Permineralised material of Rhacopteris lindseaeformis (Bunbury) Kidston and Spathulopteris obovata (Lindley & Hutton) Kidston, showing both external morphology and excellent anatomical preservation, is described from the Lower Carboniferous (?Asbian, Upper Viséan) tuffs and dolomitic ashes outcropping at Weaklaw–Gullane, East Lothian, Scotland. These specimens provide the first anatomical information on these two well-known plant compression genera. The rachises have Lyginorachis-type anatomy with distinctive characters in the two species. Spathulopteris rachises correspond to Lyginorachis kingswoodense Meyer-Berthaud, previously described from the localities of Kingswood and East Kirkton, whereas Rhacopteris shows similarities with the petiole attributed to Bilignea from Oxroad Bay. Both foliage types conform to seed-fern frond organisation. This new evidence contradicts previous interpretations of Rhacopteris as a fern or a progymnosperm. We suggest that Rhacopteris lindseaeformis and Spathulopteris obovata represent the foliage of some of the arborescent gymnosperms which are found associated in several contemporaneous localities.

An excavation in the mid-Ordovician (Caradoc) Bardahessiagh Formation at Pomeroy, Co. Tyrone, Northern Ireland in 1992 has yielded a rich fauna of invertebrates, including several specimens of the scleractiniamorph coral Kilbuchophyllia. The material is assigned to the species K. clarksoni, previously described from penecontemporaneous levels in the Kirkcolm Formation of the Northern Belt of the Southern Uplands. The diagnosis of K. clarksoni is extended to include specimens of significantly greater size than the Southern Uplands material. All the material is mouldic but includes composite moulds, which in comparison with the preservation of other faunal elements, strongly suggests an original aragonitic composition for the kilbuchophyllid skeleton. Furthermore, details of insertion of higher cycles of septa visible on one particularly well preserved specimen confirm the process of septal substitution in these corals. Septal substitution is otherwise unique to post-Palaeozoic scleractinian corals and indicates the presence of paired mesenteries in the kilbuchophyllid polyp. The significance of this for the evolution of these corals and related anemones is discussed. The discovery of kilbuchophyllid corals at Pomeroy supports the view that post-Caradoc sinistral strike-slip movement on the Southern Uplands Fault was unlikely to have exceeded 200 km.

The ontogeny of Parabolina spinulosa is described on the basis of material from Andrarum (Skåne) and Jämtland in Sweden. Protaspides are rare, and indifferently preserved, but well-preserved isolated tagmata and complete specimens from the early meraspid stages onwards were available for study. Whereas the ontogeny is broadly similar to that of the earlier Olenus wahlenbergi, there are subtle differences, notably in a greater spinosity from the earlier stages and a gradual, rather than a sudden, change of surface sculpture in the early holaspid. P. spinulosa at all stages of growth is much more variable than is Olenus. Meraspides have larger articulating halfrings anteriorly and the first thoracic segments are of greater sagittal length than in the adult; these were adaptations which enabled Parabolina to undergo cylindrical enrollment from an early stage.

Parabolina is considered to have arisen from the earlier genus Olenus, and on the basis of comparative ontogeny many, though not all, features of Parabolina appear to be of paedomorphic origin. These include the reduction of the preglabellar field, retention of the visual surface, position of the eyes set close to the glabella, retention of a conterminant hypostome, yoking of the librigenae, spinosity of the thorax and pygidium, more numerous glabellar furrows and reduction in number of thoracic segments. Olenus attenuatus has several features intermediate between those of earlier Olenus species and Parabolina, and the origin of the latter genus is best considered in terms of a mosaic paedomorphocline.

In the Proterozoic complex of the Schirmacher region of East Antarctica, a retrograde pressure–temperature (P–T) history has been inferred through quantitative geothermobarometry and fluid inclusion studies of the mafic granulites. Microthermometric investigations of the fluid phases trapped in quartz and garnet identified three types of inclusions, namely, earliest pure CO2 inclusions (0·987–1·057 g cm−3), CO2–H2O inclusions and aqueous inclusions.

