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Journal of the Geological Society

The Herefordshire Lagerstätte: fleshing out Silurian marine

life

Derek J. Siveter, Derek E. G. Briggs, David J. Siveter & Mark D. Sutton

DOI: https://doi.org/10.1144/jgs2019-110

Received 9 July 2019

Revised 19 August 2019

Accepted 21 August 2019

© 2019 The Author(s). Published by The Geological Society of London. All rights reserved. For

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The Herefordshire Lagerstätte: fleshing out Silurian marine life

Derek J. Siveter1,2*, Derek E. G. Briggs3, David J. Siveter4 and Mark D. Sutton5

1Earth Collections, University Museum of Natural History, Oxford OX1 3PW, UK

2Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK

3Department of Geology and Geophysics and Yale Peabody Museum of Natural History, Yale

University, Po Box 208 109, New Haven, CT 06520-8109, USA

4School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK

5Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK

*Correspondence: [email protected]

Abstract: The Herefordshire Lagerstätte (c. 430 Myr BP) from the UK is a rare example of

soft-tissue preservation in the Silurian. It yields a wide range of Silurian invertebrates in

unparalleled three-dimensional detail, dominated by arthropods and sponges. The fossils are

exceptionally preserved as calcitic void infills in early diagenetic carbonate concretions

within a volcaniclastic (bentonite) horizon. The Lagerstätte occurs in an outer shelf/upper

slope setting in the Welsh Basin, which was located on Avalonia in the southern subtropics.

The specimens are investigated by serial grinding, digital photography and rendering in the

round as a ‘virtual fossil’ by computer. The fossils contribute much to our understanding of

the palaeobiology and early history of the groups represented. They are important in

demonstrating unusual character combinations that illuminate relationships; in calibrating

molecular clocks; in variously linking with taxa in both earlier and later Palaeozoic

Lagerstätten; and in providing evidence of the early evolution of crown-group representatives

of several groups.

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mailto:[email protected]://jgs.lyellcollection.org/

The Herefordshire Lagerstätte is unique in preserving representatives of many major invertebrate

groups in high fidelity three-dimensions, as calcite in-fills within concretions in a marine

volcaniclastic deposit. The Herefordshire fossils are unimpressive at first sight, yet they yield

unrivalled evidence about the palaeobiology and evolutionary significance of Silurian animals. It

provides, for example, the earliest evidence for the time of origin of certain major crown-groupsi.e.

the living biota), for instance sea spiders (pycnogonids).

The locality lies in the Welsh Borderland, a historic region central to R. I. Murchison’s

pioneering research which established the Silurian System in the 1830s. In 1990 Bob King,

mineralogist and retired Curator in the Department of Geology at the University of Leicester,

collected concretions in float from the locality and presented nine of them to the Leicester

collections. Curator Roy Clements asked David Siveter to examine one of the concretions when he

was accessioning the material in 1994. What David recognised under the microscope, an arthropod

with preserved limbs (later named Offacolus kingi), was confirmed by Derek Siveter and, together

with Bob King, they identified the stratigraphic horizon and collected more concretions. In 1995

Derek Briggs joined the team and, following more visits to the locality, we published an initial paper

flagging the significance of the discovery (Briggs et al. 1996). NERC and Leverhulme Trust funding

enabled Patrick Orr and later Mark Sutton to work on the Lagerstätte, initially as postdoctoral

researchers. The support and cooperation of the site owners and help from English Nature have

been crucial in realizing its scientific potential.

Locality, age and palaeogeographic setting

The Herefordshire site lies in the Old Radnor to Presteigne area of the Welsh Borderland (Fig. 1a) in

the vicinity of the Church Stretton Fault Zone. The fossil-bearing concretions (Fig. 1b, c) occur in a

soft, fine-grained, cream-coloured, weathered and largely unconsolidated bentonite (Fig. 1b) that

crops out over about 30 metres. The bentonite is unique in the British stratigraphic record, at least, in

reaching a thickness of at least a metre in places. The bentonite was deposited within mudstones of

the Wenlock Series Coalbrookdale Formation (Fig. 1d), which rests on the slightly older Dolyhir and

Nash Scar Limestone Formation. In the Dolyhir region these coral and algal-rich limestones lie with

angular unconformity on a Precambrian sedimentary basement (Woodcock 1993). At nearby Nash

Scar, laterally equivalent carbonates sit, possibly disconformably (Woodcock 1993), on the shallow

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marine upper Llandovery Series Folly Sandstone and a hardground is developed locally on the

limestones (Hurst et al. 1978).

The host bentonite lies approximately at the boundary between the Sheinwoodian and

Homerian stages (Fig. 1d), which is radiometrically constrained to 430.5 ±0.7 Ma (Cohen et al. 2013,

updated 2018). Various evidence from brachiopods, graptolites and conodonts indicate a Wenlock

age for the Dolyhir and Nash Scar Limestone Formation in addition to the overlying Coalbrookdale

Formation (Bassett 1974; Cocks et al. 1992). The Sheinwoodian conodont Ozarkodina sagitta

rhenana has been recovered from the limestones at Dolyhir and Nash Scar (Bassett 1974; Aldridge et

al. 1981). The presence of Homerian Cyrtograptus lundgreni Biozone graptolites in the

Coalbrookdale Formation mudstones immediately above the limestones at Nash Scar (Bassett 1974)

suggests that deposition of these mudstones did not commence locally until C. lundgreni times

(Hurst et al. 1978). This is consistent with the presence of a hardground that presumably formed

during a hiatus in deposition in the late Sheinwoodian.

The recovery of the chitinozoans Margachitina margaritana, Ancyrochitina plurispinosa and

Cingulochitina cingulata from 20 cm and 50 cm below the bentonite also indicates an upper

Sheinwoodian to Homerian age for the Coalbrookdale Formation (G. Mullins, pers. comm, 2000; see

also Steeman et al. 2015). That age is unchallenged by ostracods (David Siveter, unpublished

information) and radiolarians (Siveter et al. 2007a) recovered from concretions in the bentonite.

The volcanic ash in which the Herefordshire Lagerstätte is preserved accumulated in the Welsh

Basin (Fig. 1e). This lay on the microcontinent of Avalonia, which included southern Britain (Fig. 1f;

Cocks & Torsvik 2011). Avalonia and adjacent Baltica were in southern tropical/subtropical

palaeolatitudes in the mid-Silurian, separated from Laurentia by a remnant Iapetus Ocean. Shallow

water muds characterised much of the Welsh Borderland and central England east of the Church

Stretton Fault Zone (Bassett et al. 1992; Cherns et al. 2006). Coeval fine clastics and turbidites

accumulated to the west in the deepest parts of the Welsh Basin. Palaeogeographical and

sedimentological evidence indicates that the Coalbrookdale Formation in the Dolyhir-Nash Scar area of

the Church Stretton Fault Zone accumulated in a moderately deep, outer shelf/shelf slope

environment (Briggs et al. 1996); the presence of the Visbyella brachiopod community suggests water

depths of 100-200 m (Hurst et al. 1978; Brett et al. 1993). Geochemical analyses suggest a destructive

plate margin as the source of the volcanic ash (Riley 2012). The closest known volcanic centres of

Wenlock age (Cocks & Torsvik 2005) are the Mendip Hills in southwest England (Avalonia) and the

Dingle peninsula in southwest Ireland (Avalonia). The Herefordshire bentonite is geochemically similar

to volcanic rocks in both areas (Riley 2012). A more distant candidate is the Czech Republic, then on

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Perunica, a microcontinent in the centre of the Rheic Ocean (Fig. 1f).

Box 1. The fauna of the Herefordshire Lagerstätte

(Includes Table 1 (Faunal list) and Fig. 2a, b)

Thirty-two species, including two under open nomenclature, have been described from the

Herefordshire Lagerstätte, and at least 29 await description (Table 1). Some 75% of

Herefordshire species (excluding radiolarians) are non-biomineralized but this reflects bias in

initial taxa selected for study and may fall to ~50% when other biomineralized taxa,

including trilobites, and the extensive sponge fauna, are described. Arthropods are diverse

(Fig. 2a): 19 species have been recorded, 17 of which have been fully described. They

include representatives of most major euarthropod groups: megacheirans, pycnogonids,

chelicerates, trilobites, marrellomorphs, stem mandibulates and pancrustaceans (this last by

far the most species-rich, with 9 described species) as well as one lobopodian. Sponges are

the most abundant and diverse of the other major groups, probably comprising at least 20

species, although all but one await detailed investigation. Molluscs are represented by two

species of aplacophorans and two gastropods (one uninvestigated), one bivalve and an

orthoconic nautiloid (uninvestigated). There are four echinoderm species, an asteroid,

edrioasteroid, ophiocistioid and a crinoid (the last uninvestigated), at least three brachiopods

(one an uninvestigated lingulid), an annelid, possibly two cnidarians (a coral and a possible

hydrozoan, both uninvestigated), and two hemichordates (a graptoloid and a possible

dendroid, both uninvestigated). The large number of unidentified specimens (1506; 41.0%)

reflects poorly preserved examples and also the difficulty of identifying specimens on split

concretions prior to reconstruction. Radiolarians are not included in the faunal composition

assessment (Fig. 2a) because of the difficulty in estimating their specimen numbers (which

are in the hundreds or possibly thousands). Additionally, a few thousand concretions remain

unsplit.

The chelicerate Offacolus kingi is the most abundant species at more than 800

specimens (Fig. 2b), an order of magnitude more than the mandibulate Tanazios dokeron and

the malacostracan crustacean Cinerocaris magnifica. Most of the arthropods are known from

just a few specimens (e.g. the megacheiran Enalikter aphson), or single individuals, such as

the horseshoe crab Dibasterium durgae. Of non-arthropod taxa the polychaete annelid

Kenostrychus clementsi is the most abundant at over 250 specimens. Many of the non-

arthropods, however, such as the edrioasteroid Heropyrgus disterminus, are based on a few

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tens of specimens and some, such as the bivalve Praectenodonta ludensis, on one specimen

only.

