The stresses of the Cenozoic rat race: functional support for competitive exclusion of multituberculates by rodents?
1School of Earth Sciences, University of Bristol, Bristol, UK
2Department of Archaeology, University of York, York, UK
3Centre for Anatomical and Human Sciences, Hull York Medical School, University of York, York, UK
4Institute of Biotechnology, University of Helsinki, Helsinki, Finland
Multituberculate mammals thrived during the Mesozoic, but their diversity declined from the mid-late Paleocene onwards, with last occurrences known from the late Eocene. The radiation of superficially similar eutherian rodents has been linked to multituberculate extinction through competitive exclusion. However, characteristics providing rodents with a supposed competitive advantage are currently unknown and comparative functional tests between the two groups are lacking. Here, a multifaceted approach to craniomandibular biomechanics was taken to test the hypothesis that superior skull function made rodents more effective competitors. Digital models of the skulls of four extant rodents and the Upper Cretaceous multituberculate Kryptobaatar were constructed and used (i) in finite element analysis to study feeding-induced stresses, (ii) to calculate metrics of bite force production, and (iii) to determine mechanical resistances to bending and torsional forces. Results suggest that most rodents experienced higher craniomandibular stresses and some had lower resistances to bending and torsion than the multituberculate, apparently refuting the competitive exclusion hypothesis. However, rodents optimize bite force production at the expense of higher skull stress and this may have been more functionally and selectively important. Our results therefore provide a first step to understanding the decline of multituberculates in the changing environments of the Paleogene.
Microfossils from the Late Neoproterozoic glacial-interglacial succession on Digermulen Peninsula, Arctic Norway
1University of California Santa Barbara, USA
2Tromsø University Museum, Norway
3University of Extremadura, Spain
4University of Göttingen, Germany
5Keele University, UK
6University of Cape Town, South Africa
7Uppsala University, Sweden
The late Neoproterozoic strata exposed on the Digermulen Peninsula (Arctic Norway) provide a good sedimentary record of Neoproterozoic glaciations on the Baltica palaeocontinent. The lower Vestertana Group contains two glaciogenic units, the Smalfjord and Mortensnes formations which have been correlated with the Marinoan (650 to 635 Ma) and Gaskiers glaciations (c. 579 Ma), respectively. The diamictites are bracketing the shales and siltstones of the Nyborg Formation. Samples from the Nyborg-Mortensnes succession in Guvssájohka valley were collected in 2016 by the Digermulen Early Life Research Group. Acetolysis yielded well-preserved organic-walled microfossils (OWM). Importantly, OWM were also recovered from the fine-grained diamictite matrix in Mortensnes Middle Member. The interglacial Nyborg assemblage includes various leiosphaerids, Synsphaeridium-type cell aggregates, Pterospermopsimorpha, Simia, Stictosphaeridium, and rare sculptured and ornamented acritarchs (?Ceratosphaeridium). Unusual microfossils, meshworks of aggregated tubes, occur in Member D of the Nyborg Formation. The glacial assemblage within the Mortensnes Formation is expectedly more depauperate and contains abundant unbranched bacterial filaments, small-sized leiosphaerids, and a toroidal morphotype very similar to the Tonian taxon Squamosphaera. These occurrences extend the fossil record on the Digermulen Peninsula below the levels bearing Ediacara-type macrofossils, and add to the OWM record during the end-Neoproterozoic low-to-mid latitude glaciations.
Archosauromorph extinction during the Triassic-Jurassic mass extinction was not related to body size
1School of Earth and Environment, University of Leeds
2School of Earth Sciences, University of Bristol
Previous mass extinctions destroyed swathes of standing diversity but many of the evolutionary patterns during these events are not known. Currently, it is not clear whether species’ traits or lifestyle made them more vulnerable to extinction during these events, or if mass extinctions were random killers that did not act according to the rules of background selection. Most evidence indicates previous mass extinction did not act on body size, but in modern vertebrates larger species have greater extinction risk. Here, we investigate whether body size selectivity played a role in the survival and extinction of Archosauromorpha during the Triassic-Jurassic mass extinction. Using a novel approach, we estimated a new archosauromorph maximum likelihood supertree that incorporates phylogenetic uncertainty. We used phylogenetic comparative methods to test if more closely-related species were more likely to go extinct during the Triassic-Jurassic event, and if larger species were more prone to extinction. We found that there was a significant phylogenetic signal in extinction during the Triassic-Jurassic mass extinction, but there is no correlation between body size and extinction. Previous mass extinctions did not act under body size selectivity, and current extinction risks may differ from those in deep time.
Lilliputians and Brobdingnagians: Body size changes in Lower Jurassic bivalve molluscs
1University of Leeds
Within the Blue Lias Formation (Lower Jurassic) of Britain several bivalve molluscs are seen to undergo a within-species shell size increase. This trend is seen across multiple ecological guilds and occurs in tandem with biotic recovery from the end-Triassic mass extinction event (ca. 201 Ma). The most striking example of body size increase is seen within the species Plagiostoma giganteum, which undergoes a 170% mean body size increase relative to specimens measured from its first common occurrence. Although this size increase has been noted within published literature for over 50 years, this study is the first to investigate this and other coeval body size trends in detail. Analysis of growth lines shows gigantism was achieved by a combination of increased longevity and more rapid growth. To record these trends Rhaetic and Lower Jurassic exposures were sampled in South-West Britain, Northern Ireland and North Yorkshire and supplemented with measurements of specimens housed within museum collections. This study now comprises body size data on over 100 bivalve species that provides an understanding on how Lower Jurassic ecosystems responded during the recovery from the end-Triassic mass extinction event.
Phylogeny, ecology, and time: 2D outline analysis of anuran skulls from the Early Cretaceous to Recent.
1University College London
Anura have a long fossil record. However, specimens are often severely flattened, limiting their inclusion in quantitative analyses of morphological evolution. Here we perform a 2D morphometric analysis of anuran skull outlines, incorporating 42 Early Cretaceous to Miocene species and 93 extant species across 32 families. Outlines were traced in tpsDig2 and analysed with elliptical Fourier analysis. Fourier coefficients were used in MANOVAs and disparity analyses across multiple ecological and life history groupings. As skull outlines showed significant phylogenetic signal (k=0.53, p=0.006), phylogenetic MANOVAs were also conducted. Ecological niche was a significant discriminator of skull shape (F=1.44, p=0.004), but not after phylogenetic correction. The Neotropical realm showed highest disparity. Developmental strategy had a weak effect on skull shape (R2=0.02, p=0.039), and disparity was similar in metamorphosing and direct developing frogs. Body size was associated with differences in skull shape in fossil frogs (R2=0.44, p=0.017) and extant taxa (R2=0.10, p=0.049), and this effect was only partly due to allometry, which was weak but significant in both fossil (R2=0.11, p=0.002) and extant frogs (R2=0.09, p=0.001). Finally, the shift of morphospace occupation for fossil and extant frog skull outlines appears largely phylogenetically structured, as phylogenetic correction removed any temporal shift of morphospace.
Skeletal and character completeness of the Triassic marine reptile fossil record
1University of Bath
2University of Birmingham
The marine fossil record has been traditionally considered more complete than the terrestrial. Previous work has shown that skeletons of some marine reptiles, such as ichthyosaurs and plesiosaurs, are more completely preserved than those of contemporary terrestrial animals. Here we study both the skeletal and character completeness of several Triassic groups of marine reptiles, including placodonts, nothosaurs, pachypleurosaurs, pistosaurs and thalattosaurs. These groups typically have smaller body sizes than ichthyosaurs and plesiosaurs and have distinct ecological preferences, offering a contrast to these previously studied groups. We calculated the skeletal completeness metric (SCM) and the character completeness metric (CCM) for all valid species of these groups. Provisional results show that while on average marine fossil record is more complete than the terrestrial record, this pattern is not maintained across all studied groups. Comparison between character and skeletal completeness indicates that there is not a strong correlation between both metrics and that most characters are concentrated in the most usually preserved or described skeletal regions, like the skull. No significant correlations are found between completeness and other metrics, such as diversity, size or lithology. A significant correlation was found between the completeness of a holotype and the year the species was named.
Worms on acid: how pH affects burrowing behaviour of Nereis diversicolor and its bearing on mass extinction scenarios
1University of Hull
2University of Nottingham
Mass extinctions are often characterised by a loss of bioturbators. The Early Triassic interval is dominated by laminated facies defined by the ichnofabric index (II) as having no bioturbation (II1). The Permian-Triassic is the crisis in which ocean acidification (OA) is most widely implicated, but this remains controversial. Does a relationship exist between pH and ichnofabric index? We tested the effects of altered pH on the rag worm Nereis diversicolor. Aquarium tanks were filled with coloured sand and mud and 20 individuals of N. diversicolor each. Tanks were filled with distilled water with salinity 16‰ adjusted to pH 7.0, 7.5, and 8.0 (5 replicates of each) and kept at 16°C for 5 weeks. Aquaria were photographed weekly to permit classification of their ichnofabric index. After 5 weeks, tanks at pHs 7.0, 7.5 and 8.0 had mean II of 2.6, 3.2 and 2.4 respectively. No tanks exhibited the near-total loss of bioturbation seen at the Permian-Triassic boundary, but acidification stress during that event persisted over much longer timescales than we can replicate. Nevertheless, our experiments show that altered pH reduces bioturbation activity, lending tentative support for a role for OA in extinction crises that record a drop in ichnofabric index.
What were they thinking? Exploring ceratopsian braincase morphology and palaeoneurology through ontogeny.
1University of Bristol
2Institute of Vertebrate Palaeontology and Palaeoanthropology
3Cleveland Museum of Natural History
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. Ceratopsian palaeontology currently lacks comprehensive neuroanatomical studies which can illuminate how neurology might predict behaviours that have been suggested by previous research.
Braincases are often neglected in contemporary palaeontological studies due to the high level of fusion and consequent obscurity of sutures. In the case of near sutural obliteration, landmarks on the braincase such as nerve exits and tubera can be used to map bone extent and thus allows for approximate yet reliable braincase segmentation.
