Chapter 10 Biogeography of Ordovician Linguliform and Craniiform Brachiopods

Downloaded from http://mem.lyellcollection.org/ by guest on November 27, 2013 Geological Society, London, Memoirs Chapter 10 Biogeography of Ordovician linguliform and craniiform brachiopods Leonid E. Popov, Lars E. Holmer, Michael G. Bassett, Mansoureh Ghobadi Pour and Ian G. Percival Geological Society, London, Memoirs 2013, v.38; p117-126. doi: 10.1144/M38.10 Email alerting click here to receive free e-mail alerts when new articles cite this article service Permission click here to seek permission to re-use all or part of this article request Subscribe click here to subscribe to Geological Society, London, Memoirs or the Lyell Collection Notes © The Geological Society of London 2013 Downloaded from http://mem.lyellcollection.org/ by guest on November 27, 2013 Chapter 10 Biogeography of Ordovician linguliform and craniiform brachiopods LEONID E. POPOV1, LARS E. HOLMER2*, MICHAEL G. BASSETT1, MANSOUREH GHOBADI POUR3 & IAN G. PERCIVAL4 1Department of Geology, National Museum of Wales, Cardiff CF10 3NP, UK 2Department of Earth Sciences, Palaeobiology, Uppsala University, 752 36 Uppsala, Sweden 3Department of Geology, Faculty of Sciences, Golestan University, Gorgan, Iran 4Geological Survey of New South Wales, Londonderry, 2753 NSW, Australia *Corresponding author (e-mail: [email protected]) 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 CC-BY 3.0 license. Linguliform and craniiform brachiopods comprise a relatively Ordovician, as discussed below. Recent linguliforms have a plank- minor, but distinctive component of Ordovician benthic faunas. totrophic larva with a prolonged free-swimming stage in their Linguliforms are recognized as one of the major components of ontogeny, which was retained from ancestral Cambrian stocks the Cambrian Evolutionary Fauna, together with trilobites and (Freeman & Lundelius 1999). By the beginning of the Ordovician hexactinellide sponges (Sepkoski 1981), whereas the existing they became adapted to a wide spectrum of marine environments Cambrian record of craniiforms is sparse (Popov et al. 1999a), from near-shore to abyssal depths (Bassett et al. 1999; Tolmacheva and in terms of three evolutionary faunas recognized by Sepkoski et al. 2004). In the Ordovician, linguliform brachiopods played a (1981) they can be considered as a minor component of the significant role in faunal assemblages that were characteristic of Palaeozoic Evolutionary Fauna (Harper et al. 2004). The biogeo- marginal environments, for example in near-shore mobile sands graphy of the Ordovician linguliforms and craniiforms has not and dysaerobic conditions, which explains the special biogeogra- previously been the subject of a separate comprehensive analysis, phical patterns shown by the group. The Ordovician also is charac- but has generally been considered together with biogeographical terized by distinctive benthic associations of micromorphic studies of rhynchonelliform brachiopods. Ordovician linguli- linguliform brachiopods and there is growing evidence (Mergl form and craniiform brachiopods proliferated in marginal 2002; Holmer et al. 2005) that they commonly had symbiotic marine environments where they formed low-diversity associ- relationships with sponges, a life habit which clearly affected the ations often dominated by a single taxon. Some opportunistic pattern of their biogeography. In addition, a wide range of different linguliform-dominated faunal associations, which are associated linguliform biogeographical patterns are evident in cases where with intervals with significant environmental changes, in tandem they form minor components of various benthic communities with trimerellide associations, reveal characteristic distributional that are dominated by other filter feeders, for example rhynchonel- patterns that have proved helpful in palaeogeographical recon- liform brachiopods and bryozoans. structions (Popov & Holmer 1994, 1995). Craniiforms, in particu- The quality of published global data on the biodiversity of Ordo- lar the trimerellides, have also proven biogeographically important vician linguliforms is variable. It is relatively good for Baltica and (Popov et al. 1997). However, because of the low diversity of high- to temperate-latitude Gondwana, and there are also good these associations, the conventional methods (such as cluster and data compiled for Laurentia, the Australasian sector of low lati- principal component analyses) have a limited application here. tude Gondwana, Avalonia and the Kazakhstanian terranes. By con- trast, there is only a single publication on the Mid Ordovician micromorphic linguliforms from South China, and no available Linguliform brachiopods data from Siberia and North China. Moreover, a considerable amount of data on the Ordovician linguliforms unfortunately The life strategies and evolutionary history of linguliforms differ remains unpublished, including descriptions of Late Ordovician significantly from those of other brachiopod subphyla (Bassett microbrachiopods from Ireland (Avalonia), presented in an unpub- et al. 1999). These differences are clearly reflected in their dis- lished PhD thesis by McClean (Wright & McClean 1991), and of tinctive patterns of biogeographical distribution during the the Mid Ordovician faunas of the Argentinean pre-Cordillera. From:Harper,D.A.T.&Servais, T. (eds) 2013. Early Palaeozoic Biogeography and Palaeogeography. Geological Society, London, Memoirs, 38, 117–126. http://dx.doi.org/10.1144/M38.10 # The Authors 2013. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://mem.lyellcollection.org/ by guest on November 27, 2013 118 L. E. POPOV ET AL. Early Ordovician (Tremadocian–Floian) changes. In Baltoscandia and the Alborz peri-Gondwanan terrane, this expansion occurred just prior to the onset of temperate-latitude The end of the Furongian (Late Cambrian) Epoch saw a major carbonate sedimentation, which coincided in both regions with decline in the generic diversity of linguliform brachiopods. The proliferation of benthic associations with clear characteristics of decline is best seen in outer shelf and basinal faunal associations the Palaeozoic Evolutionary Fauna (Bassett et al. 2002; Popov (Bassett et al. 1999), which in the early Tremadocian Age were et al. 2008). In Bohemia, the Thysanotus–Leptembolon fauna occupied mainly by the low- to medium-diversity Broeggeria appeared because of immigration after a period of non-deposition Association. This association was distributed widely along the corresponding to the entire Furongian Epoch (Mergl 1986). Bed- deep shelves of Gondwana, the Kazakhstanian terranes and in narczyk (1999) suggested that the Thysanotus Leptembolon fauna Baltica (Popov & Holmer 1994, 1995). The Broeggeria Associ- may have been of a peri-Gondwanan origin, and this is now sup- ation often tracks the distribution of dysaerobic environments, ported by the earliest known occurrence of Thysanotus from the which are characterized, in particular, by the olenid trilobite bio- Shirgesht Formation of Derenjal Mountains in Central Iran, facies. The Tremadocian micromorphic brachiopod associations where it is associated with the billingsellide brachiopod Protambo- mostly have a low diversity and they are dominated by Eurytreta nites and the conodont Cordylodus angulatus (Bassett et al. 1999). and Ottenbyella, which have almost cosmopolitan distribution. The Furongian to early Tremadocian interval in Baltica and Similar Tremadocian micromorphic brachiopod associations temperate-latitude Gondwana was a time of proliferation of have been documented from Baltica (Popov & Holmer 1994, spinose siphonotretides (Family Siphonotretidae), which show a 1995), Laurentia (Popov et al. 2002; Holmer et al. 2005) and distinctive geographical distributional pattern (Popov et al. Kazakhstanian terranes (Popov & Holmer 1994; Holmer et al. 2009a; Fig. 10.1). The earliest spinose siphonotretides

Load more