David Siveter | University of Leicester (original) (raw)

Papers by David Siveter

Research paper thumbnail of A monograph of the Bradoriid arthropods from the Lower Cambrian of SW China

Transactions of The Royal Society of Edinburgh-earth Sciences, 2001

... 352 HOU XIAN-GUANG ET AL. Page 7. H a n ch ia n g ella m in o r E m e iella v en u sta W u ti... more ... 352 HOU XIAN-GUANG ET AL. Page 7. H a n ch ia n g ella m in o r E m e iella v en u sta W u tin g ella b in o d o sa L ia n g sh a n ella ro tu n d a ta C o m p ta lu ta lesh a n en sis K u n m in g ella d o u v illei C o m p ta lu ta in fla ta K u n ya n g ella ch e n i N e o ku n m in g ella cf. ...

Research paper thumbnail of An exceptionally preserved vermiform mollusc from the Silurian of England

Nature, 2001

Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding the... more Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding their nearest relatives, phylogeny and ancestral characters. The Polyplacophora (chitons) and the Aplacophora are widely interpreted as the most primitive extant molluscs, but Lower Palaeozoic fossils of the former lack soft parts, and the latter were hitherto unrecognized as fossils. The Herefordshire Lagerstätte is

Research paper thumbnail of A Silurian 'marrellomorph' arthropod

Proceedings. Biological sciences / The Royal Society, Jan 22, 2007

Xylokorys chledophilia, a new arthropod with three-dimensionally preserved soft tissues, is descr... more Xylokorys chledophilia, a new arthropod with three-dimensionally preserved soft tissues, is described from the Herefordshire (Silurian) Lagerstätte of England. The head and trunk are covered by a relatively featureless ovoid carapace, which comprises a domed central part and a flange-like border. The head bears five pairs of appendages. The first is uniramous, with dorsal and ventral projections distally. Appendages two to four are biramous and each endopod terminates in two projections. Appendage five is possibly biramous. The hypostome is very long and subrectangular in outline. There are approximately 35 pairs of biramous trunk appendages. Each exopod comprises a long slender shaft bearing numerous fine filaments; each endopod comprises a ribbon-like shaft bearing paddle-like endites. Morphological comparisons and cladistic analyses of X. chledophilia indicate affinity with Vachonisia rogeri from the Lower Devonian Hunsrück Slate, within the marrellomorphs, but assignment to Marr...

Research paper thumbnail of The earliest ostracods: the geological evidence

Senckenbergiana lethaea, 2008

The oldest assumed ostracods appear in the fossil record from the Tremadocian Paltodus deltifer c... more The oldest assumed ostracods appear in the fossil record from the Tremadocian Paltodus deltifer conodont Biozone. Although geographically widespread these early ostracods have no obvious Cambrian antecedents. Their first appearance at ca. 485 Ma contrasts with molecular evidence that suggests a much earlier (latest Proterozoic or Cambrian) origin for ostracods. Some Cambrian bivalved arthropods such as Altajanella and Vojbokalina, conventionally referred to the Bradoriida, have carapace morphologies that resemble Ordovician palaeocopid ostracods, though such a relationship is unproven without soft part anatomy. Evidence from preserved soft anatomy demonstrates that Bradoriida, such as Kunmingella, and Phosphatocopida, essentially the Cambrian 'ostracod' record of traditional usage, belong outside the Eucrustacea. Early Ordovician ostracods appeared first in shallow marine, oxygenated environments on shelf margins, in a similar setting to other elements of the 'Paleozoic fauna'. Their biodiversity was low (3 named genera and ca. 12 species), though some taxa such as Nanopsis and Eopilla achieved widespread dispersal between major Ordovician palaeocontinents. As bradoriids were largely extinct by the Late Cambrian, ostracods do not appear to have directly competed with them for shallow marine environments. The rapid colonisation of these settings by ostracods may have been facilitated by the available ecospace vacated by Bradoriida.

Research paper thumbnail of Mineralized rods and cones suggest colour vision in a 300 Myr-old fossil fish

Nature communications, 2014

Vision, which consists of an optical system, receptors and image-processing capacity, has existed... more Vision, which consists of an optical system, receptors and image-processing capacity, has existed for at least 520 Myr. Except for the optical system, as in the calcified lenses of trilobite and ostracod arthropods, other parts of the visual system are not usually preserved in the fossil record, because the soft tissue of the eye and the brain decay rapidly after death, such as within 64 days and 11 days, respectively. The Upper Carboniferous Hamilton Formation (300 Myr) in Kansas, USA, yields exceptionally well-preserved animal fossils in an estuarine depositional setting. Here we show that the original colour, shape and putative presence of eumelanin have been preserved in the acanthodii fish Acanthodes bridgei. We also report on the tissues of its eye, which provides the first record of mineralized rods and cones in a fossil and indicates that this 300 Myr-old fish likely possessed colour vision.