Ceratopsian skulls were imaged using high resolution micro-CT scanners and were then reconstructed in Avizo (3D visualisation software). 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.
Callovian ammonite and brachiopod faunas from the Essaouira-Agadir Basin (Morocco). Palaeogeographic implications.
1NARG - SEES - University of Manchester
2University of Agadir
3ONYHM - Rabat
New fieldwork in the Middle and Upper Jurassic of the Essaouira-Agadir Basin of Atlantic Morocco was undertaken in the past two years. Extensive collections of ammonites and brachiopods were made bed by bed at three reference sections in the Imouzzer Ida Ou Tanane area and at Jebel Amsitene. Besides a revision of the historical collections stored at the MEM in Rabat allowed us to complement the new field data.
The ammonite faunas collected allowed to recognized the late early to early late Callovian ammonite biozones of the standard Mediterranean scale. The fauna is dominated by species of Reineckeinae, Grossouvriinae and Peltoceratinae that characterise the mediterranean successions of the northern margin of the Tethys with special reference to the standard succession of western France (Poitou).
Brachiopod assemblages span a slightly longer time interval and may already be present in the Late Bathonian. The faunas are dominated by members of the genera Kutchithyris, Bihenithyris, Kutchithyrinchia and Somalirynchia. Similar faunas are known from the horn of Africa, southern Arabia, and the Indian subcontinent and are characteristic of the Jurassic Ethiopian Province. Distribution of the assemblages in time and space will be discussed.
Bird-hipped, but bird-brained? Sensorineural trends within Neornithischia and the evolution of ornithopod social signalling structures.
1North Carolina Museum of Natural Sciences
2North Carolina State University
Numerous species of ornithischian dinosaurs, most notably hadrosaurian ornithopods, exhibited elaborate cranial crests. These crests functioned in visual and acoustic signalling, providing osteological correlates of social activity and a rare opportunity to investigate sensorineural trends associated with the evolution of complex intraspecific interactions. Reconstruction of hadrosaur endocasts has demonstrated relatively large cerebrum volumes, suggesting increased cognition associated with these social behaviours. However, sampling of endocasts from earlier diverging neornithischian lineages has been sparse, frustrating efforts to clarify trends in neurological evolution within the clade.
To address this, the endocranial space and inner ear morphology of the non-ornithopod neornithischian Thescelosaurus and an unnamed, early-diverging ornithopod from the Cedar Mountain Formation were digitally reconstructed from CT scan data, and compared to those of other ornithopod taxa in an explicit phylogenetic context. Thescelosaurus is plesiomorphic in brain morphology, with an encephalisation quotient (EQ) value intermediate between thyreophoran and ornithopod taxa. Expansion of the cerebrum and increasing EQ values are then seen through Ornithopoda, culminating in the highest observed values in hadrosaurs. This suggests that the expanded forebrains of these taxa may be the result of longer-term processes as opposed to a correlative of the evolution of elaborate crests within Hadrosauria.
Trematode traces on Recent bivalve shells
1Royal Netherlands Institute for Sea Research (NIOZ)
Parasitic digenean trematodes have a complicated life cycle with one or two intermediate hosts before they enter their terminal vertebrate host (bird, fish). They have a very low fossilization potential. They are mainly studied by biologists. Some digenean trematodes belonging to the Gymnophallidae use bivalve molluscs as their last intermediate host: they encapsulate themselves as cysts (metacercaria) between mantle and shell and leave there traces. Not all these infected bivalves are consumed: intact shells can be found which traces of these cysts such as the pits first reported in fossil shells by Ruiz & Lindberg (1967). Different trematode cyst traces exist. Whether these traces are really made by metacercaria can only be studied in living bivalves. Studying life cycles and the role of parasites in food-webs is a still growing field of research. I present pictures of trematode traces in Recent bivalve shells from the North- and Wadden Sea coast of the Island of Texel, the Netherlands. Interest in trace fossil evidence of trematode-bivalve interactions in the past is increasing (Huntley & De Baets, 2016).
Microstructural and chemical characterization of medullary bone across the bird phylogeny
1North Carolina Museum of Natural Sciences & NC State University
Medullary bone (MB) is a specialized tissue produced by female birds during the egg-laying cycle. It is commonly described as a highly vascularized and strictly woven bone tissue, endosteally deposited in the medullary cavity of hindlimb elements. Using these criteria, MB-like tissues have been identified in non-avian dinosaur specimens. However, MB’s definition mostly results from its study in domestic bird species that are not representative of bird diversity. Moreover, some avian pathological bone tissues meet these criteria, thus casting doubt on previous observations of MB in the fossil record.
With a sample of 40 bird species, the present work constitutes the first taxonomically comprehensive study of MB. Using micro-CT and histochemical techniques, our study assesses the skeletal distribution and extent of microstructural and chemical variation of MB across birds.
Our preliminary results reveal that the distribution of MB in the postcranial skeleton varies interspecifically. MB is uniformly present in the femur and tibiotarsus and consistently absent in the pes. Only few species exhibit MB in the humerus. Its chemistry is diagnostically different from pathological bone. Finally, MB presents a lamellar component in some specimens.
These new data will be used to reassess previously published identifications of MB in fossil archosaurs.
The Chris King collection - a data goldmine buried in the clay?
1Natural History Museum, Dept of Earth Sciences
The Natural History Museum, London, has been bequeathed a unique fossil collection of benthic macro- and microfauna of Paleocene/early Eocene age. Collected over forty years in southern England and north-west Belgium, this major assemblage comprises 80,000 specimens, mainly molluscs. It is currently being curated and digitized to allow us to extend research beyond its original purpose of improving stratigraphic dating and correlation. A clear research opportunity lies in analysis of the biotic response to global temperature change during the uppermost Paleocene-lower Eocene. The collection finely samples coastal sediments deposited across the southern margin of the North Sea Basin, a key area preserving excellent sedimentary records across a short duration spike in global temperatures, the Paleocene-Eocene Thermal Maximum (PETM: 55.8-60.0 Ma). During this period warming of 5-8°C occurred within just 10 kyr. The detailed response of coastal macrofauna to this episode remains largely unknown. It is anticipated that quantitative studies on this collection could substantially increase our understanding of shallow marine palaeoenviroments and taxonomic and ecological responses of their biota across the PETM. Additionally, integration of isotopic analysis with macrofaunal analysis may reveal the possible role of hyposalinity and permit characterization of biotic change at ecologically valuable stratigraphically fine scales.
Acritarchs, cryptospores : why almost all palaeontology text-books got it wrong ?
1Universite de Lille, UMR 8198 Evo-Eco-Paleo
Evitt (1963, PNAS 49 : 298–302) defined the acritarchs as an informal group of organic-walled microfossils with unknown biological affinities (that could not be attributed to a known group of phytoplankton, such as the dinoflagellates or any other biological group). Richardson et al. (1984, J. Micropal. 3:109-124) proposed the diagnosis of another informal grouping, the ‘anteturma Cryptosporites’ in order to classify primitive spore-like palynomorphs (that could not be attributed with certainty to the spores of land-plants). Since the original description of the terms ‘acritarchs’ and ‘cryptospores,’ many other definitions have been proposed for both informal groupings, creating a debate between specialists that is mainly based on the confusion between the definition (based on morphologies) and the (speculative) biological interpretation of both terms. Consequently, almost no current palaeontological text-book or website cites correctly the original definition of the ‘acritarchs’ and the ‘cryptospores’. We advocate that, as long as the exact biological affinity of most of the individual morphotypes remains unknown, the informal groupings of the acritarchs and the cryptospores are still valuable and the original definitions should be retained, based solely on morphological criteria.
Character completeness of the temnospondyl amphibian fossil record
1University of Birmingham
2University of Leeds
Changes in fossil specimen completeness can alter the amount of observable character states per species, and, therefore, affect macroevolutionary interpretations. The quality of the tetrapod fossil record has been quantified as the proportion of phylogenetic characters that can be scored for an individual species. Here, we calculate this character completeness metric (CCM) for temnospondyl amphibians using all previously published phylogenetic matrices focused solely on the group. We also use an alternate implementation of the CCM which calculates how completely known individual characters are through time. Variation in completeness across different partitions of cladistic characters may offer a potential explanation for poorly constrained areas of temnospondyl interrelationships.
The most character-rich matrices show that mean temnospondyl character completeness is consistently very high (~75–95%) for both species and characters, with little relative fluctuation through time. Completeness does not correlate with changes in diversity, which suggests that it is unlikely to be limiting our understanding of temnospondyl macroevolution; however, completeness is likely inflated due to the exclusion of poorly known taxa in phylogenetic analyses. There are also significant differences in completeness between different portions of the temnospondyl skeleton, which may be explained by preferential preservation bias of the skull.
Jurassic fish from Scotland – new finds from the calm before the teleost storm.
1University of Edinburgh, UK
2National Museums Scotland, UK
3Staffin Museum, UK
4University of Glasgow, UK
5University of Leicester, UK
6Lealt Stratigraphic Consultants Ltd., UK
7Saskatchewan Isotope Laboratory, Canada
Middle Jurassic fish assemblages provide an important and exciting insight into a time immediately before the establishment, in the Upper Jurassic, of the largest extant fish group, the crown-group teleosts. New finds from the Middle Jurassic of the Isles of Skye and Eigg, Scotland, reveal a diverse assemblage comprising chondrichthyans, new species of pycnodonts, pachycormids, stem-group teleosts but also possible perleidiforms. Additionally, specimens from the Upper Jurassic of northeast Scotland record hybodont sharks and members of the Caturidae, Furidae and Aspidorhynchidae but only one record of a pycnodont. Palaeobiogeographic analysis of the pycnodont assemblage indicates that founder event speciation and dispersal from the epicontinental seas of Europe are shown to govern pycnodont evolution similar to the dispersal pattern of Pachycormiformes. The Skye Pachycormus is contemporary with, and likely identical to, those from Strawberry Bank, Gloucester. In addition to phosphatic body fossils, three different morphotypes of otolith have been recovered including some attributable to Leptolepis. These new finds demonstrate the importance of Jurassic deposits of Scotland as a potential source of new and important taxa that will help to provide important insights immediately before the origination of the largest vertebrate group currently in existence – teleost fish.
