Marine Ostracod Provinciality in the Late Ordovician of Palaeocontinental Laurentia and Its Environmental and Geographical Expression (original) (raw)
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This paper reviews the global biogeography and affinities of the Bradoriida, a group of Cambrian–early Ordovician arthropods. Bradoriida appear in the fossil record during the early Cambrian, just prior to the earliest trilobite faunas. Seven families may form a natural (monophyletic) group of Bradoriida sensu stricto, comprising Cambriidae, Kunmingellidae, Comptalutidae, Bradoriidae, Hipponicharionidae, Beyrichonidae and Svealutidae. Amongst the Bradoriida sensu lato, some forms that lie outside these families have carapace designs that suggest an ostracod affinity, particularly Altajanella and Vojbokalina. Bradoriida formed a major element of the 'Cambrian evolutionary fauna' and are components of the Chengjiang, Burgess Shale, and Buen Formation Lagerstätten. Bradoriida achieved global distribution from the Atdabanian (early Cambrian). Their diversity peaked during the early and middle Cambrian, with highest diversity at the species and genus level amongst the palaeo-tropical faunas of the South China (17 genera) and east Gondwana palaeocontinental regions (23 genera). By contrast Laurentian faunas were of much lower diversity (10 genera for the whole Cambrian). Bradoriid diversity declined rapidly from the latest middle Cambrian, a trend that may be related to the major extinction of trilobites at the base of the late Cambrian. The youngest Bradoriida comprise a few, rare Ordovician forms. Bradoriids appear to have occupied well-oxygenated marine shelf facies. The biogeographical patterns of early and middle Cambrian Bradoriida suggest climatic control on their distribution (temperate and tropical faunas), together with palaeogeographical constraints that also reflect trilobite provinciality. Kunmingellids and comptalutids were restricted to palaeo-tropical/subtropical sites, but migrated between South China, Siberia and eastern Gondwana palaeocontinents. They are absent from the mid-and high latitude faunas of the western Gondwana, Avalonia and Baltica palaeocontinental areas that were dominated by hipponicharionids, beyrichonids and Bradoriidae. The Laurentia palaeocontinent was isolated from the main zones of bradoriid diversity, but its faunas include a number of early and middle Cambrian Bradoriidae (Indota, Bradoria, Walcottella), and the region was colonised by cosmopolitan cambriids during the early Cambrian and by supposed pelagic svealutids (Liangshanella and Anabarochilina) during the middle Cambrian. The genera Walcottella, Dielymella and Bullaluta were endemic to Laurentia. One species of Anabarochilina that possibly dwelt near the sea-surface achieved an equatorial to high southern latitude (70° S) distribution during the late middle Cambrian (Lejopyge laevigata Biozone), perhaps reflecting a reduced latitudinal temperature gradient for near surface ocean waters.
Cosmopolitan arthropod zooplankton in the Ordovician seas
Palaeogeography, …, 2003
Evidence is presented here for a zooplanktonic component in Ordovician marine ecosystems, namely the caryocaridid arthropods, that add to other well-documented midwater organisms such as graptolites, cyclopygid and telephinid trilobites, orthoconic cephalopods and the microphytoplankton (e.g. acritarchs). Although the soft anatomy of caryocaridids is largely hypothetical, their carapace design and ultrastructure, and their phyllocarid-like abdominal morphology (flattened furcal rami, telescopic segments) indicate a swimming lifestyle in midwater niches. Both functional and ecological interpretations are supported by their palaeogeographical and facies distributions and by analogies with modern pelagic ostracods. Caryocaridids occur at numerous localities on the palaeo-plates of Laurentia, Baltica, Avalonia, Perunica, Gondwana and South China and are recurrent faunal components of graptolitic black shales (mainly Tremadoc to Llanvirn). Typical faunal associates are the didymograptid and isograptid graptolites, pelagic cyclopygid and deep-sea benthic atheloptic trilobites. Their depositional environments suggest that the caryocaridids and their pelagic associates (graptolites) most probably thrived in waters above the distal shelf margins, where upwelling-controlled primary productivity possibly reached its maximum. Their exact bathymetrical range within the water column cannot be inferred from fossil evidence. However, their feeding strategies may have led them to exploit food resources across the mesopelagic^epipelagic boundaries as do numerous midwater crustaceans in present-day ecosystems. Caryocaridids represent a significant step in the post-Cambrian colonisation of midwater niches by arthropods and in the construction of complex modern foodwebs. ß
Organophosphatic brachiopods:Patterns of biodiversification and extinction in the Early Palaeozoic
Geobios, 1999
From a database of 226 Cambrian - Ordovician genera of organophosphatic-shelled brachiopods comprisingthe Subphylum Linguliformea, 11 sets of morphological characters typify all orders and superfamilies. Seven sets of these large-scale evolutionary novelties were established already by the end of the mid Cambrian, 2 more by the end of the late Cambrian, and the remaining 2 before the end of the Arenig. The earliest linguliformeans are of Tommotian age and represent some of the oldest known benthic organisms with a mineralised skeleton. Major diversification at the generic level took place during the mid and late Cambrian, by which time members of the Order Lingulida spread from near-shore to deep-water environments and became dominant in low diversity benthic assemblages that inhabited mobile sandy bottoms. There was a significant decline in diversity of linguliformeans during the latest