Taphonomy

The volcanic ash that hosts the Herefordshire biota was deposited on an erosion surface on massive

limestone and, in places, muds; the uneven topography likely reflects the original Wenlock seafloor.

The ash layer varies from a few tens of cm to over 1 m thick and is highly weathered at least at the

surface: no evidence for primary sedimentary structures is preserved. Thus, it is unclear whether the

ash represents in situ settling or was reworked, or whether there was one or several ashfalls.

Occasional examples of unsuccessful escape traces (Orr et al. 2000) indicate that at least some of the

animals were buried alive, which is consistent with the remarkable preservation. The bentonite has

yielded at least five thousand randomly distributed calcite-cemented (Fig. 3) concretions 2-25 cm in

diameter (Orr et al. 2000; Fig. 1b, c). Unusually for fossils preserved in this way, the organisms do

not appear to have influenced the size or shape of the concretions, nor are they usually in the centre

(Fig. 1c). Fossils are only preserved where they were incorporated into concretions but it is not clear

what determined the locus of concretion formation. The timing and nature of the growth of the

Herefordshire concretions merits further investigation.

The fossils show high fidelity three-dimensional preservation – the threads that attach the juveniles

to the arthropod Aquilonifer (Briggs et al. 2016), for example, are less than 50 µm in diameter (Fig.

4h). About half the taxa lacked biomineralized hard parts and the biomineralized taxa preserve

remarkable details in addition to features preserved in the normal fossil record. The soft tissues

show negligible collapse (Fig. 3a, d) indicating that the ash stiffened and recorded the outer

morphology of the animals before significant decay took place. The spherical morphology of the

concretions suggests that they formed rapidly, before sediment compaction. The fossils are

preserved as voids that were infilled with calcite (Fig. 3) at the same time as the concretions formed

(Orr et al. 2000). The biomineralized skeletons of brachiopods, gastropods, trilobites and ostracods

are preserved, but organic remains, even non-biomineralized arthropod cuticles, are absent – the

periderm of the rare graptolites is an exception. Preservation was investigated in detail in the

arthropod Offacolus (Orr et al. 2000). Sparry calcite infilled the external mould of Offacolus,

sometimes with an initial phase of finer fibrous calcite around the periphery (Figs 3a, 4c, f). Pyrite

precipitated on the boundary between calcite crystals but as a minor constituent of the void fill. Clay

minerals precipitated on and underneath the exoskeleton, and in some examples the gut trace was

replicated in calcium phosphate. Ferroan dolomite (ankerite) formed at a later stage perhaps

coincident with the transformation on burial of smectite to illite. Abundant radiolarians are evident

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on the surface of split concretions (Siveter et al. 2007a; Fig. 5x). Their preservation shows parallels to

that of Offacolus (Orr et al. 2002). Calcite and pyrite precipitated in the void vacated by the

cytoplasm within the radiolarian tests; this space was not invaded by matrix. The precipitation of

calcite retained the shape of the test when the opaline silica that formed it was replaced during

diagenesis by a mixture of ankerite and diagenetic clay minerals; replacement of silica by ankerite

has also been observed in siliceous sponge-spicules (Nadhira et al. 2019). Although there are

similarities with the diagenetic sequence displayed by radiolarians in concretions elsewhere

(Holdsworth 1967; Orr et al. 2002) the nature of the preservation of soft tissue morphology at the

Herefordshire site remains unique.

Releasing the information from the fossils

The Herefordshire concretions are collected in bulk using earth moving equipment. Each scoop is

tipped slowly onto a waste-pile; concretions roll out and are collected manually. The concretions are

split repeatedly in the laboratory with a manual rock-splitter; the process is halted if a fossil is found

(Fig. 3; ~50% of concretions). Specimens are identified provisionally, photographed with a Leica

DFC420 digital camera mounted on a Leica MZ8 binocular microscope with a thin layer of water over

the specimen to enhance contrast, and catalogued in a custom online database.

The fossils record copious anatomical information but present challenges for its extraction.

Manual or chemical preparation of specimens (see e.g. Sutton 2008) is impractical. Study of the

Herefordshire fauna is unique among invertebrate Lagerstätten in relying almost exclusively on

virtual reconstructions. Indeed, research on the fossils has played an important role in the

development of such techniques and their wider application (Sutton et al. 2001b, 2014). Non-

destructive approaches to data-capture such as X-ray computed tomography are clearly preferable

as a basis for virtual reconstructions but are largely ineffective for Herefordshire fossils: X-ray

absorption contrast between fossil and matrix is very low. Limited success has been achieved with

some specimens by using phase-contrast synchrotron tomography (see Sutton et al. 2014, p. 78) but

a destructive yet highly effective physical-optical tomography ‘serial grinding’ technique is, of

necessity, our method of choice. This takes advantage of the strong optical contrast between

specimen and matrix and has been used to reconstruct over 100 specimens.

Specimens for reconstruction are trimmed with a fine rock-saw to ~10 mm cuboids and

mounted on a Buehler ‘slide holder’ which consists of an inner metal cylinder which can be adjusted

to elevate specimens a precise distance above a hard outer ceramic disc. Specimens are ground to

remove a consistent thickness (20–50 µm), washed, and photographed. This process is repeated

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until the entire specimen has been digitised, typically in 200–400 increments. Part and counterpart

are ground separately, and large specimens are processed in several pieces which are re-united

digitally, following reconstruction, using the custom SPIERS software suite (Sutton et al. 2012b).

Reconstruction begins with manual or semi-automatic registering (aligning) of photographs using the

cut edges of cuboids as a guide. Data are then prepared for reconstruction by carefully distinguishing

pixels representing the fossil from those corresponding to matrix. Software exists to automate this

process but an understanding of the taphonomy and likely anatomy of the specimen, and of

artefacts generated by the process (e.g. 'out-of-plane' structures visible through bubbles in the

encasing resin), is essential to extract maximum morphological information. Data are ‘marked up’ to

identify separate structures for visualization, e.g. a particular arthropod appendage. Prepared

datasets are reconstructed to triangle-mesh isosurfaces using the Marching Cubes algorithm

(Lorenson & Cline 1987). These are visualised and studied using the SPIERSview component of the

software suite, which can combine multi-part models (e.g. part and counterpart) and enables

stereoscopic viewing, arbitrary rotation, scaling, dissection, and sectioning. Models are exported into

VAXML/STL format (Sutton et al. 2012b) for publication, or to the open-source rendering package

Blender (http://www.blender.org) to produce maximal-quality ray-traced images and animations

(see Sutton et al. 2014, pp. 27–31, 155–158 for details of the process). The quality of preservation is

such that a single specimen can provide abundant data for detailed analysis.

Unexpected character combinations and a possible role for evolutionary development

The reconstruction of phylogenies and the ordering and timing of character-acquisition has been an

overarching project in evolutionary biology and palaeontology for over 150 years. Reconstructing the

history of life based on the living biota alone is attractive as vast quantities of data are obtainable,

including the genetic sequences that have revolutionized phylogenetic practice in recent years.

However, such data are restricted to crown-groups; no amount of avian sequences would reveal the

origin of birds within Dinosauria, for example. Fossils document otherwise unknown character

combinations that did not survive to the present. These combinations can illuminate relationships

and evolutionary history (e.g. in arthropods: Legg et al. 2013), a reminder that the significance of

fossils may be out of proportion to their morphological information content. It is no surprise

therefore that the high-fidelity soft-tissue anatomy preserved in the Herefordshire fossils provides

important new data for determining the course of evolution in many groups, as illustrated by

molluscs.

Deep molluscan phylogeny hinges on the position of the Aplacophora which comprise two

worm-like groups, Chaetodermomorpha and Neomeniomorpha, united in lacking a shell and fully-

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developed molluscan foot. Aplacophorans were traditionally interpreted (e.g. by Salvini-Plawen

1991) as the earliest branch of the mollusc lineage (Fig. 4u), but an alternative model places them as

sister to the multivalved Polyplacophora (chitons) in a clade termed Aculifera, which is in turn the

sister group to all other molluscs (Conchifera). This ‘Aculifera hypothesis’ is supported by both

molecular and morphological data (Sigwart & Sutton 2007; Wanninger & Wollesen 2018; but see

Salvini-Plawen & Steiner 2014). Resolution of the debate is critical for reconstructing molluscan

evolution (did the ancestor of crown-group molluscs have a shell and/or foot?), and for determining

their position in the tree of life.

Aplacophorans were unknown as fossils before they were discovered in the Herefordshire

biota. Multivalved molluscs had been described from the Palaeozoic (e.g. Cherns 1998a, 1998b), but

were treated as early polyplacophorans (chitons). The discovery of Acaenoplax hayae from

Herefordshire (Sutton et al. 2001a; Sutton et al. 2004; Dean et al. 2015) revealed an aplacophoran-

like form bearing spicules, lacking a true foot and possessing a posterior respiratory cavity (Fig. 4s, t).

Nonetheless Acaenoplax shows serialisation and multiple dorsal valves reminiscent of

Polyplacophora. The subsequent discovery of Kulindroplax perissokomos (Sutton et al. 2012a)

documented an even more aplacophoran-like body with no trace of a foot but bearing a set of

typical Palaeozoic ‘polyplacophoran’ valves (Fig. 4l, m). This association appeared chimeric but only

because it represents an extinct character combination. Acaenoplax and Kulindroplax provide

support for Aculifera (e.g. Vinther 2015), indicating that the ‘simple’ morphology of aplacophorans is

derived rather than primitive for the Mollusca. Furthermore, these Herefordshire fossils reveal a

sequence of evolutionary events that cannot be deduced from extant forms: a vermiform body

predated the loss of valves, and a diversity of ‘plated aplacophorans’, previously misinterpreted as

polyplacophorans, was present during the early Palaeozoic. Modern aplacophorans evolved through

a secondary loss of valves and are a remnant of a once larger group (Fig. 4v).

