A three-dimensionally preserved fossil polychaete worm from the Silurian of Herefordshire, England.

Polychaete body fossils are rare, and are almost invariably compressed and too poorly preserved for meaningful comparison with extant forms. We here describe Kenostrychus clementsi gen. et sp. nov. from the Silurian Herefordshire Konservat-Lagerstätte of England, in which three-dimensional external morphology is preserved with a fidelity unprecedented among fossil polychaetes. The fossils, which are preserved in calcite, were serially ground and photographed at 30 microm intervals to produce computer-generated reconstructions of the original external surface. The new genus has a generalized polychaete morphology with large biramous parapodia, unspecialized anterior segments and a small prostomium with median and lateral antennae and ventral prostomial palps. Cirriform branchiae arise from the ventral surface of each notopodium, and may be homologous with the inter-ramal branchiae of the extant nephtyids. Through cladistic analysis, Kenostrychus is interpreted as a member of a stem group of either the Phyllodocida or the Aciculata (Phyllodocida + Eunicida). Direct comparison with other fossil forms is difficult, but hints that inter-ramal respiratory structures may be primitive within the Phyllodocida and/or the Aciculata.     

Crustacea with preserved soft parts from the Upper Cambrian of Sweden

Six monotypic new genera of small crustaceans with phosphatised integument are described from Upper Cambrian, mainly bituminous limestone of southern Sweden. These are Dala peilertae, Bredocaris admirabilis, Walossekia quinquespinosa, Rehbachiella kinnekullensis, Skara anulata and Oelandocaris oelandica. The well-preserved details reveal a nauplius-like organisation of the head region. At least in Bredocaris, Walossekia , and Rehbachiella the head tagma has only three to four specialised pairs of appendages; Skara and Oelandocaris have five pairs of headal limbs. The antennae and the mandibulae served for locomotion and for mastication. All species have a filter apparatus with a distinct filter groove and serially constructed appendages. Four of the six forms had developed a conspicuous median compound eye. Specialisation in the development of the limbs, etc., suggests that some of the forms were benthie, while others may have been epibcnthic and active swimmers, Crustacea , Dala, Bredocaris, Walossekia, Rehbachiella, Skara, Oelandocaris, soft-part preservation, Upper Cambrian, Sweden.     

A soft-bodied lophophorate from the Silurian of England

Soft-bodied taxa comprise an important component of the extant lophophorate fauna, but convincing fossils of soft-bodied lophophorates are extremely rare. A small fossil lophophorate, attached to a brachiopod dorsal valve, is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of England. This unmineralized organism was bilaterally symmetrical and comprised a subconical body attached basally to the host and partially enclosed by a broad ‘hood’; the body bore a small, coiled lophophore. Where the hood attached laterally, there is a series of transverse ridges and furrows. The affinities of this organism probably lie with Brachiopoda; the hood is interpreted as the homologue of a dorsal valve/mantle lobe, and the attachment as the homologue of the ventral valve and/or pedicle. The ridges are arranged in a manner that suggests constructional serial repetition, indicating that they are unlikely to represent mantle canals. Extant brachiopods are not serially structured, but morphological and molecular evidence suggests that their ancestors were. The new organism may belong to the brachiopod stem group, and might also represent a significant element of the Palaeozoic lophophorate fauna.     

Bohemograptus papilio sp. nov. three-dimensionally preserved monograptid (Graptolithina) with an adaptation to retard sinking,from the Upper Silurian Poland

An unexpected new form of Bohemograptus with unusual morphological structure has been found in the upper part of the Bohemograptus praecornutus Biozone, Upper Ludlow of the Mielnik borehole, Poland. Bohemograptus papilio sp. nov. has the characteristic rhabdosome for Bohemograptus, in addition to extraordinary paired latero-dorsal additions, not comparable to any processes typical for Bohemograptus thecal openings. The new structure, a patagium, is located in the proximal part of the rhabdosome, and is built from main rods dividing repeatedly into thinner lists with significant remnants of membranes spread between them. Another new structure is the virgellarium, a membranous addition to the virgella. Membranes of the patagium and virgellarium are not built from microfusellar tissue as additions in other bohemograptids. It is suggested that the membranous additions were orientation devices, constructed to retard the sinking of the colony in the water column.     

