textures reflect dietary similarities more than evolutionary relatedness. These results will provide a context for robust quantitative tests of dietary ecology in pterosaurs.

LTBacteria or Melanosomes?

Arindam Roy1, Christopher S. Rogers1 and Jakob Vinther1
1School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1ND, UK.

The study of fossilized melanosomes has allowed for the colour of ancient organisms to be reconstructed. The shape of melanosomes is strongly diagnostic of their colour; they occur as either sausage shaped ‘eumelanosomes’ or meatball shaped ‘phaeomelanosomes’ imparting colours that range from black to dark brown and buff to red respectively. These structures range in diameter from 0.4-2 µm. However, the view that these microstructures are misidentified preserved bacteria still persists. But this hypothesis does not explain why rod and sphere shaped microstructures are the most prevalent morphologies in the fossil record. We had set up timed decay experiments using chicken feathers (both melanized and un-melanized) in isolated jars (using bacterial inoculum in mud samples from intertidal mudflats) as well as in artificial saline tanks with a mixed assemblage of microflora and fauna. These experiments were designed to simulate decay in ancient Lagerstätten settings. The decayed feathers are visualized using scanning electron microscopy (SEM). Our results show bacteria did not selectively colonize melanized or non-melanized feathers. The morphological diversity of bacteria was recorded in terms of length, width and aspect ratio. The aspect ratio was then compared to the morphology of melanosomes from various fossil avian taxa using one way-ANOVA (Welch’s unequal variance F-statistic), followed by post-hoc Kruskal-Wallis test and both indicated statistically significant differences in variance and median respectively. Also bacterial growth occurred preferentially along the rachis (which frequently does not preserve in fossils) rather than the barbs or barbules where melanosomes are normally located, contradicting the interpretation of microstructures as bacteria.

LTMiddle Devonian ecological change and the Kazák event in Northern Spain

Alexander J. Askew1*, Charles H. Wellman1
1University of Sheffield, Sheffield

The Middle Devonian was an important time of change in the history of life on Earth, particularly on land which saw the development of the earliest forests. The Devonian was also punctuated by various extinction events, including the relatively poorly understood Ka?ák Event around the Eifelian-Givetian boundary. The Ka?ák Event is known to have caused marine extinc­tions in Middle Devonian Laurentia, but relatively little is known about its effects in Gondwana, or in a terrestrial setting in general. To address these issues we are conducting a palynological analysis of the Eifelian and Givetian age Huergas, Naranco and Gustalapiedra formations of Asturias, Castilla y León and Palencia provinces in Northern Spain. These laterally equivalent formations represent a transect from shallow nearshore marine through to deep offshore shelf deposits on Peri-Gondwana. They are comprised of large sandstone bodies, interspersed with black shales, sandwiched between the thick limestone sequences constituting the rest of the De­vonian succession. Samples have been collected from 30 exposures including four logged sections and have yielded rich assemblages of land-derived spores and marine palynomorphs (acritarchs, chitinozoans and occasional scolecodonts). Analysis of these palynological assemblages is shed­ding light on ecological and evolutionary changes taking place across both time and space, and is enabling identification and characterization of the Ka?ák event in Northern Spain, including its effect on the primary producers in both the ocean (marine phytoplankton) and on the land (terrestrial flora).

LTNew insights for the rudist phylogeny (Bivalvia, Hippuritida)

Valentin Rineau1* and Loïc Villier1
1Université Pierre et Marie Curie, Paris.

Rudists (order Hippuritida) are Heterodonts Bivalves. They appear in upper Jurassic and spread all around the Thetys in warm shallow seas, to become completely eradicated at the Cre­taceous/Paleogene boundary. This group develop completely original morphologies -probably due to a shell uncoiling -which make them recognizable at first glance. A strong development of the myocardinal apparatus constituted of the hinge and myophores, the loss of a ligament and the presence of canals in the shell that can adopt a very large diversity of morphs are some examples of astonishing morphological events occuring in rudists. Here I present a new phylogeny based on representatives of each family -from Diceratidae to Hippuritidae -to resolve the early nodes of the Rudist phylogeny. I point out the weaknesses of the unique previous phylogeny from Skelton and Smith in 2000 on the formalization of homology hypotheses. propose also a completely new set of morphological descriptors, and therefore characters, based on comparative anatomy with a decomposition of traditional “morphological wholes” (as hinge) into independent characters (i.e. anterior tooth, central tooth socket). Accessory cavities are also an example of "trash character" that is redefined. I show that the previous unique character “pallial canals” can be decomposed to point four different origins. The results are presented in three-taxon analysis, a cladistic method that uses a new formalization of homologies directly in trees and without matrix representation of characters. The cladistic analysis leads to a single most parsimonious tree (RI=0,87) computed with LisBeth 1.3.