Research on evolutionary development has demonstrated how control genes can initiate

major changes in morphology. Modern polyplacophorans (chitons) have a series of eight dorsal

valves associated with the expression of the engrailed gene (Jacobs et al. 2000) whereas Acaenoplax

and Kulindroplax (Fig. 4l, m, s, t) have only seven. Such seven-fold seriality is expressed during the

ontogeny of living aculiferans (Scherholz et al. 2013) and may reflect an ancestral morphology

evident in Kulindroplax (Wanninger & Wollesen 2018). The addition of an eighth shell, which occurs

after metamorphosis in Polyplacophora, appears to be an advanced condition (Wanninger &

Wollesen 2018). Acaenoplax is unusual in having an obvious gap between valves 6 and 7 where an

additional valve might have been placed (Sutton et al. 2001a, 2004). The ‘missing’ valve may reflect

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the ancestral 7-valve morphology or, given that the space for an additional valve is present, may

have been lost secondarily from an 8-valved form.

The remarkable details preserved in some of the Herefordshire arthropods provide evidence

of ancestral morphologies and prompt questions as to how they might have been transformed into

modern forms. Martin et al. (2016) used CRISPR/Cas9 mutagenesis and RNAi knockdown to show

how shifting Hox gene domains in a living amphipod crustacean could contribute to

macroevolutionary changes in the body plan. The limbs of the Herefordshire chelicerates

Dibasterium (Briggs et al. 2012; Fig. 4d, e, g, i) and Offacolus (Sutton et al. 2002; Fig. 4c, f) can be

homologized readily with those of the living horseshoe crab Limulus but they differ in fundamental

ways. Limbs 2 to 5 in the anterior division of the body (prosoma) of the Herefordshire Silurian forms

have two branches, an endopod and exopod, both of which are robust and segmented, whereas only

one branch is present in Limulus. Unlike the branches of limbs in other arthropods, however, the two

branches are not connected to a common basal segment: they insert in different places on the body

wall. This arrangement can be interpreted as a stage in the loss of the exopod to yield a limb with a

single ramus as in Limulus. The expression of Distal-less (Dll) in larval Limulus (Mittman & Scholtz

2001) suggests that the loss of the exopod may be developmental. Limulus shows a strong

expression of Dll associated with the origin of the endopod and a weaker expression, in the early

embryo, in an adjacent position corresponding to the insertion of the exopods in Dibasterium. This

weaker expression disappears in later embryonic stages echoing the loss of the outer ramus during

the evolution of the group (Briggs et al. 2012). The chelicera of Dibasterium (limb 1) is also unusual

in being an elongate flexible antenna-like appendage in contrast to the familiar claw of Limulus. Here

too knockdown of genes such as Dll and dachsund may have led to the loss of distal podomeres and

the evolution of the shorter chelicera in modern horseshoe crabs, echoing experimental results on

the harvestman Phalangium (Sharma et al. 2013).

Extended stratigraphic ranges and the calibration of molecular clocks

The Herefordshire Lagerstätte is one of very few windows on soft-bodied organisms during the

Silurian. It is not surprising, therefore, that the fossils provide important examples of stratigraphic

range extensions. Thanahita (Fig. 5a, b), for example, falls in a clade with the three known species of

the iconic lower to mid-Cambrian lobopodian Hallucigenia (Siveter et al. 2018b). The long slender

trunk appendages of Thanahita contrast with those of short-legged lobopodians such as the

Cambrian Antennacanthopodia (Ou et al. 2011). Long-legged lobopodians are also represented by

Carbotubulus from the late Carboniferous Mazon Creek Lagerstätte of Illinois (Haug et al. 2012)

which is some 135 Myr younger than Thanahita.

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The discovery of the arthropod Enalikter (Siveter et al. 2014a, 2015a; Fig. 5e) revealed that

megacheirans (short-great-appendage arthropods) were present in the Silurian. Phylogenetic

analysis showed that Bundenbachiellus from the Devonian Hunsrück Slate, not previously

interpreted as a megacheiran, is sister to Enalikter, extending the range of megacheirans nearly 100

Myr beyond the previously youngest known short-great-appendage arthropod Leanchoilia? sp. from

the mid-Cambrian of Utah (Briggs et al. 2008).

Xylokorys is the only known Silurian marrellomorph euarthropod (Siveter et al. 2007b; Fig.

5r, w). It belongs to the Acercostraca which, in contrast to the familiar Cambrian Marrella, is

characterized by a large shield-like carapace which covers the head and trunk. Xylokorys extends the

Cambrian (Primicaris and Skania) and Ordovician (Enosiaspis) acercostracan record and heralds the

youngest known example, Vachonisia, in the Devonian Hunsrück Slate.

Haliestes (Siveter et al. 2004; Fig. 5n, o) is arguably the best preserved and most complete of

just thirteen known species (Sabroux et al. 2019) of fossil pycnogonid. These include a putative larval

pycnogonid, Cambropycnogon klausmuelleri, from the upper Cambrian Orsten of Scandinavia

(Waloszek & Dunlop 2002), and a basal stem group pycnogonid, Palaeomarachne granulata, from

the Ordovician William Lake Lagerstätte of Canada (Rudkin et al. 2013). The Herefordshire

pycnogonid Haliestes shows reduction of the body to a small trunk projection beyond the

posteriormost limbs. This is a feature of Pantopoda, indicating that crown-group pycnogonids

extended back to the Silurian (Siveter et al. 2004; Arango & Wheeler 2007; Dunlop 2010; but see

Charbonier et al. 2007). Five pycnogonid species are known from the Devonian Hunsrück Slate, of

which Palaeopantopus maucheri and Palaeothea devonica show trunk end reduction. Three species

from the Jurassic of La Voulte-sur-Rhȏne, France, may also belong to extant pantopod families

(Charbonier et al. 2007).

Where Herefordshire taxa extend the range of particular clades back in time, they

provide fossil calibrations for the tree of life, notably in the case of arthropods. Haliestes

provides one example (Wolfe et al. 2016), the barnacle Rhamphoverritor reduncus (Briggs et

al. 2003; Fig. 4o, n) provides a calibration for crown-group Thecostraca, and the phyllocarid

Cinerocaris magnifica (Briggs et al. 2005, fig. 5c, d) for crown Malacostraca (Wolfe et al.

2016). Herefordshire ostracods (Fig. 4a, b, q, r; 4u, z, zz) provided the calibration for crown

Ostracoda (Oakley et al. 2013) prior to the discovery of Luprisca incubi from the late

Ordovician Beecher’s Trilobite Bed of New York State (Siveter et al. 2014b; Wolfe et al.

2016). Invavita piratica from the Herefordshire Lagerstätte (Siveter et al. 2015b; Fig. 4p-r),

the earliest adult pentastomid pancrustacean, is arguably a more secure calibration than

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Boeckelericambria pelturae from the Cambrian Orsten (Walossek & Müller 1994), which is

based on a larva (Wolfe et al. 2016).

The described Herefordshire biota includes five species of ostracods with preserved

appendages, all of which are myodocopes: Colymbosathon ecplecticos, Nymphatelina gravida,

Nasunaris flata, Pauline avibella and Spiricopia aurita (Siveter et al. 2003, 2007c, 2010, 2013, 2015b,

2018a). All of these, except N. gravida, represent the earliest representatives of crown group

cylinderoberidids, which are characterised by the presence of gills. The only other fossil myodocopes

with possible gill preservation are Triadocypris from the lower Triassic of Spitzbergen (Weitschat

1983) and Juraleberis from the upper Jurassic of Russia (Vannier & Siveter 1996).

The Herefordshire molluscs Acaenoplax and Kulindroplax (Sutton et al. 2001a, 2004,

2012a; Sigwart & Sutton 2007; Fig. 4l, m, s, t) also provide molecular clock calibrations.

Both represent total group aplacophorans and crown-group Aculifera (Vinther et al. 2017;

Wanninger & Wollesen 2018). The Herefordshire polychaete worm Kenostrychus represents

crown Aciculata even though its original placement as a stem-group phyllodocid (Sutton et

al. 2001c; Fig. 5s) has been revised to stem amphinomid (Parry et al. 2016).

Box 2. Other Silurian Lagerstätten

The early Ordovician Fezouata biota of Morocco (Van Roy et al. 2015) is the most diverse

open-marine Lagerstätte in the interval between the late Cambrian Weeks Formation of Utah

(Lerosy-Aubril et al. 2018) and the mid-Silurian Herefordshire Lagerstätte (other Ordovician

Lagerstätten are briefly reviewed in Van Roy et al. 2015). The Fezouata biota is much more

diverse than Herefordshire, comprising over 160 genera of which shelly taxa account for

about 50%. As in Herefordshire, sponges are diverse and panarthropods dominate (over 60

taxa). Fezouata yields a greater diversity of shelly taxa including conulariids, bryozoans,

machaeridian annelids, rostroconch and helcionelloid bivalves, hyolithoids, and echinoderms.

Apart from Herefordshire, open marine Lagerstätten of Silurian age are rare (Fig. 6).

Other exceptionally preserved faunas are almost exclusively preserved via Burgess Shale-

type pathways as degraded organic (carbonaceous) compression fossils and almost all

represent marginal marine or ‘stressed’ environments (Orr 2014). The Ludlow age Eramosa

Lagerstätte of Ontario includes three biotas representing different environments. Soft bodied

fossils are characteristic of Biota 3 which contains a diverse marine fauna of conulariids, a

lobopodian, trilobites, eurypterids, xiphosurans, diverse crustaceans, brachiopods, polychaete

annelids, echinoderms, conodonts, and possible fish. The fauna of the late Llandovery

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Waukesha Lagerstätte from Wisconsin (Mikulic et al., 1985a, 1985b) shows some similarity

to Eramosa but is peritidal. It is dominated by arthropods, especially trilobites (13 genera),

and includes a xiphosuran and phyllocarid, ostracod and thylacocephalan crustaceans.

