The Rosroe Formation comprises a series of Lower Ordovician (Llanvirn) conglomerates and sandstones, that lies on the southern limb of the South Mayo Trough, within the Iapetus Suture Zone of western Ireland. Trace element chemistry of granite boulders within the formation indicates a continental, rather than a volcanic arc character that can be correlated to latest Precambrian granites within the Dalradian Metamorphic Block, part of the deformed Laurentian margin. A minority of the clasts may correlate with syn-collisional granites, similar to, but older than, the Oughterard Granite of Connemara. Pb isotope compositions of K-feldspar grains within the sandstones, measured by both ion microprobe and conventional mass spectrometry, show a clear Laurentian affinity, albeit with greater source variability in the sand grains compared to a limited range in the proximal boulders. Palaeo-current indicators demonstrate dominant derivation from the NE, with a significant axial E–W flow. We propose that the Rosroe Formation records unroofing of a rapidly exhuming Dalradian metamorphic belt in North Mayo, following extensional collapse of the Grampian Orogen starting at ˜468 Ma, with minor input from a southerly arc source. The lack of metamorphic input from the S until deposition of the Derryeeny Conglomerate argues that the Connemara terrane was not positioned S of South Mayo Trough through strike-slip faulting until after the end of Rosroe sedimentation (460–443 Ma).

Forty-six samples, taken from the Upper Ordovician and lower Silurian strata of the Girvan district, Midland Valley of Scotland, yield moderately well-preserved and diverse assemblages of chitinozoans. The area was chosen to study the composition of the chitinozoan assemblages, rarely described before in Scotland, which lay at the south-eastern margin of the Laurentia palaeocontinent. These assemblages are compared with those of the same age on other palaeocontinents, representing a critical time when both the Iapetus and Tornquist oceans were closing, thus forming the Caledonide and associated orogens. It is possible to correlate the chitinozoan occurrences at Girvan with those of other parts of Laurentia (Quebec area), other palaeocontinents such as Baltoscandia (Sweden, Estonia), Avalonia (Wales, Brabant Massif) and some parts of Northern Gondwana (Saudi Arabia). For the lower Silurian, it is possible to correlate with the global chitinozoan biozonation, and a calibration between the chitinozoan occurrences and the graptolite biozonation of Girvan is established. Several levels within the Balclatchie, South Shore, Three Mile, Shalloch, Wood Burn, Lauchlan, Drumyork Flags and other formations are accurately dated.

Graphic correlation using graptolites and conodonts provides a high-resolution timescale for correlating from coastal to deep oceanic sections and, thereby, also a detailed record of the sequence of changes during the Mulde Secundo-Secundo Event. That interval includes sedimentary facies otherwise unknown in older Wenlock to early Ludlow strata on Gotland. The identified sequence of changes includes a detailed record of, in order: two extinctions (Datum points 1 and 1·5); widespread deposition of carbon-rich sediments extensive enough to cause a δ13C increase of c. 4.8‰, the onset, maximum and end of a sea-level fall and rise of at least 16 m during 30 kyr; a third extinction (Datum 2); a disaster fauna; and a slow faunal recovery. Thus, a secondary result of the event was a weakened greenhouse effect triggering a glaciation: the Gannarve Glaciation (new term). The order of changes proves that regression did not cause the extinctions. Faunal and sea-level changes, as well as the sedimentary succession, fit well with predictions based on an oceanic model. Extinctions were primarily caused by a severe drop in primary planktonic productivity, causing starvation among planktonic larvae in non-coastal settings. The Grötlingbo Bentonite (new term), the thickest in the Wenlock of Gotland, was deposited across the basin shortly after Datum 2. Temporal resolution is high enough to permit some comparison with Quaternary glaciations.

Two new broad-cupped camerate crinoids are reported from the Upper Ordovician (Ashgill, Rawtheyan) Lady Burn Starfish Beds of the Girvan district, Strathclyde, SW Scotland. These represent a significant addition to the limited crinoid diversity known from the Ordovician of the British Isles. The 20-armed diplobathrid Eodimerocrinites littlewoodi gen. et sp. nov. is similar to Silurian Dimerocrinites Phillips, but lacks median ray ridges and has a distinct calyx sculpture. Camerate sp. indet. differs from E. littlewoodi in the sculpture of the dorsal cup and the arrangement of the interbrachial plates, but it preserves insufficient information for it to be further classified with confidence.

New specimens of the diplobathrid gen. et sp. nov. cf Botting from the Middle Ordovician (Llanvirn, Abereiddian) of central Wales, that illustrate hitherto unknown morphological features, including a distal rhizoidal holdfast and a geniculate proximal column, suggest that this species was a rheophilic filter feeder. One specimen is one of the most complete fossil crinoids known from the Ordovician of the British Isles.

A revised reconstruction of the dermal skull roof of Acanthostega gunnari from the Upper Devonian of East Greenland is provided, incorporating modifications consequent upon further study of the specimens and in the light of new information from the Upper Devonian genus Ventastega from Latvia. The new reconstruction features a midline gap between the frontal and nasal bones and median rostrals. A revised profile for the skull and a rendition of the dermal ornament is also provided.

This present revision of Bohemian Ordovician illaenid trilobites of the Prague Basin (Czech Republic) follows the recent evaluation of their systematic position. This revision contains redescriptions and illustrations of the type species of several illaenid genera, the most up-to-date references for those genera, and an assessment of their variability and also of the palaeobiogeographic distribution of some illaenid genera. Bohemian illaenids in several cases include the type species of globally distributed taxa, whose distinction has often been uncertain and controversial. The validity of the genera Zbirovia Šnajdr, 1956 and Zdicella Šnajdr, 1956 is discussed and confirmed. The genus Alceste Hawle et Corda, 1847 stays in open nomenclature. In Ectillaenus katzeri katzeri (Barrande, 1856) allometric growth is described and Vysocania Vaněk & Vokáč, 1997 is considered to be a junior synonym of Stenopareia Holm, 1886.