The temperature and pressure of metamorphism have been estimated through different calibrations of geothermometers and geobarometers. The mineral reactions and compositional zoning in the minerals record P–T conditions from nearly 837 ± 26°C, 7·1±0·2 kbar to 652 ± 33°C, 5·9 ± 0·3 kbar. A good correlation between the fluid and mineral data is observed. The isochores typical of highdensity CO2 fluids fall well within the P–T box estimated by mineral thermobarometry. The abundance of primary CO2 inclusions in early metamorphic minerals (notably quartz and primary garnet) and the general correspondence between fluid and mineral P–T data indicate a ‘fluid-present’ carbonic regime for the high-grade metamorpism; however, from the present data largescale CO2 advection could not be envisaged. The subsequent stages involved a decrease in CO2 density, a progressive influx of hydrous fluids and the generation of retrograde amphibolite facies metamorphism in the area.

The estimated P–T conditions of the region suggest that the rocks were metamorphosed at a depth of 19–24 km, with a geothermal gradient of c. 3°5C km−1. The estimated P–T conditions of the rocks imply a clockwise P–T–t path with a gradual decrease in temperature of around 250°C and a decrease in pressure of around 1700 bar. They have a dP/dT gradient of ≈7 ± l bar °C−1, arguing for an isobaric cooling history of the terrane under normal thickened crust after the underplating of mantle-derived material.

Cindarella eucalla Chen et al. from the Early Cambrian Chengjiang fauna is the closest relative of Xandarella spectaculum Hou et al. Cindarella and Xandarella are united as Xandarellida, a further component of Cambrian arachnate diversity. Diagnostic of Xandarellida are ventral eyes, a posterior extension of the head shield that covers anterior trunk segments, and multiple somites per tergite in the rear part of the trunk. Somites and tergites are decoupled throughout the trunk in Cindarella. The bilobate structure of the exopod in xandarellids is widespread throughout the Arachnata.

A new reconstruction of the skull of Crassigyrinus scoticus (Lydekker) is provided, based on newly prepared material. A revised interpretation of the naris shows it in most respects to be like that of other Carboniferous tetrapods, lacking both an anterior tectal and a lateral rostral. However it does incorporate an enlarged septomaxilla, and part of the dorsal surface of the vomer is also visible within the naris of most specimens. Prominent paired buttresses run along the midline of the snout, and a single bowl-shaped interpremaxillary fenestra pierces the snout and palate but is not confluent with the naris or choana. A preopercular is probably absent. A new cladistic analysis places Crassigyrinus with the Viséan genus Whatcheeria, and puts those two taxa as a sister-clade to the anthracosaurs Proterogyrinus and Pholiderpeton. Temnospondyls form a clade with loxommatids, and these two arms form a dichotomy crownward to Greererpeton, Ichthyostega and Acanthostega which are successive stemward plesions.

The development of the Midland Valley of Scotland from Silurian times is re-examined. Earlier (Cambro-Ordovician) terrane accretion of the Midland Valley Terrane to the Laurentian continent by sinistral strike-slip continued to control basin development, sedimentary facies distribution and deformation from Llandovery through to at least early Devonian times. A widespread Mid- to Late-Wenlock strike-slip event has been recognised. This event is variable in its effect, but may indicate a direct link between the Midland Valley, Southern Uplands and Grampian terranes, suggesting that the terranes were juxtaposed by Mid-Wenlock times. In the Midland Valley this event was followed by a renewed phase of basin development with the deposition of ?Pridoli-Lower Devonian clastic sediments which was interrupted by the Lower Devonian volcanic event. There was a shift northwards in the focus of Lower Devonian basin development which was accompanied by a diachronous deformation event across the Midland Valley which resulted in inversion/uplift from early to middle Devonian times. This phase of deformation, uplift and erosion may be related to end-Caledonian transpression.

The new standard conodont zonation includes, in succession from below: Lower Ps. bicornis Zone, Upper Ps. bicornis Zone, Lower P. procerus Zone, Upper P. procerus Zone, Lower K. ranuliformis Zone, Upper K. ranuliformis Zone, 0. s. rhenana Zone, Lower K. walliseri Zone, Middle K. walliseri Zone, K. patula Zone, uppermost K. walliseri range, post K. walliseri interregnum, K. o. ortus Zone and 0. s. sagitta Zone. Lower boundaries for each zone are defined or redefined. A less detailed biostratigraphic nomenclature at the superzone level is suggested for use where collections are inadequate: The Pterospathodus Zonal group, the Upper Pterospathodus Zonal group, the P. amorphognathoides Zonal group, the Ps. bicornis Superzone, the P. procerus Superzone, the K. ranuliformis Superzone, the O. s. rhenana Superzone, the K. walliseri Zonal group, the Upper K. walliseri Superzone and the K. o. ortus Superzone. These partly overlap and can be used according to the taxa present. The proposed zonation is applied to most known conodont sequences. The taxonomic concept of the taxa used is discussed; new taxa include Nudibelodina sensitiva, Ozarkodina paraconfluens and O. martinssoni. The species name Ozarkodina ortus is a senior synonym of Kockelella absidata.