Session 4

For poster abstracts please see Page 33 of the: PDF iconAbstract Booklet - 2016.

Session 5

A hidden extinction in tetrapods at the Jurassic/Cretaceous boundary?

Jonathan P. Tennant1*, Philip D. Mannion1 and Paul Upchurch2
1 Imperial College London, London. 2University College London, London

Reconstructing deep time trends in diversity remains a central goal for palaeobiologists, but understanding the magnitude and tempo of extinctions and radiations is confounded by uneven sampling of the fossil record. In particular, the Jurassic/Cretaceous (J/K) transition, around 145 million years ago, remains poorly understood, despite a minor apparent extinction and radi­ation of numerous important clades. Here, a rigorous subsampling approach (SQS) is applied to a comprehensive tetrapod fossil occurrence dataset to assess their macroevolutionary dynamics across the J/K transition. Almost every higher tetrapod group was affected by a significant decline across the boundary, culminating in the extinction of many basal taxa. This is coupled with ecological release and radiation of numerous modern lineages, including eusuchians, sharks and marine turtles. The timing of this extinction varies, with some groups (e.g., sauropods) in decline prior to the boundary, and others (e.g., turtles) suffering their greatest diversity drop in the earliest Cretaceous. This is coupled with extremely high and widespread extinction rates at the J/K boundary, and suppressed origination rates in all groups throughout the earliest part of the Cretaceous, culminating in an overall wave of diversity decline and gradual ecological turnover. Maximum-likelihood modelling shows that eustatic sea level was the primary mecha­nism regulating diversity changes for most tetrapod clades through the availability of near-shore environments and shallow marine basins. Much of this pattern derives from the European fossil record, where eurybathic changes around the J/K boundary were driven by a major regression and the closure of shallow marine basins.

Exploring the phylogeny and form of Phytosauria

Andrew Jones1*, Richard Butler1 and Emily Rayfield2
1University of Birmingham, Birmingham 2University of Bristol, Bristol

The crocodile-like phytosaurs were a widespread group of carnivorous Archosauriformes in Late Triassic ecosystems (220-200 Ma), with their abundant remains demonstrating a cosmopoli­tan global range, suggesting their success and ecological importance. Functional similarities between phytosaurs and crocodilians have been proposed qualitatively on the basis of gross morphological similarities between the two clades. These hypotheses of evolutionary conver­gence require explicit testing considering the many varied phytosaur skull morphologies known, but such analysis is hampered by the lack of a complete global phylogeny to provide evolu­tionary context. To address this I here present the initial findings of a new taxonomically comprehensive cladistic analysis, based on extensive first-hand study of both European and American specimens, aimed at clarifying the in-group relationships of Phytosauria. These phy­logenetic results are then mapped onto a 2D geometric morphometric analysis of skull shape to produce preliminary estimates of cranial shape evolution throughout the group. Phylogenetic results support the monophyletic status of the genus Parasuchus as found in previous studies. By contrast, Nicrosaurus is recovered as a paraphyletic series of outgroups to Mystriosuchus. Morphometric results indicate that phytosaurs explored cranial morphospace widely even in the most basal clades, with certain derived taxa showing a homoplastic reversion toward more basal morphologies.

The articulated visceral skeleton of an acanthodian-grade stem-group chondrichthyan

Richard P. Dearden1*, Matt Friedman2, Robert Atwood3 and Martin D. Brazeau1
1 Department of Life Sciences, Silwood Park Campus, Imperial College London, Buckhurst Road, Ascot, SL5 7PY 2 Department of Earth Sciences, University of Oxford 3 Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE

Jawed vertebrates (gnathostomes) exhibit a vast variety of species and morphologies, a diver­sity based upon a unique suite of adaptations which evolved during one of the most important, yet poorly understood, transitions in vertebrate evolutionary history. The “acanthodian” fishes -a grade of prodigiously fin-spined stem-chondrichthyans from the Mid-Late Palaeozoic -are amongst the very earliest known members of the gnathostome crown-group, making them cru­cial for understanding this transition. However our knowledge of their anatomy is lacking, in particular that of their endoskeleton -a rich source of phylogenetically informative characters. Here we present the articulated endoskeleton of the “acanthodian” Diplacanthus crassissimus from the Middle Devonian ( 393-383 Mya) of Scotland. X-ray synchrotron tomography uncov­ers details of the visceral skeleton hitherto unknown in a Devonian stem-chondrichthyan, as well as novel information about the jaw, braincase, and shoulder girdle. A branchial skeleton with similarities to both the bony and the cartilaginous fishes is revealed, as well as the first evidence for endochondral mineralisation outside osteichthyans. This provides a sorely needed point of comparison for the branchial skeleton in early gnathostomes, helping inform current debates about the gnathostome branchial skeleton’s primitive state and the polarity of phylo­genetically important characters. It also gives us a more general insight into the anatomy of a member of Chondrichthyes’ poorly understood stem-group, helping identify characters that unite some chondrichthyans to the exclusion of other gnathostomes. These data help us better understand phylogenetic relationships, and correspondingly evolution, in the very earliest parts of the gnathostome crown.