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

Ostracod crustaceans are the most abundant fossil arthropods. The Silurian Pauline avibella gen. et sp. nov., from the Herefordshire Lagerstätte, UK, is an extremely rare Palaeozoic example with soft-part preservation. Based on its soft-part morphology, especially the exceptionally preserved limbs and presence of lateral eyes, it is assigned to the myodocopid myodocopes. The ostracod is very large, with an epipod on the fifth limb pair, as well as gills implying the presence of a heart and an integrated respiratory–circulatory system as in living cylindroleberidid myodocopids. Features of its shell morphology, however, recall halocyprid myodocopes and palaeocopes, encouraging caution in classifying ostracods based on the carapace alone and querying the interpretation of their shell-based fossil record, especially for the Palaeozoic, where some 500 genera are presently assigned to the Palaeocopida.     

Lasanius,an exceptionally preserved Silurian jawless fish from Scotland

The fossil record of non-biomineralizing, soft-bodied taxa is our only direct evidence of the early history of vertebrates. A robust reconstruction of the affinities of these taxa is critical to unlocking vertebrate origins and understanding the evolution of skeletal tissues, but these taxa invariably have unstable and poorly supported phylogenetic positions. At the cusp between mineralized bony vertebrates and entirely soft-bodied vertebrates is the enigmatic Lasanius, a purported anaspid from the Silurian of Scotland. Interpretations of its affinity and significance are conflicted, principally because of its poorly understood anatomy due to taphonomic distortion and loss of soft-tissues. Here we use an array of modern techniques to reassess the anatomy of Lasanius via a comprehensive study of 229 complete and partial specimens. A new reconstruction clarifies the identity and position of preserved features, including paired sensory organs, a notochord, and digestive tract, supporting the vertebrate affinities of this genus. SEM-EDS trace element mapping suggests a bone-like composition of mineralized parts, but finds no evidence for mineralized dermal armour. Phylogenetic analysis recovers Lasanius as an early stem-cyclostome, and subsequent analysis supports the rejection of alternative placements (such as stem-gnathostome). We highlight that while distinguishing between the early cyclostome and gnathostome condition is problematic, increasing confidence in the anatomy of key taxa, such as Lasanius, is vital for increased stability throughout the early vertebrate tree.     

Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes

The extinct echinoderm clade Stylophora consists of some of the strangest known deuterostomes. Stylophorans are known from complete, fully articulated skeletal remains from the middle Cambrian to the Pennsylvanian, but remain difficult to interpret. Their bizarre morphology, with a single appendage extending from a main body, has spawned vigorous debate over the phylogenetic significance of stylophorans, which were long considered modified but bona fide echinoderms with a feeding appendage. More recent interpretation of this appendage as a posterior “tail-like” structure has literally turned the animal back to front, leading to consideration of stylophorans as ancestral chordates, or as hemichordate-like, early echinoderms. Until now, the data feeding the debate have been restricted to evaluations of skeletal anatomy. Here, we apply novel elemental mapping technologies to describe, for the first time, soft tissue traces in stylophorans in conjunction with skeletal molds. The single stylophoran appendage contains a longitudinal canal with perpendicular, elongate extensions projecting beyond hinged biserial plates. This pattern of soft tissues compares most favorably with the hydrocoel, including a water vascular canal and tube feet found in all typical echinoderms. Presence of both calcite stereom and now, an apparent water vascular system, supports echinoderm and not hemichordate-like affinities.     

An ostracod-like arthropod with appendages preserved from the lower Ordovician of England

A tiny arthropod with a thin, possibly poorly mineralized, bivalved carapace and a pair of annulated, uniramous, probable frontal appendages is described from lower Ordovician marine mudstones in boreholes from central England. It represents only the fifth Ordovician example of a conservation deposit with soft integument preserved. Its systematic position is unresolved, but it may belong to the Ostracoda; if so, it is a rare example of an ostracod with fossilized appendages. Arthropoda, Ostracoda, appendages, Tremadoc Series, Ordovician, England.     

Preservation of soft tissues in Silurian graptolites from Latvia

The contractile stalks of graptoloid zooids are preserved as organic carbon residues in thecae of the middle Llandovery graptoloid graptolites Rastrites geinitzii and Neolagarograptus? sp. from the Aizpute‐41 core, Latvia. The contractile stalks are surrounded by equant pyrite crystals, resulting in three‐dimensional preservation of the graptolite rhabdosomes, and are associated with sediment of similar composition to, and derived from, the adjacent matrix. Matrix entered the thecae after pyrite crystal growth and filled some of the space left by collapse of the contractile stalks and some intercrystalline cavities; other space is partially infilled by diagenetic minerals. The contractile stalks are parallel‐sided and occupy up to one‐half the metathecal width, which is not inconsistent, assuming post‐mortem shrinkage, with the suggestion that graptoloid zooids filled their thecal tubes in life. The location of the preserved soft tissues, towards the distal ends of the metathecae, is very different from that predicted by decay experiments on the extant pterobranch hemichordate Rhabdopleura; the latter's soft tissues may thus not be a reliable analogue for those of these Silurian graptoloids.     

