Annual Meeting 2014: Abstracts of Oral Presentations

* Candidates for the President’s Prize are marked with an asterisk.
Underlined author denotes designated speaker.

Thaumaptilon walcotti and the early evolution of the Cnidaria

Jonathan B Antcliffe¹

¹University of Oxford

The Cambrian Burgess Shale from British Columbia, Canada has provided generations of palaeontologists with new and wonderful puzzles concerning the early evolution of animal life. Thaumaptilon is one of the most intriguing of these as it links to two major problems in early animal evolution. First is the possible connection between enigmatic Ediacaran age (c. 565Ma) taxa such as Charnia and their possible successors such as Thaumaptilon from the Cambrian. It has been thought that if we could understand the relationships of Thaumaptilon to modern animals, then by inference we could understand the relationship of the critically important Ediacaran biota. Second is that Thaumaptilon has been interpreted as an early soft bodied cnidarian. The early evolution of the Cnidaria is poorly understood as Cambrian cnidarians are rare and often poorly preserved. This is particularly problematic as the bilateria appear in the fossil record at the same time, if not even before, the earliest reliable cnidarian fossils. Here new ontogenetic, anatomic, and decay data are presented that aims to resolve these major questions with implications for the earliest evolution of the Cnidaria and the battle between convergent and contingent patterns of evolution in the Cambrian Explosion.

Modelling Functional Morphology and Extinction selectivity in Ammonites.

^*Timothy Astrop¹, Matthew Wills¹, Qilong Ren¹, Michael Carley¹, Sylvain Gerber² and Stefan Angioni¹

¹University of Bath
²University of Cambridge

Ammonites famously survived three major pulses of extinction at the Devonian/Carboniferous, Permian/Triassic & and Triassic/Jurassic boundaries. They radiated rapidly after each of these events via unique trajectories, but ultimately occupied the same regions of morphospace inhabited by their ancestral counterparts. They therefore offer an excellent model system for studying extinction dynamics and the subsequent processes of diversification and radiation. Although traditional Raupian measurements (and cardinal conch parameters) have been successful in identifying trends in conch geometry through ontogeny, linear measurements often miss the more complex aspects of shape associated with the functional biology of the organism. By using a novel sliding semi-landmark morphometric approach we have begun to describe detailed shape trends in the aperture ('living space') of ammonoids and by extension an aspect of their biology throughout ontogeny.

Together with high quality 3D scanning and printing technology, this constitutes a unique set of methods for to investigating how hydrodynamic parameters vary with shell growth patterns and adult morphology across the Devonian/Carboniferous extinction boundary. By using extant analogues to produce biologically sound velocity profiles to explore likely locomotive behaviours for different ammonite  morphotypes in analytical flow-tanks we begin to identify the morphological, developmentaland functional parameters that determine susceptibility to extinction. 

Cladistic analysis of the enigmatic Polychelidan lobsters.

^*Denis Audo¹, Sylvain Charbonnier² and Jean-Paul Saint Martin²

¹Université de Rennes 1, EA 7316 'Biodiversité et Gestion des Territoires'
²UMR 7207 (CR2P) MNHN/UPMC, Département Histoire de la Terre, Muséum national d’Histoire naturelle, Paris, France

Polychelida is an unusual group of decapod crustaceans characterized by their four to five pairs of claws, a flattened body and a reduced rostrum. The systematic of this group is still poorly studied and no phylogenetic analysis focused on fossil species is available. Our study has systematically reviewed all species of fossil Polychelida. Among valid species, all species with well-preserved specimens have been considered in the phylogenetic analysis. Our study includes 37 fossil species and 4 extant species of Polychelida, and is therefore the most complete cladistic analysis to date on this group. Our preliminary results show that Palaeopentachelidae are sister taxa of Eryonidae. Coleiidae and Coleia, respectively the most diversified family and genus, are not monophyletic but correspond to a paraphyletic group from which Tetrachelidae and Polychelidae (the latter comprising all extant species) have been artificially excluded. These new results allows the partial reconstruction of the evolutionary history of polychelidans. For instance, we trace the origin of Polychelidae at least to the Early Jurassic (Toarcian-Aalenian). We also suggest that the well-known shallow-water plattenkalks from the Solnhofen-type localities (Germany) were colonised by groups originating from deeper water settings, such as those of Lyme-Regis (England), Holzmaden (Germany) or La Voulte (France).

Aragonite / Calcite seas and the evolution of biomineralization

Uwe U.B. Balthasar¹

¹Plymouth University

The vast majority of marine invertebrate skeletons are composed of the CaCO₃ polymorphs aragonite and calcite, yet the influence of seawater composition on the evolution of calcareous skeletal composition is poorly understood. Conventional thinking is that a threshold in the marine Mg:Ca ratio determines CaCO₃ polymorph formation with Phanerozoic Mg:Ca oscillations resulting in periods of “aragonite seas” or “calcite seas”: the principal environmental context in which the evolution of biogenic CaCO₃ is assessed. I present data from CaCO₃ precipitation experiments to show that the concept of a distinct threshold is misleading because Mg:Ca ratio and temperature combined result in a Phanerozoic continuum of co-existing aragonite-calcite seas with aragonite-facilitating conditions existing throughout the Phanerozoic in shallow warm-water (>20° C) environments. The comparison between Phanerozoic models of Mg:Ca (expressed as percent of non-biogenic aragonite) and the Phanerozoic occurrence of skeletal aragonite shows that the skeletal composition of reefs tracks the marine Mg:Ca ratio with a lag of 10s of millions of years. This pattern cannot be explained by mass extinctions or changing skeletal mineralogy and thus points to a more complex influence of seawater composition on biocalcification than previously appreciated.

Morphology or environment: factors affecting preservation of the Middle Triassic actinopterygian Saurichthys

^*Susan R. Beardmore¹ and Heinz Furrer²

¹Elgin Museum, 1 High Street, Elgin, Moray, IV30 1EQ
²Paläontologisches Institut und Museum der Universität Zürich, Karl Schmid-Strasse 4, CH-8006, Zürich

Excavations of Middle Triassic strata at Monte San Giorgio (Switzerland-Italy) have famously recovered a range of reptiles described extensively regarding their affinities, morphology and preservation. Less well known but equally diverse is the contemporaneous fish fauna that has yet to be described as thoroughly. To address this, a comprehensive taphonomic study was undertaken using the actinopterygian Saurichthys, a relatively abundant taxon found in the Besano Formation (Anisian-Ladinian) and Cassina Beds of the Meride Formation (Ladinian). Specimens from each horizon were scored for articulation and completeness across 10 anatomical units, the resulting datasets being used to determine a taphonomic model for each and preservational variation through time. Saurichthys showing moderate to high articulation and high completeness occur in both horizons but states of low articulation and moderate completeness are only present in the Besano Formation. The same feature is apparent in corresponding unit plots, suggesting environmental differences between each horizon. An investigation of body length versus articulation and, separately, completeness infers a slight increase in overall preservation with increasing length, suggesting morphology might also have had some influence. Adhesion to substrate, rolling of carcasses and rupture of the body cavity are evident in specimens from both horizons.

Extratropical peaks in Cretaceous terrestrial vertebrate diversity: the influence of primary producers on vertebrate species distribution

^*Mark A. Bell¹, Paul Upchurch¹, Philip D. Mannion², Roger B. J. Benson³ and Anjali Goswami¹

¹University College London
²Imperial College London
³University of Oxford

The Latitudinal Biodiversity Gradient (LBG), a poleward decline in species richness, is well documented in the modern world, but poorly understood. This pattern has been attributed to temperature, seasonality, the geographical extent of landmasses, and other causes. Previous studies have demonstrated that palaeotemperate peaks are prevalent in greenhouse worlds. The Cretaceous, with its global greenhouse conditions and well-constrained climate history, provides an important counterpoint to the modern LBG.

We examine the evolution and causes of the Cretaceous LBG using the most comprehensive dataset of terrestrial vertebrates, comprising ~2500 species. Estimates of latitudinal diversity were calculated at 10^o intervals using Shareholder Quorum Subsampling. Generalized least-squared regression was used to examine the fit of variables representing the latitudinal distribution of fossil sampling, non-marine land area, temperature, and plant diversity.

Species diversity shows a palaeotemperate peak in the northern hemisphere across the entire dataset and for physiological, taxonomic and spatial subsets. Multivariate modelling supports a combination of plant diversity and sampling, with an AICc weight of 0.70, as the best fit to subsampled vertebrate diversity. These results suggest that latitudinal climatic distribution did not directly cause the Cretaceous extratropical peak in terrestrial vertebrate diversity, but that primary producers controlled terrestrial vertebrate distributions.

Repeat colonisation of temporary water-bodies by Early Carboniferous invertebrates

^*Carys Bennett¹, Peter Brand², Sarah Davies¹, Tim Kearsey², Dave Millward², Tim Smithson³ and Mark Williams¹

¹University of Leicester
²British Geological Survey
³University Museum of Zoology, Cambridge

The TW:eed Project investigates the rebuilding of Carboniferous ecosystems following the end Devonian mass extinction. New fossils populate ‘Romer’s Gap’ with a diversity of tetrapods, fish (gyracanthids, lungfish, rhizodonts, actinopterygians and chondrichthyans), invertebrates (malacostracans, eurypterids, scorpions and myriapods) and plants. The fossil-bearing Ballagan Formation was deposited on an extensive low relief, coastal-alluvial, vegetated floodplain, with temporary pools and shallow lakes. Bivalves and ostracods are the most numerous invertebrates in the formation and are here described from the 502 metre thick Norham West Mains Core. Present in over 150 horizons, euryhaline/non-marine Modiolus bivalves and Leiocopida and Podocopida ostracods dominate, with an associated fauna of fish (actinopterygians, chondrichthyans and dipnoans, which likely predated the ostracods and bivalves), and rarer eurypterids, Spinicaudata, gastropods and Spirorbis. The majority of these fossils occur in sedimentary deposits that overlie palaeosols or desiccation horizons, indicating the repeated occupation of temporary pools and lakes after periods of desiccation. Most of the bivalve specimens are juveniles suggesting short-lived aquatic environments. Living freshwater Unionidae bivalves attach to the gills of fish in a phoretic parasitic larval stage, as a mechanism for dispersal. We explore the links between Early Carboniferous fish, bivalves and ostracods in their radiation into these temporary environments.

Dinosaur body size maxima driven by global temperature

Roger Benson¹, Nicolas Campione², Philip Mannion³ and David Evans⁴

¹Oxford University
²Uppsala University
³Imperial College, London
⁴Royal Ontario Museum

Interactions between organismal body and physical climatic variation depend on thermal physiology. For example, mammals acheived their largest body sizes during globally cool intervals. To estimate the relationship between maximum body size and global climate in dinosaurs we used a comprehensive dataset of circa 500 dinosaurian body masses estimated using robust scaling relationships, and compared these to the δ¹⁸O palaeotemperature proxy using time series regression approaches. Dinosaurs acheived large body masses by the Late Jurassic, exceededing 50 tonnes in sauropodomorphs, five tonnes in stegosaurian ornithischians, and three tonnes in allosauroid theropods. Subsequently, ornithischians attained their body size maximum around 15 tonnes, during globally cool intervals in the Early Cretaceous and again in the Campanian–Maastricthian. In contrast, sauropodomorphs attained their body size maximum, exceeding 50 tonnes, during globally warm intervals, in the Late Jurassic and early Late Cretaceous. A strong (R2=0.80), statistically significant (p<0.001) positive correlation between maximum body mass and temperature in sauropodomorphs is distinct from the negative association seen in ornithischians and modern endotherms, and suggests that physiological rates of sauropods were controlled by environmental temperatures (i.e. poikilothermy). Our results indicate distinct evolutionary responses to climate change among major groups of dinosaurs, and suggests that sauropodomorph physiology was distinct from that of ornithischians, and also from that of mammals.

A surfeit of sponges: unexpected Ordovician diversity in central Wales, UK

Joseph P. Botting¹ and Lucy A. Muir¹

¹Independent

Sponges are generally considered to be minor components of Ordovician communities in siliciclastic settings, but this may be an underestimate due to their low preservation potential. The Builth Inlier (Middle and Late Ordovician) yields abundant articulated sponges, providing a unique opportunity to assess the ecological distribution of different sponge groups and to estimate their true palaeobiodiversity.

Long-term fieldwork has more than 100 new sponge species from a range of sites. Clear patterns are evident in the distribution of particular groups, with more derived taxa occupying shallow water, and the more primitive reticulosans dominating offshore communities. One new fauna from intermediate depth contains a diverse protomonaxonid-dominated sponge assemblage resembling that of the Burgess Shale.