Constraining the Timing of Whole Genome Duplication in Plant Evoltionary History
1University of Bristol
Whole genome duplication (WGD) has occurred in many lineages within the tree of life and is invariably invoked as causal to evolutionary innovation, increased diversity, and extinction resistance. Testing such hypotheses is problematic, not least since the timing of WGD events has proven hard to constrain. Here we show that WGD events can be dated through molecular clock analysis of concatenated gene families, calibrated using fossil evidence for the ages of species divergences that bracket WGD events. We apply this approach to dating the two major genome duplication events shared by all seed plants (ζ) and flowering plants (ε), estimating the seed plant WGD event at 399-381 Ma, and the angiosperm WGD event at 319-297 Ma. These events thus took place early in the stem of both lineages, precluding hypotheses of WGD conferring extinction resistance, driving dramatic increases in innovation and diversity, but corroborating and qualifying the more permissive hypothesis of a ‘lag-time’ in realising the effects of WGD in plant evolution.
Rooting the tree and investigating the evolutionary history of Bacteria
1University of Bristol
A rooted tree of Bacteria is essential to reconstruct the evolutionary history of Bacteria, including ancestral gene content, metabolism and physiology. Many current ideas pertaining to the nature of bacterial evolution are informed by hypotheses of prokaryotic phylogeny. However, rooting the tree of Bacteria has proven difficult. Recent discoveries of a huge diversity of new uncultured phyla further complicate matters, and the relationships between the major bacterial phyla still have little resolution. We attempt to construct a rooted tree of bacteria using probabilistic gene tree-species tree reconciliation methods. These are hierarchical models in which horizontal gene transfers (HGTs), gene duplications and gene losses are integrated into an overall model of genome evolution using amalgamated likelihood estimation (ALE), where patterns of gene family evolution contain information about the root of the tree. Using these methods, we may produce a rooted tree and reconstruct ancestral gene content and metabolism for the internal nodes, including the last bacterial common ancestor (LBCA), and can infer information about the early evolution of life. We also investigate HGTs through time, and look at the evolution of membrane lipids across the tree of Bacteria to ascertain whether the so-called ‘lipid divide’ between Bacteria and Archaea exists.
Initial steps in ordering events of the Late Ordovician mass extinction: chitinozoan contributions to Maquoketa Group holostratigraphy (Upper Katian, Wisconsin, USA).
1Department of Geology, Ghent University
2Indiana Geological and Water Survey, Indiana University
3Central Mineral and Environmental Resources Science Center, US Geological Survey
The Maquoketa Group contains a series of carbonate carbon isotope excursions that record ocean-geochemical disturbances during the run-up to the Late Ordovician mass extinction and glacial maximum. To enhance understanding of the processes active during these times of severe climatic, oceanic and biospheric change, ordering the regional stratigraphic succession to the global chronostratigraphic scheme is crucial. Preliminary chemostratigraphy and facies analysis shows significant regional differences within the Maquoketa Group along a continental interior to margin transect. We hypothesize that this variability reflects a diachronous succession that in total captures one of the most complete and well-preserved records of the Upper Ordovician in the world. Here, to test this hypothesis, we develop a chitinozoan biostratigraphy for the Gardner Kiln core (Wisconsin, USA), which penetrates the entire Maquoketa Group. Thirty-two samples yield rich and well-preserved assemblages with 6084 chitinozoan specimens assigned to 47 species. Preliminary correlations are drawn with sections across North America for which chitinozoan biostratigraphy is available (i.e., Oklahoma, Kentucky, and Québec). The exceptionally well-preserved palynomorphs from the Maquoketa Group illustrate the potential for this group to become a key biostratigraphic tool in high-resolution integrated stratigraphy of the Upper Ordovician in the US Midcontinent region.
Chitinozoans from the Rheidol Gorge Section, Central Wales, UK: a GSSP replacement candidate for the Rhuddanian/Aeronian boundary
3University of Leeds
5St. Francis Xavier University
6University of Leicester
As part of an effort to evaluate potential replacement sections for the existing Aeronian base stratotype, 28 samples from the Rhuddanian/Aeronian boundary interval of the Rheidol Gorge section (central Wales, UK) were studied for chitinozoans. Famously known through the work of Jones (1909) and Sudbury (1958), the sampled succession comprises a graptolite-bearing sequence of laminated black shales alternated with thinner sparsely graptolitic grey mudstone intervals, deposited under anoxic and oxic-to-dysoxic seafloor conditions, respectively. The exposed section of approximately twenty meters spans the middle part of the upper Rhuddanian Monograptus (Coronograptus) cyphus Zone through the lower Aeronian Monograptus (Demirastrites) triangulatus Zone of the mid-Llandovery Series. Despite our increased sampling viz-à-vis preliminary reports and the presence of numerous and moderately well-preserved specimens, the chitinozoan analysis demonstrates a species assemblage that remains more-or-less uniform throughout the entire exposed succession. The assemblage is characteristic of that of the Spinachitina maennili Biozone, which is globally recognised around the base of the Aeronian. Chitinozoans from the Rheidol gorge section can thus be directly correlated to the original type Llandovery area and to many lower Silurian Rhuddanian/Aeronian boundary successions in other parts of the world.
Testing the link between beak shape and functional performance in birds
1School of Earth Sciences, University of Bristol
Bird beaks are often cited example of the tight relationship between morphological form and function. Despite this, recent work has suggested that skull and beak morphology is a surprisingly weak predictor of dietary ecology, and instead beak shape is constrained by size, phylogeny and integration with the braincase. While these studies have tested the link between shape and ecology, the link between shape and function remains largely unexplored. The aim of this study was therefore to test how variation in bird beak shape relates to mechanical function. Beginning with a 2D morphospace of skull shape in 227 passeriform taxa, we created 25 3D hypothetical beak shapes that capture the variation in form across axes 1 and 2 of the morphospace, capturing 77% of skull shape variation. Finite element analysis (FEA) was used to estimate beak stress in response to a load at the beak tip. Our results show a significant exponential relationship between axes 1 and 2 of the morphospace and the ability of the shape to dissipate stress. Some underpopulated regions of the morphospace perform just as well as some of the more populated areas, suggesting other links between shape and function are yet to be quantified.
The apparatus composition and architecture of Erismodus quadridactylus and its implications for the prioniodinin apparatus bauplan
1University of Oxford
2University of Birmingham
3USGS National Center
4University of Bristol
The apparatus composition and architecture of prioniodinin conodonts is poorly understood, largely because few prioniodinin taxa are represented by articulated ‘natural assemblages’, but also due to the highly variable gradational morphology of their constituent elements that makes apparatus reconstruction problematic. We describe a natural assemblage of Erismodus quadridactylus (Stauffer, 1935), a basal prioniodinin conodont, from the Sandbian (Late Ordovician) of North Dakota, USA. The assemblage demonstrates that the apparatus architecture of Erismodus is similar to those of Late Palaeozoic prioniodinins, namely, Kladognathus Rexroad and Hibbardella Bassler, but also has similarities with ozarkodinin apparatuses. There is evidence to suggest that E. quadridactylus also shared topological similarities to ‘prioniodontid’ architecture, with respect to the position of its inferred P elements. This apparatus reconstruction suggests, at least with respect to the M-S array, an ‘ozarkodinin-type’ bauplan is likely more widely representative across ozarkodinids. Furthermore, element morphotypes traditionally considered to lie within the S array are M elements, whereas others traditionally interpreted as P elements are found in the S array. These observations are used as a basis for revising the prioniodinin apparatus bauplan and for refining concepts of element homology among other prioniodinin conodonts and their closest relatives.
Cranial osteology of Martillichthys renwickae [Neopterygii; Pachycormiformes], and ecological implications for suspension-feeding pachycormids
1Department of Earth Sciences, University of Oxford, UK
2Museum of Palaeontology, University of Michigan, USA
3Department of Earth Sciences, Natural History Museum, London
4Bayerische Staatssammlung für Paläontologie und Geologie, Munich, Germany
Pachycormids are a modestly diverse family of putative stem teleosts, ranging in age from the Early Jurassic to the Late Cretaceous, and found in marine deposits across the globe. While some members of the group are well represented in the fossil record, the most famous pachycormids — the giant suspension feeders including the enigmatic Leedsichthys — are almost exclusively known from crushed, disarticulated material, and have been largely characterised by fragments, limiting understanding of their ecology and evolution. Here, we use CT scanning to re-describe an articulated, though flattened, cranium of Martillichthys renwickae from the Middle Jurassic (Callovian) Oxford Clay of the UK. This scan reveals internal details of perhaps the most complete suspension feeding pachycormid skull known, and revises several details of the anatomy of Martillichthys. Most significantly, Martillichthys shows specialized characters with an apparently restricted distribution among suspension-feeding pachycormids, including gill rakers with elongated ‘needle teeth’ and a greatly extended occipital stalk. Our virtual models of Martillichthys reinforce past systematic interpretations of the interrelationships of suspension feeding pachycormids, and provide a model for interpreting the less complete remains of other members of this enigmatic but long-lived group of fishes.