Research paper thumbnail of Evidence that Early Carboniferous ostracods colonised coastal flood plain brackish water environments

Palaeogeography, Palaeoclimatology, Palaeoecology, 2006

A study of the stable isotope composition (d 18 O, d 13 C) of biogenic (ostracod, mollusc) and au... more A study of the stable isotope composition (d 18 O, d 13 C) of biogenic (ostracod, mollusc) and authigenic carbonates in the Ballagan Formation, Lower Carboniferous of Scotland, coupled with evidence from sedimentology and associated fossil fauna and flora, supports the argument that this formation was deposited in a coastal flood plain setting, in brackish (0.5 b 30x NaCl) and hypersaline (N 40x NaCl) waters, but in the absence of persistent normal marine conditions. The oxygen isotope data from the Ballagan Formation divide into three clusters: a diagenetic field defined by low d 18 O (b À 11x VPDB); an intermediary field (d 18 O À11x to À 9x) composed of a mixture of known primary and secondary (diagenetic) carbonates; and samples within the range of À 9x to À 4x which, as far as we can ascertain, are largely unaltered. No samples give typical Early Carboniferous d 18 O marine values. Average marine carbonates from Europe have d 18 O between À 4x to À 3x. The Ballagan Formation carbonates were probably deposited in evaporated freshwater and/or brackish water. This conclusion is supported by the presence of evaporites (gypsum, anhydrite, halite pseudomorphs) and common desiccation-cracked mudstone surfaces throughout the Ballagan Formation, suggesting conditions of fluctuating salinity in ephemeral bodies of water. The stable isotope data support the notion that the ostracod assemblages of the Ballagan Formation were colonising brackish water and hypersaline ecologies on a coastal flood plain during the Early Carboniferous, a stage of development that may have encouraged their colonisation of fully non-marine (limnetic) environments during the later Carboniferous. The ostracods include cyther-0031-0182/$ -see front matter D (M. Williams).

Research paper thumbnail of Upper Ordovician ostracods from the Cautley district, northern England: Baltic and Laurentian affinities

Geological Magazine, 2001

The Cautley Mudstone Formation and Cystoid Limestone Member of the Ashgill Formation (Windermere ... more The Cautley Mudstone Formation and Cystoid Limestone Member of the Ashgill Formation (Windermere Supergroup; Ashgill Series), from the Cautley district of northern England, has yielded an ostracod fauna of more than 30 species. Many of these have short ranges, permitting recognition of ...

Research paper thumbnail of The Silurian pelagic myodocope ostracod Richteria migrans

Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2007

A study of type and newly collected material of the Silurian ostracod Richteria migrans (Barrande... more A study of type and newly collected material of the Silurian ostracod Richteria migrans (Barrande, 1872) demonstrates that it had wide distribution, occurring in at least the Czech Republic, France, Sardinia, Wales, central Asia and probably Poland. R. migrans has biostratigraphic value, as an indicator for the mid to late part of the Ludlow Series. It was almost certainly pelagic, living predominantly in probable shelf topographic lows to marginal/off-shelf environments, characteristically with cephalopod-graptolite-bivalve-dominant associates. It had at least five to six growth stages, exhibits polymorphic variation, and its morphology provides evidence to endorse the notion that 'entomozoaceans' are myodocopes.

Research paper thumbnail of Pedicle preservation in a Silurian rhynchonelliformean brachiopod from Herefordshire, England: soft-tissue or an artefact of interpretation?

Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2007

The interpretation of pedicle soft tissue preservation in a unique brachiopod specimen of Wenlock... more The interpretation of pedicle soft tissue preservation in a unique brachiopod specimen of Wenlock (Silurian) age from Herefordshire, western England, is re-assessed. Bethia serraticulma, assigned originally to the Orthida, is more probably a member of the Strophomenida (Plectambonitoidea). The supposed pedicle structure is more plausibly a weakly mineralised pedicle sheath, which is a common morphological and functional development in the early ontogeny of a number of Palaeozoic brachiopod lineages.

Research paper thumbnail of Collective Behavior in an Early Cambrian Arthropod

Science, 2008

Examples that indicate collective behavior in the fossil record are rare. A group association of ... more Examples that indicate collective behavior in the fossil record are rare. A group association of specimens that belong to a previously unknown arthropod from the Chengjiang Lagerstätte, China, provides evidence that such behavior was present in the early Cambrian (about 525 million years ago), coincident with the earliest extensive diversification of the Metazoa, the so-called Cambrian explosion event. The chainlike form of these specimens is unique for any arthropod, fossil or living, and most likely represents behavior associated with migration.