Most articulated faunas in the inlier are diverse, with little taxonomic overlap between different assemblages. This indicates higher α- and β-diversity than any other co-occurring group, and/or very low sampling saturation. These factors imply that, despite being the most diverse group known in these deposits, all aspects of their diversity are underestimated. If the Builth Inlier is typical of Ordovician ecosystems in general, then palaeontologists are missing an unexpectedly large component of biodiversity during the Great Ordovician Biodiversification Event.

Global Dinoflagellate Diversity and Temperature Preference Compared to Neogene Climate Development

^*Jamie L Boyd¹, Matthew J Pound², Jim B Riding³, Alan M Haywood¹ and Ruza F Ivanovic¹

¹The University of Leeds
²Northumbria University
³The British Geological Survey

The Neogene (23.03-2.59 Ma) is a period of progressive global cooling, interrupted by the Middle Miocene Climatic Optimum, that led to the glacial-interglacial cycles of the Pleistocene.  We have tested the role of Neogene climate change on the evolution, diversity and biogeography of dinoflagellates. Using the Tertiary Oceanic Parameters Information System (TOPIS) database, 500 globally distributed sites and 28,100 dinoflagellate occurrences from the Neogene have been synthesised.  We found that during the Neogene the number of Warm-Water Species (WWS) reduces in the higher latitudes, but the global diversity of both WWS and Cold-Water Species (CWS) increases.  These results suggest that dinoflagellate evolution, diversity and biogeography is, in part, controlled by climate.  The WWS migrated away from the poles due to the cooling climate and narrowing warm water zone but because more species are thought to originate in the tropics than the poles, we still see a rise in the diversity in the WWS, even as their habitat decreases. This suggests that some of the CWS of today may have originated in tropical regions and then expanded into the higher latitudes.

Deciphering brachiopod origins:  The Cambrian Explosion, small shelly fossils and early evolutionary history of Lophotrochozoa.

^*Aodhàn D. Butler¹, Michael Streng¹, Zhifei Zhang², Russell Garwood³ and Lars E. Holmer¹

¹Uppsala University
²Northwest University, ELI
³University of Manchester

The fossil record of life on earth is strongly biased towards organisms composed of hard parts - biomineralised tissues such as shells or skeletons. The Cambrian explosion, once considered as the initial appearance of life, in fact, partially results from the evolution of hard parts and their seemingly sudden appearance in the fossil record. This event is predated by the appearance of a group of problematic microfossils known as the small shelly fauna (SSF). A consensus has emerged that many of the taxa comprising the SSF are stem-group representatives of extant phyla that emerged during the Cambrian, although this is not without controversy. We provide a review of the current synthesis of tommotiid research including novel data retrieved using SEM and CT scanning techniques that strengthen the purported link of a tommotiid sub-group, the tannuoliniids, with stem-group brachiopods such as Mickwitzia and the acrotretids. Generation of a comparative dataset based on broad high resolution CT sampling of these enigmatic animals has also allowed investigation of patterns of growth and development in these early Cambrian organisms. Determining suites of homologous characters through such a comparative approach allows us to unravel the pattern of tommotiid interrelationships and their affinities to extant Lophotrochozoa.

Craniodental biomechanical character evolution within the Sauropodomorpha, and the influence of dietary evolution on gigantism.

^*D. J. Button^1,2

¹University of Bristol
²Natural History Museum

The Sauropodomorpha included the largest known terrestrial vertebrates and were the first dinosaur group to achieve a global distribution. This success is associated with the early adoption of herbivory by the group; in particular sauropod gigantism has been hypothesized to be related to specialization towards bulk-feeding and obligate high-fibre herbivory. A combination of biomechanical character analysis, osteological and myological reconstruction, finite-element modelling and comparative phylogenetic methods was employed in order to investigate the evolution of herbivory in this clade.

Results identify a functional shift towards increased cranial robustness, increased bite force and the onset of tooth occlusion at the base of the Sauropoda, consistent with a shift towards bulk-feeding.  Convergent trends towards more specialized foraging apparatuses are observed in the Diplodocoidea and Titanosauriformes, potentially relating to ecological expansion of the latter following Diplodocoid extinction.

Modelling of craniodental character and body mass evolution demonstrates that these functional shifts are not correlated with shifts in evolutionary rate; evidence for coincident rate shifts in body mass and craniodental evolution is weak. Instead, the significant correlation of body mass and characters related to bite force and cranial robustness suggest a correlated-progression evolutionary mode, with positive-feedback loops between mass and dietary specializations fuelling sauropod gigantism.

Long snouted lungfish and the variable dipnoan endocranium

Tom Challands¹ and Alexey Pakhnevich²

¹University of Edinburgh
²Russian Academy of Sciences · Paleontological Institute, Moscow

In 1963 Erik Stensiö suggested that the dipnoan brain ‘type’ had developed by the beginning of the Devonian and has not undergone any significant changes since that time. Here we present new data from the endocast of a long-snouted Upper Devonian lungfish, Orlovichthys limnatis from the Orel region of central Russi. This endocast demonstrates, along with other recently described Devonian dipnoan endocasts and endocasts of extant lungfish, that the dipnoan brain cavity is not and has not been held in evolutionary stasis since the beginning of the Devonian. This supports recent interpretations that dipnoan rates of morphological evolution persisted well beyond the Devonian as far as the split between the Neoceratodid-Lepidosirenid lineages. Furthermore, the new data from Orlovichthys presents the most exceptionally preserved hypophysial recess region of any fossil dipnoan shedding light onto the function and homology of this structure in fossil Dipnoi.

Disparity trends in the shell shape of non-heteromorph ammonoids (Cephalopoda)

Matthew E. Clapham¹

¹University of California, Santa Cruz

The shape of non-heteromorph ammonoid shells can be described by simple geometric parameters, enabling quantification of conch shape and assessment of trends in disparity during successive replacements of dominant taxonomic groups, across mass extinctions, and with changes in prey, competitors, or predators. I collated measurements of shell diameter, whorl width and height, and umbilical diameter from published papers, totalling more than 8200 Emsian-Maastrichtian specimens from over 2500 species. I performed principal components analysis on dimensions normalised to shell diameter and quantified the disparity of shell shapes by the sum of variances. Shell-shape disparity peaked in the Early and Middle Permian, dropping precipitously with the shift to ceratite-dominated faunas in the Late Permian. Despite the high diversity of Mesozoic ammonoids, disparity never recovered to Paleozoic values. High Permian disparity partly resulted from the coexistence of prolecanitid and goniatite lineages, which had different shell shapes. However, goniatites alone had much more disparate shell shapes than ceratites or ammonites. Non-heteromorph ammonites rarely re-occupied morphospace characterized by high width:diameter ratio shells, previously occupied by goniatites, perhaps because that ecological niche was instead filled by heteromorph ammonites, by non-ammonoid competitors, or was unfeasible at the larger body sizes typical of ammonites.

Patterns of morpho-functional disparity during the explosive radiation of acanthomorph fishes

^*Roger A Close¹, Matt Friedman¹, Zerina Johansen², Hermione Beckett¹ and Dan Delbarre¹

¹University of Oxford
²Natural History Museum

Three-dimensional fossil fishes from the Late Cretaceous (Cenomanian-Campanian) English Chalk and Eocene (Ypresian) London Clay have been known and collected for nearly two centuries. Despite excellent preservation, fishes from these exceptional localities have received little attention outside of monographs that are all now over 50 years old. The application of computed tomography (CT) has permitted us to efficiently extract considerable new morphological and functional information from large numbers of fossil fishes from the English Chalk and the London Clay. In addition to providing a wealth of anatomical information on early representatives of many major eurypterygian lineages, CT scanning 3D fish crania permits the acquisition of 1) data on morphological shape variation that is lost in compression fossils, and 2) functional and ecomorphological measurements previously only accessible from neontological datasets. Harnessing the mature framework for quantifying feeding ecomorphology in fish allows us to critically test previous hypotheses relating to changes functional diversity between the Mesozoic and Cenozoic in acanthomorph (spiny-finned) teleosts, one of the most successful radiations of modern vertebrates. Using ground-truthed measures of biomechanical performance, we show a substantial increase in acanthomorph cranial functional diversity between the Late Cretaceous and Eocene, corroborating inferences drawn from sparse cranial landmark constellations applied to taphonomically flattened material from other localities.

A diverse late Ediacaran skeletal fossil assemblage from central Spain

^*Iván Cortijo Sánchez¹, Mónica Martí Mus¹, Sören Jensen¹ and Teodoro Palacios¹

¹Universidad de Extremadura, Badajoz

Knowledge of late Ediacaran (ca. 551-541 Ma) skeletal fossils is critical to unravel the earliest evolution of animals, including the acquisition of biomineralised hard parts. However, fossils of this age are scarce and their diversity remains poorly known. Late Ediacaran platform carbonates from the Ibor Group in the area of Villarta de los Montes, central Spain, have recently yielded a diverse skeletal fossil assemblage. Fossils occur as moulds in siliciclastic levels and mineralised (preserving a carbonatic composition or secondarily pyritised or phosphatised) in carbonate beds. The assemblage is dominated by Cloudina, a millimetric tubular fossil consisting of stacked funnel-shaped elements. Two species, C. hartmannae and C. carinata, that differ both in funnel morphology and imbrication pattern, are present. Particularly well-preserved C. carinata have been also found in related olistostromic levels within the Valdelacasa anticline. The Villarta de los Montes assemblage also includes the first Sinotubulites baimatuoensis specimens from north-west Gondwana. Sinotubulites is a millimetric fossil with a tube-in-tube construction and a folded, irregular ornamentation in the outermost layers. Small, winding tubular fossils and flask-shaped fossils similar to Protolagena have been also observed. Such relatively high diversity in a late Ediacaran assemblage has been previously described only from South China.

Enameloid microstructure in sharks and bony fishes: What do we really know?

Gilles Cuny¹, Sébastien Enault², Guillaume Guinot³ and Martha Koot⁴

¹UMR CNRS 5276, University Claude Bernard 1, France
²UMR CNRS 5554, University Montpellier 2, France
³Department of Geology and Palaeontology, Natural History Museum, Geneva, Switzerland
⁴25 Honicknowle Lane, Plymouth, PL2 3QS, UK

Since the German palaeontologist Wolf-Ernst Reif's studies in the seventies, enameloid microstructure has been widely used to differentiate between teeth belonging to hybodont and neoselachian sharks despite a limited taxonomic scope. The recent discovery in cladodontomorph sharks of a Parallel Bundled Enameloid (PBE), a microstructural feature long supposed to be specific to neoselachian sharks has blurred the use of this kind of structure for taxonomic purposes. To this, one should add a number of other recent observations that make the understanding of the evolution of this tissue even more complicated: a typical “triple-layered” enameloid is absent in batomorphs, so that this structure is diagnostic of the Selachimorpha only, and not of the Neoselachii as a whole; the discovery of enameloid microstructures more complex than the usual Single Crystallite Enameloid (SCE) in hybodont sharks; a wide diversity of microstructures among ctenacanth sharks, going from very simple SCE to the presence of PBE; the strong resemblance between the enameloid microstructure of selachimorphs and the acrodine of some actinopterygian fishes. It is thus time to re-assess our understanding of the evolution of this hypermineralized tissue among fishes and to establish whether the current terminology really fits the variations observed.

Palaeoecology of benthic marine communities in the wake of the Late Permian mass extinction event.

^*W.J. Foster¹, R.J. Twitchett² and S Danise³

¹School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth, PL4 8AA. UK; Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD. UK
²Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD. UK
³School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth, PL4 8AA. UK

The Late Permian extinction event was the largest biotic crisis of the Phanerozoic and is associated with an extreme climate warming event. Here, we use multivariate analyses to investigate the temporal and environmental distribution of fossil benthic invertebrates from the Lower Triassic succession of the Aggtelek Kast, Hungary, which was deposited in a mixed siliciclastic-carbonate ramp setting on the northwestern margin of the Palaeotethys Ocean. There were no significant changes in alpha diversity or community structure through the Induan of the study site, and only minor differences with the Smithian. The Spathian communities, however, show significant increases in alpha diversity and the re-establishment of deep infaunal and erect tiers. Furthermore, the Spathian biofacies show a strict environmental control: siliciclastic inner ramp settings are characterised by low diversity assemblages whereas mixed carbonate-siliciclastic shoal to outer ramp settings show the greatest alpha diversity. Ecologically most of the Early Triassic assemblages were dominated by infaunal suspension feeders, apart from the mid-ramp setting during the Spathian which is characterised by slow-moving grazers. Our data, therefore, demonstrate the importance of the depositional environment in the restructuring of benthic communities following the late Permian mass extinction event.