Radiological study of the sequence of dental mineralization, eruption and replacement in hipparionine horses from the Miocene of Spain
1Doñana Biological Station-CSIC (Seville, Spain)
2National Museum of Natural Sciences-CSIC (Madrid, Spain)
3Faculty of Veterinary Medicine. Complutense University of Madrid (Madrid, Spain)
4Military Centre of Veterinary. Ministry of Defence (Madrid, Spain)
Hipparionine horses are ubiquitous in Neogene continental fossil sites of Eurasia, Africa and North America so they have been the object of iconic biostratigraphical, evolutionary and palaeoecological studies. Cerro de los Batallones palaeontological complex (Madrid Basin, Spain) is composed of 9 fossil sites that contain a massive amount of remains belonging to a diverse Late Miocene mammalian fauna. Among these sites, Batallones-10 stands out for containing exceptionally well-preserved remains of herbivores, with the equid Hipparion sp. being the best represented taxon. Hipparion sp. maxilla and mandibles with teeth in place are very abundant at Batallones-10, contrary to what is usual in most of the mammalian fossil sites, where teeth are commonly found in isolation. This fact allowed us to analyse mandibles of 27 Hipparion sp. individuals from Batallones-10 with radiological techniques (X-ray and CT scan) with the aim of: 1) describing the sequence of mineralization, eruption and replacement of teeth in a complete hipparionine horse ontogenetic series that includes an abundant representation of juvenile individuals for the first time and 2) inferring whether the Hipparion sp. individuals from Batallones-10 died as a consequence of a gradual (attritional) process or a catastrophic event.
The exceptional diversity of trilobite moult configurations from the Emu Bay Shale, South Australia
1University of Oxford
2University of Adelaide
3South Australian Museum
4University of Lausanne
The Emu Bay Shale (EBS) is a Cambrian Stage 2 Konservat-Lagerstätte dominated by preserved carcasses and moulted exoskeletons of two extremely numerous trilobite species, Estaingia bilobata and Redlichia takooensis. Moult configurations of these species capture the movement of the trilobite and pattern of sclerite disarticulation, therefore allowing an unparalleled detailed interpretation of behaviour during moulting events. This exceptional in-situ preservation results from a lack of disruptive abiotic and biotic processes (currents, bioturbation), and rapid burial at the EBS.
The extensive collections of E. bilobata and R. takooensis housed in the South Australian Museum, Adelaide, were surveyed, and a number of specimens displaying the full observable range of variation in moulting behaviour chosen for closer examination. Rare moulting events utilising unusual movements (such as disarticulation of the entire cephalon), which are often not preserved at localities with greater disruption, are discernable. Several new moult configurations were named on the basis of these specimens, and other names resurrected from the literature. These will be used as a tool to interpret trilobite moulting at other Palaeozoic Konservat-Lagerstätte. The EBS results demonstrate hitherto undescribed intraspecific moulting behaviour flexibility, particularly during early trilobite evolution. Fieldwork is planned to quantify this moulting variability.
A new myriacanthid holocephalian from the Early Jurassic of Bornholm, Denmark
1The Natural History Museum
A new myriacanthid holocephalian is described from the Hasle Formation (probably Uptonia jamesoni subzone to Acanthopleuroceras valdani subzone, Early Pliensbachian, Early Jurassic) of Bornholm (Denmark) on the basis of isolated upper posterior (palatine) and lower posterior (mandibular) tooth plates. Oblidens bornholmensis gen. et sp. nov. differs from all other myriacanthids for which the same dental elements are known, in the distribution of the hypermineralised tissue covering the occlusal surfaces of the tooth plates, and the arrangement of the ridges transecting the tooth plate surface and so varying their surface relief. Oblidens is the first myriacanthid holocephalian to be recorded both from the Pliensbachian and from Denmark. The presence of a further, undetermined myriacanthid tooth plate is noted from the same locality.
The frondose Ediacaran macrofossil Arborea arborea is a eumetazoan
1University of Bristol
2University of Cambridge
The Ediacaran frond Arborea arborea from South Australia is an iconic member of the soft-bodied Ediacaran macrobioa. Largely recognised from fragmentary remains, Aborea possesses a distinctive frondose body plan, and could reach almost two metres in size. However, it has been little studied when compared to the other main frondose component of the Ediacaran biota, the rangeomorphs.
Examination of multiple Arborea specimens from the Ediacara Member of South Australia reveals a previously unrecognised suite of morphological characters. These include an inflatable holdfast disc, front-back differentiation, and a stem that exhibits considerable variation in its length within populations. Exceptionally preserved specimens reveal features that we interpret as preserved internal anatomical structures. These reveal differentiation of tissues, and a network of bundled linear tubular structures that raise the possibility that Arborea was a colonial organism. In conjunction with previously recognised features including apico-basal differentiation, we propose that to the exclusion of all non-metazoan possibilities, Arborea was a total-group eumetazoan.
The Late Triassic Latitudinal Biodiversity Gradient
1University of Birmingham
The latitudinal biodiversity gradient (LBG), the increase in species richness towards the equator, is one of the most widely recognised patterns in macroecology. This gradient has been extensively documented in modern terrestrial vertebrate faunas, yet the evolution and drivers of this pattern through time remain uncertain. The fossil record offers a deep time perspective on the LBG; however, previous studies have been hampered by uneven spatial and temporal sampling, particularly very poor sampling of low-latitude regions. The Late Triassic tetrapod fossil record provides a unique opportunity to study the LBG in deep time, as sampling in low- and mid-latitude regions during this interval has been extensive, and the climate and continental configuration were very different from today’s. Here, we explore the relationships between Late Triassic tetrapod diversity, palaeolatitude, and climate using data from the Paleobiology Database, sampling standardisation, and tree-based biogeographic and character-mapping approaches. Results suggest that Late Triassic tetrapods do not conform to a modern-type LBD; instead diversity is higher at mid-latitudes than at low-latitudes. We also examine the distribution of major Late Triassic tetrapod groups (e.g. dinosaurs, temnospondyls, and pseudosuchians) and how this relates to global climate to uncover the drivers of spatial variation in global tetrapod diversity.
Decreasing influence of calcite – aragonite seas on marine calcifiers in the Phanerozoic
1School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
2School of Computing, Electronics and Mathematics, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK
3GeoZentrum Nordbayern, Department of Geography and Geosciences, Universität Erlangen-Nürnberg, Loewenichstraße 28, 91054 Erlangen, Germany
Aragonite-calcite sea conditions describe Phanerozoic fluctuations of abiotic marine aragonite vs calcite precipitation, which is thought to be driven by oscillations in seawater Mg:Ca ratio, temperature, and pCO2. Despite many examples of groups of marine calcifiers originating or diversifying when aragonite-calcite sea conditions favoured their skeletal mineralogy, no convincing quantitative evidence currently supports these inferences at Phanerozoic time scales. Here, we apply Summed Common species Occurrence Rate (SCOR) to fossil occurrence data from the Paleobiology Database (PBDB) to assess the relative success of marine aragonite-shelled organisms in the context of fluctuating aragonite-calcite sea conditions. We find that covariation between aragonite-calcite sea conditions and skeletal composition is time dependent with the Ordovician – Carboniferous showing the best correlation, followed by the Permian, but becomes insignificant for the remainder of the Phanerozoic. We propose a combination of changes in the taxonomic composition and CaCO3 saturation state to explain the observed patterns.
Evolutionary tempo in Permo-Triassic terrestrial amniotes
1University of Bristol
2University of Lincoln
3University of Leeds
Simpson’s ground-breaking “Tempo and Mode in Evolution” laid the foundation for modern phylogenetic comparative analyses. Many studies based on palaeontological datasets focused on the “mode” of evolution, neglecting the equally important “tempo”. Furthermore, most analyses assumed homogeneous evolutionary rates and did not account for potentially variable evolutionary rates.
Here we present the first comprehensive analysis of rates of body size evolution in Permo-Triassic terrestrial amniotes. We show that heterogeneous evolutionary rates are ubiquitous in the fossil record of early amniotes. Exceptionally high rates can be found in various clades of parareptiles and therapsids. Both Parareptilia and Therapsida experience an increase in evolutionary rates through time. Archosauromorphs, on the other hand, follow a homogeneous rate model, even when accounting for different postulated topologies. Elevated evolutionary rates appear to be associated with drastic changes in body size, diet and short-term diversification events. High rates of body size evolution do not seem to confer long-term advantages over competing clades, and might in fact indicate stress in the respective groups. Comparisons with published analyses that did not account for variable rates indicate that those inferences of evolutionary mode might have been biased for various amniote clades (e.g. Anomodontia).
The function of colouration in Confuciusornis
1University of Bristol
Techniques using the morphology of fossilized melanosomes make it possible to reconstruct the colours of melanin-based integumentary patterns and thus provide insight into the ecology and behaviour of extinct organisms. We studied a well-preserved specimen of the Cretaceous bird Confuciusornis to shed light on its palaeobiology. Using data taken from preserved melanosomes, we identified different melanin-based colours of the head, chest, coverts, remiges, and rectrices. Our analyses indicate that Confuciusornis wore grey on most of its body. Our data have implications for signalling. The streamer-like rectrices found on some specimens of Confuciusornis have been hypothesized to play a role in sexual signalling. However, as the rectrices present in the specimen we sampled were grey, our data do not support that pigmentation augmented this purported function. Despite the inferences made here, definitive conclusions on the ecology and behaviour of Confuciusornis cannot be made without a comparison of more specimens. As this taxon potentially exhibits dimorphism in the presence or absence of long rectrices, there is potential for sexual dichromatism. This could be tested in the future by analysing additional specimens.
The Natural History Museum’s Fossil ExplorerApp: A Smartphone application to help non-specialistsidentify common UK fossils
1Natural History Museum
As of September 2017, the app has 6000+ users making 100,000 screen visits. The app has high return usage with and average usage times demonstrating market appetite and practical use. Simple design and user journeys have contributed to its success.
Size change in Chalk Sea echinoids from southern England during the Cenomanian-Turonian extinction event.
1Natural History Museum
2Imperial College London
The Cenomanian/Turonian boundary (CTB) was a time of global change, with mid-latitude seawater temperatures exceeding 27°C, elevated primary productivity, widespread marine anoxia and marine extinctions. Approximately 7% of marine families and 27% of marine genera are thought to have become extinct at this time. Given these climatic and biotic changes, we would expect body sizes of marine animals to become temporarily smaller due to elevated temperatures, lower levels of dissolved oxygen and the post-extinction Lilliput effect. To test this hypothesis, we measured 1659 individuals, representing 6 echinoid orders, spanning the upper Albian to Santonian from sites in southern England, UK. Significant reductions in body size across the CTB were recorded in Saleniidae (Salenioida), Camerogalerus (Discoididae, Holectypoida) and Hemiasteridae (Spatangoida). The Holasteroida also reduced in size, but not significantly. Unexpectedly, Conulus (Conulidae, Echinoneoida) and Cidaroida both increased in size, although this change was not significant in the Cidaroida due to a paucity of Turonian samples. The within-lineage size increase in Conulus is associated with a change in inferred feeding and tiering. Size reductions at family and ordinal level were associated with shifts in taxonomic composition, with apparent loss of larger genera and replacement by smaller genera through time.