Conulariids and graptolites are common, but brachiopods, bryozoans, corals, molluscs and

echinoderms are rare or absent. The Přídolí Bertie Group of Ontario and New York State is

dominated by eurypterids, xiphosurans, scorpions and phyllocarids preserved in fine

carbonate muds (Clarke & Ruedemann 1912: Copeland & Bolton 1985). The presence of salt

hoppers was long regarded as evidence of hypersaline conditions, but it is likely that they

were precipitated in the sediment after deposition and the Bertie Group represents a shallow

subtidal setting (Vrazo et al. 2016). The deeper marine Herefordshire fauna includes

numerous sponges, two trilobite genera, and a greater representation of major arthropod

groups, as well as four major (fully stenohaline) echinoderm taxa (Box 1, Table 1).

The other major Silurian Lagerstätten show a greater terrestrial influence. Late

Llandovery to early Wenlock Lagerstätten in the Midland Valley of Scotland from the

Priesthill and Waterhead groups of Lesmahagow, and correlatives in the Hagshaw and

Pentland Hills, represent restricted quasi-marine to lacustrine settings and are typically

dominated by eurypterids, phyllocarids and fish (Allison & Briggs 1991; Ritchie 1968, 1985;

Rolfe 1973; Siveter 2010a). The Stonehaven Lagerstätte (Siveter & Palmer 2010) in

Scotland, which yields millipedes (Wilson & Anderson 2004), was considered to be of late

Wenlock/Ludlow age on the basis of palynomorphs (Marshall 1991, Wellman 1993) but has

recently been radiometrically dated as lowermost Devonian, Lochkovian (Suarez et al. 2017;

see also Shillito & Davies 2017 for ichnological evidence). The basal Přídolí Ludlow Bone

Bed Lagerstätte at Ludford Lane and Corner in the Welsh Borderland yields, in addition to

fish bone fragments and thelodonts, centipedes, arthropleurid and kampecarid myriapods,

eurypterids and scorpions (Jeram et al. 1990; Siveter 2000; Siveter 2010b).

Mode of life and palaeoecology

Herefordshire taxa reveal aspects of gender, larval development and brood care in fossil arthropods.

The recognition of hemipenes in the myodocope ostracod Colymbosathon (Siveter et al. 2003; Fig.

4a) and eggs and a juvenile, in situ, within the carapace of the myodocope Nymphatelina (Siveter et

al. 2007c, 2015b; Fig. 4b) allows male and female to be distinguished in early Palaeozoic animals.

The brood care strategy evident in Nymphatelina remains essentially unchanged in myodocopes

today. A more complex and unique brooding behaviour is preserved in the stem mandibulate

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Aquilonifer; the presumed female carries ten tiny juveniles each within a cuticular capsule tethered

by a delicate thread (Briggs et al. 2016; Fig. 4h). Such data help suggest that complexity of brooding

strategies probably evolved early in the history of the Arthropoda. Specimens representing a free-

living ‘cyprid’ larval stage and an attached juvenile of the barnacle Rhampoverritor reduncus

demonstrate that the lifecycle of cirripedes has remained essentially the same over 430 million years

(Briggs et al. 2005; Fig. 4o, n). A boring through a valve of Rhampoverritor (Fig. 4n) also provides

evidence of predation in the biota. The discovery of a pentastomid pancrustacean, Invavita piratica,

parasitic on the ostracod Nymphatelina gravida is the only known fossil pentastomid preserved with

its host and suggests that the group may have originated as ectoparasites on marine invertebrates

(Siveter et al. 2015b; Fig. 4p-r). Bethia serreticulma is the only recorded fossil rhynchonelliformean

brachiopod with preserved soft parts (Fig. 4k). Evidence of its mode of life, shell size and lophophore

configuration indicates that the only known specimen is an immature example. Its unusual pedicle

morphology differs from that in living species urging caution in inferring stem-group anatomy based

on crown-group species (Sutton et al. 2005a). The specimen of B. serreticulma bears an in vivo

epifauna including a tiny unmineralised lophophorate, Drakozoon kalumon (Fig. 4 j), which may

allude to a widespread occurrence of similar but unknown lophophorates in the Palaeozoic (Sutton

et al. 2010).

The majority of the 63 known Herefordshire species lived on the seafloor (Table 1; Fig. 7),

either as sessile or vagile epibenthos. Unless the Herefordshire animals were transported from

significantly shallower waters, it appears that the benthic components of the biota lived in dim light

conditions at best. Several of the benthic animals lack eyes and there is an absence of photic-zone

indicators such as algae. Given the evidence for rapid burial it is likely that the water column biota is

underrepresented. Sponges are the dominant sessile element, with brachiopods, echinoderms (the

edrioasteroid Heropyrgus and a crinoid), a cirripede, coral, and a possible dendroid graptolite and

gastropod (Platyceras?) as minor components. Most of the vagile epibenthos are arthropods, but

this group also includes two echinoderms (the asteroid Bdellacoma and ophiocistioid Sollasina), the

aplacophoran mollusc Acaenoplax, a gastropod and a bivalve mollusc. The nektobenthos is made up

entirely of arthropods, with ostracods the most species abundant. A nautiloid is the only nektonic

element. A graptolite and radiolarians comprise the pelagic plankton. A possible infaunal/semi-

infaunal mode of life is interpreted for just three taxa, a lingulid brachiopod, the aplacophoran

Kulindroplax and the annelid Kenostrychus. The numerical dominance of Offaculus within the biota is

probably real rather than representing an artefact of sampling, as concretions are selected and split

randomly and, as one of the smaller taxa, its high yield is unlikely to result from being selectively

preserved. The biota includes representatives of many major invertebrate groups but there is no

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obvious reason why some groups known from the Silurian of the Welsh Basin elsewhere, such as

vertebrates and bryozoans, have not been found in the concretions.

Why is the Herefordshire Lagerstätte apparently unique?

The Herefordshire biota is one of a number of examples of soft tissue preservation in concretions.

Concretion formation requires carbonate (or more rarely silica) supersaturation and the presence of

a nucleus. In some cases, a buried carcass can provide both. Soft tissues can be preserved within

concretions in a number of ways (McCoy et al. 2015): as carbonaceous remains, as a result of

replication in a variety of authigenic minerals, or by void fill as in the case of the Herefordshire biota.

Exceptional preservation is promoted where concretion growth is rapid, and void fills are more likely

to occur where cementation occurs from the inside out, slowing diffusion at an early stage and

isolating the organism from its environment (McCoy et al. 2015). An analysis of factors associated

with exceptional preservation in concretions (based on 88 concretion sites of which 20% preserve

soft-tissues) showed that concretion formation enhances the chances of exceptional preservation

only where other conditions are favourable, such as burial in fine grained sediment (McCoy et al.

2015). The volcanic ash that buried the Herefordshire organisms may have played a role in their

exceptional preservation. Fine grain size may have promoted anoxia within the sediment and

inhibited scavengers.

Predictably perhaps, most examples of exceptional preservation associated with volcanic ash

are in terrestrial settings (Briggs et al. 1996), in lacustrine and fluvial environments. Preservation of

plant materials in volcanic ash may be enhanced by rapid burial and anoxic conditions, as in the

Cretaceous of Argentina (Lafuente Diaz et al. 2018) and the Miocene Clarkia Beds of Idaho, USA

(Ladderud et al. 2015). The Triassic Chañares Formation of Argentina yields a diversity of tetrapods

in carbonate concretions in volcanic ash that likely formed where microbial decay promoted

carbonate precipitation (Rogers et al. 2001) but concretion biotas are rare in terrestrial

environments. Giant radiodontids are preserved in silica-chlorite concretions in the lower Fezouata

Formation of Morocco including silica, iron and aluminium thought to be sourced from volcanic ash

(Gaines et al. 2012). A volcanic influence has also been reported impacting fossil preservation in

other marine settings, including some from the Silurian of the UK and Ireland. Coral communities in

the Llandovery Kilbride Formation of Co. Mayo, Ireland are buried by volcanic ash (Harper et al.

1995) as are shelly fossils in the Wenlock Ballynane Formation of the Dingle Peninsula, Co. Kerry,

Ireland (Ferretti & Holland 1994), but soft tissue preservation is unknown and associated concretions

have not been reported. The cuticle of decapod moults and the ligament of bivalves are preserved in

concretions in the Cretaceous Bearpaw Formation of Alberta (Bentonite number 5) following rapid

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burial in volcanic ash (Heikoop et al. 1996) but carbonate concretions associated with volcanics in

marine settings are rare.

Preservation of the Herefordshire fossils involved an unusual combination of circumstances:

rapid burial of small living animals in thick, fine grained volcanic ash in a marine setting, and very

rapid formation of near-spherical carbonate cemented concretions. Other biotas preserved in a

similar fashion to the Herefordshire example have yet to be discovered. The tiny crystalline infills are

unlikely to attract the interest of a casual collector and the fossils are often off centre and may not

be intersected by the plane of splitting. Silurian bentonites are widespread in the UK, but they are

generally only a few centimetres thick (Cave & Loydell 1998). Examples of concretions within ashes

of any age merit serious scrutiny but early formed concretions in fine grained marine mudstones

may also yield exceptionally preserved fossils depending, perhaps, on the clay minerals present.

Box 3: Outstanding questions

(1) Precisely when and how were the Herefordshire concretions formed? (2) Will more sensitive scanning techniques become available in the future which can

facilitate imaging the fossils, even if only for initial identifications?

(3) What will be revealed when additional fossils are reconstructed? A diversity of sponges, as well as cnidarians, brachiopods, molluscs, trilobites and other

arthropods, crinoids and other echinoderms, graptolites and various microfossils

remain to be investigated.

(4) How does the Lagerstätte fauna compare with that of the interbedded

Coalbrookdale Formation mudstones?

(5) What further insights on the palaeoecology will emerge when more taxa have

been described?

(6) Lagerstätten rarely prove unique. Where are there other examples in the

stratigraphic record preserved in a similar fashion to the Herefordshire example?

