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: Abstract Booklet - 2016.
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
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
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.
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
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.
Macroevolution of parareptiles
Armin Elsler1*, Michael J. Benton1, Marcello Ruta2 and Alex Dunhill3
1 University of Bristol, Bristol, *email@example.com 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
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.
For poster abstracts please see Page 33 of the: Abstract Booklet - 2016.
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
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
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?