The affinity of some peculiar macrofossils from Sirius Passet, North Greenland
1University of Bristol
3Korea Polar Research Institute
4University of Copenhagen
Reflective patches are commonly found in the early Cambrian Sirius Passet Lagerstätte, North Greenland. A very distinct morphotype is characterised by having a prominent ridge and a specific growth trajectory. Analysing specimens ranging from 3.2mm to 180.3mm in length allows classification of the fossils into three morphogroups: oval / quasi-oval, extended and irregular, due to differences in geometry. Due to their peculiar anatomy, we review their likely biogenic status and affinity, including: microbially induced sedimentary structures, rip-up clasts from microbial mats, sponges, placozoans as well as colonial and multicellular cyanobacteria. Some specimens preserve articulated arrays of spicules, suggesting affinities with sponges, while others lack such features. We can reject a fungal, biofilm, or stromatolite affinity as we cannot demonstrate that the adjacent sediments were deformed or sediment was agglutinated, and a placozoan affinity as we observe possible amalgamation in the larger forms. Although these fossils currently have no obvious affinity, they are very distinct, which suggest that these organisms are a new group of organisms with an, as yet, unclear affinity.
Seagrass and the history of cuttlefish
Cuttlefish possibly had an origin in the late Cretaceous and subsequently radiated globally. By the Middle Eocene cuttlefish may have evolved into Sepia s.l. The record of cuttlefish in the New World ceased by the end of the Eocene possibly as a result of climate cooling. The lack of cuttlefish in the New World continues to the present day. Later fossil records are mostly from Europe. Cuttlefish are currently found in seagrass and other environments globally, except for the New World and Antarctica. Rare fossil forms belonging to Belosaepiidae s.l. and Sepiidae are recorded in faunal collections that may have come from the proximity of past seagrass environments. This relationship may have been formed in the late Cretaceous and continues to the present day. The fidelity exhibited may be due to cuttlefish behaviours in seagrass including feeding, protection and reproduction. In particular seagrass acting as nursery may be important.
British Zechstein palynomorphs suggests a wetter Late Permian environment
1University of Sheffield
The Late Permian Zechstein Sea was a semi-isolated inland sea occupying the Southern Permian Basin at equatorial latitudes. The sea endured for 5 to 7 million years during which time it underwent five cycles of evaporation. In the context of an increasingly arid Late Permian climate, classic Zechstein reconstructions show cyclic regressions accompanied by evaporative down draw leading to hypersaline conditions. This resulted in dramatic short term reductions in biotic abundance and diversity in both the marine and terrestrial realms. However, it is hypothesised that transgression phases experienced sufficient precipitation to allow ecosystem recovery in both marine and terrestrial environments.
Palynological investigation of borehole material from northeast Yorkshire has yielded unexpected palynomorph abundance from the Carnallitic Marl Formation in the fourth cycle. The palynomorph assemblage is dominated by taeniate and striate bisaccate pollen accompanied by monosaccates and trisaccates. Typical Late Permian taxa Lueckisporites, Protohaploxypinus, Nuskoisporites, Perisaccus, Klausipollenites, Vittatina, Labiisporites, Vestigisporites and Illenites have been identified and lend support to a transient gymnosperm-dominated late Zechstein vegetation.
The presence of such an abundance of palynomorphs questions previous assumptions that Late Permian equatorial climates were continuously arid. These findings suggest the climate was at times damp enough to support extensive gymnosperm forests.
Ostracod fauna of the Aras Valley section (NW-Iran) indicates sustained oxygenated conditions during the end-Permian mass extinction
1Museum für Naturkunde Berlin, Germany
2CR2P, MNHN-UMPC-CNRS Paris, France
3School of Earth and Environment, University of Leeds, UK
Several drivers, such as global temperature rise, marine deoxygenation and ocean acidification have been suspected to explain the end-Permian mass extinction. Although supportive evidence exists for all three scenarios (e.g. geochemical, sedimentological and palaeontological data), environmental parameters accompanying the extinction are still a matter of debate.
In our study, the exceptionally high ostracod content of the Aras Valley (NW-Iran) section was investigated to examine environmental conditions during the extinction and the recovery phase. The “Boundary Clay” of this section shows a continuous sedimentary succession, deposited after the extinction event in an outer shelf setting. Its investigation yielded a high species richness of 70, belonging to 23 genera, mainly including typical Palaeozoic taxa, such as Palaeocopids, Platycopids of the genera Cavellina and Sulcella, as well as Bairdiidae. Mass occurrences of Praezabythocypris ottomanensis in the upper part of the “Boundary Clay”, correlated to a persistent temperature rise and marking a replacement within the assemblage by Podocopids suggest a changing environment. However, the generally high species richness and high abundance of Bairdioidea, which indicate normal marine conditions, lead to the assumption that anoxic conditions were not significantly affecting the Aras Valley section.
Microbial communities and decay: how their diversity and succession affects the fossil record.
1School of Geology, Geography and the Environment, University of Leicester
2Department of Infection, Immunity and Inflammation, University of Leicester
Understanding decay is fundamental to the correct interpretation of fossils, especially exceptionally preserved soft bodied remains. Decay influences the preservation potential of characters, and it has been shown that patterns of character loss are conserved between related taxa, even under different conditions. These patterns undoubtedly reflect both the nature of soft tissues and the results of microbial decomposition, yet little is known about the latter. Previous work has investigated the formation of bacterial biofilms, how clays affect microbial communities, and patterns of microbial succession in terrestrial vertebrates (in a forensic context), but how the diversity and succession of microbial communities during decay relates to rates and sequences of character loss in unknown. Here we present the first investigation of this problem, documenting the diversity and abundance of whole microbial communities (bacteria, archaea, and fungi) during controlled decay of amphioxus under a range of experimental conditions. Our study addresses important questions regarding both the design of experiments to investigate exceptional preservation, and the degree to which variation in microbial succession controls the sequence and rate of character loss through decay.
Quantitative assessment of evolutionary trends in a late Triassic conodont lineage
1Université Lyon 1
2Institut de Génomique Fonctionnelle de Lyon
A debate still remains about the origin of form in evolutive biology, whether it is driven ‘externally’ by environmental factors and natural selection, or ‘internally’ by developmental constraints. Owing to their long and rich fossil record, conodonts have a great potential for shedding light on this debate. Some recent studies (Jones et al. 2012, Martínez-Pérez et al. 2016) have highlighted how some conodont morphologies/traits might have constituted the basis for functional adaptation to weaker or harder food. Nevertheless, too little is currently known about potential developmental constraints in conodont elements.
Here we scanned and analyzed about 160 P1 elements of three phylogenetic related genera originating from a GSSP candidate Carnian-Norian Boundary located in Sicily. This material has been the focus of an array of recent interesting studies by Mazza and coworkers (Mazza et al. 2012, 2015, 2016). In particular they performed cladistics analyses, and qualitatively described evolutionary trends. Moreover, the material preservation is usually pristine, so its good quality allows such quantitative analyses. Using both Elliptic Fourier contour analysis and landmark or sliding-landmark-based geometric morphometrics, we quantitatively test the suggested evolutionary trends, and identified patterns of covariation through the phylogeny that may reflect underlying developmental rules.
The Downton Bonebed: insights into a lost world.
1University of Portsmouth
The Downton Bonebed is a multitaxic Fossil Concentration-Lagerstätte located in the Platyschisma Shale Member of the Downton Castle Sandstone Formation c. 1.5 m above the Ludlow Bonebed. The Downton Bonebed has received little direct study since its discovery over a century ago. The aims of this study were to catalogue for the first time the fossil contents of the Downton Bonebed, and to look at the sedimentology to define the depositional environment that the bonebed formed in, as well as its wider global context. The bonebed is rich in fossils with a broad diversity of vertebrates, invertebrates, plants and allies, however with each group the diversity is low suggesting that the Downton Bonebed was formed in a restricted environment. The sedimentology reveals evidence of two energy conditions shifting between quiet low energy setting with trace fossils present and periods of rapid burial in which all of the other fossils are found associated with swaley and hummocky cross laminations suggesting large storms. The environmental setting for the Downton Bonebed is a quiet hyposaline inlet/lagoon in close proximity to a terrestrial freshwater source, cut off from the Downton Sea by a barrier or barrier beach.
The palaeobiology of Ediacaran Palaeopascichnus: new insights from morphometric and geochemical analysis
1Department of Earth Sciences, Memorial University of Newfoundland, St. Johns, Canada
2Oxford University Museum of Natural History, Oxford, UK
The Palaeopascichnida are a relatively understudied component of the enigmatic Ediacaran biota. The structure is comprised of series of mm-scale, oval-shaped elements previously interpreted as: evidence of movement; feeding traces; and alternatively as body fossils of various affinities. Palaeopascichnus has been compared to the Xenophyophora, an extant group of large, benthic protists found in deep marine habitats that are characterized by their large size and possession of stercomata within their cells.
The biological construction and test interpretations of phylogenetic affinity for Palaeopascichnus was assessed using material from the Ediacaran of Newfoundland, Canada. Quantitative morphological analysis of 125 well-preserved specimens shows complex branching and well-constrained growth patterns, and multivariate statistical and cluster analysis both identifies natural groupings within that dataset, allowing quantification of similarities with extant taxa. Petrographic analysis combined with SEM backscatter imaging and elemental mapping also revealed enrichment of metallic elements (Ti, Ba, Fe) within the oval-shaped walls that, with morphometric analysis, supports a foraminiferan affinity.