Research paper thumbnail of Microplankton associations, biofacies and palaeoenvironment of the type lower Ludlow Series, Silurian

Review of Palaeobotany and Palynology, 2004

The acritarchs and prasinophyte algae from the type lower Ludlow Series of the Goggin Road sectio... more The acritarchs and prasinophyte algae from the type lower Ludlow Series of the Goggin Road section, Ludlow, England, are resolved into seven recurrent associations comprising taxa with similar environmental preferences. Endemic and environmentally sensitive associations of acritarchs and prasinophytes are identified and high-resolution fluctuations in the early Ludlow palaeoenvironment are established. An early Ludlow crisis in the acritarchs is recognized

Research paper thumbnail of A new probable stem lineage crustacean with three-dimensionally preserved soft parts from the Herefordshire (Silurian) Lagerstatte, UK

Proceedings of the Royal Society B: Biological Sciences, 2007

A new arthropod with three-dimensionally preserved soft parts, Tanazios dokeron, is described fro... more A new arthropod with three-dimensionally preserved soft parts, Tanazios dokeron, is described from the Wenlock Series (Silurian) of Herefordshire, England, UK. Serial grinding, digital photographic and computer rendering techniques yielded 'virtual fossils' in the round for study. The body tagmata of T. dokeron comprise a head shield and a long trunk. The head shield bears six pairs of horn-like spines and the head bears five pairs of appendages. The antennule, antenna and mandible are all uniramous, and the mandible includes a gnathobasic coxa. Appendages four and five are biramous and similar to those of the trunk: each comprises a limb base with an endite, an enditic membrane, and two epipodites, plus an endopod and exopod. The hypostome bears a large cone-like projection centrally, and there may be a short labrum. The trunk has some 64 segments and at least 60 appendage pairs. A very small telson has the anus sited ventrally in its posterior part and also bears a caudal furca. Comparative morphological and cladistic analyses of T. dokeron indicate a crustacean affinity, with a probable position in the eucrustacean stem group. As such the epipodites in T. dokeron are the first recorded in a eucrustacean stem taxon. The new species is interpreted as a benthic or nektobenthic scavenger.

Research paper thumbnail of Fossilized soft tissues in a Silurian platyceratid gastropod

Proceedings of the Royal Society B: Biological Sciences, 2006

Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknow... more Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknown, and have not been reported previously from the Palaeozoic. Here, we describe a Silurian (approx. 425 Myr) platyceratid gastropod from the Herefordshire Lagerstätte that preserves the oldest soft tissues yet reported from an undoubted crown-group mollusc. The digestive system is preserved in detail, and morphological data on the gonads, digestive gland, pedal muscle, radula, mouth and foot are also available. The specimen is preserved three-dimensionally, and has been reconstructed digitally following serial grinding. Platyceratids are often found attached to echinoderms, and have been interpreted as either commensal coprophages or kleptoparasites. The new data provide support for an attached mode of life, and are suggestive of a coprophagous feeding strategy. The affinities of the platyceratids are uncertain; they have been compared to both the patellogastropods and the neritopsines. Analysis of the new material suggests that a patellogastropod affinity is the more plausible of these hypotheses.

Research paper thumbnail of Metamorphosis in a Silurian barnacle

Proceedings of the Royal Society B: Biological Sciences, 2005

Exceptionally preserved fossils from the Wenlock Series (Silurian) of Herefordshire, UK, provide ... more Exceptionally preserved fossils from the Wenlock Series (Silurian) of Herefordshire, UK, provide unique evidence of metamorphosis from free-swimming cyprid larva to attached juvenile in a Palaeozoic barnacle. The larva had large brush-like anterior limbs. The juvenile shows the head transformed into a stalk and the development of the primordial condition of five mineralized plates within the carapace. The discovery of a cyprid larva indicates that crown group cirripedes had evolved by the Silurian.

Research paper thumbnail of Brood care in a Silurian ostracod

Proceedings of the Royal Society B: Biological Sciences, 2007

An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, England, p... more An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, England, preserves eggs and possible juveniles within its carapace, providing an unequivocal and unique view of parental brood care in the invertebrate fossil record. The female fossil is assigned to a new family and superfamily of myodocopids based on its soft-part anatomy. It demonstrates a remarkably conserved egg-brooding reproductive strategy within these ostracods over 425 Myr. The soft-tissue anatomy urges extreme caution in classifying 'straight-hinged' Palaeozoic ostracods based on the carapace alone and fundamentally questions the nature of the shell-based Palaeozoic ostracod record.

Research paper thumbnail of A new mid-Cambrian trilobite fauna from Shropshire

Proceedings of the Geologists' Association, 2007

ABSTRACT An attempt to re-investigate the Acrothele prima Shale, formerly recorded as of Early Ca... more ABSTRACT An attempt to re-investigate the Acrothele prima Shale, formerly recorded as of Early Cambrian age, resulted in the discovery of a diverse Middle Cambrian trilobite fauna — a fortunate result considering the erroneous information surrounding the investigation of the Acrothele prima Shale. The new fauna, whose age approximates to the boundary between the gibbus Zone and fissus Zone, contains species not recorded previously in Shropshire: the trilobites are discussed and species described originally from New Brunswick are recorded from Britain for the first time, including Eccaparadoxides acadicus and Ctenocephalus (Hartella) matthewi.

Research paper thumbnail of Appendages of the Arthropod Kunmingella from the Early Cambrian of China: Its Bearing on the Systematic Position of the Bradoriida and the Fossil Record of the Ostracoda

Philosophical Transactions of the Royal Society B: Biological Sciences, 1996

The first discovery of the appendages belonging to the Bradoriida s. str. Arthropoda-generally su... more The first discovery of the appendages belonging to the Bradoriida s. str. Arthropoda-generally supposed to have been ostracodes until now-is reported in Kunmingella from the early Cambrian soft-bodiedChengjiang'Lagerstatte of China. Although this evidence does ...