Articulated thelodonts, Loganellia scotica (Traquair), Shielia gen.n. taiti (Stetson), Lanarkia horrida Traquair, L. spinulosa Traquair and Turinia pagei (Powrie) from the Silurian and Devonian of Scotland are re-described. A new species, Lanarkia lanceolata sp.n. from the Wenlock, Lower Silurian, is established. For each species, diagnosis is specified, varieties of scale morphology are given, the branchial area is described and body morphology is detailed. A paired ventral fin in Shielia gen.n. taiti and Lanarkia lanceolata sp.n. has been discovered. A new reconstruction of Loganellia and Shielia, and diagnosis for thelodonts from Scotland are given. The locality list of Scottish agnathans is reviewed and the biostratigraphical distribution discussed.

The causes of hydrothermal alteration in dolerite dykes intruding Caledonian rocks of W Connacht are investigated using stable isotope, water content and K–Ar data for whole rocks and mineral separates. Using an isochron approach the Logmór dyke in the north is re-dated to 308±4 Ma; previously determined older whole-rock ages reflect excess 40Ar. The ∼ 305 Ma age previously proposed for the Teach Dóite suite in the south is reinforced by a 305 Ma age on a pyroxene separate, although the severe resetting of most samples is emphasised by other pyroxene and plagioclase ages of ∼210 Ma. Pyroxene δ18O values for these Upper Carboniferous dykes are mostly 5·5 to 6·1%, indicating negligible crustal contamination. Logmór whole-rock samples have water contents of 1·7–2·1 wt.%, δ5D= 59 to –47‰ and δ18O = 9·4 to 9·6‰; plagioclase shows little mineralogical alteration but its δ18O is 9·7‰. Hydrothermal alteration involving a local formation or metamorphic water took place at high fluid/rock ratios and high temperature during cooling after intrusion, most probably in a thermally-driven convection system. Teach Dóite dykes have water contents of 2·0–4·2 wt.%. δD= –58 to –38‰ and δ18O = 3·6 to 9·2‰, and were mostly altered in two stages; hydration upon intrusion to ∼ 2 wt.% water by contemporaneous meteoric water at low fluid/rock ratios was followed by extensive chemical and isotopic alteration at ∼210 Ma (Upper Triassic) by surface waters. This latter event could also have caused the extensive alteration observed in the host rocks.

A new member of the Tristichopteridae (=Eusthenopteridae), Mandageria fairfaxi gen. et sp. nov., is described from the Late Devonian (Famennian) Mandagery Sandstone outcropping near Canowindra, NSW, Australia. It is represented by several complete or partial heads and bodies, preserved as natural moulds. Mandageria shares derived characters with the Late Famennian tristichopterid Eusthenodon wängsjöi from East Greenland; the pineal plate series is large and kite-shaped and is posterior to the middle of the parietals, the intertemporal does not contact the posterior supraorbital, a posterior process of the premaxilla divides the apical fossa, the anteriormost premaxillary tooth is enlarged, the postorbital is excluded from the orbit by a supraorbital–lacrimal contact, and the coronoids lack marginal teeth except posteriorly. Mandageria fairfaxi differs from Eusthenodon in superficial fusion of the supratemporal, tabular and postparietals, in the lateral extrascapulars being separated by only 2–3 mm in the midline anteriorly, and in having proportionately smaller scales. It also has an elongate supracleithrum, which is probably autapomorphic. The postcranial skeleton is comparable to that of the Frasnian genus Eusthenopteron, but differs in the more posterior position of the median fins, the poorly ossified vertebral column, and the flattened ectepicondyle. Mandageria fairfaxi is the second osteolepiform described from Canowindra (the first, Canowindra grossi) and, other than the now-reinterpreted Marsdenichthys, the first tristichopterid described from Australia.