Palaeoclimate analysis of the flora of the latest Eocene Insect Limestone of the Isle of Wight, southern England
1Natural History Museum, London, UK
2Royal Holloway University of London, Egham, UK
The latest Eocene flora from the Insect Limestone, Isle of Wight, is an important representative of British Paleogene vegetation, indicative of European environmental conditions near the onset of global change. New collections, and those in the Natural History Museum, the Dinosaur Isle Museum and made by Andy Yule, have been studied. Plant remains occur in concentrations of debris within an horizon of very fine micrite near the base of the Bembridge Marls Member, Bouldnor Formation, Solent Group. Nearest living relatives of the most abundant fossils are wetland herbs, e.g. Azolla, Sabrenia, and most commonly, Typha. Less common trees and shrubs include representatives of the Juglandaceae, Lauraceae and other flowering plants, with some conifers. Despite fairly poor preservation, detailed drawings of angiosperm leaf architecture combined with multivariate statistics has enabled the recognition of distinct morphotypes. Palaeoclimate inferences are based on physiognomic features of the angiosperm leaves in combination with nearest living relatives. Angiosperm leaf taxa with toothed margins are comparatively rare, suggesting a warm climate. Small leaf size points to low rainfall. Plants such as Acrostichum, Daphnogene, Neolitsea, Palaeocarya, Hooleya are characteristic of warm temperate to subtropical mixed mesophytic vegetation today, whilst sclerophyllous elements (e.g. Zizyphus) suggest drier conditions.
Digital Devonian Dipnomorpha: 3D morphometrics and the phylogenetic impact of endocast characters in dipnomorph fish
1University of Edinburgh
2University of Oxford
3University of Amsterdam
The Dipnomorpha include the extinct Porolepiformes and the extant Dipnoi (lungfish) and, being sister to tetrapodomorphs, are important to our understanding of early sarcopterygian evolution. Cranial endocasts are now known from most stem-sarcopterygian groups including actinistians and tetrapodomorphs, which phylogenetically bracket the Dipnomorpha, and this proliferation of digital endocasts presents a wealth of data that can contribute to resolving phylogenies. Until the polarity of endocast characters can be reliably identified, however, the efficacy of the information they carry remains unclear. Notably, the first digital endocast of a porolepiform, Glyptolepis paucidens, presents difficult questions surrounding the polarity of endocast characters. Recent Devonian lungfish endocasts, alongside Glyptolepis, present an opportunity to conduct 3D geometric morphometrics on a sample spanning the Dipnomorpha to identify informative endocast characters unambiguously and define their polarity. The endocast of Glyptolepis occupies an area of morphospace between that of primitive and derived lungfish, though aligns more closely with derived taxa. With this information, and concerns about the validity of endocast characters in mind, the impact of inclusion of these characters in phylogenetic analyses, and resultant differences in taxonomic resolution, are presented and discussed.
A taxonomic review and phylogenetic analysis of Clevosaurus latidens Fraser, 1993
1University of Bristol
The Rhynchocephalia is a group of reptiles that had a high diversity and morphological disparity in the early Mesozoic. Among Mesozoic rhynchocephalians, one of the most diverse and widely distributed taxa was the genus Clevosaurus; this genus is currently represented by nine species: C. bairdi, C. brasiliensis, C. convallis, C. latidens, C. minor, C. mcgilli, C. petilus, C. sectumsemper and C. wangi. However, during recent years some taxonomic and phylogenetic studies have highly questioned the validity of a number of Clevosaurus species, particular attention has been focused in the three Chinese species as well as in the poorly known C. latidens from the fissure deposits of Cromhall Quarry, England. In order to clarify the taxonomic identity of C. latidens and its possible relationships with herbivorous taxa, we reexamined and recoded characters of type specimens and other associated material. Additionally, we performed a phylogenetic analysis using parsimony and Bayesian approaches. Our results demonstrate that taxonomically C. latidens is not related to Clevosaurus, which is also supported by our phylogenetic analyses that recovered similar topologies for both parsimony and Bayesian approaches that suggests that C. latidens represents a new genus of an early diverging opisthodontian.
Downtown, deeper and down: Aspidella and the bathymetry of Ediacaran taxa.
1University of Hull
The palaeoenvironments in which Ediacaran organisms lived, in particular the bathymetry of these settings, is critical to interpretations of their ecological preferences and biological affinities. A sample of muddy sandstone from the Fermeuse Formation is described here from downtown St John’s, Newfoundland, Canada, which bears specimens of Aspidella terranovica. Sedimentological analysis indicates that the muds and sands were deposited by a mixture of tidal and wave-driven processes in a shallow marine environment. The affinities of Aspidella have long been debated, but the potential that it lived in nearshore settings, in the photic zone, raises broader questions about the ecology and biology of Ediacaran taxa.
Impact of Eocene-Oligocene global cooling on the size of lamniform sharks.
1Univeristy College London
2Natural History Museum, London
Body size is a key attribute in organisms, as it reflects interactions between life history, developmental, physiological and ecological processes. Bergmann’s rule states that body size increases with increasing latitude or decreasing temperatures. The Eocene-Oligocene transition saw an abrupt climatic cooling, recording one of the major shifts in Earth’s climate. Lamniform sharks, a clade which still occupies the highest trophic-level in extant marine ecosystems, lived through that transition, and this study tested whether Eocene-Oligocene cooling drove an increase in the body size of lamniform sharks. In total, twelve morphometric variables from 690 fossil teeth of four genera (Carcharodon, Isurus, Lamna and Odontaspis) were studied. We found significant increases in tooth size across the Eocene/Oligocene boundary in all four genera, supporting the hypothesis that decreases in global temperature lead to increases in the size of marine organisms. Body size and tooth shape are closely linked to diet and feeding ecology. Within each genus, tooth morphospace is distinct in each time bin, and also differs from the morphospace occupied by extant representatives, suggesting significant changes in feeding ecology through time. Techniques used in this study can be applied to other climatic events, to better understand how lamniform ecology changed through time.
Walking in sthenurine kangaroos: armed or not?
1University of Bristol
2University of Oxford
Sthenurines were the “short-faced giant kangaroos” of the Australian Pleistocene. Hindlimb anatomy evidences bipedal striding rather than hopping, and especially rather than the pentapedal (four legs plus tail) slow locomotion of extant kangaroos. What evidence could support the hypothesis that sthenurines did not use their arms like their extant relatives?
Proximal humeral morphology is indicative of forelimb weight-bearing. Terrestrial mammals have larger humeral tuberosities than arboreal ones, for the rotator cuff muscles stabilizing the body over the limb. We obtained 2-D landmark geometric morphometric data on the shape of the proximal humerus of 74 species of extant mammals classified by locomotor mode – arboreal, scansorial or terrestrial – plus 10 extant and 6 extinct species of kangaroos.
Canonical Variates Analysis of the reference group provided 82% correct classification by locomotor mode. Various permutations of entering extant and extinct kangaroos as known or unknown groupings always resulted in a non-overlapping distinction between the two groups: sthenurines tended to cluster with the arboreal reference species when entered as unknowns, and were distinct from all extant mammals when entered as a known group. The results support the hypothesis that sthenurines used their forelimbs in differently to extant kangaroos, and that their arms were not weight-bearing.
Molecules meet fossils – an integrated approach to studying palaeodiversity in cheilostome bryozoans
1Natural History Museum
2University of Oslo
Understanding the processes that underlie diversity dynamics through time is a pivotal quest in evolutionary biology. In the past, these dynamics were commonly reconstructed using either fossil evidence or lineage-through-time plots inferred from molecular phylogenies. In our recently commenced project we integrate both types of evidence to study diversity dynamics in the Cheilostomata, the dominant order of bryozoans in modern marine assemblages which first appeared in the fossil record in the Late Jurassic. We aim to produce a time-calibrated molecular phylogeny of ~300 Recent and a further ~300 fossil taxa. Speciation and extinction rates through time will be inferred from these data using the Bayesian birth-death skyline process. These rates will be tested for trait-dependent diversification associated with key innovations, and density-dependent slowdown of diversification.
Here, we present results of exploratory total-evidence and fossilized-birth-death process analyses using an existing molecular framework of 25 species and newly collated evidence from a further 25 fossil species. Furthermore, we highlight the challenges associated with constructing a morphological matrix for both fossils and Recent taxa for the total-evidence dating methodology, as convergent evolution has been shown to be rife amongst cheilostomes.
Teleosaurids (Crocodylomorpha: Thalattosuchia) from the Toarcian (Early Jurassic) of Luxembourg
1University of Edinburgh
2Musée national d’histoire naturelle Luxembourg
Thalattosuchia was a unique group of marine crocodylomorphs that flourished during the Mesozoic Era, evolving a range of wide feeding specializations and environmental adaptations. One of the two major groups within Thalattosuchia is Teleosauridae, a distinctive clade that superficially resembled modern gharials. They attained a near-globally distribution that frequented shallow marine and brackish ecosystems throughout the Jurassic. Teleosaurids from the Toarcian (Early Jurassic) are commonly found in some European countries, most notably the UK, Germany, and France and are well described in the literature. However, Toarcian teleosaurids from Luxembourg have received little research attention. We studied multiple Toarcian teleosaurids housed in the Musée national d’histoire naturelle Luxembourg (MNHNL), all collected from southern Luxembourg, and highlight their anatomy and diversity. The presence of more common species such as Steneosaurus gracilirostris and S. bollensis, in addition to the enigmatic Platysuchus, shows that multiple European teleosaurid taxa occupied Luxembourg at the same time during the lower Toarcian.
Forgotten phytosaurs of the Germanic Basin
1University of Birmingham
2Natural History Museum of Utah
Phytosaurs are ‘crocodile-like’ reptiles from the Late Triassic (c. 232–201 Mya) with a near-global distribution. In Europe, the Germanic basin yields the most extensive record of phytosaurs in terms of abundance, stratigraphic range and taxonomic diversity; exceeded only by the southwestern USA. However, most historic work has focused on a subset of species from the best-sampled part of the Germanic Basin in SW Germany (Baden-Württemberg).
