A unique specimen of the micromorphic fossil lingulate (organophosphatic-shelled) brachiopod Linnarssonia constans Koneva, 1983 from the late Lower Cambrian Shabakty Group of the Malyi Karatau Range in Kazakhstan, Central Asia, preserves evidence of infestation within the mantle cavity by a vermiform animal, leading to the growth of an internal tubular protuberance (Fig. 1) resulting from symbiosis some 520 million years ago. Examples of symbiotic relationships between metazoans in the early Paleozoic are sparse (Conway Morris, 1981, 1990; Conway Morris and Crompton, 1982). Descriptions of a variety of galls and tumorlike swellings in some trilobites extend records back to the Middle Cambrian (Conway Morris, 1990), but their interpretation as traces of endoparasitic activity remains somewhat speculative. Thus galllike swellings on the stems of Silurian echinoderms (Franzen, 1974), vermiform tubes on some early Ordovician dendroid graptolites (Conway Morris, 1990), and various tubes and blisters on graptoloid graptolites (see Bates and Loydell, 2000 for review) are among the hitherto earliest known convincing records of host-parasite relationships within metazoans. Our example reported here predates the oldest of these previous records by approximately 35 to 40 million years, and demonstrates that symbiosis involving complex adaptations (e.g., larval settlement on or within living tissue and exploitation of feeding systems of the host) and codependent life cycles were already established soon after the ‘explosive’ evolutionary radiation of marine metazoans in the early Cambrian. The fossil evidence of infestation on lophophorates is especially sparse, at best. The oldest hitherto undoubted records are both from brachiopods of Devonian age, in the Lower Devonian Emsian Stage of eastern Australia and in the Middle Devonian Givetian Stage of the Holy Cross Mountains in Poland, respectively.

The cardiarinide brachiopod Lambdarina glaphyra n. sp. from the upper Tournaisian (lower Carboniferous) rocks of Belgium is only the fourth described species in the genus. Ontogeny involves growth from a non-lobate, triangular, brephic stage of shell outline to distinct bilobation through neanic and adult stages, with maturity attained at a length of < 2 mm. Known occurrences of the new species are from within low-energy, mud-dominated proximal peri-reefal facies adjacent to Waulsortian buildups.

In 1892 the Swedish paleontologist Johan Christian Moberg described and illustrated what he interpreted as a fossil insect (Hemiptera) from beds of early Ordovician age in the southernmost limestone quarry at Killeröd, Smedstorp Parish in Skåne [Scania], southern Sweden. In a later paper in the same year (Moberg, 1892b), he also made a further passing reference to the presence of the same fossil when describing the accompanying graptolite fauna from Killeröd. One of his main reasons for recording this find was his conclusion (Moberg, 1892a, p. 122) that “it is evidently of great interest with full certainty to be able to prove the presence of airbreathing (terrestrial) animals as far back in time as that during which the oldest strata of the lower Silurian [i.e., Ordovician] were formed” [translation from Swedish].

Brachiopods of the order Chileida have been recorded previously only from rocks of early to mid-Cambrian age (Botomian–Amgaian). They are typified by having a calcareous strophic shell with a delthyrium and colleplax, and these characters are shown to be present in species of the two new genera Tolen and Trifissura, from the Late Ordovician of Kazakhstan and the Silurian of Sweden and Britain, respectively. In specimens of Trifissura, the triangular colleplax is phosphatized secondarily by bacterial activity. It is suggested that the phosphatized colleplax represents an organic pad and that served as the original attachment structure of Trifissura by encrustation. Tolen and Trifissura represent the first post-Cambrian record of chileides from the Ordovician and Silurian; the new family Trifissuridae forms the first phylogenetic link between Cambrian chileides and Carboniferous–Permian isogrammides.

Machaeridians are marine Palaeozoic fossils, known from sediments of early Ordovician to mid Permian age (Bengtson, 1978; Cooper and Grant, 1972; Kaasa, 1992). Rare, completely articulated specimens reveal that they were long, slender, bilaterally symmetrical animals, covered by a dorsal scleritome comprising longitudinally arranged series of calcite sclerites (e.g., Adrain et al., 1991; Högström and Taylor, 2001a, 2001b). However, most known machaeridians, including those described in this paper, comprise isolated disarticulated sclerites. Until recently, the taxonomic affinities of the group were uncertain, and historically they were assigned to a number of different phyla (e.g., see Adrain, 1992). However, the recent account of an exceptionally preserved specimen with soft tissue anatomy, from the Lower Fezouata Formation (Lower Ordovician, Tremadocian) of Morocco, now indicates that machaeridians were annelid worms (Vinther et al., 2008).

