Chapter 11 Biodiversity, biogeography and phylogeography of Ordovician rhynchonelliform brachiopods

Abstract

The phylogeographical evolution and the consequent changing distribution and diversity of rhynchonelliform brachiopods through the Ordovician are linked to the dynamic palaeogeography of the period. The Early Ordovician (Tremadocian and Floian) is characterized by globally low-diversity faunas with local biodiversity epicentres, notably on the South China Palaeoplate; low-latitude porambonitoid-dominated faunas with early plectambonitoid and clitambonitoid representatives, as well as high-latitude assemblages mostly dominated by orthoids, can be recognized, but many taxa are rooted in Late Cambrian stocks. The Early Ordovician displays a steady increase in rhynchonelliformean biodiversity, which was mostly driven by the increasing success of the Porambonitoidea and Orthoidea, but the billingsellids and early plectambonitoids also contributed to this expansion. During the Early to Mid Ordovician (Dapingian–Darriwilian), marine life experienced an unprecedented hike in diversity at the species, genus and family levels that firmly installed the suspension-feeding benthos as the main component of the Palaeozoic fauna. However, this may have occurred in response to an early Darriwilian annihilation of existing clades, some of which had been most successful during the Early Ordovician. New clades rapidly expanded. The continents were widely dispersed together with a large number of microcontinents and volcanic arcs related to intense magmatic and tectonic activity. Climates were warm and sea-levels were high. Pivotal to the entire diversification is the role of gamma (inter-provincial) diversity and by implication the spread of the continents and frequency of island arcs and microcontinents. The phylogeographical analysis demonstrates that this new palaeogeographical configuration was particularly well explored and utilized by the strophomenides, especially the Plectambonitoidea, which radiated rapidly during this interval. The porambonitoids, on the other hand, were still in recovery following the early Darriwilian extinctions. Orthides remained dominant, particularly at high latitudes. Biodiversity epicentres were located on most of the larger palaeoplates, as well as within the Iapetus Ocean. Provincial patterns were disrupted during the Sandbian and early Katian with the migration of many elements of the benthos into deeper-water regimes, enjoying a more cosmopolitan distribution. Later Katian faunas exhibit a partition between carbonate and clastic environments. During the latest Katian, biogeographical patterns were disrupted by polewards migrations of warm-water taxa in response to the changing climate; possibly as a consequence of low-latitude cradles being developed in, for instance, carbonate reef settings. Many clades were well established with especially the strophomenides beginning to outnumber the previously successful orthides, although this process had already begun, regionally, in the mid to late Darriwilian. At the same time, atrypoid and pentameroid clades also began to radiate in low-latitude faunas, anticipating their dominance in Silurian faunas. The Hirnantian was marked by severe extinctions particularly across orthide-strophomenide clades within the context of few, but well-defined, climatically controlled provincial belts.Supplementary material:The individual localities and a reference list for the data sources are provided at:http://www.geolsoc.org.uk/SUP18667

The oldest brachymetopid trilobite record from the European peri-Gondwana

“…This pattern of distribution is also observed in other groups, such as brachiopods (e.g. Rasmussen 2011, Harper et al 2013 lichocephala are older than the Boda event and the associated faunal migrations.…”

Late Ordovician rostroconchs (Mollusca) from fluvial erratics in northwestern Europe

“…The oldest taxa are known from Australia, Argentina and France and show a general early distribution in low latitude areas and a subsequent spread into high latitude areas during the Lower Ordovician (Amler & Rogalla 2013). Australia belongs to the low latitude province and Argentina and France the high latitude province following Harper et al (2013).…”

Late Ordovician deep-water brachiopod fauna from Raheen, Waterford Harbour, Ireland

“…The database is that assembled in Harper et al (2013) where the results of that analysis were illustrated (figs 11.10, 11.11). The additional data from Raheen have been added and analysed; Raheen plots close to a number of the Laurentian, Laurentian marginal, Asian and Anglo-Welsh localities (Fig.…”