Here we present taxonomic revisions of two neglected German phytosaur species: ‘Angistorhinopsis’ ruetimeyeri from Lower Saxony and Coburgosuchus goeckeli from Bavaria. These taxa were included in a comprehensive phylogenetic analysis of Phytosauria.
‘Angistorhinopsis’ ruetimeyeri represents the largest European phytosaur specimen, the stratigraphically youngest from Germany, and one of the youngest and most derived phytosaurs worldwide. Like specimens from the Rhaetian of North America, this taxon is robust compared to its close relatives, possibly representing an evolutionary trend in phytosaurs immediately prior to their extinction.
Coburgosuchus goeckeli is contemporaneous with four other Norian phytosaurs from Baden-Württemberg, suggesting this ecosystem could support numerous phytosaur species in a relatively restricted area. European phytosaur taxa do not form a distinct endemic clade and are interspersed with North American taxa in our phylogeny, suggesting high dispersal between these regions.
Ecological niche modelling in deep time: constraining the transitional distribution ranges of reef corals
1Imperial College London
2University of Bristol
3Getech Group plc
Ecological niche modelling (ENM) has been used to predict species distributions in a variety of modern habitats and to evaluate the impact of environmental change. The use of ENM in deep time studies is, however, in its infancy and this largely results from the rarity of global environmental datasets. However, deep time environmental data has recently become available from Earth system modelling, providing an opportunity to incorporate ENM into palaeontology to evaluate bias and biodiversity patterns through time. Using this novel experimental approach, we compared distributional ranges of reef corals between the modern and last interglacial (LIG; 125 ka) to environmental niche distribution calculated using the machine-learning algorithm MaxEnt. Reef coral occurrence data was taken from the Ocean Biogeographic Information System and the Paleobiology Database, whilst environmental data came from the HadCM3 climate model. Our results indicate that warmer temperatures drove LIG reef corals to have a more poleward distribution than their modern day counterparts, supporting previous studies based solely on the fossil record. With validation of this approach, we look to apply this novel methodology to determine the distribution of reefs in older geological intervals, in particular, to understand the cause of the reef gap following the Triassic/Jurassic boundary.
Upware revisited – a fresh look at the ‘coprolites’ of the Lower Greensand (Aptian, Early Cretaceous) in Cambridgeshire
1CASP, University of Cambridge
3Department of Geography, University of Cambridge
A temporary Lower Greensand section and its unconformity with underlying Upware Limestone and Ampthill Clay members (West Walton Formation, Oxfordian, Jurassic) is discussed. For the first time since the cease of commercial ‘coprolite’ workings here in the late 19th century, phosphate-rich Lower Greensand is well exposed. At the base of the Lower Greensand rounded blocks of Upware Limestone are heavily bored by flask-shaped Gastrochaenolites; locally fresh-shelled brachiopods are common; higher-up, Entolium and exogyrine oysters occur; the ammonite Ancyloceras hillsi from earlier collections indicates a Late Aptian age for these indigenous faunas.
The lower 2 m of the Lower Greensand contain three beds rich in reworked phosphatised clasts, many with common Late Jurassic and Early Cretaceous fossil moulds. The clasts vary from fine grained mudrock to very coarse sandstone, and are heavily phosphatised, often rounded and blackened, hence their naming as ‘coprolites’ by early commercial exploiters. True coprolites are rare. The phosphatised faunas so far indicate: Oxfordian: Amoeboceras; Kimmeridgian-Volgian: perisphinctids, Pleuromya; Mid Volgian-Ryazanian: ?Subcraspedites, Dicranodonta, Myophorella, Lyapinella, Rouillieria; Early Aptian: Deshayesites; Mid Aptian: Cheloniceras.
Pleistocene reworking of the Lower Greensand gave rise to poorly bedded sands and pebble beds resulting from collapse of permafrost-bound cliff into ephemeral Fenland flood lakes.
Meiofaunal bioturbation in the late Ediacaran: occurrence and modern analogues
1Department of Earth Sciences, Memorial University of Newfoundland
2Earth & Environmental Sciences Department, Vanderbilt University
3Department of Chemical and Physical Sciences, University of Toronto Mississauga
4Department of Geological Sciences, Stanford University
The Ediacaran—Cambrian boundary is defined by the appearance of the complex trace fossils. A large diversity of ichnotaxa are now known from late Ediacaran strata globally, and typically record simple movement traces of macroscopic metazoans. Recent discoveries of coeval and older meiofaunal traces have the potential to revolutionise not only our understanding of the evolution of the earliest animals, but also of the development of the mixed layer and its influence on early animal evolution and preservation.
We here report wide stratigraphic occurrence of meiofaunal (<0.5mm wide) trace fossils from the Urusis Formation of southern Namibia. These traces are restricted to fine-grained siliciclastic horizons, and vary in length from a few millimetres to a few centimetres. They are typically undulose, recording simple horizontal movement traces, but some traces branch. Density varies from single trace occurrences on a bed to densely bioturbated horizons, occasionally co-occurring with larger traces. Experimental aquaria containing simple ecdysozoans, lophotrochozoans and agglutinating foraminifera test potential modern analogues for the meiofaunal traces, providing critical insight into the diversity and likely behavioural complexity of microscopic trace makers in the late Ediacaran.
Diverse and dense trace fossil assemblages from the Ediacaran of Namibia
1Department of Earth Sciences, Memorial University of Newfoundland
2Earth & Environmental Sciences Department, Vanderbilt University
3Geology Department, University of Saskatchewan
4University of the Free State, Bloemfontein
5Natura Viva cc, South Africa
The Ediacaran—Cambrian boundary records one of the most iconic and fundamental transitions in the history of life. It encompasses the change from the microbially-dominated world of the Proterozoic to the animal-dominated one of the Phanerozoic. Although research has traditionally focused on the Ediacaran macrofauna, it is the trace fossil record that constrains the evolution of early animal bodyplans, diversity, and behaviours.
The latest Ediacaran strata of southern Namibia host a moderate diversity of trace fossil taxa, the majority of which record simple, horizontal locomotion traces. We report here the first association of the macrofossil Vendotaenia in direct association with treptichnid–like traces, recording direct co-occurrence between metazoan bioturbation and a classic Ediacaran taxon. Where bioturbation has been recorded in Ediacaran beds, it is typically not intense, and of low ichnodiversity. In contrast, a thin sandstone interbed near the base of the Spitskop Member (c. 543 Ma) is densely bioturbated and hosts an assemblage of three distinct and disparate ichnogenera, including sediment bulldozing trace fossils, U-shaped burrows, and simple horizontal structures. The diversity and density of bioturbation in this bed is unprecedented for rocks of this age, and likely records colonisation in fully marine settings on the Spitskop carbonate ramp.
Tetriary Conidae malacofauna of Crete (Greece) enriched, with the help of UV light.
1National & Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Dept. of Historical Geology-Paleontology
2Muséum National d’Histoire Naturelle, Département Histoire de la Terre, Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, Paris, France
Residual color patterns of shells have been used for the identification of fossil gastropod species. Many Conus species (Conidae, Neogastropoda) were identified and named using UV light in Miocene deposits of the Paratethys and Proto-Mediterranean.
Our first goal is to create to add new data on Conus species from the Tortonian (Late Miocene) of Crete (Heraklion basin, Greece). This is important for understanding migrations of Conus from the Paratethys and Proto-Mediterranean gateways. A comparison of the faunas (Karaman basin, Karpathian and Cretan areas), will yield results for species paleoenvironment and dispersal in the Late Miocene. A second goal of this work is to collect data on fossil Conidae diversity in Greece from the Miocene through the Pliocene. This will help us understand the evolution of the most diversified genus of marine invertebrates throughout time in a specific area.
Using UV light, a non-destructive method, evidence for the residual color patterns of the fossil shell, is revealed and used for taxonomy. UV light was used on Conidae from the Tortonian of Crete. Over 19 Conus species were identified, many of which are reported for the first time in the Eastern Mediterranean.
Does sample size affect diversity estimates for fossil microgastropods?
1National & Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Dept. of Historical Geology-Paleontology
2Goulandris Natural History Museum, Kifissia, Greece
Micromorphic gastropods (<2cm) are used because of their large diversity that can provide a full picture of faunas that existed in geological times, as well as more reliable data for paleoecology and biostratigraphy. Furthermore, because of their small size, they are more likely to be present in samples of smaller volume. This relation between sample size and diversity is what is being investigated presently with an aim to find which sample size is more suitable for assessing diversity and having reliable paleoenvironmental results.
Samples of three different sizes (small, medium and larger) were used, containing gastropods from the Early Pliocene of Greece (Aghia Triada, S. Peloponese). All samples are taken from the same bed. Diversity was compared to 3 levels: family, genus and species. Variation of specific diversity is plotted for the three samples, and diversity indexes are calculated with an aim of comparing the results of each size sample. The differences in diversity are more striking at the species-level, whereas they are fewer at the family-level. Generic-level seems to be more informative for all 3 samples. The largest sample is the most diverse, as expected, but the medium-sized sample is informative enough for the acquisition of reliable results.
Serpukhovian-Bashkirian (Namurian) ammonoids from the Shannon Basin, western Ireland
2Department of Geology, Trinity College Dublin, Dublin 2, Ireland
33 Sheelin Road, Caherdavin Park, Limerick, Ireland
4National University of Ireland (NUI) Galway, Ireland
Ammonoid assemblages in the Carboniferous Shannon Basin, western Ireland, have not been investigated since the 1950-60s and many of the Serpukhovian-Bashkirian ammonoids occurring there are in need of revised descriptions. Recent, intensive field sampling in the outcrops of the Clare Shale Formation, a deep-water shale sequence, and the Ross Sandstone Formation, a sand-rich, deep-water fan system, has yielded many rich and previously undescribed assemblages of Serpukhovian-Bashkirian ammonoids, mostly preserved as flattened impressions within shale-dominated condensed sections. Systematic data are presented for the following taxa which occur in the basin: Homoceras beyrichianum de Koninck, Homoceras smithii Brown, Homoceras undulatum Brown, Isohomoceras subglobosum Bisat, Homoceratoides prereticulatus Bisat, Homoceratoides varicatus Schmidt, Hodsonites magistrorum Hodson, Hudsonoceras proteus Brown, Reticuloceras pulchellum Foord, and Phillipsoceras paucicrenulatum Bisat & Hudson. Since most specimens are preserved as 2D moulds, particular attention is paid to growth line ontogeny in order to aid future systematic and biostratigraphic work in the Shannon Basin and in coeval Serpukhovian-Bashkirian sections worldwide.