The role of petalichthyid placoderms in early jawed vertebrate evolution: old problems, new insights and future prospects

Marco Castiello1* and Martin D. Brazeau1
Department of Life Sciences, Imperial College London, Silwood Campus, Buckhurst Road, Ascot SL5 7PY, United Kingdom

Placoderms are the only known stem-group jawed vertebrates with jaws and their phyloge­netic relationships have become central to the question of how gnathostomes evolved. Among placoderms, the petalichthyids are a focal point of research as they possess an unusual combina­tion of jawed and jawless vertebrate features. Recent discoveries and investigations have raised questions about the phylogenetic relationships of placoderms as a whole, and consequently their impact on understanding of early gnathostome anatomical conditions. Here we explore the phy­logenetic importance of petalichthyids within these competing hypotheses. We summarise extant knowledge about their anatomy and add new observations thanks to new computed tomographic datasets. In particular, we examine the significance of petalichthyid cranial morphology, com­paring the strengths and weaknesses of competing scenarios of placoderm relationships. Within the Petalichthyida, some members exhibit features that recall the ostreostracans-the jawless sister group of gnathostomes. This fact has been central to arguments in favour of placoderm paraphyly. By contrast, some petalichthyids present features which could nest them with the arthrodires-the group most commonly considered a close sister group to the jawed vertebrate crown group. Previously, the monophyly of Petalichthyida has been based on probably ple­siomorphic dermal bone characters and never tested in a global analysis of placoderm taxa. This discrepancy prevents us from having a clear understanding of petalichthyids. The question of their monophyly and relationships to other placoderms is pivotal in understand the role of placoderm characters in our hypotheses on gnathostomes bodyplan evolution.

Towards Improved Predictions of Centre of Mass Position, and its Pivotal Importance in Modelling Locomotion

Sophie Macaulay1*
1University of Liverpool, Liverpool

An organism’s centre of mass (CoM) position is a primary determinant of its stability at rest and in motion. CoM is therefore critical in determining posture and locomotor capabilities. As a result, CoM has been used extensively as an indirect predictor of locomotion in extinct taxa, where motion cannot be observed directly. It is recognised that, in order to maximise the accuracy of any estimates made, predictions should be grounded in a thorough knowledge of the same traits in closely related extant taxa. Previous analyses however, have included only limited data from extant taxa and basic validation steps. Here, I examine CoM in a range of extant archosaurs, with unprecedented model detail and validation. The digital models produced consist of flesh (i.e. muscle, bone, viscera etc.) and air cavities, in addition to integumental structures, which have never previously been included in models of avian CoM. Improved density data for the ‘flesh’ component is also incorporated. This culminates in the most comprehensive digital models of archosaurian mass properties to date. Results are validated in two extant avian species, comparing physically and digitally derived CoM estimates in order to assess the accuracy of the approach. Post-validation, this methodology will be applied to a range of avian species, in order to assess patterns in CoM position according to other biological factors such as locomotor type. Additionally, application of the improved methodology to members of Dinosauria has the potential to provide new insights into the biology of these enigmatic taxa.

LTThe first evidence of eggs in a Eocene stingray from Bolca, Italy

Gabriele Mazzuferi1*
1Museo Geologico Giovanni Capellini. Alma Mater Studiorum, Università di Bologna, Via Zamboni 63, 40126 Bologna, Italy.