Cambrian. Following recovery in the late Tremadoc-early Arenig, they then became one of the most distinctive components of benthic assemblages inhabiting marginal environments, e.g. eutrophic basins, shallow mobile sands, and abyssal depths. During the Llanvirn, there was a significant, worldwide turnover in linguliformean brachiopod faunas, when the majority of epibenthic lingulides of the families Obolidae, Zhanatellidae and Elkaniidae became extinct and were replaced, in shallow marine biofacies, by assemblages dominated by bivalved molluscs and burrowing lingulides. There is no trace until the mid Ashgill of a significant decline of micromorphic taxa in linguliformean assemblages characteristic of outer shelf environments. However, all siphonotretides, paterinides and most acrotretide genera disappeared towards the end of the late Ordovician pre-Hirnantian Dicellograptus anceps Biozone.D'après une base de données de 226 genres de brachiopodes à coquille organophosphatée du Cambro-Ordoviciencomprenant le subphylum Linguliformea, 11 ensembles de caractères morphologiques distinguent tous les ordres et superfamilles. Sept ensembles de ces innovations évolutives à grande échelle étaient déjà établies à la fin du Cambrien moyen, 2 autres à la fin du Cambrien supérieur et les 2 restantes à la fin de l'Arenig. Les premiers linguliformes sont du Tommotien et représentent quelques-uns des plus anciens organismes benthiques connus à squelette minéralisé. Une diversification majeure au niveau générique se produisit au cours du Cambrien moyen et supérieur alors que des représentants de l'ordre Lingulida s'étendaient des milieux côtiers à des environnements plus profonds et devenaient dominants dans les assemblages benthiques à faible diversité qui occupaient les fonds sableux mobiles. Il y eut un déclin significatif de la diversité des linguliformes au cours du Cambrien terminal. A la suite de la reconquête au Tremadoc supérieur-Arenig inférieur, ils devinrent l'un des constituants les plus marquants des communautés benthiques des environnements marginaux, c'est-à-dire de bassins eutrophiques, des sables mobiles peu profonds et des profondeurs abyssales. Au Llanvirn intervint un changement mondial important des faunes de brachiopodes linguliformes quand la plus grande partie des lingulides épibenthiques des familles Obolidae, Zhanatellidae et Elkaniidae disparurent et furent remplacées, dans les faciès marins peu profonds, par des assemblages dominés par des mollusques bivalves et des lingulides fouisseurs. Il n'y a pas trace jusqu'à l'Ashgill moyen d'un déclin significatif des taxons micromorphes dans les assemblages de linguliformes caractéristiques des environnements de la plateforme externe. Cependant, tous les genres de siphonotrétides, patérinides et la plupart de ceux des acrotrétides disparurent vers la fin de la biozone pré-hirnantienne à Dicellograptus anceps de l'Ordovicien supérieur.
Chapter 21 Biogeographical patterns of Ordovician ostracods
Geological Society, London, Memoirs, 2013
The biogeography of marine shelf ostracod genera is analysed for two Ordovician time slabs, the earliest Late Ordovician and the terminal Ordovician, that have been considered to reflect comparatively warmer and cooler global climate states, respectively. The earlier time slab is equivalent to the Nemagraptus gracilis graptolite interval (centred about 460 Ma), and defined as the total range of the eponymous species. The Hirnantian time slab comprises the Normalograptus extraordinarius and Normalograptus persculptus graptolite biozones (445.6-443.7 Ma). The ostracod dataset consists of 160 taxa from 24 early Late Ordovician localities and 86 taxa from 10 Hirnantian localities. Ordination and variation partitioning analyses show that patterns in ostracod distribution in the gracilis time slab are largely related to palaeocontinental affinity of the samples and to a lesser degree to palaeolatitude. Some decrease of provincialism can be suggested for the Hirnantian, although the ostracod dataset is limited for this interval.
The spatial and temporal diversification of Early Palaeozoic vertebrates
… Society, London, Special …, 2002
Recent discoveries have dramatically altered traditional views of the stratigraphic distribution and phylogeny of Early Palaeozoic vertebrates and permit a reappraisal of biogeographic patterns and processes over the first 120 million years of vertebrate evolution. Stratigraphic calibration of the phylogenetic trees indicates that most of the pre-Silurian record can be inferred only through ghost ranges. Assessment of the available data suggests that this is due to a shift in ecological niches after the latest Ordovician extinction event and a broadening of geographical range following the amalgamation of Euramerica during the early Silurian. Two major patterns are apparent in the biogeographic data. Firstly, the majority of jawless fishes with dermoskeletal, plated 'armour' were highly endemic during Cambrian-Ordovician time, with arandaspids restricted to Gondwana, galeaspids to China, and anatolepids, astraspids and, possibly, heterostracans confined to Laurentia. These Laurentian groups began to disperse to other continental blocks as the 'Old Red Sandstone continent' amalgamated through a series of tectonic collisions. The second maj or pattern, in contrast, encompasses a number of microsquamous and naked, jawed and jawless primitive vertebrates such as conodonts, thelodonts, placoderms, chondrichthyans and acanthodians, which dispersed rapidly and crossed oceanic barriers to attain cosmopolitan distributions, although many have Laurentian origins. A clear difference in dispersal potential exists between these two types of fishes. Overall, the development of biogeographic patterns in Early Palaeozoic vertebrates involved a complex interaction of dispersal, vicariance and tectonic convergence.