Phylogeny of the barnacles  –  combining molecular and morphological approaches.

Andy Gale¹

¹University of Portsmouth

Models of barnacle evolution have been based largely on evidence from the ontogeny of living forms (“ontogeny recapitulates phylogeny”) weakly supported by the sparse early fossil record of the group. New molecular phylogenies provide evidence of a very different evolutionary history, in which secondary character loss occurred a number of times, contradicting  morphological hypotheses. The molecular approach works very well for this group which has undergone iterative parallel evolution.

However, much of early barnacle evolution is known only from fossil material and there is therefore a need to combine molecular and morphological datasets in order to reconstruct phylogeny. The first step to this approach has been to develop morphological trees which are congruent with the molecular ones; fossils can then be slotted into the morphological trees.

Using this methodology, it has proved possible to reconstruct major events in thoracican history, most notably the origin and early evolution of the sessilian barnacles (verrucomorphs and balanomorphs). The stalked scalpellomorphs are  more problematical, as there is extensive paraphyly, and many taxa have no extant relatives. However, the broad evolutionary history of the group is becoming better known, and major events can be identified.

Use and misuse of cladistic matrices for morphospace analyses

Sylvain Gerber¹

¹University of Cambridge

Morphospaces have become standard tools in palaeobiology to analyse patterns of morphological evolution. Despite their common purpose, morphospaces gather a heterogeneous set of mathematical objects with unequal potential for biological inferences. Here, I focus on morphospaces constructed from discrete character data. These spaces have become increasingly popular in recent years. This trend mostly results from the exaptation of cladistic matrices as input data for carrying out disparity analyses. Cladistic matrices provide morphological descriptions of taxa as combinations of character states and thus appear (if not conceptually, at least mathematically) comparable to discrete character spaces found in numerical taxonomy. Hence, cladistic datasets seem to constitute an abundant source of data readily available for morphospace analyses. Discrete character spaces have been generally described as more flexible than morphospaces capturing continuous shape variation. The discrete coding of morphology allows morphospaces to accommodate more disparate morphologies, and the ability of discrete character frameworks to handle missing data is also often emphasized. This flexibility comes at a cost, however. Discrete character spaces have weaker geometric structures than their reduced-space ordinations suggest, and meaningful uses of distance-based approaches are not guaranteed. In this talk, I highlight some pitfalls and suggest possible ways to avoid them.

Exceptionally preserved Devonian actinopterygian skull presents a new model for early ray-fin evolution

^*Sam Giles¹, Laurent Darras², Gaël Clément³ and Matt Friedman¹

¹University of Oxford
²University of Leicester
³Muséum National d’Histoire Naturelle

Actinopterygians (ray-finned fishes) today account for over half of living vertebrate diversity, but their early evolution, particularly during the Devonian ‘Age of Fishes’, is poorly resolved. Despite recent advances in our understanding of the relationships and evolution of gnathostomes and sarcopterygians, comprehension of actinopterygian origins has changed little since detailed descriptions of Mimipiscis and Moythomasia were published three decades ago. Here we present an exceptionally preserved ray fin from the Late Devonian (Frasnian) of Northern France. This new taxon is represented by a single articulated specimen preserving a near-complete dermal cranium, braincase and articulated mandibular, hyoid and gill arches. The new actinopterygian displays many primitive ray fin characters, such as a notched jugal, short aortic canal bearing a prominent midline notch, long lateral dorsal aortae, an open spiracular canal, and poorly developed ascending processes of the parasphenoid. When combined with endoskeletal data from the braincase of Cheirolepis, the new taxon helps to paint a new picture of primitive ray fin cranial anatomy. Our results suggest that many anatomical aspects of Mimipiscis, which is often used as a model of a primitive actinopterygian, are specialized rather than generalities of the earliest ray-finned fishes. 

A 3D approach: investigating dietary evolution in Archaeocete whales (Cetacea: Archaeoceti) using tooth microtextures

^*Robert H Goodall¹, Mark A Purnell¹, Julia M Fahlke² and Katharina A Bastl³

¹University of Leicester, Department of Geology, Leicester, UK
²Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
³HNO-Klinik der Medizinischen Universität Wien, Forschungsgruppe Aerobiologie und Polleninformation, Vienna, Austria

The major dietary transition in whale evolution was from terrestrial omnivory/herbivory to aquatic piscivory/carnivory. This occurred between the evolution of the earliest Pakicetidae (early Eocene ca. 52.5 Ma) and the emergence of crown group whales near the Eocene/Oligocene boundary (ca. 33.7 Ma). Morphological analysis suggests an extensive mid-late Eocene semi-aquatic stem lineage, preceding obligate aquatic lifestyles in later stem clades. Isotope data suggest a rapid transition to the marine realm. Neither morphological nor isotope data reveal direct evidence of trophic ecology. Recent analysis of low magnification 2D tooth microwear suggests a subtle dietary shift to mixed semi-aquatic diets, similar to modern pinnipeds, in the cetacean stem lineage (early-mid Eocene), but quantitative 3D-microtextural analysis of tooth wear has the potential to reveal more details of ecological transitions in whale evolution. This approach is well established for dietary analysis in terrestrial mammals, but has not been applied to aquatic mammals. Statistical comparison and multivariate analysis of microtextures in extant pinnipeds and odontocete whales (including different dietary ecotypes of killer whale) combined with analysis of early fossil whales shows that microtextures of tooth wear vary with diet in aquatic mammals, allowing us to shed new light on the terrestrial-marine transition in whale evolution.

‘Fish’ (Actinopterygii and Elasmobranchii) diversification patterns through deep time

^*Guillaume Guinot¹ and Lionel Cavin¹

¹Department of Geology and Palaeontology, Natural History Museum of Geneva, Switzerland

Direct reading of raw palaeobiodiversity curves is hampered by various biases affecting the fossil record quality. Hence, analytical approaches are needed to correct observed diversity patterns in order to achieve more realistic pictures of palaeobiodiversity variations. Because phylogenetic trees and stratigraphic ranges of corresponding terminal taxa provide two independent sets of data, comparing both datasets represents a unique way of testing the historical pattern of evolution. Although ‘fish’ groups represent the major component of marine and freshwater vertebrates since the Palaeozoic, patterns of the ‘fish’ evolutionary history remain largely unknown. This talk presents an assessment of various phylogenetic hypotheses for two major ‘fish’ groups: actinopterygians and elasmobranchs. Disparities and resemblances in the fossil record quality of both groups as well as within different ray-finned fish groups are discussed. Corrected family and genus-level palaeobiodiversity patterns are presented, critically reviewed and quantitatively assessed for both marine and freshwater taxa. Possible main drivers of observed major palaeodiversity events over the Meso-Cainozoic are proposed and discussed.

Loriciferan SCFs from the Cambrian of Canada: the origins of a meiofaunal phylum

Thomas H. P. Harvey¹ and Nicholas J. Butterfield²

¹Department of Geology, University of Leicester
²Department of Earth Sciences, University of Cambridge

Miniature animals that inhabit interstitial spaces in sediments (the meiofauna) are scarcely represented in the fossil record, and are often under-sampled in molecular phylogenetic analyses. Therefore, there are few constraints on the timings or mechanisms of their evolution. Here, we report miniature scalidophoran worms, with particular characters of the phylum Loricifera, from the middle/upper Cambrian Deadwood Formation of Saskatchewan, Canada. The specimens (n=72) occur as small carbonaceous fossils (SCFs) extracted using hydrofluoric acid from mudrock. Most specimens consist of an empty cuticular lorica, but a few contain remnants of the introvert appendages (scalids), and one specimen preserves an intact introvert with several hundred scalids. Despite the adult morphology of the introvert, the total body length does not exceed c. 300 µm, suggesting a meiofaunal ecology, as in modern loriciferans. At the same time, the fossils share some characters with extant larval priapulids and extinct “macro-loricate” worms, consistent with loriciferans being miniaturized priapulids. We discuss the implications for ecdysozoan phylogeny and the evolution of the meiofauna.

Using growth models to test the vendobiont hypothesis for the Ediacara Biota

^*Renee S. Hoekzema¹ and Martin Brasier¹

¹Department of Earth Sciences, University of Oxford

Although macrofossils from the Ediacara biota (575-542 Ma) have often been interpreted as containing the ancestors of various different metazoan clades, many were united by Seilacher (1989) into a single clade he called the Vendozoa, on the basis of a shared, ‘quilted pneu’ manner of construction. We here test this ‘vendobiont’ hypothesis by comparing the growth mechanisms of macroscopic branches within three iconic and distinct Ediacaran fossil taxa: Dickinsonia costata, Charnia masoni and Charniodiscus spp. These have often been regarded as representatives of distinct clades. We find, however, that these three seemingly disparate forms share very similar modes of growth, involving not only apical insertion of branches either side of a growth axis but also branches that grew in two distinct stages. For every branch in each of these taxa, we can distinguish a juvenile phase of fast growth and a mature phase of slower inflationary growth, for which the ratio remains similar throughout ontogeny. Our evidence strengthens the view that many macro-organisms of the Ediacara biota should be re-considered as members of a single vendobiont clade, as yet lacking clear relationships with modern metazoan groups.

Eccentric conodonts from extreme environments: specialized biota of late Wenlock (Silurian) sabkhas

^*Emilia Jarochowska¹ and Axel Munnecke¹

¹GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Conodonts are one of the key groups in Palaeozoic biostratigraphy and fossil-based geochemistry. Although biofacies models are well established for late Palaeozoic conodonts, they are nearly lacking for Silurian conodont faunas, resulting in that sea-level and facies control over local conodont diversity is underappreciated. We show an example from the latest Wenlock – the conodont record of this time is dominated by taxa representing highly specialized biofacies, characteristic for restricted, upcratonic settings.

The Ustya Fm. in Podolia, Ukraine, and Rootsiküla Fm. in Estonia represent hypersaline, tidal carbonate settings dominated by dolomite-precipitating microbial mats. These evaporitic, periodically emerged environments were hostile to most skeletal organisms except for rare eurypterids and ostracods. The only organisms to thrive in these conditions were stromatoporoids, porostromate problematica, and calcifying cyanobacteria. These extreme environments are associated with a distinct conodont fauna dominated by diverse species of Ctenognathodus characterized by large and robust elements.

Conodont diversity estimates for the late Wenlock indicate a major drop in the taxonomic richness and shift towards low-diversity assemblages, followed by slow recovery at the Wenlock/Ludlow boundary. These estimates appear to be biased by the coincident eustatic sea level fall resulting in a wider spread of shallow-water depeauperate conodont biofacies and, in extreme cases, monospecific Ctenognathodus faunas.

The cause of late Cenozoic mass extinction in the western Atlantic: insights from sclerochronology

Andrew L.A. Johnson¹, Annemarie Valentine¹, Melanie J. Leng², Donna Surge³ and Mark Williams⁴

¹Department of Natural Sciences, University of Derby, Derby DE22 1GB, UK
²NERC Isotope Geosciences Laboratory, Keyworth, Nottingham NG12 5GG, UK
³Department of Geological Sciences, University of North Carolina, Chapel Hill, NC 27599-3315, USA
⁴Department of Geology, University of Leicester, Leicester LE1 7RH, UK

Heavy late Cenozoic extinction amongst marine molluscs in the western Atlantic has traditionally been interpreted as a consequence of climatic deterioration. However, the pattern of extinction was not the same in the eastern Atlantic, where conditions also became colder. A fall in primary productivity, suggested by a decline in phosphate deposition, may be the real explanation for western Atlantic extinctions. Evidence in support comes from isotopic- and increment-based (sclerochronological) indications of growth rate in Pliocene scallops. A western Atlantic genus that has survived to the present (Placopecten) had the same moderate growth rate in the Pliocene as now, while two genera that became extinct (Carolinapecten and Chesapecten) had growth rates as fast as any known amongst living scallops. Such rapid growth implies abundant food. Selective extinction of a fast-growing species has also been documented amongst Pliocene oysters in the Caribbean region and attributed to a decline in primary productivity. The likely cause of this is the development of the Central American Isthmus and the consequent reorganization of oceanic circulation in the Gulf of Mexico and wider North Atlantic.