Research paper thumbnail of The ‘Orsten’—More than a Cambrian Konservat-Lagerstätte yielding exceptional preservation

Palaeoworld, 2006

In several areas of southern Sweden, limestone nodules, locally called Orsten occur within bitumi... more In several areas of southern Sweden, limestone nodules, locally called Orsten occur within bituminous alum shales. These shales and nodules were deposited under dysoxic conditions at the bottom of what was most likely a shallow sea during the late Middle to Upper Cambrian (ca. 500 million years ago). Subsequently, the name 'Orsten' has been referred to particular, mainly arthropod, fossils from such nodules, and, in a wider sense, to the specific type of preservation of minute fossil through secondarily phosphatization. This preservation is exceptional in yielding uncompacted and diagenetically undeformed three-dimensional fossils. 'Orsten'-type preservation resulted from incrustation of a thin external layer and also by impregnation by calcium phosphate and, therefore, mineralization of the surface of the former animals during early diagenesis. Primarily, this type of preservation seems to have affected only cuticle-bearing metazoans such as cycloneuralian nemathelminths and arthropods. 'Orsten' preservation in this sense seems to be limited by size, in having yielded no partial or complete animals larger than 2 mm. On the other end of the scale, even larvae 100 m long are preserved, often more complete than larger specimens, and details such as setules and pores smaller than 1 m can be observed. Fossils preserved in such a manner are almost exclusively hollow carcasses, but can be filled secondarily; less common are completely phosphatized compact specimens. The high quality of preservation makes the Swedish 'Orsten' a typical Konservat-Lagerstätte. Yet, its special type of preservation is more widespread in time and geographical distribution than assumed initially, and the origin of the phosphate is not necessarily restricted just to one source. Subsequent to the first discoveries of limb fragments of Cambrian arthropods in 1975, animals in this special preservational type have been discovered in several continents and across a broad stratigraphic range including even Proterozoic strata. The latter have yielded early cleavage and metazoan embryonic stages, expanding knowledge on the preservational capacities of the 'Orsten'. Here, we report the recent status of our research on the * Corresponding author.

Research paper thumbnail of Computer reconstruction and analysis of the vermiform mollusc Acaenoplax hayae from the Herefordshire Lagerstatte (Silurian, England), and implications for molluscan phylogeny

Palaeontology, 2004

Acaenoplax hayae is a spinose worm-like animal from the Silurian Herefordshire Lagerstätte of Eng... more Acaenoplax hayae is a spinose worm-like animal from the Silurian Herefordshire Lagerstätte of England, a deposit that preserves high-fidelity soft-part morphology of invertebrates in three dimensions. Specimens have been serially ground and reconstructed by computer to their three-dimensional form. Acaenoplax bears serially repeated transverse ridges dorsally, each with an array of probably aragonitic spines inclined posteriorly. Oblique ventral loberows correspond in position to the dorsal ridges. Aragonitic dorsal valves overlie every third ridge; the penultimate valve is absent leaving a total of seven. The anterior termination is disk-like, surrounding an antero-medial mouth. At the posterior termination there is a cavity between the posteriormost dorsal and a posteroventral valve, from which soft-part projections extend. Acaenoplax is interpreted as a creeping epibenthic animal that fed on sessile prey. It is an 'aculiferan' mollusc, combining unique autapomorphic structures with characters typical of the Polyplacophora and Aplacophora. Its morphology can be accommodated within both of the competing schemes of molluscan phylogeny, and its closest living relatives in both cases are aplacophorans. The highly serialized morphology of Acaenoplax is unique within the Mollusca, but the pattern it highlights is an attractive candidate for the primitive state of serial repetition within the phylum.

Research paper thumbnail of THE SYSTEMATICS AND PHYLOGENETIC RELATIONSHIPS OF VETULICOLIANS

Palaeontology, 2007

Vetulicolians have variously been considered to be unusual arthropods, stem-group deuterostomes o... more Vetulicolians have variously been considered to be unusual arthropods, stem-group deuterostomes or relatives of the tunicates. They are known from a number of Cambrian Lagerstätten, and are particularly diverse in the Chengjiang biota of Yunnan Province, China. We recognize two classes, Vetulicolida and Banffozoa, which together form a monophyletic group. Within the Chinese collections we also identify two new species and recognize one new genus: Vetulicola monile sp. nov. and Bullivetula variola gen. et sp. nov. The evidence from new and previously described specimens is used to undertake a phylogenetic analysis and to evaluate a range of hypotheses for the affinities of vetulicolians. Given the difficulties of interpreting features in enigmatic fossils and the apparently contradictory set of characters possessed by vetulicolians, it is not possible on current evidence to reach an unequivocal conclusion regarding the phylogenetic position of the group. One possibility is that they are a sister group of arthropods that lost limbs but gained gill structures analogous to those of deuterostomes, but several features remain unexplained by this model. If they are protostomes, a more generally parsimonious position is close to the kinorhynchs. An alternative is that they are deuterostomes, although a placement at the base of the clade is not supported by the evidence. If they are deuterostomes, it is more likely that they are close to the tunicates.

