Abstract
AbstractThe 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.
Highlights
Linguliform and craniiform brachiopods comprise a relatively minor, but distinctive component of Ordovician benthic faunas
Linguliforms are recognized as one of the major components of the Cambrian Evolutionary Fauna, together with trilobites and hexactinellide sponges (Sepkoski 1981), whereas the existing Cambrian record of craniiforms is sparse (Popov et al 1999a), and in terms of three evolutionary faunas recognized by Sepkoski (1981) they can be considered as a minor component of the Palaeozoic Evolutionary Fauna (Harper et al 2004)
The results of the Cluster Analysis (Euclidean distance, using the PAST statistical package distributed by Hammer et al 2001) of 17 Darriwilian, one early Sandbian and one Dapingian lingulate microbrachiopod assemblages from peri-Gondwana (Cuyania, Alborz and Bohemia), Baltica, Laurentia, Kazakhstanian terranes, New Zealand and South China show the significance of climatic control of the distribution of taxa incorporated into micromorphic linguliform brachiopod assemblages
Summary
Linguliform and craniiform brachiopods comprise a relatively minor, but distinctive component of Ordovician benthic faunas. The major features of temperate-latitude lingulate brachiopod faunas can be typified by those described from the Mid Ordovician of Baltica (Gorjansky 1969; Holmer 1989), Iran (Popov et al 2008) and South China (Zhang 1995).
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