Implications for the foraminifera over the Toarcian (Early Jurassic) Oceanic Anoxic Event (TOAE), following development of the freeze-thaw extraction technique

^*Alice E. Kennedy¹ and Angela L. Coe¹

¹The Open University

The Toarcian Oceanic Anoxic Event (TOAE) is marked by the widespread deposition of organic-rich mudrocks and pronounced changes in palaeoenvironmental conditions. The interval between the Pliensbachian-Toarcian boundary and the TOAE is associated with a mass extinction. Microfossils, including foraminifera are highly sensitive to the environment around them and therefore suitable as a proxy for examining the impacts of palaeoenvironmental change. This study has investigated a range of processing techniques for the extraction of foraminifera from organic-rich mudrocks, using samples from the TOAE on the North Yorkshire coast. These included the widely used hydrogen peroxide (H₂O₂) and a modification of the freeze-thaw technique. Those processed with H₂O₂ contained fewer foraminifera, lower diversity and damaged tests (Kennedy and Coe, 2014). In this presentation we will show the results from our modified freeze-thaw technique (Kennedy and Coe, 2014) which call into question the previously observed changes in foraminifera: including size decrease, lower diversity and barren interval associated with the TOAE that may be an artefact of sampling and processing. Our study highlights the importance of high resolution sampling and careful extraction techniques and has implications for other microfossil groups when they are in low abundance. 

High-resolution of the Changhsingian succession in Iran and correlation with China

Dieter Korn¹, Abbas Ghaderi², Lucyna Leda¹ and Martin Schobben¹

¹Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany
²Department of Geology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad-Iran

We investigated the Changhsingian Stage in six sections in the area of Julfa (Aras Valley) for their lithology (petrography and carbonate facies), geochemistry (stable isotopes), conodonts and ammonoids. Revision of the biostratigraphy led to the separation of ten Changhsingian conodont zones and eight ammonoid zones. This refined scheme serves as a basis for studies on the proximate causes of the end-Permian mass extinction. The detailed subdivision of the Changhsingian by means of ammonoids has some potential for the correlation of sections within the Tethyan realm. However, ammonoids have only rarely been used for the correlation of the Transcaucasian/Iranian with the Chinese sections, but nevertheless they played a role in discussions about the completeness or incompleteness of the central Tethyan sections. This resulted in the statement that the Iranian assemblages represent only the lower part of the Changhsingian. Correlation of the Late Permian ammonoid successions in Iran and China reveals major problems, which are rooted in the significant differences of the assemblages on the family level. The morphological differences demonstrate that, in terms of sutural development (notching of individual lobes), the Tethyan forms are even more advanced than the Chinese forms.

Favourable Impressions: Ammonoids Taxonomy and Biostratigraphy in the Carboniferous Shannon Basin, Western Ireland.

^*Anthea Lacchia¹

¹Trinity College Dublin

In the Carboniferous Shannon Basin, Western Ireland, ammonoids are largely preserved as 2D moulds. Taxonomy of 2D ammonoids relies on knowledge of shell ornament which varies with ontogeny.  A detailed study of ontogenetic changes, based on the systematic description of 3D shells, is needed in order to provide robust taxonomic identifications but is not yet available for many ammonoids in the basin, whose fill spans part of the Alportian and Kinderscoutian Substages.

Ammonoids are present throughout the succession, but are concentrated in thin dark shales, which are thought to represent intervals of sediment starvation and are referred to as condensed sections or “ammonoid bands”.

The make-up of the ammonoid assemblages in these bands shows that, while some bands are distinctive and useful in both intrabasinal and extrabasinal correlation, the faunas of others are far more diverse than previously thought. This puts into question the idea of a series of discrete, widespread ammonoid bands in the Namurian Stage, each with a diagnostic assemblage.

The Winneshiek Lagerstätte (Middle Ordovician, Darriwilian) of Iowa yields the oldest known eurypterids

^*James C. Lamsdell¹, Derek EG. Briggs^1,2 and Huaibao P. Liu³

¹Department of Geology and Geophysics, Yale University, New Haven, CT, USA
²Yale Peabody Museum of Natural History, New Haven, CT, USA
³Iowa Geological Survey, University of Iowa, Iowa City, IA, USA

The Winneshiek Lagerstätte, which occurs in the Decorah meteorite impact crater in northeast Iowa, has yielded a diverse fauna including conodont assemblages, early vertebrates, brachiopods, phyllocarids, and large eurypterids. The eurypterids are preserved as carbonaceous cuticle and probably represent exuviae. They are the oldest recorded members of the group, predating the previously known earliest occurrence by about eight million years. Preliminary study of approximately 300 specimens has revealed the presence of at least two species. The ornamentation of the large body segments of the more common species and the nature of fragments of cercal blades indicate an affinity with Megalograptus. The prosomal doublure and posterior appendages, however, more closely resemble those of Carcinosomatidae, suggesting that the species is a basal megalograptid or intermediate between the two groups. The second species appears related to Orcanopterus, another Ordovician predatory form known from Canada. These taxa are relatively derived within eurypterid phylogeny, and their presence in the Middle Ordovician hints at an explosive radiation earlier in the Ordovician or a cryptic Cambrian radiation. Early North American eurypterids appear to be limited to members of two clades and may represent successful immigrants from less well-sampled palaeobiogeographic regions.

Dark and disturbed or just disturbed?  Modelling thermal tolerance to determine habitat preferences in early angiosperms

^*Alexandra P Lee¹

¹The University of Nottingham

Despite more than a century of research, some key aspects of habitat preference and ecology of the early angiosperms remain poorly constrained. Proposed ecology has varied widely—from opportunistic weedy species growing in full sun to slow-growing species limited to the shaded understory of gymnosperm forests. Evidence suggests that the earliest angiosperms possessed low transpiration rates - the gas exchange rates for extant basal angiosperms are low, as are the reconstructed gas exchange rates for the oldest known angiosperm leaf fossils. Leaves with low transpirational capacity are vulnerable to overheating in full sun, favouring the hypothesis that early angiosperms were limited to the shaded understory. Here, modelled leaf temperatures are used to examine the thermal tolerance of some of the earliest angiosperms. Our results indicate that small leaf size could have mitigated low transpirational cooling capacity of many early angiosperms, enabling many species to survive in full sun. We propose that during the earliest phases of angiosperm evolution, angiosperms were not limited to the understorey and that some species were able to compete with ferns and gymnosperms in both shaded and sunny habitats, especially in the absence of competition from more rapidly growing and transpiring advanced lineages of angiosperms.

Automated generation of large phylogenies and a probabilistically time-scaled 1,000-taxon phylogenetic hypothesis for Mesozoic dinosaurs: dating the origins of flight and crown-birds

Graeme T. Lloyd¹, David W. Bapst², Katie E. Davis³ and Matt Friedman⁴

¹Macquarie University
²South Dakota School of Mines and Technology and University of California Davis
³University of Bath
⁴University of Oxford

Generating phylogenies that sample large numbers of fossil taxa remain challenging for palaeontology. Here we outline a novel approach implements several methodological improvements over previous “supertree” approaches, including: 1) increased automation, 2) increased input tree information, 3) inclusion of greater taxonomic data, 4) weighting of non-independent data sets, 5) up-weighting of more recent studies, and 6) safe taxonomic reduction. We apply these new techniques to 663 cladistic analyses of Mesozoic dinosaurs to produce a phylogenetic hypothesis containing over 1,000 taxa.

The resulting tree was used to compare two different phylogenetic dating techniques (cal3 and a novel method that uses successive outgroup ages) to ask: 1) What is the probability that dinosaurs emerged prior to the end-Permian mass extinction? 2) When did avian flight first evolve? 3) When did crown birds originate?

In both cases a pre-Mesozoic origin for dinosaurs cannot be rejected at an alpha of 0.05. Other estimates agree closely, with avian flight estimated at 152.39-172.69 Ma or 156.6-167.9 Ma, and crown-birds estimated at 70.12-107.52 Ma or 70.7-97.8 Ma (95% CIs). This last set of dates is younger than typical molecular clock estimates and suggests elevated rates of molecular evolution at the base of the extant dinosaur radiation.

Post-Chicxulub radiation and dispersal of Worm Lizards (Amphisbaenia)

^*Nicholas R Longrich¹, Jakob Vinther², Alexander Pyron³, Davide Pisani² and Jacques Gauthier⁴

¹University of Bath
²University of Bristol
³George Washington University
⁴Yale University

Amphisbaenians, or worm-lizards, are burrowing squamates that are highly specialized for life as subterranean predators. Their underground existence would seem to limit dispersal, and yet worm lizards are widespread throughout Europe, North America, Africa, South America, and the Caribbean. This pattern was traditionally explained by continental drift, with modern distributions resulting from Mesozoic fragmentation of Pangaea. However, molecular data and fossils suggest a Paleogene radiation. Phylogenetic analysis, combining molecular and morphological data, including fossils from, Europe, Africa, and North America, shows that worm lizards originated in North America, then radiated in the Paleocene in the wake of the K-Pg mass extinction. This scenario requires three trans-Atlantic dispersals: one from North America to Europe, one from North America to Africa, and one from Africa to South America and the Caribbean. Rafting in tree root-balls or in rafts of vegetation is the most likely mechanism of dispersal. The amphisbaenians provide a striking case study in biogeography, and suggest that the role of continental drift in biogeography is overstated. Instead, the patterns seen here support Darwin and Wallace’s hypothesis that the geographic ranges of modern clades result from dispersal, including trans-oceanic rafting. Mass extinctions may facilitate dispersal events by eliminating competitors and predators that would otherwise prevent dispersing populations from becoming established. 

Solving Darwin’s Dilemma? Differential taphonomy reveals tissue biochemistry dependence of mould/cast exceptional fossil preservation

^*Breandán Anraoi MacGabhann^1,2,3, James D. Schiffbauer⁴, James W. Hagadorn⁵, Peter Van Roy⁶, Edward P. Lynch^3,7, Liam Morrison³ and John Murray³

¹Department of Geography, Edge Hill University
²School of GeoSciences, The University of Edinburgh
³Earth and Ocean Sciences, National University of Ireland, Galway
⁴Department of Geological Sciences, University of Missouri
⁵Department of Earth Sciences, Denver Museum of Nature & Science
⁶Department of Geology and Geophysics, Yale University
⁷Geological Survey of Sweden

Molecular palaeontology suggests that animals emerged nearly 800 million years ago—perplexingly, over 200 million years before the oldest known megascopic fossils.  The enigmatic cast-and-mould siliciclastic preservation of these first fossils is widespread in Neoproterozoic deposits, suggesting predominance of taphonomic conditions unlike modern Earth.

However, by examining and comparing fossil eldonids preserved as moulds and casts in the Ordovician Tafilalt Lagerstätte in Morocco, and as compressions in the Burgess Shale, we have shown the former taphonomic mode to depend on the formation of aluminosilicate and/or iron sulphide moulds on specific organic surfaces. This occurs via adsorption of reduced iron ions onto tissues composed primarily of high molecular weight biopolymers which require enzymatic degradation prior to decay, and nucleation of sulphides or aluminosilicates around adsorbed ions. Animals lacking tissues primarily composed of such high molecular weight biopolymers, which must have included the first animals to evolve, thus could not have been fossilized in this style. Understanding the origin and earliest evolution of metazoans will therefore require a focus on alternative modes of fossilization.

Burgess Shale-type preservation of ‘shelly’ metazoans

Monica Marti Mus¹

¹Universidad de Extremadura, Badajoz

Most studies of Burgess Shale-type preservation have understandably focussed on soft-bodied organisms, but ‘shelly’ metazoans are also preserved as carbonaceous films. Common examples include brachiopods, trilobites, spiculate sponges and hyolithids. In such cases, the carbonaceous films are usually interpreted as coherent organic layers that were originally present in the mineralised elements, mostly external sheaths or periostracal layers. Using the example of hyolithids it is shown that these films do not represent original cuticular ‘layers’. Instead, they are a composite carbonaceous compression resulting from the coalescence of all the preservable organic matter originally present in the skeletal element. The diagenetic processes that led to Burgess Shale-type preservation (which involve the polymerisation of organic matter and the loss of original internal structure and chemical integrity of the original tissues) are compatible with, and can account for, the characteristics observed in the fossil films of hyolithid skeletal elements. These observations have general implications for the interpretation of other mineralised organisms, such as the diverse and often problematic Cambrian sponges. The observations summarised in this work suggest that all sponge spicules, regardless their original mineralogy or precise phylogenetic affinities, could be preserved as carbonaceous films.