Research paper thumbnail of A monograph of the Bradoriid arthropods from the Lower Cambrian of SW China

Transactions of The Royal Society of Edinburgh-earth Sciences, 2001

... 352 HOU XIAN-GUANG ET AL. Page 7. H a n ch ia n g ella m in o r E m e iella v en u sta W u ti... more ... 352 HOU XIAN-GUANG ET AL. Page 7. H a n ch ia n g ella m in o r E m e iella v en u sta W u tin g ella b in o d o sa L ia n g sh a n ella ro tu n d a ta C o m p ta lu ta lesh a n en sis K u n m in g ella d o u v illei C o m p ta lu ta in fla ta K u n ya n g ella ch e n i N e o ku n m in g ella cf. ...

Research paper thumbnail of An exceptionally preserved vermiform mollusc from the Silurian of England

Nature, 2001

Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding the... more Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding their nearest relatives, phylogeny and ancestral characters. The Polyplacophora (chitons) and the Aplacophora are widely interpreted as the most primitive extant molluscs, but Lower Palaeozoic fossils of the former lack soft parts, and the latter were hitherto unrecognized as fossils. The Herefordshire Lagerstätte is

Research paper thumbnail of A Silurian 'marrellomorph' arthropod

Proceedings. Biological sciences / The Royal Society, Jan 22, 2007

Xylokorys chledophilia, a new arthropod with three-dimensionally preserved soft tissues, is descr... more Xylokorys chledophilia, a new arthropod with three-dimensionally preserved soft tissues, is described from the Herefordshire (Silurian) Lagerstätte of England. The head and trunk are covered by a relatively featureless ovoid carapace, which comprises a domed central part and a flange-like border. The head bears five pairs of appendages. The first is uniramous, with dorsal and ventral projections distally. Appendages two to four are biramous and each endopod terminates in two projections. Appendage five is possibly biramous. The hypostome is very long and subrectangular in outline. There are approximately 35 pairs of biramous trunk appendages. Each exopod comprises a long slender shaft bearing numerous fine filaments; each endopod comprises a ribbon-like shaft bearing paddle-like endites. Morphological comparisons and cladistic analyses of X. chledophilia indicate affinity with Vachonisia rogeri from the Lower Devonian Hunsrück Slate, within the marrellomorphs, but assignment to Marr...

Research paper thumbnail of The earliest ostracods: the geological evidence

Senckenbergiana lethaea, 2008

The oldest assumed ostracods appear in the fossil record from the Tremadocian Paltodus deltifer c... more The oldest assumed ostracods appear in the fossil record from the Tremadocian Paltodus deltifer conodont Biozone. Although geographically widespread these early ostracods have no obvious Cambrian antecedents. Their first appearance at ca. 485 Ma contrasts with molecular evidence that suggests a much earlier (latest Proterozoic or Cambrian) origin for ostracods. Some Cambrian bivalved arthropods such as Altajanella and Vojbokalina, conventionally referred to the Bradoriida, have carapace morphologies that resemble Ordovician palaeocopid ostracods, though such a relationship is unproven without soft part anatomy. Evidence from preserved soft anatomy demonstrates that Bradoriida, such as Kunmingella, and Phosphatocopida, essentially the Cambrian 'ostracod' record of traditional usage, belong outside the Eucrustacea. Early Ordovician ostracods appeared first in shallow marine, oxygenated environments on shelf margins, in a similar setting to other elements of the 'Paleozoic fauna'. Their biodiversity was low (3 named genera and ca. 12 species), though some taxa such as Nanopsis and Eopilla achieved widespread dispersal between major Ordovician palaeocontinents. As bradoriids were largely extinct by the Late Cambrian, ostracods do not appear to have directly competed with them for shallow marine environments. The rapid colonisation of these settings by ostracods may have been facilitated by the available ecospace vacated by Bradoriida.

Research paper thumbnail of Mineralized rods and cones suggest colour vision in a 300 Myr-old fossil fish

Nature communications, 2014

Vision, which consists of an optical system, receptors and image-processing capacity, has existed... more Vision, which consists of an optical system, receptors and image-processing capacity, has existed for at least 520 Myr. Except for the optical system, as in the calcified lenses of trilobite and ostracod arthropods, other parts of the visual system are not usually preserved in the fossil record, because the soft tissue of the eye and the brain decay rapidly after death, such as within 64 days and 11 days, respectively. The Upper Carboniferous Hamilton Formation (300 Myr) in Kansas, USA, yields exceptionally well-preserved animal fossils in an estuarine depositional setting. Here we show that the original colour, shape and putative presence of eumelanin have been preserved in the acanthodii fish Acanthodes bridgei. We also report on the tissues of its eye, which provides the first record of mineralized rods and cones in a fossil and indicates that this 300 Myr-old fish likely possessed colour vision.