No other Silurian locality has yet been identified, even within the Welsh Basin.

Acknowledgements and Funding

Carolyn Lewis (Oxford University Museum of Natural History) is thanked for technical assistance.

Funding is gratefully acknowledged from the Leverhulme Trust (grant no. EM-2014-068), the Natural

Environment Research Council (grant no. NF/F0108037/1), the Yale Peabody Museum of Natural

History Invertebrate Paleontology Division, and English Nature. We are grateful for insightful

comments from Patrick Orr, Robert Gaines and a third anonymous reviewer.

References

ACCE

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MAN

USCR

IPT



Aldridge, R.J., Dorning, K.J. & Siveter, D.J. 1981. Distribution of microfossil groups across

the Wenlock Shelf of the Welsh Basin. In: Neale J.W. & Brasier, M.D. (eds), Microfossils

from Recent and fossil Shelf Seas. British Micropalaeontological Society, 18-30.

Allison, P.A. & Briggs, D.E.G. 1991. Taphonomy of nonmineralized tissues. In: Allison, P.A. & Briggs,

D.E.G. (eds), Taphonomy: Releasing the Data Locked in the Fossil Record. Plenum Press, New York,

United States, 25–70.

Arango, C.P. & Wheeler, W.C. 2007. Phylogeny of the sea spiders (Arthropoda, Pycnogonida) based

on direct optimization of six loci and morphology. Cladistics, 23, 255–93.

Bassett, M.G. 1974. Review of the stratigraphy of the Wenlock Series in the Welsh

Borderland and South Wales. Palaeontology, 17, 745-77.

Bassett, M.G., Bluck, B.J., Cave, R., Holland, C.H. & Lawson, J.D. 1992. Silurian. In:

J.C.W. Cope, J.K. Ingham & P.F. Rawson (eds), Atlas of Palaeogeography and Lithofacies.

Memoir of the Geological Society of London, No. 13, 37-56.

Brett, C.E., Boucot, A.J. & Jones, B. 1993. Absolute depths of Silurian benthic assemblages. Lethaia,

26, 24-40.

Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 1996. Soft-bodied fossils from a Silurian

volcaniclastic deposit. Nature, 382, 248-250.

Briggs, D.E.G., Sutton, M.D. Siveter, David J. & Siveter, Derek J. 2003. A new phyllocarid

(Crustacea) from the Silurian Fossil-Lagerstätte of Herefordshire, England. Proceedings of

the Royal Society of London B, 271, doi10.1098/rspb.2003.2593.

Briggs, D.E.G., Sutton, M.D. Siveter, David J. & Siveter, Derek J. 2005. Metamorphosis in a Silurian

barnacle. Proceedings of the Royal Society of London B, 272, 2365-2369.

doi:10.1098/rspb.2005.3224.

Briggs, D.E.G., Lieberman B.S., Hendricks J.R., Halgedahl S.L. & Jarrard R.D. 2008. Middle Cambrian

arthropods from Utah. 2008. Journal of Paleontology, 82, 238 – 254, doi:10.1666/ 06-086.1.

ACCE

PTED

MAN

USCR

IPT



Briggs, D.E.G., Siveter, Derek J., Siveter, David J., Sutton, M.D., Garwood, R.J. & Legg, D. 2012.

Silurian horseshoe crab illuminates the evolution of arthropod limbs. Proceedings of the National

Academy of Sciences, 109, 15702-15705.

Briggs, D.E.G., Siveter, Derek J., Siveter, David J., Sutton, M.D. & Legg, D. 2016. Tiny

individuals attached to a new Silurian arthropod suggest a unique mode of brood care.

Proceedings of the National Academy of Sciences, 113, 4410-4415,

doi/10.1073/pnas.1600489113.

Briggs, Derek E.G., Siveter, Derek J., Siveter, David J., Sutton, Mark D & Rahman, Imran A.

2017. An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the

nature of the water vascular system in an extinct echinoderm. Proceedings of the Royal

Society of London B, 284, 20171189.

Cave R. & Loydell, D.K. 1998. Wenlock volcanism in the Welsh Basin. Geological Journal, 33, 107–

120.

Charbonier, S. Vannier, J. & Riou, B. 2007. New sea spiders from the Jurassic La VouIte-sur-Rhône

Lagerstätte. Proceedings of the Royal Society B, 274, 2555-2561.

Cherns, L. 1998a. Chelodes and closely related Polyplacophora (Mollusca) from the Silurian of

Gotland, Sweden. Palaeontology, 41, 545–573.

Cherns, L. 1998b. Silurian polyplacophoran molluscs from Gotland, Sweden. Palaeontology, 41, 939–

974.

Cherns, L., Cocks, L.R.M., Davies, J.R., Hillier, R.D., Waters, R.A. & Williams, M. 2006. Silurian: the

influence of extensional tectonics and sea-level changes on sedimentation in the Welsh Basin and on

the Midland Platform. In: Brenchley, P.J. & Rawson, P.F. (eds), The Geology of England and Wales.

Geological Society of London, 5-102.

Clarke, J.M. & Ruedemann, R. 1912. The Eurypterida of New York. Memoirs of the New York State

Museum, 14, 1-439.

Cocks, L.R.M., Holland, C.H. & Rickards, R.B. 1992. A revised Correlation of Silurian Rocks in the

British Isles. Special Report of the Geological Society of London, No 21, 32 pp.

Cocks, L.R.M. & Torsvik, T.H. 2005. Baltica from the late Precambrian to mid-Palaeozoic times: the

ACCE

PTED

MAN

USCR

IPT



gain and loss of a terrane’s identity. Earth Science Reviews, 72, 39-66.

Cocks, L.R.M. & Torsvik, T.H. 2011. The Palaeozoic geography of Laurentia and western Laurussia: a

stable craton with mobile margins. Earth Science Reviews, 106, 1-51.

Cohen, K.M., Finney, S.C., Gibbard, P.L. & Fan, J.-X. 2013 (updated 2018) The ICS International

Chronostratigraphic Chart. Episodes, 36, 199-204.

Copeland, M. & Bolton, T.E. 1985. Fossils of the Ontario Part 3: The Eurypterids and phyllocarids.

Royal Ontario Museum Life Sciences Miscellaneous Publications, 48 pp.

Cramer, B.D., Condon, D.J, Söderlund, U., Marshall, C., Worton, G.J., Thomas, A.T., Calner, M., Ray,

D.C., Perrier, V., Boomer, I., Patchett, P.J. & Jeppson, L. 2012. U-Pb (zircon) age constraints on the

timing and duration of Wenlock (Silurian) paleocommunity collapse and recovery during the “Big

Crisis”. Geological Society of America Bulletin, 124, 1841-1857.

Dean, C.D., Sutton, M.D., Siveter, Derek J. & Siveter, David J. 2015. A novel respiratory architecture

in the Silurian mollusk Acaenoplax. Palaeontology, 58, 839–847. doi: 10.1111/pala.12181.

Dunlop, J.A. 2010. Geological history and phylogeny of Chelicerata. Arthropod Structure &

Development 39, 124-142.

Ferretti, A. & Holland, C.H. 1994. Biofacies and palaeoenvironmental analysis of a limestone lens,

unique in the Irish Silurian from the Dingle Peninsula, County Kerry. Irish Journal of Earth Sciences,

13, 83-89.

Fu, H.L.K. 2016. A Silurian bivalve with soft tissues. Newsletter of the Palaeontological Association,

94, 88-89.

Gaines, R.R., Briggs, D.E.G., Orr, P.J. & Van Roy, P. 2012. Preservation of giant anomalocaridids in

silica-chlorite concretions from the early Ordovician of Morocco. Palaios 27, 317-325.

Harper, D.A.T., Scrutton, C.T. & Williams, D.M. 1995. Mass mortalities on an Irish Silurian sea-floor.

Journal of the Geological Society, 152, 917-922.

Haug J.T., Mayer G., Haug C. & Briggs D.E.G. 2012. A Carboniferous non-onychophoran lobopodian

reveals long-term survival of a Cambrian morphotype. Current Biology, 22, 1673–1675,

doi:10.1016/j.cub.2012.06.066.

ACCE

PTED

MAN

USCR

IPT



Heikoop, J.M., Tsujita, C.J., Heikoop, C.E., Risk, M.J. & Dicken, A.C. 1996. Effects of volcanic ashfall

recorded in ancient marine benthic communities: Comparison of a nearshore and an offshore

environment. Lethaia, 29, 125-139.

Holdsworth, B.K. 1967. Dolomitization of siliceous microfossils in Namurian concretionary

limestones. Geological Magazine, 104, 148-154.

Hurst, J.M., Hancock, N.J. & McKerrow, W.S. 1978. Wenlock stratigraphy and palaeogeography of

Wales and Welsh Borderland. Proceedings of the Geologists’ Association, 89, 197-222.

Jacobs, D.K., Wray, C.G., Wedeen, C.J., Kostriken, R., Desalle, R., Staton, J.L., Gates, R.D. & Lindberg,

D.R. 2000. Molluscan engrailed expression, serial organization, and shell evolution. Evolution and

Development, 2, 340–347.

Jeram, A.J., Selden, P.A. & Edwards, D. 1990 Land animals in the Silurian: Arachnids and

myriapods from Shropshire, England. Science, 250, 658-661.

Ladderud, J.A., Wolff, J.A., Rember, J.C. & Brueseke, M.E. 2015. Volcanic ash layers in the Miocene

Lake Clarkia Beds: Geochemistry, regional correlation, and age of the Clarkia Flora. Northwest

Science, 89, 309-323.

Lafuente Diaz, M.A., D'Angelo, J.A., Del Fueyo, G.M. & Zodrow, E.L. 2018. Fossilization model for

Squamastrobus tigrensis foliage in a volcanic-ash deposit: Implications for preservation and

taphonomy (Podocarpaceae, Lower Cretaceous, Argentina). Palaios, 33, 323-337.