Systematic excavation in the Lower Ordovician Fezouata Lagerstätte (Zagora area, Morocco)

^*Emmanuel L. O. Martin¹, Ninon Allaire², Abdelfattah Azizi³, Khadija El Hariri³, Khaoula Kouraiss³, Juan Carlos Guttiérez-Marco⁴, Bertrand Lefebvre¹, Rudy Lerosey-Aubril¹, Ahmid Hafid³, Moussa Masrour⁵, Elise Nardin⁶, Bernard Pittet¹, Abel Prieur¹, Emmanuel Robert¹, Peter Van Roy⁷, Jean Vannier¹, Romain Vaucher¹, Muriel Vidal⁸ and Daniel Vizcaïno⁹

¹Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (UMR 5276, CNRS), Université Claude Bernard Lyon 1, Villeurbanne, France
²Laboratoire Géosystèmes (UMR 5217, CNRS) , Université Lille 1, Villeneuve d'Ascq, France
³Faculté des Sciences et Techniques, Université Cadi Ayyad, Marrakech, Morocco
⁴Instituto de Geociencias (CSIC, UCM), 28040 Madrid, Spain
⁵Faculté des Sciences, Université Ibn Zohr, Agadir, Morocco
⁶Géosciences Environnement Toulouse, Observatoire Midi-Pyrénées, Toulouse, France
⁷Department of Geology and Geophysics, Yale University, New Haven, CT 06511, U.S.A.
⁸Département des Sciences de la Terre, Université de Bretagne Occidentale, Brest, France
⁹Maquens, Carcassonne, France

The Lower Fezouata Formation (Lower Ordovician, Morocco) has yielded a remarkably diverse exceptionally-preserved biota, which provides unique insights into the transition between the Cambrian and Palaeozoic Evolutionary Faunas. Until recently, fossils from these deposits were collected from small isolated excavations, the stratigraphic positions of which relative to one another were poorly constrained. These collections were also biased by a greater interest for non-biomineralized fossils. This approach has been fruitful for documenting the diversity of the biota, but it does not permit to explore the spatial and stratigraphic evolution of fossil assemblages. To address this question, we initiated a long-term systematic excavation at Bou Izargane, a locality exposing a 18-m-thick section within one of the two stratigraphic intervals with exceptional preservation recently identified within the Lower Fezouata Formation. Our first campaign has shown that exceptional preservation occurs in three discrete horizons within the section, each preserving an abundant but weakly diverse fauna. These characteristics are suggestive of episodes of environmental stress, as are the presence of abnormally small trilobites or the abundance of stylophorans. Ongoing sedimentological and geochemical studies shall provide new data on the environmental context that facilitated soft-tissue preservation in these deposits.

Evolving phytoplankton stoichiomentry in response to marine-terrestrial interactions: the late Palaeoeozoic "Phytoplankton Blackout"

Ron Martin¹, Thomas Servais², Alexander Nützel³

¹Department of Geological Sciences, University of Delaware, Newark DE 19716, USA

²Géosystèmes, UMR 8217 du CNRS, Université Lille1, SN5, Cité Scientifique, F-59655 Villeneuve d’Ascq Cedex, France

³Bayerische Staatssammlung für Paläontologie und Geologie, Richard Wagner Strasse 10, 80333 München, Germany

The appearance of modern taxa of phytoplankton through the Palaeozoic-Mesozoic transition indicates a major shift in nutrient availability and phytoplankton stoichiometry.   Acritarch abundance and diversity declined toward the end of the Devonian, with no recovery during the Permo-Carboniferous.  Riegel (1996) termed this the “phytoplankton blackout.”  The absence of larger cysts of phytoplankton during the Permo-Carboniferous has been used to infer decreased nutrient runoff and primary productivity (Tappan, 1968), but Martin (1996) inferred just the opposite based on the spread of forests, widespread orogeny, and a broad increase of strontium isotope (87Sr/86Sr) ratios.  Although larger cysts (> 20 µm) are absent in the fossil record, smaller specimens (2-20 µm) are very abundant and diverse (Lei et al., 2013), while benthic filter feeders such as brachiopods and bryozoans and planktotrophic larval stages of gastropods are also present (Nützel, 1998, 2014).  It is therefore unlikely that the apparent scarcity of phytoplankton in the late Palaeozoic indicates a total lack of phytoplankton or low primary production.  We infer that the Permo-Carboniferous marks a time of significant increase in nutrient availability that continued through the Meso-Cenozoic, as also reflected by the nutrient preferences and C:P ratios of the dominant phytoplankton taxa appearing in the Mesozoic. 

Sediment permeability and exceptional preservation within concretions

^*Victoria E. McCoy¹, Robert T. Young² and Derek E.G. Briggs¹

¹Yale University
²Clark Energy Group

Concretions are an important source of soft bodied fossils. In order to determine the controls on exceptional fossilization within concretions, we scored 88 concretion-bearing sites for different states of 11 variables, and analyzed their effects on the presence/absence of soft-tissue preservation using qualitative logistic regression. Fine grained host lithology correlates with the presence of soft-tissue preservation, suggesting that low permeability sediments promote soft tissue fossilization within concretions by 1. inhibiting decay and 2. promoting the precipitation of authigenic minerals.  We tested these two effects with decay experiments on fish tissue in glass beads of three different sizes and therefore of different permeability.   We measured decay using infrared gas analysis and mineral precipitation using micro CT scanning.  The results showed that decay is inhibited and mineral precipitation enhanced in lower permeability sediments. Thus a process of positive feedback promotes exceptional preservation during concretion formation where decay is inhibited and early cementation results in a rapid decrease in permeability.

A fight for survival: Megalodon vs the Great White shark

^*L Mclennan¹ and M Purnell¹

¹Department of Geology, University of Leicester, Leicester, UK

The Great White Shark (Carcharodon carcharias) and the extinct Megalodon (Carcharocles megalodon) have iconic status as oceanic apex predators. Recent research suggests that Megalodon was driven to extinction through dietary competition with Great Whites during the early Pliocene. This hypothesis is controversial, not least because evidence of competitive replacement in the fossil record is extremely rare. Current consensus, based on tooth morphology, is that both species consumed large marine mammals. Tooth morphology alone, however, cannot provide enough evidence for dietary competition between these species. Here we test the hypothesis of dietary competition using newly developed 3D-microtextural analyses of teeth.

Microtextural analysis has never been applied to sharks, but our analysis of extant Lamniform sharks reveals that 3D-microtextures vary with diet. Application of the same methods to Megalodon and Great White shark teeth, from the same sedimentary horizons, allows us to test the hypothesis that their diets were the same, thus addressing the question of dietary competition between the two. This study provides the first non-morphological evidence of diet in Megalodon and Great Whites, and the first 3D-microtextural analysis of fossil shark teeth. This approach opens the gateway for further analysis of dietary influence on evolutionary patterns in fossil sharks.

Non-actualistic Ediacaran conditions drove the formation of Salter’s (1856) Longmyndian discoidal fossils

^*Latha R. Menon¹, Duncan McIlroy², Alexander G. Liu³ and Martin D. Brasier^1,2

¹Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK
²Department of Earth Sciences, Memorial University of Newfoundland, St John's, NL, A1B 3X5, Canada
³School of Earth Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK

Discoidal impressions are often presented as evidence of complex life deep in the Neoproterozoic. This study demonstrates the wide dynamic effect of microbial mats on Ediacaran sediments, and the importance of allowing for non-actualistic processes when interpreting ancient discoidal impressions. The discoidal impressions in late Precambrian rocks of the Long Mynd, Shropshire, UK, were first described in the mid 19^th century by John Salter as evidence of the activity of metazoans. Darwin mentions these ‘traces of life’ below the Cambrian in The Origin. Although their biogenicity has subsequently been debated, they have recently been regarded as showing affinities with the Ediacaran taxa Medusinites, Beltanelliformis, and Intrites. We here present a reassessment of several discoidal forms observed in the c. 560 Ma, marine upper Burway Formation of the Longmyndian Supergroup at Ashes Hollow. We show that all these discs can be explained as surface expressions of a fluid escape regime operating at millimetre scales – far smaller than most injection features – and driven by the sealing effect of microbial mat layers. The mats also influence the shapes of the discoidal impressions, now recognized as pseudofossils. Ornaments such as radial grooves, central bosses, and lobes are insufficient in themselves to demonstrate biogenicity.

Denticle Déjà Vu, and the Evolution of Speed

^*Tom Merrick-Fletcher¹, John D Altringham², Jeff Peakall¹, Paul B Wignall¹, Robert M Dorrell¹ and Gareth M Keevil¹

¹School of Earth and Environment, University of Leeds
²School of Biology, University of Leeds

Thelodont and acanthodian scales exhibit remarkable convergence with those of modern sharks, whose functions include drag reduction, abrasion defence, parasite resistance, and luminescence. Of these, drag-reduction has been a focus in biomechanical and engineering investigations particularly the riblets that ornament the dermal denticles of pelagic sharks. These structures are known to reduce skin friction by up to 10%, improving the efficiency and speed of movement. Modern shark scales have significantly narrower riblet spacing in faster-moving species, implying a functional optimum for higher speeds. Furthermore there is no significant difference between the riblet spacing of fast modern sharks, thelodonts, and acanthodians.

More broadly, scales along the flank may be inducing turbulent flow on purpose to delay boundary layer separation (stall), and reduce wake. To test this, and the efficacy of riblets in fossil taxa, flume studies were performed on plates of rapid prototyped Palaeozoic fish scales. Laser Doppler anemometry revealed that the majority of morphologies did not reduce flow velocity relative to the smooth control plate. This suggests that even without riblets ornamenting the crowns, having a rougher scale surface helps reduce drag. Our results demonstrate that novel and sophisticated drag-reduction adaptations existed at a remarkably early stage of vertebrate evolution.

Recognising the reproductive mode of Fractofusus through spatial analysis

^*Emily G. Mitchell¹, Alex G. Liu¹, Charlotte G. Kenchington¹ and Nicholas J. Butterfield¹

¹University of Cambridge

Fractofusus is one of the most distinctive members of the Rangeomorpha, a clade of fractally branching Ediacaran macroscopic fossils that has defied palaeobiological resolution.  Fractofusus positions were mapped out on three bedding planes (‘D’ and ‘E’ Surfaces, Mistaken Point and H14 surface, Bonavista Peninsula) in Newfoundland, Canada (565-570 Ma), allowing spatial distributions to be analysed and shedding light on their reproductive biology.   For each bedding plane, the spatial patterns of fossils were described using pair correlation functions and the patterns were compared with different types of clustering models. All three of the Fractofusus populations were found to exhibit recurrent, species-specific spatial clustering indicative of reproductive processes.  On ‘E’ and H14 we identified three generations of Fractofusus, but only two on ‘D’.  Where body-size was recorded (H14), Fractofusus specimens in the smallest size class preferentially cluster around those in the medium size class, which preferentially cluster around those in the largest size class.   Comparison of pair correlation functions, cluster directionality and mean cluster radius suggest that Fractofusus grew via a process of stolon-like reproduction, similar to that seen in plants that propagate via asexual runners. The identification of this reproduction strategy represents a fundamental new level of palaeobiological understanding of rangeomorphs.

Turtle diversity in the Mesozoic

^*David B. Nicholson¹, Roger B. J. Benson², Patricia A. Holroyd³, Matthew T. Carrano⁴ and Paul M. Barrett¹

¹The Natural History Museum, London, UK
²University of Oxford, UK
³University of California, Berkeley, USA
⁴National Museum of Natural History, Smithsonian Institution, Washington DC, USA

Turtles have successfully endured for over 220 million years through several major environmental perturbations. Inhabiting marine, freshwater and terrestrial environments, abundant as fossils, with a well-established taxonomy and well-understood habitat preferences, turtles are a model system for studying the responses of ectothermic vertebrates to long-term environmental change. However, few studies have documented long-term trends in richness in the context of sampling biases, biotic events, or environmental change. Mesozoic chelonian occurrences downloaded from the Paleobiology Database (PBDB) (comprising 1706 genus-level occurrences in 1012 PBDB collections) were analysed to remove sampling biases, providing fair estimates of changes in Mesozoic turtle diversity, using Shareholder Quorum Subsampling (SQS). Uncorrected data show a general increase in diversity through the Mesozoic, however the Jurassic and earlier Cretaceous mainly comprises data from Asia and Europe whereas North American records dominate the latest Cretaceous. SQS analyses of continental records indicate that turtle diversity in Early Cretaceous Europe was comparable to the North American latest Cretaceous, suggesting that apparent exponential increase in turtle global diversity through the Cretaceous is an artefact of sampling biases. The sharp increase in North American diversity towards the K-Pg boundary is genuine and matched by a similar increase in Asia.