Research paper thumbnail of Evidence that Early Carboniferous ostracods colonised coastal flood plain brackish water environments

Palaeogeography, Palaeoclimatology, Palaeoecology, 2006

A study of the stable isotope composition (d 18 O, d 13 C) of biogenic (ostracod, mollusc) and au... more A study of the stable isotope composition (d 18 O, d 13 C) of biogenic (ostracod, mollusc) and authigenic carbonates in the Ballagan Formation, Lower Carboniferous of Scotland, coupled with evidence from sedimentology and associated fossil fauna and flora, supports the argument that this formation was deposited in a coastal flood plain setting, in brackish (0.5 b 30x NaCl) and hypersaline (N 40x NaCl) waters, but in the absence of persistent normal marine conditions. The oxygen isotope data from the Ballagan Formation divide into three clusters: a diagenetic field defined by low d 18 O (b À 11x VPDB); an intermediary field (d 18 O À11x to À 9x) composed of a mixture of known primary and secondary (diagenetic) carbonates; and samples within the range of À 9x to À 4x which, as far as we can ascertain, are largely unaltered. No samples give typical Early Carboniferous d 18 O marine values. Average marine carbonates from Europe have d 18 O between À 4x to À 3x. The Ballagan Formation carbonates were probably deposited in evaporated freshwater and/or brackish water. This conclusion is supported by the presence of evaporites (gypsum, anhydrite, halite pseudomorphs) and common desiccation-cracked mudstone surfaces throughout the Ballagan Formation, suggesting conditions of fluctuating salinity in ephemeral bodies of water. The stable isotope data support the notion that the ostracod assemblages of the Ballagan Formation were colonising brackish water and hypersaline ecologies on a coastal flood plain during the Early Carboniferous, a stage of development that may have encouraged their colonisation of fully non-marine (limnetic) environments during the later Carboniferous. The ostracods include cyther-0031-0182/$ -see front matter D (M. Williams).

Research paper thumbnail of Upper Ordovician ostracods from the Cautley district, northern England: Baltic and Laurentian affinities

Geological Magazine, 2001

The Cautley Mudstone Formation and Cystoid Limestone Member of the Ashgill Formation (Windermere ... more The Cautley Mudstone Formation and Cystoid Limestone Member of the Ashgill Formation (Windermere Supergroup; Ashgill Series), from the Cautley district of northern England, has yielded an ostracod fauna of more than 30 species. Many of these have short ranges, permitting recognition of ...

Research paper thumbnail of The Silurian pelagic myodocope ostracod Richteria migrans

Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2007

A study of type and newly collected material of the Silurian ostracod Richteria migrans (Barrande... more A study of type and newly collected material of the Silurian ostracod Richteria migrans (Barrande, 1872) demonstrates that it had wide distribution, occurring in at least the Czech Republic, France, Sardinia, Wales, central Asia and probably Poland. R. migrans has biostratigraphic value, as an indicator for the mid to late part of the Ludlow Series. It was almost certainly pelagic, living predominantly in probable shelf topographic lows to marginal/off-shelf environments, characteristically with cephalopod-graptolite-bivalve-dominant associates. It had at least five to six growth stages, exhibits polymorphic variation, and its morphology provides evidence to endorse the notion that 'entomozoaceans' are myodocopes.

Research paper thumbnail of Pedicle preservation in a Silurian rhynchonelliformean brachiopod from Herefordshire, England: soft-tissue or an artefact of interpretation?

Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2007

The interpretation of pedicle soft tissue preservation in a unique brachiopod specimen of Wenlock... more The interpretation of pedicle soft tissue preservation in a unique brachiopod specimen of Wenlock (Silurian) age from Herefordshire, western England, is re-assessed. Bethia serraticulma, assigned originally to the Orthida, is more probably a member of the Strophomenida (Plectambonitoidea). The supposed pedicle structure is more plausibly a weakly mineralised pedicle sheath, which is a common morphological and functional development in the early ontogeny of a number of Palaeozoic brachiopod lineages.

Research paper thumbnail of Collective Behavior in an Early Cambrian Arthropod

Science, 2008

Examples that indicate collective behavior in the fossil record are rare. A group association of ... more Examples that indicate collective behavior in the fossil record are rare. A group association of specimens that belong to a previously unknown arthropod from the Chengjiang Lagerstätte, China, provides evidence that such behavior was present in the early Cambrian (about 525 million years ago), coincident with the earliest extensive diversification of the Metazoa, the so-called Cambrian explosion event. The chainlike form of these specimens is unique for any arthropod, fossil or living, and most likely represents behavior associated with migration.

Research paper thumbnail of Microplankton associations, biofacies and palaeoenvironment of the type lower Ludlow Series, Silurian

Review of Palaeobotany and Palynology, 2004

The acritarchs and prasinophyte algae from the type lower Ludlow Series of the Goggin Road sectio... more The acritarchs and prasinophyte algae from the type lower Ludlow Series of the Goggin Road section, Ludlow, England, are resolved into seven recurrent associations comprising taxa with similar environmental preferences. Endemic and environmentally sensitive associations of acritarchs and prasinophytes are identified and high-resolution fluctuations in the early Ludlow palaeoenvironment are established. An early Ludlow crisis in the acritarchs is recognized

Research paper thumbnail of A new probable stem lineage crustacean with three-dimensionally preserved soft parts from the Herefordshire (Silurian) Lagerstatte, UK