Postembryonic development of Fritzolenellus (Trilobita) from the Cambrian Series 2 strata of Newfoundland
1University of Lausanne
2Freie Universität Berlin
Trilobites of Olenellina were a major component of the Cambrian Series 2 ecosystems and are characteristic by absence of dorsal ecdysial sutures and calcified protaspid stage. Herein we describe postembryonic development of olenelline trilobite Fritzolenellus lapworthi.
Numerous specimens of F. lapworthi were collected in dark-grey shales of the Forteau Formation (Labrador Group, Newfoundland). The material is represented by isolated cephala and by articulated individuals in various stages of their development. The smallest cephala are about 0.95 mm long and 1 mm wide, the largest ones are about 25 mm long and 38 mm wide. The size of the smallest cephala of F. lapworthi is exceeding the size of the smallest known cephala of Olenellus and Nephrolenellus. The morphological changes during the postembryonic development of F. lapworthi comprises mainly the modification of the cephalic shape from sub-circular to semi-circular, expansion of the frontal glabellar lobe, gradual shortening of intergenal spines and prolongation of genal spines. The articulated individuals have five to 15 postcephalic segments preserved and show long macropleural spines. The axial spine is not developed in specimens with less than 15 postcephalic segments.
This research is supported by the Palaeontological Association Callomon Award no. PA-CA201601.
Three dimensional soft tissue preservation of acritarch-like cysts from the Ediacaran Weng'an Biota
1School of Earth Sciences, University of Bristol
2State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences
While undisputed fossil evidence of animals is not known before the Cambrian, molecular clocks estimate animal evolutionary history to extend deep into the Neoproterozoic. The 609 Ma Weng’an Biota of South China provides one of the few Lagerstätten with which to test such estimates and has famously yielded microfossils that have been interpreted controversially as the embryos of animals. The biota is more diverse, however, and not all of its components have been described. Here we introduce a new class of embryo-like fossil characterized by a marginal excystment structure resembling acritarch cysts. The excystment structure varies in its extent, approaching half the circumference at its greatest extent. The majority of the internal volume is comprised of a granular matrix with a variable chemistry reflected in differences in X-ray attenuation. The matrix is permeated by micrometer scale unconnected pores. Many specimens preserve a central inner body, exhibiting a low X-ray attenuation, some with an inner core with a homogeneous high attenuation mineralogy. These central structures are reminiscent of the structures interpreted as nuclei preserved in the embryo-like Tianzhushania from the same samples. We consider the affinity of this new class of Weng’an fossil within protist, algal and animal milieu.
Systematic revision of the family Cothurnocystidae (Echinodermata, Stylophora)
1Lyon 1 University, Villeurbanne, France
2Field Museum, Chicago, USA
The family Cothurnocystidae represents a relatively well-defined group of cornute stylophorans, characterized by a delicate, boot-shaped marginal frame, posteriorly closed by two small skeletal elements (M5-M'5 bridge) on the lower thecal surface. Most cothurnocystids possess typical respiratory structures (cothurnopores) in the right anterior corner of their upper thecal surface. The recent description of a new cothurnocystid from the Furongian of Nevada, USA (Cardiocystella prolixora) and the discovery of new Ordovician cothurnocystids in the Anti-Atlas, Morocco (Fezouata Shale: late Tremadocian; Izzeguirene Formation: early Sandbian) and in Bohemia, Czech Republic (Libeň Formation: early Sandbian) prompted the systematic revision of the family Cothurnocystidae. Four distinct genera can be identified, based on their plate patterns. 'Cothurnocystis' fellinensis (late Tremadocian, Montagne Noire) represents the plesiomorphic condition in cothurnocystids and should be assigned to a new genus. All three other genera are characterized by a more reduced number of skeletal elements: loss of one lateral marginal (Mc) in Arauricystis; loss of A0 in Procothurnocystis; and loss of both A0 and M4 in Cothurnocystis. In this revised systematic scheme, Cardiocystella appears as a junior synonym of Procothurnocystis.
Palaeobiogeographic implications of new scotiaecystid cornutes (Echinodermata, Stylophora) from the Ordovician of the Anti-Atlas (Morocco) and Bohemia (Czech Republic)
1Lyon 1 University, Villeurbanne, France
2Beroun, Czech Republic
Scotiaecystid cornutes form a well-defined clade of Ordovician stylophoran echinoderms, characterized by the possession of a highly distinctive, rhomb-shaped respiratory structure (the lamellate organ), always located in the right anterior corner of the upper thecal surface. Their phylogenetic position within stylophorans is not entirely clarified yet, but they very likely derive from cornutes possessing a proto-lamellate organ (i.e. consisting of numerous, adjoining cothurnopores), as for example in Proscotiaecystis melchiori (Early Ordovician, Montagne Noire). The family Scotiaecystidae comprises the two genera Thoralicystis (Early-Middle Ordovician) and Scotiaecystis (Middle-Late Ordovician). New occurrences of scotiaecystids are reported here from the Anti-Atlas (Fezouata and Izzeguirene formations) and Bohemia (Letna and Vinice formations). They confirm that the palaeogeographic distribution of Thoralicystis is apparently restricted to high-latitude, peri-Gondwanan areas: Anti-Atlas (T. zagoraensis, T. n. sp.), Bohemia (T. bouceki), and Montagne Noire (T. griffei, T. ubaghsi). They also confirm that the same pattern is observed for all late Darriwilian to Sandbian occurrences of Scotiaecystis: Anti-Atlas and Bohemia (S. n. sp.), Brittany (S. guilloui), and Central Iberian Zone (S. jefferiesi). In contrast, the two youngest (late Katian) representatives of the genus Scotiaecystis are both known from Laurentia: northern Ireland (S. collapsa) and Scotland (S. curvata).
Evolution and extinction of the 'Siberian unicorn' Elasmotherium sibiricum
1Natural History Museum
The giant, one-horned rhinoceros Elasmotherium sibiricum was believed to have gone extinct in the Middle Pleistocene, well before the Late Quaternary megafaunal extinction event (50-4 ka). Here we show, by AMS radiocarbon dating of 21 individuals, including cross-validation and single amino-acid dating, that the species survived in Eastern Europe and Central Asia until at least 33,000 years ago, and therefore forms part of the 'late Quaternary megafaunal exticntion'. Stable isotope data indicate a dry steppe niche for E. sibiricum and, together with morphology, a highly specialised diet that likely contributed to its extinction under changing environmental conditions. We further demonstrate, by the first ancient DNA sequence data from the Elasmotheriinae, a very deep phylogenetic split between that subfamily and the Rhinocerotiinae that includes all the living rhinos, corroborating fossil evidence that the two lineages had diverged by the Eocene. As the last surviving elasmotheriine, the demise of the ‘Siberian unicorn’ represents an extinction not just species but at subfamily level.
Paleogene and Neogene Caribbean and South American methane seep communities
1University of Leeds
2University of Leicester
3Queen's University Belfast
4University of Southampton
5The Natural History Museum London
6Naturhistoriska riksmuseet Stockholm
The Caribbean and Northern South American regions have a rich fossil record of methane seep communities from the Paleogene and Neogene. The Caribbean seep communities from Cuba, the Dominican Republic, Barbados and Trinidad range in age from the Eocene to the Pliocene. The South American examples are Oligocene to Miocene in age. Although there are some faunal similarities between the fossil seeps and those from modern seeps in the Gulf of Mexico, the Caribbean and the Pacific and Atlantic sides of Central America, there are also many fossil taxa that are absent from these modern sites. These include large elongate lucinids (e.g. Elongatolucina and Elliptiolucina), large globular lucinids (e.g. Meganodontia and Cubatea), vesicomyids (Pleurophopsis), large thick-shelled bivalves superficially resembling vesicomyids, and tall abyssochrysoid gastropods (e.g. Hokkaidoconcha, Ascheria and Humptulipsia). These gastropods have origins in Mesozoic seeps and are now extinct; some bivalves, such as Meganodontia and the large elongate lucinids, are now only found only in the central Indo-Pacific Ocean; other bivalves were endemic and are now also extinct. These differences show there was considerable biogeographic interchange between the seep faunas of the Pacific and the Caribbean region prior to the closure of the Isthmus of Panama.
Structure and Growth of Heterostracan Bodywall Extensions and the Evolution of Vertebrate Paired Fins
1University of Bristol
2University of Manchester
Paired appendages, alongside jaws, are a key component of the gnathostome bodyplan, yet their evolutionary origin has long courted controversy. Palaeozoic jawless vertebrates show an array of fin-like structures, however, this debate has often neglected the significance of the ability to extend the bodywall laterally. This is a key innovation which must, paradigmatically, underpin the origin of paired fins. We investigate the nature of the earliest lateral bodywall outgrowths, found in heterostracans, and find their structure and perceived development shares fundamental similarities to the dorsal spine in the same taxa. We propose spine growth begins with a rounded tubercle which splits medially, allowing apposition of successive generations of tubercles. This process is facilitated by resorption, which also allows thickening of a compact vascular layer, possibly strengthening the spine. This implies that heterostracan skeletogenesis is more dynamic than previously suggested. We also reconstruct the distribution of paired bodywall outgrowths and find that lateral bodywall extensions appear to have arisen independently at least twice in early vertebrate history. This leads us to suggest that a fin competency region may have been duplicated as early as 542 million years ago.