Derived ornithopod dinosaurs: a case of evolutionary parallelism and convergence

David B Norman¹

¹University of Cambridge

Derived ornithopod dinosaurs were abundant and widespread geographically during the latter half of the Mesozoic Era. Recent discoveries and new research on iguanodontians from the Wealden of southern England have led to alterations to the systematics and implied phylogeny of these dinosaurs. As a consequence it is now necessary to revise current understanding of the taxonomic content of the clade Iguanodontia, and to recognise a distinct higher-order clade of clypeodonts that are divisible into the Hypsilophodontia and Iguanodontia. Hypsilophodontia is a clade that includes ornithopods such as the eponymous Hypsilophodon, as well as rhabdodontids, Muttaburrasaurus and tenontosaurs. In marked contrast, the clade Iguanodontia includes Iguanodon, dryosaurids, camptosaurs and a wide range of styracosternan ornithopods, culminating in the abundant and diverse euhadrosaurs of the Late Cretaceous. Both hypsilophodontians and iguanodontians diversified and produced animals of medium-to-large body size independently; as a consequence these animals display a tendency to converge anatomically because their bodies were subjected to similar biomechanical regimes.

Teasing apart anatomical convergence from the phylogenetic signal is instructive because it offers insights into the processes of biological evolution and diversification within clades of animals that were dominant in the terrestrial environment during the Mesozoic.

Decoupling of the terrestrial and marine record during the Eocene-Oligocene transition

^*Matthew J Pound¹ and Ulrich Salzmann¹

¹Northumbria University

The Eocene–Oligocene transition is a key step from the greenhouse to the icehouse world. Geochemical marine records show both surface and bottom water cooling, associated with the expansion of Antarctic glaciers. However, the global response of the terrestrial biosphere is less well understood. We present a new global vegetation and climate reconstructions of the Priabonian (late Eocene; 38–33.9 Ma) and Rupelian (early Oligocene; 33.9–28.45 Ma) to explore the terrestrial response.

By synthesising 215 pollen and spore localities into an ArcGIS–Microsoft Access database it has been possible to investigate global vegetation changes in response to the Eocene – Oligocene transition. Using presence/absence data of pollen and spores with multivariate statistics has allowed the reconstruction of vegetation groups without relying on modern analogues; such as biomes. The reconstructed vegetation groups show no geographic change from the Priabonian to the Rupelian. Reconstructions of mean annual temperature show no statistically significant difference between the Priabonian and the Rupelian. Our new reconstructions differ from previous global syntheses and our terrestrial based climate reconstructions are in stark contrast to marine based climate estimates. Our results raise new questions on the nature and extent of global climate change at the Eocene–Oligocene transition.

Function and evolution of theropod jaws

Emily J Rayfield¹, Roger BJ Benson² and Philip SL Anderson³

¹University of Bristol
²University of Oxford
³Duke University

Ecomorphological variation can be used as a proxy for variation in feeding ecology in extinct animals, where behaviour cannot be directly observed. Whether inferences from ecomorphology are congruent with inferences of feeding behaviour from biomechanical analysis within clades is unclear. Here we use Geometric Morphometrics (GMM) and finite element (FE) modelling to discern the variation in mandibular shape and function in non-avian theropod dinosaur taxa. Six two-dimensional landmarks and 50 semilandmarks were used to capture the variation in jaw shape from 103 taxa. Principal Component Analysis (PCA) demonstrates that the largest proportion of variation is explained by changes in jaw robustness (mandibular length and depth), with a change in the relative size of coronoid process playing a key role. Oviraptorids are morphologically and biomechanically distinct to all other taxa in the analysis (NPMANOVA, p<0.05). There is some partitioning of taxa based on feeding ecology, with supposed omnivorous and herbivorous taxa occupying statistically distinct regions of morphospace from carnivorous taxa (NPMANOVA, p<0.05). We find that jaw strength is tied to morphological variance, and demonstrate how changes in morphology influence the feeding capabilities of the theropod jaw. 

Epibioses of fossil crustaceans: insights on specific palaecoecology and true palaeosymbioses

^*Ninon Robin¹, Sylvain Charbonnier², Barry Van Bakel³, Sylvain Bernard⁴, Jennyfer Miot⁴ and Gilles Petit¹

¹Muséum national d'Histoire naturelle, Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements CNRS-MNHN-UPMC. 8, rue Buffon, 75005 Paris.
²Muséum national d'Histoire naturelle, Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements CNRS-MNHN-UPMC.8, rue Buffon, 75005 Paris.
³Oertijdmuseum De Groene Poort, Bosscheweg 80, NL-5283 WB Boxtel.
⁴Université Pierre et Marie Curie, UMR 7202, CNRS-MNHN-UPMC-IRD, Institut de minéralogie, de physique des matériaux et de cosmochimie. 4 place Jussieu, 75005 Paris

Because their study may reveal possible palaeosymbioses, organisms fossilized in direct association deserve a true consideration. However, their syn-vivo or post-mortem nature is not always obvious. Focusing on decapod crustaceans as hosts, we report here two studied kind of epibioses: a case of post-mortem meeting which brings insights on the palaeocology of associated organisms, and a true palaeosymbiosis. The first epibiosis involves one of the earliest brachyuran crabs of the world and two bryozoan colonies fixed on its dorsal side. We described this precious Bathonian crab (Sarthe, France) and placed it within the Homolodromioidea. Systematic, sizes and structures of the bryozoan colonies demonstrates their post-mortem settlement on the crab, what enabled to conclude on a probable higher thickness of the carapace of Homolodromiodea in the past than today. A cohabitation of hermit crabs in the palaeoenvironment of this crab may also be presumed. The second epibiosis, described in both fossil (La Voulte Lagerstätte, France) and extant record, involves calcifying bacterial colonies living on Penaeoidea shrimps. This association has been identified as a syn-vivo one, and shows even parasitic features. These studies show the ability of punctual fossil epibioses to reveal aspects of both palaeoenvironments and life habit of associated organisms.

Unlocking geological and sea level biases reveals cryptic evolutionary history of early vertebrates

Robert Sansom¹, Emma Randle¹ and Philip C. J. Donoghue²

¹University of Manchester
²University of Bristol

The fossil record of early vertebrates has been influential in elucidating the evolutionary assembly of the gnathostome bodyplan. Understanding of the timing and tempo of vertebrate innovations remains, however, mired in a literal reading of the fossil record. Early jawless vertebrates (ostracoderms) exhibit restriction to shallow-water environments. The distribution of their stratigraphic occurrences therefore reflects not only flux in diversity, but also secular variation in facies representation of the rock record. Using stratigraphic, phylogenetic and palaeoenvironmental data, we assessed the veracity of the fossil records of the jawless relatives of jawed vertebrates (Osteostraci, Galeaspida, Thelodonti, Heterostaci). Non-random models of fossil recovery potential using Palaeozoic sea-level changes were used to calculate confidence intervals of clade origins. These intervals extend the timescale for possible origins into the Upper Ordovician; these estimates ameliorate the long ghost lineages inferred for Osteostraci, Galeaspida, and Heterostraci, given their known stratigraphic occurrences and stem-gnathostome phylogeny. Diversity changes through the Silurian and Devonian were found to lie within the expected limits predicted from estimates of fossil record quality indicating that it is geological, rather than biological factors, that are responsible for shifts in diversity. Environmental restriction also appears to belie ostracoderm extinction and demise rather than competition with jawed vertebrates.

A global perspective of the Trigoniida (Bivalvia: Palaeoheterodonta), with a focus on their Mesozoic and Cenozoic representatives

^*Simon Schneider¹ and Simon R K Kelly¹

¹CASP

The Trigoniida Dall, 1889 are a globally important group of dominantly marine Bivalvia, which had their acme during the Mesozoic, when they played an influential role in shallow marine communities. The anticipated revision of the bivalve volumes of the 'Treatise' has fostered the authors’ attempt on a global genus-level systematic arrangement for the Mesozoic and Cenozoic Trigoniida. Currently, classification is not based on rigid phylogenetic analysis, but on qualitatively defined apomorphies. Nevertheless, it allows for identification of several palaeogeographically and stratigraphically well-constrained clades. Other clades, in particular the Myophorellidae and Pterotrigoniidae are considerably less resolved and their subdivision is controversially discussed, mainly due to conflicting genus-level concepts. A circum-Pacific origin seems obvious for most of the Triassic clades of the Trigoniida. Subsequently, the break-up of Pangaea and later Gondwana created space for global expansion across shelf seas. At the same time, isolation forced more localized radiations of several groups. We present chronostratigraphic range charts for the genera currently recognized as valid, supplemented by palaeogeographic distribution maps for selected taxa. We further exemplarily discuss difficulties of generic assignment in the Myophorellidae. Finally, we propose a revised classification for the Trigoniida that is put up for discussion.

The role of microbial anaerobic respiration in the end-Permian mass extinction

^*Martin Schobben¹, Alan Stebbins², Abbas Ghaderi³, Harald Strauss⁴, Dieter Korn¹, Robyn Hannigan² and Christoph Korte⁵

¹Museum für Naturkunde, Leibniz Institut für Evolutions- und Biodiversitätsforschung, Invalidenstr 43, D-10115 Berlin, Germany
²School for the Environment, University of Massachusetts Boston, 100 Morrissey Blvd, Boston, MA 02125, US
³Department of Geology, Faculty of Sciences, Ferdowsi University of Mashhad, Azadi Square, 9177948974 Mashhad, Iran
⁴Institut für Geologie und Paläontologie, Westfälische Wilhelms Universität Münster, Corrensstraße 24, 48149 Münster, Germany
⁵Department of Geosciences and Natural Resource Management, University of Copenhagen, ØsterVoldgade 10, DK-1350, Copenhagen, Denmark

Changes in plankton productivity have been connected with the end-Permian mass extinction. A box-model – proxy data comparison suggests that an increase of microbial sulphate reduction (MSR) can explain excursions in δ³⁴S_CAS and δ¹⁸O_CAS. These fluctuations are contemporaneous with the biodiversity crisis and are probably related to enhanced availability of organic substrates. This caused MSR to increase proportionally and induce the observed positive δ¹⁸O_CAS excursion. The scenario would only require an increase in the oceans organic carbon inventory – a suggestion that can be linked to the climate warming and elevated continental weathering at that time. These physical processes are linked to the short-term carbon cycle, as ocean fertilization by nutrient input stimulated primary productivity.

Enhanced microbial activity can be regarded as the killing agent because of increased oxygen consumption (aerobic respiration) and H₂S (MSR) production. This caused a rapid global expansion of euxinic water and resulted in iron limitation in the ocean water. This, together with decreased iron supply due to a change in fluviatile regimes, reduced pyrite burial, explaining a negative δ³⁴S_CAS excursion. This suggests that the latest Permian ocean was not dead (‘strange love ocean’) but rather alive, and that microbial life can create adverse conditions for eukaryotic organisms. 

Rudist myophores: constructional constraints and phylogenetic informativeness

Peter W. Skelton¹

¹The Open University

Molluscan muscle/shell attachment is mediated by adhesive epithelium, which secretes a collagenous ‘tendon sheath’ bonded to the shell by embedded fibres.  Serial detachment and re-attachment of muscle fibres allows growth migration of the muscles across the epithelium. But tendon sheath adhesion to the shell constrains normal growth of the latter.  Hence, for the adductors to maintain their relative positions in the shell during growth, the insertion surfaces must remain coplanar with their growth trajectories.  In most bivalves, muscle scars thus lie flush on the inner valve surfaces, tracking the radial growth of the valve margins. 

Primitive rudists maintained this pattern, albeit with the posterior adductor migrating helicospirally along myophoral ledges that limited the muscle’s length.  With further muscle shortening the myophores became flat extensions of the hinge plates. But with the onset of uncoiled valve growth accompanying ligamentary invagination, the adductor insertions had to tilt away from the commissural plane to allow them to track the now orthogonally growing valve margins.  Different clades of uncoiled rudists followed contrasting options for such myophoral tilting.  Each re-arrangement proved virtually irreversible, however, so imparting a reliable phylogenetic signal, as illustrated for example by contrast between the caprinoid families Caprinidae and Caprinuloideidae.

A new problematic colonial organism from the Cambrian of Morocco

Christian Skovsted¹ and Sebastién Clausen²

¹Swedish Museum of Natural History
²UFR Sciences de la Terre, Université Lille 1

A large number of minute colonial fossils have been found in the Cambrian Brecce a Micmacca Limestone at Lemdad in the High Atlas Mountains, Morocco. The fossils are formed by replacement and/or infill of iron oxides and most specimens are represented by internal moulds of the cone-shaped internal cavity of individual elements, often with triangular or quadratic cross-sections. Individual elements were closely juxtaposed and arranged in sub-parallel or radiating bundles that were attached to larger skeletal elements (eg. trilobites or archaeocyathans). The largest composite specimens contain more than 20 individual elements.