Within the Soom Shale Lagerstätte of South Africa (Upper Ordovician, Hirnantian), two brachiopod taxa preserve traces of organic tissue. In Trematis, presumed bands of periostracum are preserved on the flanks of the pedicle notch, and clay mineral casts of the pedicle are preserved in many specimens of Kosoidea. Both these genera are organophosphatic-shelled Linguliformea, together with a third genus identified as Plectoglossa. A fourth brachiopod taxon in the fauna belongs within the calcitic-shelled Rhynchonelliformea (Plectothyrella). Kosoidea cedarbergensis is a new species of discinoidean.

The poorly known type species of Lingulella, Lingula davisii M'Coy, 1851b, is redefined from new material collected from the type locality and horizon (Upper Cambrian, North Wales). Lingulella is similar to Obolus and to Ungula in its musculature mantle canals, and pseudointerareas, but has a thinner shell and irregular pits over its internal surface, concentrated in the visceral areas. A dissolution method that can facilitate the study of lingulate brachiopods preserved in clastic lithologies is described, and its wider adoption is recommended in order to reveal diagnostic morphological characters.

The brachiopod fauna of the Gorran Quartzites of south Cornwall is described; it comprises five orthid genera. Three taxa are described under open nomenclature, and one new species is assigned to a new genus (Schalidomorthis stubblefieldi). The fauna supports the Llandeilo age suggested by accompanying trilobites. There is no brachiopod evidence to indicate that the quartzite pebbles of the Triassic Budleigh Salterton Pebble Bed are derived directly from the Ordovician of Cornwall.

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

Biogenic apatite preserved in 148 samples of conodonts and organophosphatic-shelled brachiopods from Cambrian through Ordovician successions of the Baltoscandian Basin (Baltica Plate) preserves a sensitive record of early Palaeozoic sea-water chemistry interpreted via neodymium isotope ratios. Consistent ${\uvarepsilon}$Nd(t) values of −9.6 to −8.3 for Lower to Middle Cambrian samples suggest no significant lateral or temporal variation across the region. Average Upper Cambrian values are −7.2 to −7.7. Sedimentary analysis suggests that the influence of continental weathering from Baltica as a major source of radiogenic Nd was negligible. Ordovician samples show a rise to −5 to −6 in the early Arenig, early–mid Llanvirn and late Caradoc. Sea-water mixing from the southeast Iapetus Ocean was a constant factor throughout Cambrian–Ordovician times. The rise reflects erosion of obducted volcanic arc complexes along the Caledonian margin, and probably also relates to pollution of the Baltica sector of Iapetus from the approaching Avalonia Plate. Patterns of evolutionary biodiversity and palaeobiogeographical linkages support the geochemical signatures in interpreting the tectonic history of the region. Extinction of lingulate brachiopod faunas in the Tremadoc, followed by subsequent recovery and emergence of benthic assemblages typical of the Ordovician Evolutionary Fauna in the Billingen–early Volkhov regional stages coincide with significant changes in geochemical characteristics of water masses across the Baltoscandian basin. The early and mid Ordovician (Arenig to Llandeilo) brachiopod faunas of the North Estonian Confacies Belt are characterized by high endemism and low turnover rates, whereas increased immigration resulted in the extinction of a number of local lineages in the late Llanvirn. From the mid Caradoc to mid Ashgill, when Baltica was drifting on a course to collide eventually with Avalonia and gradually approach Laurentia, brachiopod assemblages were characterized by higher turnover rates. At the same time they gradually became more cosmopolitan and less influenced by the invasion of new faunas.

In this paper, on page 375, we published an Arenig palaeogeography in Figure 6 which showed the subduction zone off Laurentia as dipping northwards. This was a drafting error. The subduction zone should have dipped southward away from Laurentia. We apologise for this error and publish here a revised Figure 6 for the Arenig.

The available data from Newfoundland, the British Isles and Scandinavia suggest that by late Ordovician–early Silurian times the ocean separating Laurentia from Eastern Avalonia and Baltica had partly closed with the consumption of intervening oceanic crust. Marine seaways, however, persisted until the middle or late Silurian. Phases of crustal transtension and transpression, predominantly under a major sinistral shear couple, occurred throughout the Silurian and early Devonian until the remnant Iapetus Ocean was completely destroyed. The most appropriate Recent plate tectonic models for Silurian sedimentation between Eastern Avalonia and Laurentia are probably the deep-marine foreland basins between Timor and the northern Australian margin, or between Taiwan and mainland China.