Cambrian anemones with preserved soft tissue from the Chengjiang biota, China

The group Cnidaria includes 'jellyfish', soft-bodied anemone and anemone-like forms and calcified corals. These diploblastic organisms have a fossil record extending back to the earliest metazoans of the Neoproterozoic; however certain cnidarians of the subclass Zoantharia, characterized by soft-bodied anemone-like forms, are absent or poorly represented in the fossil record. Despite the paucity of fossils, it is thought that calcification by soft anemone-like animals was responsible for producing the skeleton that allowed the preservation of the first corals. We report discovery of an abundant assemblage of in situ soft-bodied polyps with tissues. They are preserved in exquisite detail and come from the well-known Lower Cambrian Chengjiang biota of Yunnan, China. The soft-bodied polyps display a simple anatomy that is comparable to some extant anemones of the order Actinaria. The new fossils are assigned to Archisaccophyllia kunmingensis n. gen. et n. sp. Their simple and conservative form suggests that these fossils may represent some kind of ancestral rootstock. The preserved life assemblage provides a unique snapshot of Lower Cambrian anemone life and provides clues for relationships with extant actiniarians as well as calcified corals.     

Silurian Chitinozoa from the type Wenlock and Ludlow of Shropshire,England

Chitinozoa recorded from the Wenlock and Ludlow from the type areas in Shropshire and other localities in the Welsh Basin are listed, and the ranges of 35 taxa of stratigraphic value plotted.     

Silurian acritarchs from the type Wenlock and Ludlow of Shropshire,England

Acritarch taxa are recorded and listed from the Wenlock and Ludlow from the type areas in Shropshire, England, and other localities in the Welsh Basin of South Wales and the Welsh Borderland of England. The ranges of 141 taxa of stratigraphic value are plotted. Five new genera are described: Hogklintia, Lepto brachion, Rhaco brachion, Salopidium and Wrensnestia. 36 new species are described, and 32 new combinations proposed. Seven acritarch zones are recognised in the Wenlock and Ludlow.     

A probable thecate hydroid from the upper cretaceous of southern England preserved by bioimmuration

An inferred thecate hydroid, moulded on the attachment scar of the bivalvePycnodonte vesiculare, is described from the Santonian Chalk of Kent. The living hydroid was evidently overgrown by theP. vesiculare shell and is preserved as a bioimmuration.Eisenackiella thanetensis gen. et sp. nov. is characterized by a hydrorhiza whose stolons bear hydrothecae alternately to the left and right, and a hydrocaulus consisting of several unbranched stems with alternating hydrothecae. The widely spaced stolonal hydrothecae have adnate proximal parts and erect distal parts. Assignment to an extant hydroid family is difficult: whereas the hydrorhiza resembles that of the Family Lafoeidae, the hydrocaulus is reminiscent of the Family Sertulariidae.     

A Silurian porpitoid hydrozoan from Cumbria, England, and a note on porpitoid relationships

A porpitoid hydrozoan, Pseudodiscophyllum windermerensis gen. et sp. nov., from Cumbria, represented by a well-preserved internal float (pneumatophore), is only the fourth porpitoid reported from Silurian rocks world-wide and the first to be found in any geological formation in England. Its circular pneumatophore is more than 110 mm in diameter. Because of the paucity of hard parts, these animals are not common as fossils but may have been important elements of the Palaeozoic oceanic plankton. Although the new species is superficially similar to the Ordovician Discophyllum , there are what appear to be fundamental differences. Similarities to species of Paropsonema , from the Devonian and Silurian, are also probably superficial. The wider relationships of these animals have long been misinterpreted in the palaeontological literature. They are not siphonophores. Correct understanding involves a complete re-interpretation of various homologies and of the evolutionary history of the group.     