Proceedings of the Royal Society B: Biological Sciences, 2007

A new arthropod with three-dimensionally preserved soft parts, Tanazios dokeron, is described fro... more A new arthropod with three-dimensionally preserved soft parts, Tanazios dokeron, is described from the Wenlock Series (Silurian) of Herefordshire, England, UK. Serial grinding, digital photographic and computer rendering techniques yielded 'virtual fossils' in the round for study. The body tagmata of T. dokeron comprise a head shield and a long trunk. The head shield bears six pairs of horn-like spines and the head bears five pairs of appendages. The antennule, antenna and mandible are all uniramous, and the mandible includes a gnathobasic coxa. Appendages four and five are biramous and similar to those of the trunk: each comprises a limb base with an endite, an enditic membrane, and two epipodites, plus an endopod and exopod. The hypostome bears a large cone-like projection centrally, and there may be a short labrum. The trunk has some 64 segments and at least 60 appendage pairs. A very small telson has the anus sited ventrally in its posterior part and also bears a caudal furca. Comparative morphological and cladistic analyses of T. dokeron indicate a crustacean affinity, with a probable position in the eucrustacean stem group. As such the epipodites in T. dokeron are the first recorded in a eucrustacean stem taxon. The new species is interpreted as a benthic or nektobenthic scavenger.

Research paper thumbnail of Fossilized soft tissues in a Silurian platyceratid gastropod

Proceedings of the Royal Society B: Biological Sciences, 2006

Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknow... more Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknown, and have not been reported previously from the Palaeozoic. Here, we describe a Silurian (approx. 425 Myr) platyceratid gastropod from the Herefordshire Lagerstätte that preserves the oldest soft tissues yet reported from an undoubted crown-group mollusc. The digestive system is preserved in detail, and morphological data on the gonads, digestive gland, pedal muscle, radula, mouth and foot are also available. The specimen is preserved three-dimensionally, and has been reconstructed digitally following serial grinding. Platyceratids are often found attached to echinoderms, and have been interpreted as either commensal coprophages or kleptoparasites. The new data provide support for an attached mode of life, and are suggestive of a coprophagous feeding strategy. The affinities of the platyceratids are uncertain; they have been compared to both the patellogastropods and the neritopsines. Analysis of the new material suggests that a patellogastropod affinity is the more plausible of these hypotheses.

Research paper thumbnail of Metamorphosis in a Silurian barnacle

Proceedings of the Royal Society B: Biological Sciences, 2005

Exceptionally preserved fossils from the Wenlock Series (Silurian) of Herefordshire, UK, provide ... more Exceptionally preserved fossils from the Wenlock Series (Silurian) of Herefordshire, UK, provide unique evidence of metamorphosis from free-swimming cyprid larva to attached juvenile in a Palaeozoic barnacle. The larva had large brush-like anterior limbs. The juvenile shows the head transformed into a stalk and the development of the primordial condition of five mineralized plates within the carapace. The discovery of a cyprid larva indicates that crown group cirripedes had evolved by the Silurian.

Research paper thumbnail of Brood care in a Silurian ostracod

Proceedings of the Royal Society B: Biological Sciences, 2007

An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, England, p... more An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, England, preserves eggs and possible juveniles within its carapace, providing an unequivocal and unique view of parental brood care in the invertebrate fossil record. The female fossil is assigned to a new family and superfamily of myodocopids based on its soft-part anatomy. It demonstrates a remarkably conserved egg-brooding reproductive strategy within these ostracods over 425 Myr. The soft-tissue anatomy urges extreme caution in classifying 'straight-hinged' Palaeozoic ostracods based on the carapace alone and fundamentally questions the nature of the shell-based Palaeozoic ostracod record.

Research paper thumbnail of A new mid-Cambrian trilobite fauna from Shropshire

Proceedings of the Geologists' Association, 2007

ABSTRACT An attempt to re-investigate the Acrothele prima Shale, formerly recorded as of Early Ca... more ABSTRACT An attempt to re-investigate the Acrothele prima Shale, formerly recorded as of Early Cambrian age, resulted in the discovery of a diverse Middle Cambrian trilobite fauna — a fortunate result considering the erroneous information surrounding the investigation of the Acrothele prima Shale. The new fauna, whose age approximates to the boundary between the gibbus Zone and fissus Zone, contains species not recorded previously in Shropshire: the trilobites are discussed and species described originally from New Brunswick are recorded from Britain for the first time, including Eccaparadoxides acadicus and Ctenocephalus (Hartella) matthewi.

Research paper thumbnail of Appendages of the Arthropod Kunmingella from the Early Cambrian of China: Its Bearing on the Systematic Position of the Bradoriida and the Fossil Record of the Ostracoda

Philosophical Transactions of the Royal Society B: Biological Sciences, 1996

The first discovery of the appendages belonging to the Bradoriida s. str. Arthropoda-generally su... more The first discovery of the appendages belonging to the Bradoriida s. str. Arthropoda-generally supposed to have been ostracodes until now-is reported in Kunmingella from the early Cambrian soft-bodiedChengjiang'Lagerstatte of China. Although this evidence does ...