Legg, D.A. 2016 An acercostracan marrellomorph (Euarthropoda) from the Lower

Ordovician of Morocco. The Science of Nature, 103, 21 pp. doi:10.1007/s00114-016-1352-5.

Legg, D.A., Sutton, M.D. & Edgecombe, G.D. 2013. Arthropod fossil data increase congruence of

morphological and molecular phylogenies. Nature Communications, 4,

2485, doi: 10.1038/ncomms3485.

Lerosy-Aubril, R., Gaines, R.R., Hegna, T.A., Ortega-Hernández, J., Van Roy, P., Kier, C. &

Bonino, E. 2018. The Weeks Formation Konservat-Lagerstätte and the evolutionary

transition of Cambrian marine life. Journal of the Geological Society,

https://doi.org/10.1144/jgs2018-042.

ACCE

PTED

MAN

USCR

IPT


https://doi.org/10.1144/jgs2018-042http://jgs.lyellcollection.org/

Lorensen, W.E. & Cline, H.E. 1987. Marching cubes: a high resolution 3D surface construction

algorithm. Computer Graphics, 21, 163–169.

Marshall, J.E. 1991, Palynology of the Stonehaven Group, Scotland: evidence for a Mid Silurian age

and its geological implications. Geological Magazine, 128, 283-286.

Martin, A., Serano, J.M., Jarvis, E., Bruce, H.S., Wang, J., Ray, S., Barker, C.A., O’Connell, L.C. & Patel,

N.H. 2016. CRISPR/Cas9 mutagenesis reveals versatile roles of Hox genes in crustacean limb

specification and evolution. Current Biology, 26, 14–26.

McCoy, V.E., Young, R.T. & Briggs, D.E.G. 2015. Factors controlling exceptional preservation in

concretions. Palaios, 30, 272-280.

Mikulic, D.G., Briggs, D.E.G. & Kluessendorf, J. 1985a. A Silurian soft-bodied biota.

Science, 228, 715–717. doi:10.1126/science.228.4700.715.

Mikulic, D.G, Briggs, D.E.G. & Kluessendorf, J. 1985b. A new exceptionally preserved biota

from the Lower Silurian of Wisconsin, U.S.A. Philosophical Transactions of the Royal

Society of London B, 311, 75–85. doi:10.1098/rstb.1985.0140.

Nadhira, A., Sutton, M.D., Botting, J. P., Muir, L. A., Gueriau, P., King, A., Briggs, D.E.G.,

Siveter, David J. & Siveter, Derek J. 2019 (in press). Three-dimensionally preserved soft-

tissues and calcareous hexactins in a Silurian sponge: implications for early sponge evolution.

Royal Society Open Science.

Oakley, T.H., Wolfe, J.M., Lindgren, A.R. & Zaharoff, A.K. 2013. Phylotranscriptomics to

bring the understudied into the Fold: Monophyletic Ostracoda, fossil placement, and

Pancrustacean phylogeny. Molecular Biology and Evolution, 30, 215–233.

Orr, P.J. 2014. Late Proterozoic-early Phanerozoic ‘taphonomic windows’: the environmental

and temporal distribution of recurrent modes of exceptional preservation. In: Laflamme, M.,

Schiffbauer, J.D. & Darroch S.A.F. (eds), Reading and Writing of the Fossil Record:

Preservational Pathways to Exceptional Fossilization. The Paleontological Society Papers,

20, 289-313.

ACCE

PTED

MAN

USCR

IPT



Orr, P.J., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2000. Three-dimensional preservation of

a non-biomineralized arthropod in concretions in Silurian volcaniclastic rocks from Herefordshire,

England. Journal of the Geological Society, 157, 173-186.

Orr, P.J., Siveter, David J., Briggs, D.E.G. & Siveter, Derek J. 2002. Preservation of radiolarians in the

Herefordshire Konservat-Lagerstätte (Wenlock, Silurian), England, and implications for the

taphonomy of the biota. Special Papers in Palaeontology, 67, 205-224.

Ou Q., Liu J., Shu D., Han J., Zhang Z., Wan X. & Lei Q. 2011 A rare onychophoran-like lobopodian

from the Lower Cambrian Chengjiang Lagerstätte, southwestern China, and its phylogenetic

implications. Journal of Paleontology, 85, 587–594. doi:10.1666/09-147R2.1.

Parry L.A., Edgecombe G.D., Eibye-Jacobsen D. & Vinther J. 2016. The impact of fossil data

on annelid phylogeny inferred from discrete morphological characters. Proceedings of the

Royal Society of London B, 283, 20161378. http://dx.doi.org/10.1098/rspb.2016.1378.

Rahman, I.A., Thompson, J.R, Briggs, D.E.G., Siveter, David J., Siveter, Derek J. & Sutton,

M.D. 2019. A new ophiocistioid with soft-tissue preservation from the Silurian Herefordshire

Lagerstätte, and the evolution of the holothurian body plan. Proceedings of the Royal Society

of London B 286, 20182792. http://dx.doi.org/10.1098/rspb.2018.2792.

Riley, D.A. 2012. Preservation and taphonomy of the fossils of the Herefordshire (Silurian) Konservat-

Lagerstätte. Unpublished PhD, University of Leicester.

Ritchie, A. 1968. New evidence on Jamoytius kerwoodi White, an important ostracoderm from the

Silurian of Lanarkshire, Scotland. Palaeontology, 11, 21-39.

Ritchie, A. 1985. Ainiktozoon loganense Scourfield, a protochordate? from the Silurian of Scotland.

Alcheringa, 9, 117-142.

Rogers, R.R., Arcucci, A.B., Abdala, F, Sereno, P.C., Forster, C.A. & May, C.L. 2001. Paleoenvironment

and taphonomy of the Chañares Formation tetrapod assemblage (Middle Triassic), northwestern

Argentina: Spectacular preservation in volcanogenic concretions. Palaios, 16, 461-481.

Rolfe, W.D.I. 1973. Silurian arthropod and fish assemblages from Lesmahagow, Lanarkshire. In:

Bluck, B.J. (Ed.), Excursion Guide to the Geology of the Glasgow District. Geological Society of

Glasgow, 119-126.

ACCE

PTED

MAN

USCR

IPT


http://dx.doi.org/10.1098/rspb.2016.1378http://dx.doi.org/10.1098/rspb.2018.2792http://jgs.lyellcollection.org/

Rudkin, D.M., Cuggy, M.B., Young, G.A. & Thompson, D.P. 2013. An Ordovician

pycnogonid (sea spider) with serially subdivided ‘head’ region. Journal of Paleontology, 87,

395-405.

Sabroux, R., Audo, D., Charbonnier, S., Corbari, L. & Hassanin, A. 2019. 150-million-year-

old sea spiders (Pycnogonida: Pantopoda) of Solnhofen, Journal of Systematic

Palaeontology, doi: 10.1080/14772019.2019.1571534

Salvini‐Plawen, L.V. 1991. Origin, phylogeny and classification of the phylum Mollusca. Iberus, 9, 1–

33.

Salvini‐Plawen, L.V. & Steiner, G. 2014. The Testaria concept (Polyplacophora + Conchifera) updated.

Journal of Natural History, 48, 2751-2772, doi: 10.1080/00222933.2014.964787.

Scherholz, M., Redl, E., Wollesen, T., Todt, C. & Wanninger, A. 2013. Aplacophoran molluscs evolved

from ancestors with polyplacophoran-like features. Current Biology, 23, 2130–2134.

Sharma, P.P., Schwager, E.E., Giribet, G., Jockusch, E.L. & Extavour, C.G. 2013. Distal‐less and

dachshund pattern both plesiomorphic and apomorphic structures in chelicerates: RNA interference

in the harvestman Phalangium opilio (Opiliones). Evolution and Development, 15, 228-242.

Shillito, A.P. & Davies, N.S. 2017. Archetypally Siluro-Devonian ichnofauna in the Cowie Formation,

Scotland: implications for the myriapod fossil record and Highland Boundary Fault movement.

Proceedings of the Geologists’ Association, 128, 815-828.

Sigwart, J.D. & Sutton, M.D. 2007. Deep molluscan phylogeny: synthesis of palaeontological and

neontological data. Proceedings of the Royal Society B, 275, 1587–1593. doi: 10.1098/

rspb.2007.0701.

Siveter, David J. 2000. Ludford Lane and Ludford Corner. In: Aldridge, R.A., Siveter, David

J., Siveter, Derek J., Lane, P.D., Palmer, D. & Woodcock, N.H., British Silurian stratigraphy.

Joint Nature Conservation Committee, Peterborough, 432-437.

Siveter, Derek J. 2010a. Dunside, South Lanarkshire; Gutterford Burn, East Lothian and

Midlothian; Slot Burn, Ayrshire. In: Jarzembowski, E., Siveter, D.J., Palmer, D. & Selden,

P.A., Fossil arthropods of Great Britain. Joint Nature Conservation Committee,

Peterborough, 57-71.

ACCE

PTED

MAN

USCR

IPT



Siveter, Derek J. 2010b. Ludford Lane and Ludford Corner. In: Jarzembowski, E., Siveter,

D.J., Palmer, D. & Selden, P.A., Fossil arthropods of Great Britain. Joint Nature

Conservation Committee, Peterborough, 93-97.

Siveter, Derek J. & Palmer, D. 2010. Stonehaven. In: Jarzembowski, E., Siveter, D.J.,

Palmer, D. & Selden, P.A., Fossil arthropods of Great Britain. Joint Nature Conservation

Committee, Peterborough, 79-85.

Siveter, David J., Sutton, M.D., Briggs, D.E.G. & Siveter, Derek J. 2003. An ostracode

crustacean with soft parts from the Lower Silurian. Science, 300, 1749-1751.

Siveter, Derek J., Sutton, M.D., Briggs, D.E.G. & Siveter, D.J. 2004. A Silurian sea spider. Nature, 431,

978–80.

