Abstract The biogeographical patterns shown by Ordovician linguliform and craniiform brachiopods are greatly influenced by their dominance in low-diversity associations in marginal environments. This is particularly evident in the Early Ordovician, when linguliform-dominated dysaerobic assemblages are widely distributed along the deep shelves of Gondwana, the Kazakhstanian terranes and in Baltica. By the Darriwilian, micromorphic linguliforms are characteristic components of the pantropical climatic-controlled faunas of Laurentia, Cuyania and Kazakhstanian terranes, which – in spite of separation by extensive oceans – retain a distinct similarity. Analysis of craniiform biogeographical distribution is impeded significantly by the poor state of craniide taxonomy and lack of reliable data from most regions. However, in general their biogeographical dispersion is similar to other groups of the Palaeozoic Evolutionary Fauna. Unlike the linguliforms, which are important members of the Cambrian Evolutionary Fauna, there is no convincing Cambrian craniiform record; they may have evolved and dispersed from Gondwana and associated microcontinents and island arcs. The earliest well-established record is from the late Tremadocian of temperate to high-latitude peri-Gondwana. During most of the Ordovician, they have a peri-Iapetus distribution. They are very rare or absent in tropical Gondwana, South China and Kazakhstanian terranes and are not yet documented from Siberia. The trimerellides probably evolved in tropical peri-Gondwanan island arc settings. Their dispersion and major features of biogeography mirror those of atrypides. Gold Open Access: This article is published under the terms of the http://creativecommons.org/licenses/by/3.0/ .

Abstract The Neoproterozoic to early Cambrian breakup of the ancient amalgamated supercontinent of Rodinia spawned a heterogeneous realignment of cratonic masses that involved the construction of the mega-terrane of Gondwana. Such reconfiguration took place from about 650 Ma, mostly via the conjunction of Australasian, Indian, Antarctic, African, South American and some Arabian crustal fragments (e.g. see Cocks & Torsvik 2002, 2006; Pankhurst & Vaughan 2009). For much of its earliest history, Gondwana formed a non-marine heartland, straddling South Polar environments across northern South America and North Africa through the late Vendian–late Silurian (Cocks & Torsvik 2002, figs 2–8). However, around the margins of this continental core and in relatively adjacent regions, was an assortment of terranes embracing a variety of marine and non-marine environments. This volume focuses on various aspects of the tectonic and biogeographical evolution around the Gondwanan margin and its adjacent terranes. It is the outcome of a 1 day symposium, under the same title, comprising the annual Lyell Meeting for 2007 held at The Geological Society of London, Burlington House, and organized jointly with The Palaeontological Association. Close to 100 delegates attended. There were 14 presentations at the meeting, plus one paper read in title and abstract only but which is published here in full (Benedetto et al. 2009). Four of the papers presented at the symposium were not submitted subsequently for publication because they were scheduled for publication elsewhere. Nigel Hughes (University of California, Riverside) analysed the complex structural and faunal relationships of the Himalayan margin within

Abstract Two separate tectonic blocks in the southwestern segment of the Kazakhstanian orogen, the Chu–Ili terrane and the Karatau–Naryn terrane (with particular attention to Malyi Karatau), are selected to illustrate their geological history and major biogeographical signatures from the Cambrian to the early Silurian. Mid- to Late Ordovician brachiopod and trilobite faunas of Chu–Ili show increased endemicity of shallow shelf assemblages, whereas distinct links to equatorial (‘east’) peri-Gondwanan are more evident in trilobite assemblages of the outer shelf. In the Late Ordovician, strong biogeographical affinities to equatorial Gondwanan faunas became firmly established and they are also traceable into the Silurian. Early Cambrian faunas of Malyi Karatau show remarkable similarity to those of South China. From the Middle Cambrian this region evolved as an isolated carbonate seamount, but until the Early Ordovician links to South China faunas were still evident. Benthic faunas from both regions show weak links to contemporaneous faunas of Baltica and little in common with Cambrian and Ordovician faunas of the Siberian craton. This suggests their location in low southern latitudes, in relative proximity to East Gondwana, which places some constraints on plate-tectonic reconstructions in relation to the southern cluster of Kazakhstanian terranes, including Karatau–Naryn, North Tien Shan and Chu–Ili.

Abstract Brachiopod-dominated palaeocommunities incorporating a structure typical of faunal groups within the Palaeozoic Evolutionary Fauna were already present in North and East Gondwana and associated terranes as early as the mid-Cambrian, confined exclusively to shallow marine, inshore environments. The late Cambrian and Tremadoc record of these faunas is incomplete, because of pronounced global sea-level lowstand and subsequent break-up and destruction of the Cambrian Gondwanan margin. It is likely, however, that those groups later forming the core of the Palaeozoic Evolutionary Fauna evolved originally in shallow-water environments of low-latitude peri-Gondwana, and dispersed widely when favourable ecological conditions developed. Conspicuous sea-level rise through the early to mid-Arenig provided newly available habitats in the expanding epeiric seas, where the new faunas evolved and diversified by the mid-Ordovician, when rapid drift separated the early Palaeozoic continents. Relatively short-lived precursor and transitional brachiopod assemblages can be identified on most of the main palaeocontinents prior to the Ordovician radiation of the Palaeozoic Evolutionary Fauna.