Research paper thumbnail of The ‘Orsten’—More than a Cambrian Konservat-Lagerstätte yielding exceptional preservation

Palaeoworld, 2006

In several areas of southern Sweden, limestone nodules, locally called Orsten occur within bitumi... more In several areas of southern Sweden, limestone nodules, locally called Orsten occur within bituminous alum shales. These shales and nodules were deposited under dysoxic conditions at the bottom of what was most likely a shallow sea during the late Middle to Upper Cambrian (ca. 500 million years ago). Subsequently, the name 'Orsten' has been referred to particular, mainly arthropod, fossils from such nodules, and, in a wider sense, to the specific type of preservation of minute fossil through secondarily phosphatization. This preservation is exceptional in yielding uncompacted and diagenetically undeformed three-dimensional fossils. 'Orsten'-type preservation resulted from incrustation of a thin external layer and also by impregnation by calcium phosphate and, therefore, mineralization of the surface of the former animals during early diagenesis. Primarily, this type of preservation seems to have affected only cuticle-bearing metazoans such as cycloneuralian nemathelminths and arthropods. 'Orsten' preservation in this sense seems to be limited by size, in having yielded no partial or complete animals larger than 2 mm. On the other end of the scale, even larvae 100 m long are preserved, often more complete than larger specimens, and details such as setules and pores smaller than 1 m can be observed. Fossils preserved in such a manner are almost exclusively hollow carcasses, but can be filled secondarily; less common are completely phosphatized compact specimens. The high quality of preservation makes the Swedish 'Orsten' a typical Konservat-Lagerstätte. Yet, its special type of preservation is more widespread in time and geographical distribution than assumed initially, and the origin of the phosphate is not necessarily restricted just to one source. Subsequent to the first discoveries of limb fragments of Cambrian arthropods in 1975, animals in this special preservational type have been discovered in several continents and across a broad stratigraphic range including even Proterozoic strata. The latter have yielded early cleavage and metazoan embryonic stages, expanding knowledge on the preservational capacities of the 'Orsten'. Here, we report the recent status of our research on the * Corresponding author.

Research paper thumbnail of Computer reconstruction and analysis of the vermiform mollusc Acaenoplax hayae from the Herefordshire Lagerstatte (Silurian, England), and implications for molluscan phylogeny

Palaeontology, 2004

Acaenoplax hayae is a spinose worm-like animal from the Silurian Herefordshire Lagerstätte of Eng... more Acaenoplax hayae is a spinose worm-like animal from the Silurian Herefordshire Lagerstätte of England, a deposit that preserves high-fidelity soft-part morphology of invertebrates in three dimensions. Specimens have been serially ground and reconstructed by computer to their three-dimensional form. Acaenoplax bears serially repeated transverse ridges dorsally, each with an array of probably aragonitic spines inclined posteriorly. Oblique ventral loberows correspond in position to the dorsal ridges. Aragonitic dorsal valves overlie every third ridge; the penultimate valve is absent leaving a total of seven. The anterior termination is disk-like, surrounding an antero-medial mouth. At the posterior termination there is a cavity between the posteriormost dorsal and a posteroventral valve, from which soft-part projections extend. Acaenoplax is interpreted as a creeping epibenthic animal that fed on sessile prey. It is an 'aculiferan' mollusc, combining unique autapomorphic structures with characters typical of the Polyplacophora and Aplacophora. Its morphology can be accommodated within both of the competing schemes of molluscan phylogeny, and its closest living relatives in both cases are aplacophorans. The highly serialized morphology of Acaenoplax is unique within the Mollusca, but the pattern it highlights is an attractive candidate for the primitive state of serial repetition within the phylum.

Research paper thumbnail of THE SYSTEMATICS AND PHYLOGENETIC RELATIONSHIPS OF VETULICOLIANS

Palaeontology, 2007

Vetulicolians have variously been considered to be unusual arthropods, stem-group deuterostomes o... more Vetulicolians have variously been considered to be unusual arthropods, stem-group deuterostomes or relatives of the tunicates. They are known from a number of Cambrian Lagerstätten, and are particularly diverse in the Chengjiang biota of Yunnan Province, China. We recognize two classes, Vetulicolida and Banffozoa, which together form a monophyletic group. Within the Chinese collections we also identify two new species and recognize one new genus: Vetulicola monile sp. nov. and Bullivetula variola gen. et sp. nov. The evidence from new and previously described specimens is used to undertake a phylogenetic analysis and to evaluate a range of hypotheses for the affinities of vetulicolians. Given the difficulties of interpreting features in enigmatic fossils and the apparently contradictory set of characters possessed by vetulicolians, it is not possible on current evidence to reach an unequivocal conclusion regarding the phylogenetic position of the group. One possibility is that they are a sister group of arthropods that lost limbs but gained gill structures analogous to those of deuterostomes, but several features remain unexplained by this model. If they are protostomes, a more generally parsimonious position is close to the kinorhynchs. An alternative is that they are deuterostomes, although a placement at the base of the clade is not supported by the evidence. If they are deuterostomes, it is more likely that they are close to the tunicates.