The new fossils resemble some poorly known Cambrian colonial organisms such as Labyrinthus Kobluk, 1979 and Rosellatana Kobluk, 1984 which has been compared to corals. However, the Moroccan specimens are preserved in a fundamentally different way compared to previous accounts, allowing better resolution of important internal structures. These include potential connecting structures between individual elements and the origination of the colony as well as the addition of new elements during growth which can be studied in three dimensions. Thanks to the new data it is possible to evaluate the suggested affinity of these problematic fossils to corals and elucidate their potential role in the early evolution of the Anthozoa.

A quantitative comparison of dispersed spores/pollen and plant megafossil assemblages from a Middle Jurassic plant bed from Yorkshire, UK

^*Sam M. Slater¹ and Charles H. Wellman¹

¹Department of Animal and Plant Sciences, University of Sheffield, UK.

Detailed quantitative data has previously been collected from palaeobotanical plant megafossil assemblages from a Middle Jurassic (Aalenian) plant bed from Hasty Bank, North Yorkshire, UK. We conducted a similar analysis of palynological dispersed sporomorph (spores and pollen) assemblages collected from the same section using the same sampling regime. Both dispersed sporomorph and plant megafossil assemblages display consistent changes in composition, diversity and abundance through time. However, the dispersed sporomorph and plant megafossil datasets provide conflicting evidence for the nature of the parent vegetation. Multivariate analysis of sporomorph occurrence/abundance and palynofacies data suggests that temporal variation in sporomorph/plant megafossil assemblages is the result of depositional change between claystone, siltstone and grey clay lithologies, which reflect discrete depositional environments and different vegetation types. The reproductive strategies of parent plants are considered to be a principal factor in shaping many of the major abundance and diversity irregularities between dispersed sporomorph and plant megafossil data sets that seemingly reflects different parent vegetation. Preferential occurrence/preservation of sporomorphs and equivalent parent plants is a consequence of a complex array of biological, ecological, geographical, taphonomic and depositional factors that act inconsistently between and within fossil assemblages, which results in significant discrepancies between data sets.

Hallucigenia’s head and the Cycloneuralian ancestry of Panarthropoda

^*Martin R. Smith¹ and Jean-Bernard Caron²

¹University of Cambridge
²Royal Ontario Museum & University of Toronto

Hallucigenia is the most stubbornly problematic of the Cambrian’s palaeontological enigmas.  Although its affinity has recently been resolved – its claws place it in the onychophoran stem group – fundamental problems remain, not least the question of which end represents its head.

This question is at last resolved by our detailed analysis of all available material from the Burgess Shale, including dozens of new specimens collected by the Royal Ontario Museum.  A pair of simple eyes demonstrate that Hallucigenia boasted visual capabilities similar to modern onychophorans’; they imply an independent origin of vision in each panarthropod phylum.  A differentiated foregut occupies an elongate neck, with a ventrally oriented terminal mouth.  The animal’s mouthparts comprised circumoral spines and pharyngeal teeth; the arrangement of these scalids recalls the foregut armature of cycloneuralian worms (Priapulida + Nematoida).  In light of Hallucigenia’s phylogenetic position, this suggests that the panarthropod pharynx is a derived homologue of the cycloneuralian introvert.  This interpretation provides palaeontological support for a molecular hypothesis which interprets cycloneuralians as paraphyletic with respect to panarthropods.

Chondrichthyan diversity and distribution in the Early Carboniferous: new evidence from the Tournaisian of northern Britain

Timothy R Smithson¹, Kelly R Richards¹, Rebecca Bennion¹ and Jennifer A Clack¹

¹University of Cambridge

The end-Devonian extinction event marked a profound change in the diversity of fishes. The dominant Devonian taxa, the acanthodians, placoderms and sarcopterygians, were suddenly replaced by minor components of the fauna, the actinopterygians and chondrichthyans. This replacement began in the Early Carboniferous but the evidence for it is poor.  Until recently, the earliest Carboniferous chondrichthyans were known mainly from teeth from localities in China, Russia and North America.  In the UK, the entire Tournaisian chondrichthyan fauna was represented by two teeth. Collecting at two new sites in the Scottish Borders has uncovered an extraordinarily diverse fauna of chondrichthyans. Represented by well-preserved cladodont, xenacanth and bradyodont teeth, most of the taxa are new and undescribed. The bradyodont teeth have been found in large numbers and exhibit a broad range of shapes and sizes. This is adding to growing evidence that, in the UK, immediately after the end-Devonian extinction, a durophagous feeding habit was common. The UK Tournaisian bradyodonts were much larger than their younger relatives from the later Carboniferous. In contrast, the cladodont and xenacanth sharks were relatively smaller. All known Tournaisian chondrichthyan sites are in tropical palaeolatitudes, suggesting that sharks may have had a restricted distribution following the extinction event.

An exceptional three-dimensionally preserved Pararaucaria (Cheirolepidiaceae) ovuliferous cone from the late Jurassic of Southern England: non-destructive recovery of full anatomical and histological detail using Diamond Light Source synchrotron.

^*Alan R.T. Spencer¹, Paul Kenrick², Dave C. Steart², Russell J. Garwood³, Jason Hilton⁴, Martin Munt² and John Needham⁵

¹Imperial College London, London, United Kingdom
²Natural History Museum London, London, United Kingdom
³The University of Manchester, Manchester, United Kingdom
⁴University of Birmingham, Birmingham, United Kingdom
⁵[Non-Institutional], Tisbury, Wiltshire, United Kingdom

The Cheirolepidiaceae are an extinct group of conifers with an extensive Mesozoic fossil record well-documented by foliage, wood, pollen and reproductive organs. Three-dimensionally preserved Cheirolepidiaceous ovuliferous cones are rare, with few known species. Here we use X-Ray computed micro-tomography at the Diamond Light Source Synchrotron (Oxfordshire, UK) to non-destructively image the internal anatomy of a recently discovered petrified ovuliferous cone from a Jurassic (Tithonian ~145 Ma) forest in southern England. The cone is derived from a suite of silicified plant materials, most of which were permineralised in situ in a hyper saline lagoonal setting during a shallow transgressive phase.

Tomographic datasets were used to fully describe the histology of the cone and produce three-dimensional models of the gross morphology. These images revealed a remarkable degree of information on the internal tissues of the cone by resolving cellular level details.  The results demonstrate that the cone belongs to the extinct genus Pararaucaria (Cheirolepidiaceae) that has only previously been reported from South and North America, and forms only the fourth species to be systematically described.  This new species extends the known geographic range of Pararaucaria to the Europe and emphasises the wide distribution of Pararaucarian conifers during the Jurassic.

Oxygen, age and facies controls on the appearance of Ediacaran and Cryogenian macroscopic fossils in the Mackenzie Mountains, Northwest Territories, Canada

^*Erik A Sperling¹, Calla Carbone², David T Johnston¹, Guy M Narbonne² and Francis A Macdonald¹

¹Harvard University
²Queens University

The causes behind the appearance of abundant macroscopic fossils at the end of the Neoproterozoic remain debated. Iron geochemical analysis of fossiliferous Ediacaran successions in Newfoundland suggested that first appearances there were correlated with an oxygenation event. A similar relationship was claimed to exist in the Mackenzie Mountains, Canada, although recent stratigraphic studies indicate the sections analyzed for geochemistry were incorrectly correlated with those hosting the fossils. To directly connect fossils with geochemistry, we conducted a multi-proxy iron, carbon, sulfur, and trace element geochemical analysis of the sections hosting the Cryogenian ‘Twitya discs’ at Bluefish Creek and Ediacaran fossils at Sekwi Brook. There is no oxygenation event correlated with the appearance of macroscopic body fossils in either section, or simple bilaterian burrows in the Blueflower Formation, although partial oxygenation appears correlated with increasing burrow width higher in the Blueflower. Data from Sekwi Brook suggest that these organisms were periodically colonizing a predominantly anoxic basin, and requires assumptions of differing timescales between redox proxy data and ecological responses in order to reconcile fossil and geochemical data. Thus, hypotheses directly connecting ocean oxygenation with the appearance of macrofossils may be too simplistic or not apply to all areas of a heterogeneous Ediacaran ocean.   

Minerals in the gut: Scoping a Cambrian digestive system

^*Katie M. Strang¹, David A T. Harper¹ and Howard A. Armstrong¹

¹University of Durham

The Sirius Passet Lagerstätte of North Greenland contains exceptionally-preserved fossils, including an abundance of iconic arthropod and other gut tracks. Understanding the taphonomy leading to this preservation is key to accurately reconstructing these past ecosystems. High-resolution photography, Scanning Electron Microscopy, EDAX and elemental mapping have been carried out on a variety of gut specimens from this Cambrian locality to determine the exact mode of preservation. Preliminary results show a high concentration of Ca₃(PO₄)₂ and SiO₂ present in the mid gut glands and surrounding appendages. It is postulated that the precipitation of calcium phosphate is a result of an initially high organic content in the organisms’ digestive tracts. Further analysis is revealing more information regarding the distribution of elements relating to the gut morphology, allowing a clear taphonomic pathway to be developed and providing an insight into the trophic relationships of this Early Cambrian Lagerstätte.

Fungal and fungal-like interactions with plants in early terrestrial ecosystems : state of the art and future direction

^*Christine Strullu-Derrien¹ and Paul Kenrick¹

¹Department of Earth Sciences, The Natural History Museum, London, UK

Fungi were of key importance to the early evolution of life on land, yet direct fossil evidence of plant fungal interactions is still limited. Fossil evidence of fungal-like microorganisms (oomycetes) is rarer still. We are investigating the evolution of these relationships through re-examination of historic slide collections and through the analysis of new materials, focussing on the Devonian and Carboniferous Periods. Our general approach is to compare and contrast the nature of the interactions in pre- and post-arborescence ecosystems. We are using a suite of methods, including Confocal Laser Scanning Microscopy. Results show that historic slide collections harbour a hidden diversity of plant-associated microorganisms. Recently, we have documented a new form of mycorrhizal relationship in the Rhynie Chert involving Mucoromycotina, overturning the paradigm that early symbioses involved exclusively Glomeromycota. Our analysis of Carboniferous seed ferns provides the earliest evidence of parasitism in oomycetes.  A new putative oomycete from the Rhynie chert will be presented showing the difficulties encountered in discriminating oomycetes from fungi. Generating new data on fossil fungi and fungal-like microorganisms provides much needed direct evidence for the calibration for molecular clocks and is crucial to developing our knowledge of the impact and diversity  of interactions in ancient ecosystems.

Puckered, Woven and Grooved: the Importance of Substrate for Ediacara Paleoecology, Paleoenvironment and Taphonomy

^*Lidya G. Tarhan¹, Mary L. Droser² and James G. Gehling³

¹Yale University
²University of California, Riverside
³South Australian Museum

The Ediacara Biota, Earth’s earliest complex, macroscopic, multicellular ecosystem, is preserved in terminal Ediacaran strata worldwide. In the Ediacara Member of South Australia, Ediacara fossil assemblages occur in intimate association with iterated or patterned macroscopic organosedimentary structures, known as “textured organic surfaces” (TOS). These widespread surfaces encompass considerable variability in size and complexity and likely included densely packed eukaryotic as well as prokaryotic benthic communities.

We documented considerable heterogeneity in the composition and facies of Ediacara fossil assemblages through systematic sedimentary and paleoecological analysis of 27 fossiliferous beds (>300 m²). Particular TOS commonly occur in association with distinct fossiliferous facies. For instance, the TOS “weave,” which consists of iterated rectilinear elements branching at acute angles, occurs only along amalgamated, sandy, storm-deposited event beds. Conversely, “micropucker,” which consists of discrete patches of closely-packed dimples, occurs only along silty, planar-laminated and tool-marked sandstone beds deposited below storm wave base.

Intimate spatial and facies associations of TOS and body fossils suggest that TOS communities strongly influenced the benthic ecology of Ediacara macrofaunal ecosystems. TOS stabilized the substrate, fostered the development of unique benthic life modes and significantly shaped the biostratinomic and early diagenetic pathways responsible for the preservation of Ediacara communities.