Siveter, David J., Aitchison, J.C., Siveter, Derek J. & Sutton, M.D. 2007a. The Radiolaria of the Silurian

Konservat-Lagerstätte of Herefordshire, England. Journal of Micropalaeontology, 26, 1-8.

Siveter, Derek J., Fortey, R.A., Sutton, M.D., Briggs, D.E.G. & Siveter, David J. 2007b. A Silurian

‘marrellomorph’ arthropod. Proceedings of the Royal Society of London B, 274, 2223-2229,

doi:10.1098/rspb.2007.0712.

Siveter, David J., Siveter, Derek J., Sutton, M.D. & Briggs, D.E.G. 2007c. Brood care in a

Silurian ostracod. Proceedings of the Royal Society of London B, 247, 465-469.

doi:10.1098/rspb.2006.3756.

Siveter, Derek J., Sutton, M.D., Briggs, D.E.G. & Siveter, David J. 2007d. A new probable

stem lineage crustacean with three-dimensionally preserved soft-parts from the Herefordshire

(Silurian) Lagerstätte, UK. Proceedings of the Royal Society of London B, 274, 2099-2107.

doi:10.1098/rspb.2007.0429.

Siveter, David J., Briggs, D.E.G., Siveter, Derek J. & Sutton, M.D. 2010. An exceptionally preserved

myodocopid ostracod from the Silurian of Herefordshire, UK. Proceedings of the Royal Society of

London B, 277, 1539-1544, doi:10.1098/rspb.2009.2122.

Siveter, David J., Briggs, D.E.G., Siveter, Derek J., Sutton, M.D. & Joomun, S.C. 2013. A Silurian

myodocope with preserved soft parts: cautioning the interpretation of the shell-based ostracod

record. Proceedings of the Royal Society of London B, 280, 20122664, doi:10.1098/rspb.2012.2664

(Published online 12 December 2012).

ACCE

PTED

MAN

USCR

IPT



Siveter, Derek J., Briggs, D.E.G., Siveter, David J., Sutton, M.D., Legg, D. & Joomun, S.C. 2014a. A

Silurian short-great-appendage arthropod. Proceedings of the Royal Society of London B, 281,

20132986, http://dx.doi.org/10.1098/rspb.2013.2986.

Siveter, David J., Tanaka, G., Farrell, Ú.C.,

Martin, M.J., Siveter, Derek J. & Briggs, D.E.G. 2014b.

Exceptionally preserved 450-million-year-old Ordovician ostracods with brood care. Current Biology,

24, 801-806.

Siveter, Derek J., Briggs, D.E.G., Siveter, David J. & Sutton, M.D. 2015a. Enalikter aphson is an

arthropod: a reply to Struck et al. (2014). Proceedings of the Royal Society of London B, 282,

20142663, http://dx.doi.org/10.1098/rspb.2014.2663.

Siveter, David J., Briggs, D.E.G., Siveter, Derek J. & Sutton, M.D. 2015b. A 425–million-year-old

Silurian pentastomid parasitic on ostracods. Current Biology, 25, 1-6.

http://dx.doi.org/10.1016/j.cub.2015.04.035.

Siveter, David J., Briggs, D.E.G., Siveter, Derek J., Sutton, M.D. & Legg, D.A. 2017. A new crustacean

from the Herefordshire (Silurian) Lagerstätte, UK, and its significance in malacostracan evolution.

Proceedings of the Royal Society of London B 284, 20170279.

http://dx.doi.org/10.1098/rspb.2017.0279.

Siveter, David J., Briggs, D.E.G., Siveter, Derek J. & Sutton M.D. 2018a. A well-preserved respiratory

system in a Silurian ostracod. Biology Letters, 14, 20180464.

http://dx.doi.org/10.1098/rsbl.2018.0464.

Siveter, Derek J., Briggs, D.E.G., Siveter, David J., Sutton, M.D. & Legg, D. 2018b. A three-

dimensionally preserved Silurian lobopodian from the Herefordshire (Silurian) Lagerstätte, UK. Royal

Society Open Science, 5, 172101, http://dx.doi.org/10.1098/rsos.172101.

Steeman, T., Vandenbroucke, T.R.A., Williams, M., Verniers, J., Perrier, V., Siveter, David J.,

Wilkinson, J., Zalasiewicz, J. & Emsbo, P. 2015. Chitinozan biostratigraphy of the Silurian Wenlock-

Ludlow boundary succession of the Long Mountain, Powys, Wales. Geological Magazine, 153, 95-

109. doi.org/10.1017/S0016756815000564.

Suarez S.E., Brookfield, M.E., Catlos, E.J. & Stöckli, D.F. 2017. A U-Pb zircon age constraint on the

oldest-recorded air-breathing land animal. PLoS ONE, 12, e0179262, https://doi.org/

10.1371/journal.pone.0179262.

ACCE

PTED

MAN

USCR

IPT


http://dx.doi.org/10.1098/rspb.2013.2986http://dx.doi.org/10.1098/rspb.2014.2663http://dx.doi.org/10.1016/j.cub.2015.04.035http://dx.doi.org/10.1098/rspb.2017.0279http://dx.doi.org/10.1098/rsbl.2018.0464http://dx.doi.org/10.1098/rsos.172101http://dx.doi.org/10.1017/S0016756815000564https://doi.org/http://jgs.lyellcollection.org/

Sutton, M.D. 2008. Tomographic techniques for the study of exceptionally preserved fossils.

Proceedings of the Royal Society B, 275, 1587–1593. doi: 10.1098/rspb.2008.0263.

Sutton, M.D., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2001a. An exceptionally preserved

vermiform mollusc from the Silurian of England. Nature, 410, 461–463. doi: 10.1038/35068549.

Sutton, M.D., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2001b. Methodologies for the

visualization and reconstruction of three-dimensional fossils from the Silurian Herefordshire

Lagerstätte. Palaeontologia Electronica, 4, 1A.

Sutton, M.D., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2001c. A three-dimensionally

preserved fossil polychaete worm from the Silurian of Herefordshire, England. Proceedings of the

Royal Society of London B, 268, 2355-2363.

Sutton, M.D., Briggs, D.E.G., Siveter, David J., Siveter, Derek J. & Orr, P.J. 2002. The arthropod

Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based

morphological reconstructions and phylogenetic affinities. Proceedings of the Royal Society, London

B, 269, 1195-1203.

Sutton, M.D., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2004. Computer reconstruction and

analysis of the vermiform mollusc Acaenoplax hayae from the Herefordshire Lagerstätte (Silurian,

England), and implications for molluscan phylogeny. Palaeontology, 47, 293–318.

Sutton, M.D., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2005a. A Silurian articulate

brachiopod with soft parts. Nature, 436, 1013-1015. doi:10.1038/nature0384.

Sutton, M.D., Briggs, D.E.G., Siveter, David J., Siveter, Derek J. & Gladwell, D.J. 2005b. A starfish with

three-dimensionally preserved soft parts from the Silurian of England. Proceedings of the Royal

Society of London B, 272, 1001-1006. doi:10.1098/rspb.2004.2951

Sutton, M.D., Briggs, D.E.G., Siveter, David J. and Siveter, Derek J. 2006. Fossilized soft tissues in a

Silurian platyceratid gastropod. Proceedings of the Royal Society of London B, 273, 1039-1044.

doi:10.1098/rspb.2005.3403.

Sutton, M.D., Briggs, D.E.G., Siveter, David J. & Siveter, Derek J. 2010. A soft-bodied lophophorate

from the Silurian of England. Biology Letters, 7, 146-149. doi:10.1098/rsbl.2010.0540.

Sutton, M.D., Briggs, D.E.G., Siveter, David J., Siveter, Derek J. & Sigwart, J.D. 2012a. A Silurian

armoured aplacophoran and implications for molluscan phylogeny. Nature, 490, 94-97.

doi:10.1038/nature11328.

ACCE

PTED

MAN

USCR

IPT



Sutton, M.D., Garwood, R.J., Siveter, David J. & Siveter, Derek J. 2012b. SPIERS and VAXML; a

software toolkit for tomographic visualisation and a format for virtual specimen

interchange. Palaeontologia Electronica, 15, 5T, doi: 10.26879/289.

Sutton, M.D., Rahman, I.A. & Garwood, R.J. 2014. Techniques for Virtual Palaeontology.

Wiley, Chichester, 208 pp.

Vannier, J.M.C. & Siveter, D.J. 1996. On Juraleberis jubata gen. et sp. nov. Stereo-Atlas of Ostracod

Shells 22 [for 1995], 86-95.

Van Roy, P., Briggs, D.E.G., & Gaines, R.R. 2015. The Fezouata fossils of Morocco; an

extraordinary record of marine life in the Early Ordovician. Journal of the Geological

Society, doi:10.1144/jgs2015-017.

Vinther, J. 2015. The origins of molluscs. Palaeontology, 58, 19–34, doi: 10.1111/pala.12140.

Vinther, J., Parry, L., Briggs, D.E.G. & Van Roy, P. 2017. Ancestral morphology of crown-group

molluscs revealed by a new Ordovician stem aculiferan. Nature, 542, 471-475.

Vrazo, M.B., Brett, C.E. & Ciurca, S.J. 2016. Buried or brined? Eurypterids and evaporites in

the Silurian Appalachian basin. Palaeogeography, Palaeoclimatology, Palaeoecology, 444,

48–59.

Walossek, D. & Müller, K.J. 1994. Pentastomid parasites from the Lower Palaeozoic of Sweden.

Transactions of the Royal Society of Edinburgh, Earth Sciences, 85, 1–37.

Waloszek, D. & Dunlop, J.A. 2002. A larval sea spider (Arthropoda: Pycnogonida) from the Upper

Cambrian ‘Orsten’ of Sweden, and the phylogenetic position of pycnogonids. Palaeontology, 45,

421–6.

Wanninger, A. & Wollesen, T. 2018. The evolution of molluscs. Biological Reviews, 94, 102–115, doi:

10.1111/brv.12439.