A new cephalopod with soft parts from the Upper Carboniferous Francis Creek Shale of Illinois, USA

A ten armed fossil from the Pennsylvanian Francis Creek Shale and belonging to the famous Mazon Creek biota is described as a cephalopod. Apart from a superficial resemblance to the coleoids, there is little basis for an assessment of the animal's affinities. A mineralized Bask shaped structure preserved in calcite and seen in both part and counterpart in fragmentary form may represent the fossilized remains of an internal organ such as the stomach or ink sac A small, dark circular spot positioned anterior to the appendages could be the animal's eye although mere is no internal structure visible. The extremely rare occurrence of Palaeozoic cephalopods with soft parts has so far been Ended to the Francis Creek Shale and the Devonian Hunsrückschiefer of Germany. The Mazon Creek biota includes many fossils which show a remarkable standard of soft part preservation which in some cases includes the fossilization of eye spots and stomach traces. Previously deserted Mazon Creek cephalopods have included the tentacular impression of a squid complete with arm hooks, and the radulae and shells of both coleoids and nautiloids. The specimen described here is the first from the Palaeozoic to show any hint of organ preservation.     

Hope springs eternal in the starfish gonad: preserved potential for sexual reproduction in a single-clone population of a fissiparous starfish

Among echinoderms, asexual reproduction by fission occurs in few species. This strategy is considered a temporary response to stressful conditions and usually alternates with sexual reproduction events; thus, monoclonal populations are extremely rare. The occurrence of a single-clone population of the starfish Coscinasterias tenuispina at Llançà (NW Mediterranean) allowed us to study intra-clonal variation of the reproductive cycle during a two-year study. The few developed gonads (all male) were found in winter months, coinciding with the minimum photoperiod (ρ = ?0.82; P < 0.001) and lowest temperatures (ρ = ?0.75; P < 0.001), only in best-fed individuals, indicating that food availability influences individual ability for gonad development. Fissiparity happened throughout all the sampled period, but its rate increased with warm temperatures (ρ = 0.68; P < 0.0001). In contrast to what has been reported in other species, no correlation between fission rates and population density was found. The population was maintained over time by asexual reproduction and remained monoclonal. Although sexual reproduction has probably not occurred in this all-male population for a long time, the ability to yearly produce mature gonads is retained by some individuals, indicating that potential to reproduce sexually may be preserved, even in the case of strictly asexual populations.     

First record of preserved soft parts in a Palaeozoic podocopid (Metacopina) ostracod, Cytherellina submagna: phylogenetic implications

The metacopines represent one of the oldest and most important extinct groups of ostracods, with a fossil record from the Mid-Ordovician to the Early Jurassic. Herein, we report the discovery of a representative of the group with three-dimensionally preserved soft parts. The specimen--a male of Cytherellina submagna--was found in the Early Devonian (416 Ma) of Podolia, Ukraine. A branchial plate (Bp) of the cephalic maxillula (Mx), a pair of thoracic appendages (walking legs), a presumed furca (Fu) and a copulatory organ are preserved. The material also includes phosphatized steinkerns with exceptionally preserved marginal pore canals and muscle scars. The morphology of the preserved limbs and valves of C. submagna suggests its relationship with extant Podocopida, particularly with the superfamilies Darwinuloidea and Sigillioidea, which have many similar characteristic features, including a large Bp on the Mx, the morphology of walking legs, Fu with two terminal claws, internal stop-teeth in the left valve, adductor muscle scar pattern, and a very narrow fused zone along the anterior and posterior margins. More precise determination of affinities will depend on the soft-part morphology of the cephalic segment, which has not been revealed in the present material.     

Crinoid holdfasts from the Silurian of Gotland

Crinoid holdfasts occur throughout the Silurian sequence of Gotland, with a marked concentration to reefs and immediate reef surroundings. Four morphological groups are recognized: (1) Discoid holdfasts. (2) Cirriferous holdfasts, represented by (a) Rhizocrinus -like holdfasts, (b) large radices with stout, often branching cirri, and (c) rhizoid holdfasts, formed by a complicated net of pseudocirri. (3) Creeping stems attached to the substrate by thin strands of stereome. (4) Coiling stems. Discoid attachments, cirriferous holdfasts (types b and c) and coiling stems show little preference to substrate and adapt morphologically to conditions at hand. Rhizoid holdfasts display the greatest variation and apparently occur within many different groups of crinoids. Rhizocrinusttke holdfasts have been found only in quiet-water deposits, while creeping stems were concentrated to more turbulent environments. Coiling stems were epizoic, attached to rugose corals, bryozoans, crinoid stems and similar supports. Growth, mode of life (attached or free), settling and fixation of larvae, and relation to substrate and other organisms ate discussed.