Paleocene forests and climates of Antarctica: signals from fossil wood

^*Laura Tilley¹, Jane Francis², Vanessa Bowman² and Alistair J Crame²

¹University of Leeds
²British Antarctic Survey

During the greenhouse world of the Paleocene the Antarctica Peninsula was covered in forests. Fossil wood has been systematically collected from Paleocene marine sequences of Seymour Island and has been studied in order to reconstruct the forest composition and evolution of the vegetation throughout the Paleocene. Trees that lived in the forests included <i>Nothofagus</i>, Myrtaceae, <i>Weinmannia</i>, <i>Araucaria</i>, <i>Phyllocladus</i> and podocarp conifers. These tree types can be found in cool temperate forests in Chile and New Zealand today. Mean growth ring analysis shows a trend towards narrow growth rings in the early-mid Paleocene, which suggests cooler climates. Mean sensitivity calculated from tree ring width generally shows growth under an equable climate. Vulnerability Index (VI) and Mesomorphy Index (MI) have been calculated using angiosperm vessels as an indicator of water availability, and more precise MI values indicate sufficient water availability. Specific gravity has been linked to a plants adaption to water availability in its environment as well as growth strategy. Most of the fossil wood types show medium specific gravity (0.40 – 0.75) values, which is expected for temperate forests. Investigating these factors is essential for understanding how sensitive vegetation is to climate change.

The curious case of chaetae in brachiopods from the middle Cambrian Burgess Shale 

^*Timothy P. Topper¹, Lars E. Holmer¹, Luke Strotz², Noel Tait², Zhifei Zhang³ and Jean-Bernard Caron^4,5

¹Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, SE - 752 36 Uppsala, Sweden
²Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
³Early Life Institute and Department of Geology, State Key Laboratory for Continental Dynamics, Northwest University, Xian 710069, China
⁴Department of Natural History (Palaeobiology Section), Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, M5S2C6
⁵Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S3B2, Canada

The Burgess Shale Lagerstätte has over the years given us a range of extraordinary creatures, exquisitely preserved in the dark shales of the Canadian Rockies. In a community dominated by arthropods, brachiopods are the forgotten phylum in the Lagerstätte deposit, yet as the second most abundant benthic filter feeder, brachiopods were undoubtedly an essential component of the Burgess Shale community. One of the more remarkably preserved brachiopods from the Cambrian Stage 5, Burgess Shale is Micromitra burgessensis. Micromitra is exceptionally preserved, exhibiting elongate chaetae that fringe the mantle and extend far beyond the margin of the biomineralized shell. Chaetae of extant brachiopods have been interpreted as potentially performing a range of defensive and sensory functions in addition to assisting in feeding, burrowing and actively warding off encroaching organisms. The shape, size and frequency of the chaetae possessed by M. burgessensis are unique amongst Recent and fossil brachiopod taxa and here we explore the potential function/s of these distinctive chaetae. Chaetae have now been documented from a variety of extant and fossil brachiopod groups and the wide morphological variation observed across families indicate that chaetae may be a potentially significant tool for taxonomic, phylogenetic and palaeoecological studies of the phylum.

Finding food efficiently: the origin and evolution of optimal foraging strategies

Richard J. Twitchett¹, Andrew M. Reynolds², Nicolas E. Humphries³, Emily J. Southall³, Victoria J. Wearmouth³, Brett Metcalfe⁴ and David W. Sims^3,5

¹Natural History Museum, London, SW7 5BD, UK
²Rothamstead Research, Harpenden, AL5 2JQ, UK
³Marine Biological Association, Plymouth, PL1 2PB, UK
⁴VU University Amsterdam, 1081 HV, Amsterdam, The Netherlands
⁵University of Southampton, Southampton, SO17 1BJ, UK

How best to search for sparse food resources in heterogeneous landscapes is a universal problem facing mobile organisms. Living animals use a theoretically optimal scale-free random search known as a Lévy walk, composed of many small move steps interspersed by rarer long steps, but little is known of the origins and evolution of foraging behaviour and the search strategies of extinct animals. Computer simulations show that patterns that are consistent with Lévy walks may emerge from very simple behaviours, such as random strophotaxis (i.e. U-turns), and thus may have an ancient origin. To test this, we used a novel path-analysis technique to analyse Eocene examples of Cosmorhaphe, Helminthorhaphe and Scolicia, and found the first evidence of Lévy-like search strategies in the fossil record. Specimens of Cosmorhaphe and Helminthorhaphe are quantitatively similar to the simple Brownian random walks that approximate short-range, localized foraging movements of extant animals, implying homogenously distributed food. In contrast, those of Scolicia exhibited more complex behaviours analogous to Lévy walks, indicating that the echinoid trace-makers were optimally searching for patchily distributed food resources in their deep-sea habitats. Thus, Lévy-like behaviour has been used by foragers since at least the Eocene, but likely has a deeper origin.

Death Metal in the Early Palaeozoic

Thijs R. A. Vandenbroucke¹, Poul Emsbo² and Axel Munnecke³

¹UMR 8217 du CNRS: Géosystèmes, Lille1 University, Avenue Paul Langevin - bâtiment SN5, 59655 Villeneuve d'Ascq, France
²USGS, CMERSC, Denver Federal Center, Denver, CO 80225, USA.
³Universität Erlangen-Nürnberg, GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Loewenichstr. 28, D-91054, Erlangen, Germany.

Some, if not most, of the major Ordovician-Silurian extinction events coincided with glacial episodes. However, it has become increasingly clear that cooling, itself, is not a viable kill-mechanism to explain these extinctions. Interestingly, these events are announced by the appearance of malformed organic-walled fossil zoo- and phytoplankton. New geochemical analyses (using ToF-SIMS and LA-ICP-MS) of these teratological microfossils and their host rocks, through a mid-Pridoli event, show a correlation between teratology and a dramatic increase in redox sensitive metals. By analogy with metal-induced teratology in modern marine environments, our results suggest that these in vivo teratological reactions result from the pollution of the Silurian marine environment by toxic metals. These new data appear to link the initiation of the mass extinctions with the cycling of harmful redox sensitive metals likely related to Ocean Anoxic Events (OAEs), rather than with climate change. Our work introduces metal-induced teratology as a potential and independent proxy for the monitoring of palaeo-ocean geochemistry in deep time. 

Chitons of the Permian Capitan Reef, and the nature of late Palaeozoic Polyplacophora

Michael J. Vendrasco¹, Richard D. Hoare², Jr. Bell³ and Jonena M. Hearst³

¹University of Granada, Spain
²Bowling Green State University, Ohio, USA
³Guadalupe Mountains National Park, Texas, USA

A diverse assemblage of exceptionally preserved chiton shell plates has been extracted from the Permian Bell Canyon Formation in the Guadalupe Mountains of west Texas, USA. The chitons were found in thin debrites shed from the massive Capitan Reef. These fossils show fine details of tegmental sculpture and configuration of aesthete canals, and they add to the already high diversity of chitons known from the Permian of Texas. A rarefaction analysis of these assemblages indicates that diversity of late Palaeozoic chitons was probably much higher than recorded. The fossils show high variability in overall shape, tegmental coverage and sculpture, as well as shape and extent of incisions in insertion plates. Mesozoic chitons, in contrast, are sparse and morphologically uniform. Thus it seems many chiton lineages died out during the end Permian mass extinction and along with diversity went disparity. The Capitan fossils confirm convergent evolution in the Polyplacophora of both tegmentum reduction as well as incisions in the articulamentum. Otherwise the presence of such slits in insertion plates might provide an upper bound for the origin of the chiton crown group. In either case the crown group Polyplacophora probably originated during the late Palaeozoic, by which time some chitons had shell plate morphology very similar to modern forms.

The Middle Permian Mass Extinction in High Latitudes

Paul B. Wignall¹ and David P.G. Bond²

¹School of Earth & Environment, University of Leeds
²Department of Geography, Environment and Earth Sciences, University of Hull

The mass extinction at the end of the Permian is one of the best-known crises of the Phanerozoic. However, it was preceded by a little known extinction around 10 million years earlier. This Capitanian crisis was first identified 20 years ago and affected taxa from shallow-water tropical sites such as fusulinids, rugose corals and brachiopods. However, the impact of the crisis on higher latitude communities has not been addressed. The Kapp Starostin Formation is a mixed carbonate – spiculite ramp unit that accumulated at mid-high Boreal latitudes. It contains an abundant benthic fauna of brachiopods, bryozoans, corals, sponges and bivalves but mostly lacks stratigraphically useful fossils such as conodonts and ammonoids. Chemostratigraphic evidence (from strontium and carbon isotope variations) suggests the Middle/Late Permian boundary is ~80m from the top of the Formation. Range charts in the Kapp Starostin reveal that there is a major and abrupt extinction event in the latest Middle Permian. The Capitanian mass extinction is thus developed in both low and mid latitudes. The benthic communities in the Kapp Starostin Formation subsequently recover and consist of a diverse brachiopod/bivalve/ bryozoan/ sponge assemblage.

A Morphological Analysis of the Pectoral Girdle Skeleton of Soaring Birds

^*Megan E Williams¹

¹University of Cambridge

Soaring flight conserves energy by gaining lift from environmental air movements rather than flapping the wings. Its habitual use in the form of static (energy from thermals) and dynamic (energy from windshear) soaring has evolved convergently within neoavians. Previous research has found associations of aspects of skeletal morphology with soaring flight.

This study uses traditional and geometric morphometric techniques to investigate the morphology of the bones of the pectoral girdle associated with dynamic and static soaring relative to non-soaring species.

All bones of the pectoral girdle were found to be diagnostic of flight style, with the strongest associations found in the coracoid, and the weakest associations found in the geometric morphometric analysis of the furcula. Diagnostic accuracy was reduced but not removed when the effects of allometry were taken into account, suggesting that, while body size is associated with flight style, there are further associated morphological features unrelated to body size.

This work in charactering the skeletal morphology associated with soaring flight allows further research into the origins of soaring flight and the flight styles of extinct avian taxa. There is potential for this study to also identify key osteological features in the initial evolution of powered flight.

Life and death at high latitudes: a reassessment of the Cretaceous-Paleogene (K-Pg) mass extinction event in Antarctica

^*James D. Witts¹, Paul B. Wignall¹, Jane E. Francis², Robert J. Newton¹, J. Alistair Crame², Vanessa C. Bowman² and Rowan J. Whittle²

¹School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, UK, LS2 9JT
²British Antarctic Survey, High Cross, Madingley Road, Cambridge, UK, CB3 0ET

The Cretaceous-Paleogene (K-Pg) extinction of 66 Ma is a key event in Earth history, with extinction of many previously dominant terrestrial and marine groups providing a foundation for the subsequent evolution and expansion of the modern fauna during the Cenozoic. The highest southern latitude site for studying this interval is Seymour Island, Antarctica (65°S today, and during the Late Cretaceous). Here, a thick and abundantly fossiliferous Maastrichtian-Danian (~70 – 65 Ma) section is preserved within a sedimentary sequence deposited in a back-arc basin to the East of the Antarctic Peninsula.

We have produced stratigraphic range data for major macrofossil groups as well as stable isotope records (carbon and sulphur isotopes) based on new sedimentary sections and a taxonomic reassessment of the fauna from the ~1100 m thick López de Bertodano Formation exposed on Seymour Island. Our results show a stable Maastrichtian community, with fluctuations in the diversity of the fauna up-section probably related to sea-level and other latest Cretaceous environmental changes, before a single pulse of extinction coincident with the K-Pg boundary. These new data do not support claims for a double extinction pulse in Antarctica, and allow us to examine latitudinal and taxonomic selectivity of this major mass extinction event.

An agglutinated early Cambrian actinotroch-like phoronid from the Chengjiang Lagerstātten and its implications

Zhifei Zhang¹ and Lars E. Holmer²

¹Early Life Institute, State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, 710069, China
²Uppsala University, Department of Earth Sciences, Palaeobiology, Villavägen 16, SE-752 36, Uppsala, Sweden

The lophophorates are united by the presence of a fan of ciliated tentacles surrounding the mouth. Although considerable advance have recently been made in unveiling the Cambrian morphology and diversity of brachiopods, and other lophophorate animals, the most conspicuous phylogenetic gap in the Cambrian fossil record is for the Phoronida. Iotuba (= Eophoronis Chen) was proposed as a phoronid candidate, but it has more recently been considered as a sipunculid.

New abundant well preserved material of Archisaccophyllia kunmingensis Hou et al., from the Cambrian (Series 2) Chengjiang deposits, is here reinterpreted as a stem-group phoronid with actinotroch-like larval characters. The phoronid affinity is supported by the sessile body plan and interior soft anatomy. The body consists of an upper agglutinated calyx and a lower stout stalk with a distal holdfast. The soft anatomy includes a U-shaped gut with a mouth surrounded by a fan of flexible tentacles. Archisaccophyllia kunmingensis differs from extant phoronid actinotroch larvae in being much larger with a sessile lifestyles, as well as in having the calyx covered by agglutinated quartz grains that is reminiscent of agglutination that is known in both extant adult phoronid and the stem-group brachiopod Yuganotheca recently reported from the Chengjiang fauna.