Weitschat, W. 1983 Myodocopid ostracodes with preserved appendages from the Lower Triassic of

Spitsbergen. Paläontologische Zeitschrift, 57, 309-323.

Wellman, C. 1993 A land plant microfossil assemblage of Mid Silurian age from the Stonehaven

Group, Scotland. Journal of Micropalaeontology, 12, 47-66.

ACCE

PTED

MAN

USCR

IPT



Wellman, C.H. & Richardson, J.B. 1993. Terrestrial plant microfossils from Silurian inliers of the

Midland Valley of Scotland. Palaeontology, 36, 155-193.

Wilson, H.M. & Anderson, L. 2004. Morphology and taxonomy of Paleozoic millipedes (Diplopoda:

Chilognatha: Archipolypoda) from Scotland. Journal of Palaeontology, 78, 169-184.

Wolfe, J.M., Daley, A.C., Legg, D.A. & Edgecombe, G.D. 2016. Fossil calibrations for the arthropod

Tree of Life. Earth Science Reviews, 160, 43-110.

Woodcock, N.H. 1993. The Precambrian and Silurian succession of the Old Radnor to Presteigne

area. In: Woodcock, N.H. & Bassett, M.G. (eds), Geological Excursions in Powys, Central Wales.

University of Wales Press, National Museum of Wales, Cardiff, 209-228.

Won, M-Z., Blodgett, R.B. & Nestor, V. 2002. Llandoverian (Early Silurian) radiolarians from the Road

River Formation of east-central Alaska and the new family Haplotaeniatumidae. Journal of

Paleontology, 76, 941–964.

Boxes, Table, Figures

Figure 1. Provenance and palaeogeography. (a) Welsh Borderland location of the Herefordshire

Lagerstätte with regional geology. (b) The volcanic ash (bentonite), with concretions in situ, in

contact with Coalbrookdale Formation shales above. (c) Typical concretion, 6 cm by 4 cm,

concentrically weathered, lacking the blue-grey hearted centre of calcium carbonate that is present

in partially weathered examples, and incorporating an eccentric specimen of the aplacophoran

Acaenoplax. (d) Local stratigraphy of the Dolyhir-Presteigne area. Radiometric dates are those given

in Cohen et al. (2013, updated 2018), the International Commission on Stratigraphy (ICS)

Chronostratigraphic Chart. Cramer et al. (2012) give marginally different radiometric dates for some

of the boundaries based on sampling from Gotland and the West Midlands, UK, for example 429.5

Ma for the Sheinwoodian-Homerian boundary. However, the majority margin of error on these

dates (±0.7 Ma) provides overlap with the dates given in the ICS Chronostratigraphic Chart. (e) Welsh

Basin palaeogeography at approximately the Sheinwoodian-Homerian boundary; modified from

Cherns et al. (2006, fig. 4.13a). (f) Eastern Laurussian palaeogeography during the Wenlock (modified

from Cocks & Torsvik 2005, fig. 9).

Box 1. The Faunal composition of the Herefordshire Lagerstätte

Includes Table 1 (Faunal list), Figure 2a, b

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Table 1, Faunal list

Figure 2a. Faunal composition of the major groups of the Herefordshire Lagerstätte. Percentage

abundance is based on number of specimens (n = 3670); some specimens as yet undescribed and

unassigned at species level are included, and radiolarians are excluded.

Figure 2b. Panarthropod faunal composition of the Herefordshire Lagerstätte. Percentage

abundance is based on number of specimens (n = 982). The chelicerate Offacolus is by far the best

represented species (833 specimens = 84.8% of the total number); all other species are represented

by less than 10 specimens each (= less than 1%), except for the mandibulate Tanazios (88 specimens

= 9.0%) and the malacostracan Cinerocaris (18 =1.8%).

Figure 3. Examples of Herefordshire animals on the split surface of nodules. (a) Longitudinal

horizontal section of the chelicerate Offacolus kingi. (b) Longitudinal subcentral section of the

edrioasteroid Heropyrgus disterminus. (c) Longitudinal subcentral section of the sponge

Carduispongia pedicula. (d) Longitudinal subcentral section of the aculiferan Acaenoplax hayae. (a)

and (c) show grey-light blue coloured carbonate-rich matrix of the nodule, within and around the

fossil, and (b) and (d) show orange-yellow coloured matrix of the nodule, indicating weathered

(leached) examples. Scale bars are all 1 mm.

Figure 4. Herefordshire Lagerstätte species. (a) Colymbosathon ecplecticos, valves removed, lateral

view. (b) Nymphatelina gravida, left valve removed, posterolateral view. (c, f) Offacolus kingi, dorsal,

ventrolateral views (see Fig. 3a). (d, e, g, i) Dibasterium durgae, ventrolateral stereo-pair, dorsal

view; chelicerae (first appendages), lateral view; prosomal area and anterior part of opisthosoma,

ventral view. (h) Aquilonifer spinosus, dorsal view. (j) Drakozoon kalumma, ventral view. (k) Bethia

serraticulma, with attached Drakozoon kalumma and ?atrypide brachiopod, lateral view. (l, m)

Kulindroplax perissokomus, lateral, dorsal views. (n, o) Rhamphoverritor reduncus, attached juvenile,

free swimming stage, lateral views. (p) Invavita piratica, lateral view. (q, r) Nymphatelina gravida,

with valves and valves removed, with an attached and an internal specimen of Invavita piratica,

lateral views. (s, t) Acaenoplax hayae, anterior part of body, dorsal and lateral view; main and

posterior parts of body, dorsal and lateral view (see Fig. 3d). (u, v) Cladograms depicting competing

molluscan phylogenies (simplified from Wanninger & Wollesen 2018). (u) 'Testaria' hypothesis, one

of several phylogenetic models in which aplacophorans are primitive with respect to all other

molluscs. (v) 'Aculifera' hypothesis, in which aplacophorans and polyplacophorans form a sister clade

(Aculifera) to all other molluscs (Conchifera). Scale bars are all 500 µm.

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Figure 5. Herefordshire Lagerstätte species. (a, b) Thanahita distos, dorsal, right lateral views. (c, d)

Cinerocaris magnifica, right lateral, posterior ventrolateral views. (e) Enalikter aphson, dorsal view.

(f - i) Bdellocoma sp., isolated example of pedicellaria with one valve removed, internal, lateral

views; pedicellariae attached to arm; portion of arm with spines and podia, sub-adoral view. (j, k)

Heropyrgus disterminus, dorsal, lateral views (see Fig. 3b). (l, m) Cascolus ravitus, anterolateral,

dorsal views. (n, o) Haliestes dasos, dorsal, anterolateral view. (p, t) Tanazios dokeron, dorsal,

anterolateral views. (q) Sollasina cthulhu, aboral view. (r, w) Xylokorys chledophilia, ventrolateral,

dorsal views. (s) Kenostrychus clementsi, anterolateral view. (u) Spirocopia aurita, valves removed,

right lateral view. (v) Platyceras sp., anterior part of shell removed, view from position normal to

viscera. (x) Inanihella sagena. (y) Carduispongia pedicula, lateral view (see Fig. 3c). (z) Nasunaris

flata, right valve removed, lateral view. (zz) Pauline avibella, right lateral view. Scale bars are all 500

µm.

Box 2. Comparison of Silurian Lagerstätten.

Includes Figure 6.

Figure 6. Stratigraphic occurrence of Silurian Lagerstätten

The radiometric dates are those given in Cohen et al. (2013, updated 2018), the International

Commission on Stratigraphy (ICS) Chronostratigraphic Chart.

Figure 7. Ecological types and percentage abundance based on number of species (n = 63). It

includes the four radiolarian species, and some species belonging to other major groups that

are as yet undescribed and unassigned at species level.

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Table 1 Faunal composition of the Herefordshire Lagerstätte

The relevant primary reference is given after the species name. Other relevant references are

given throughout the text.

Sponges

Carduispongia pedicula (Ardianty et al. 2019; Fig. 4y)

Some 20 other species (uninvestigated)

Cnidarians

? hydroid (uninvestigated colonial organism)

Coral (uninvestigated)

Brachiopods

Bethia serraticulma (Sutton et al. 2005a; Fig. 3k)

At least two other brachiopod species (both uninvestigated), one of them a lingulid

Lophophorate indet.

Drakozoon kalumon (Sutton et al. 2010; Fig. 3j)

Annelids

Kenostrychus clementsi (Sutton et al. 2001c; Fig. 4s)

Molluscs

Aplacophorans

Acaenoplax hayae (Sutton et al. 2001a; Fig. 3s, t)

Kulindroplax perissokomos (Sutton et al. 2012a; Fig. 3l, m)

Bivalvia

Praectenodonta ludensis Reed, 1931 (Fu 2016)

Gastropods

Platyceras? sp. (Sutton et al. 2006; Fig. 4v)

A high spired species (uninvestigated)

Cephalopods

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Nautiloids (uninvestigated)

Panarthropods

Lobopodians

Thanahita distos (Siveter et al. 2018b; Fig. 4a, b)

Megacheirans

Enalikter aphson (Siveter et al. 2014a; Siveter et al. 2015a; Fig. 4e)

Pycnogonids

Haliestes dasos (Siveter et al. 2004; Fig. 4n, o)

Chelicerates

Offacolus kingi (Orr et al. 2000; Fig. 3c, f)

Dibasterium durgae (Briggs et al. 2012; Fig. 3d, e, g, i)

Trilobites

Dalmanites sp. (uninvestigated)

Tapinocalymene sp. (uninvestigated)

Marrellomorphs

Xylokorys chledophilia (Siveter et al. 2007b; Fig. 4w, r)

Mandibulates

Aquilonifer spinosus (Briggs et al. 2016; Fig. 3h)

Tanazios dokeron (Siveter et al. 2007d; Fig. 4p, t)

Crustaceans

Malocostracans

Cinerocaris magnifica (Briggs et al. 2003; Fig. 4c, d)

Cascolus ravitis (Siveter et al. 2017; Fig. 4l, m)

Cirripedes

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