Known for its exceptionally preserved fossils since the 16th century, Pesciara di Bolca Konservat-Lagerstätte represents one of the most intensively sampled Eocene marine localities. This late Ypresian Lagerstätte chronologically coincides with or immediately postdates the Early Eocene Climatic Optimum (EECO), thus documenting the earliest occurrences of numerous shallow marine fish families. The Bolca fauna provides an unparalleled data set to tract a key ques­tion: how the Cenozoic climatic patterns correlated with early evolution of modern fish lineages and shaped the rise of modern shallow marine communities. The long-term collecting efforts have accumulated more than 250 species representative of 82 families of vertebrates. Among them, chondrichthyans taxa have received surprisingly little attention beyond alpha taxonomy, despite a sample of fully articulated individuals with exquisite soft tissue preservation. A full restoration of a nicely preserved ray from the Pesciara di Bolca housed at the Museo Geologico Giovanni Capellini (Bologna, Italy) allowed for a complete analyses of the specimen and a revi­sion of its taxonomic status. Historically referred to as Platyrhina bolcensis (Myliobatiformes: Platyrhinidae), the specimen is assigned to the genus Dasyatis (Myliobatiformes: Dasyatidae), represented in the Bolca localities by the species muricata and dezignoi. A comparison with specimens housed in the collections of Padova and Verona indicate that such species may be synonymous. Exquisite preservation of soft tissues in the Bologna specimen (MGGC 7456) al­lowed to observe overall disc morphology, shape and size of pelvic fins, the finely serrated tail spine, as well as cartilages and gills. Most importantly, it was possibly to identify the individual as sexually mature female based on the presence of the left oviduct bearing four eggs. This is the first report of preserved fossilized eggs for stingrays. Shape, microscopic structure and relative size compared to the overall body size of specimen indicate an early stage of development of the eggs but also provide an incredible opportunity to compare fossil and extant representative of this genus. Being a sexually mature female, this specimen also support the postulated Eocene ‘nursery’ habitat for the Bolca locality. Finally, this research aims to underline the incredible potential of neglected specimens included in ‘historical collections’ and their potential in the field of vertebrate paleobiology.

LTQuantifying Biodiversity During the Terrestralisation of Life

Emma Dunne1*, Richard Butler1, Roger Benson2 and Roger Close1
1 University of Birmingham, Birmingham, UK. 2 Oxford University, Oxford, UK

Tetrapods (four-limbed vertebrates) first invaded the land during the late Devonian, 370 million years ago. Over the next 200 million years they diversified into a spectacular range of morphologies and body sizes, surviving two mass extinctions at the Permian/Triassic and Triassic/Jurassic boundaries. Recent attempts to track Carboniferous-Jurassic tetrapod biodi­versity have shown there is widespread disagreement on the major patterns of diversity change, stemming from the ongoing debate on the importance of spatial and temporal sampling biases in distorting observed diversity signals.

The end of the Carboniferous saw a major environmental transition when the tropical rain­forests collapsed. Previous studies noted a rise in tetrapod diversity immediately following this time, resulting from increased endemism on the newly created fragmented landscape. These studies, however, did not account for spatial and temporal biases in sampling amongst the data used.

A comprehensive occurrence-based dataset of global tetrapod species diversity and distri­bution is currently being developed within the framework of the Paleobiology Database. Once fully assembled, this dataset will be amenable to rigorous sampling standardisation, allowing genuine diversity patterns through the Palaeozoic and into the Mesozoic to be estimated. These analyses will also investigate how sampling of the early tetrapod record varies in space and time, and to what extent these biases limit our ability to identify genuine diversity patterns during periods of environmental change, such as that at the end of the Carboniferous.

LTLate Triassic Cassian Formation -Significance for the estimation of fossil and modern biodiversity

Imelda M. Hausmann1*, Alexander Nützel1, Hubert Domanski2 and Martin Zuschin3
1 SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Department für Geo und Umweltwisschenschaften, Paläontologie & Geobiologie, Geobio-Centre, Ludwig-Maximilians-Universität München, 80333 Munich, Germany. 2 Uni­versity of Vienna, Department of Geodynamics and Sedimentology, Althanstrasse 14, 1090 Vienna, Austria. 3 University of Vienna, Department of Palaeontology, Althanstrasse 14, 1090 Vienna, Austria

Taphonomic loss prevents in many cases a reliable evaluation of biodiversity in fossil assem­blages and therefore impedes a meaningful comparison with extant faunas. The Late Triassic Cassian Formation offers a solution for this major problem, because of its exceptionally good preservation of marine fossils. The Cassian Formation is situated in the Dolomites (north Italy) and yields a highly diverse tropical marine invertebrate-dominated fauna. Surface and bulk samples were collected from different sampling spots within the Cassian Formation and sieved with 0.5 mm mesh size as lower limit. After sorting and species identification, all species and specimens were quantified to conduct statistical analyses, including rarefaction, rank-abundance, and calculation of diversity indices. One dataset from a locality named Stuores Wiesen showed a remarkably high diversity and was dominated by molluscs, expecially by gastropods. Pre­liminary comparisons to other Cassian localities, which comprise different palaeoevironments, indicated that Cassian localities can vary greatly in diversity and taxonomic composition. A first comparison between the Late Triassic tropical assemblage from the Stuores Wiesen to compa­rable recent assemblages from the Gulf of Aqaba (Jordan) indicated that Late Triassic tropical molluscan assemblages were already in a similar diversity range as recent ones. The following questions will be adressed in the near future: (1) Is the time-saving analysis of the three most abundant species, instead of considering all species in fossil and recent assemblages, an appro­priate approach for diversity assessments? (2) Can fossil surface samples be used for rapid and meaningful palaeodiversity estimations? 

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