The Middle to Late Ordovician was a time of profound biotic diversification, paleoecological change, and major climate shifts. Yet studies examining speciation mechanisms and drivers of dispersal are lacking. In this study, we use Bayesian phylogenetics and maximum likelihood analyses in the R package BioGeoBEARS to reanalyze ten published data matrices of brachiopods and trilobites and produce time-calibrated species-level phylogenetic hypotheses with estimated biogeographic histories. Recovered speciation and biogeographic patterns were examined within four time slices to test for changes in speciation type across major tectonic and paleoclimatic events. Statistical model comparison showed that biogeographic models that incorporate long-distance founder-event speciation best fit the data for most clades, which indicates that this speciation type, along with vicariance and traditional dispersal, were important for Paleozoic benthic invertebrates. Speciation by dispersal was common throughout the study interval, but notably elevated during times of climate change. Vicariance events occurred synchronously among brachiopod and trilobite lineages, indicating that tectonic, climate, and ocean processes affected benthic and planktotrophic larvae similarly. Middle Ordovician interoceanic dispersal in trilobite lineages was influenced by surface currents along with volcanic island arcs acting as “stepping stones” between areas, indicating most trilobite species may have had a planktic protaspid stage. These factors also influenced brachiopod dispersal across oceanic basins among Laurentia, Avalonia, and Baltica. These results indicate that gyre spin-up and intensification of surface currents were important dispersal mechanisms during this time. Within Laurentia, surface currents, hurricane tracks, and upwelling zones controlled dispersal among basins. Increased speciation during the Middle Ordovician provides support for climatic facilitators for diversification during the Great Ordovician Biodiversification Event. Similarly, increased speciation in Laurentian brachiopod lineages during the Hirnantian indicates that some taxa experienced speciation in relation to major climate changes. Overall, this study demonstrates the substantial power and potential for likelihood-based methods for elucidating biotic patterns during the history of life.
Paleobiology, 2006
The analysis of morphological disparity and of morphospace occupation through the macroevolutionary history of clades is now a major research program in paleobiology, and increasingly so in organismal and comparative biology. Most studies have focused on the relationship between taxonomic diversity and morphological disparity, and on ecological or developmental controls. However, the geographic context of diversification has remained understudied. Here we address geography quantitatively. Diversity, disparity, and paleogeographic dispersion are used to describe the evolutionary history of an extinct echinoderm clade, the class Stylophora (cornutes, mitrates), from the Middle Cambrian to the Middle Devonian (about 128 Myr subdivided into 12 stratigraphic intervals). Taxonomic diversity is estimated from a representative sample including 73.3% of described species and 92.4% of described genera. Stylophoran morphology is quantified on the basis of seven morphometric parameters derived from image analysis of homologous skeletal regions. Three separate principal coordinates analyses (PCO) are performed for thecal outlines, plates from the lower thecal surface, and plates from the upper thecal surface, respectively. PCO scores from these three separate analyses are then used as variables for a single, global, meta-PCO. For each time interval, disparity is calculated as the sum of variance in the multidimensional morphospace defined by the meta-PCO axes. For each time interval, a semiquantitative index of paleogeographic dispersion is calculated, reflecting both global (continental) and local (regional) aspects of dispersion. Morphospace occupation of cornutes and mitrates is partly overlapping, suggesting some morphologic convergences between the two main stylophoran clades, probably correlated to similar modes of life (e.g., symmetrical cornutes and primitive mitrocystitids). Hierarchical clustering allowed the identification of three main morphological sets (subdivided into 11 subsets) within the global stylophoran morphospace. These morphological sets are used to analyze the spatiotemporal variations of disparity. The initial radiation of stylophorans is characterized by a low diversity and a rapid increase in disparity (Middle Cambrian-Tremadocian). The subsequent diversification involved filling and little expansion of morphospace (Arenig-Middle Ordovician). Finally, both stylophoran diversity and disparity decreased relatively steadily from the Late Ordovician to the Middle Devonian, with the exception of a second (lower) peak in the Early Devonian. Such a pattern is comparable to that of other Paleozoic marine invertebrates such as blastozoans and orthid brachiopods. During the Lower to Middle Ordovician, the most dramatic diversification of stylophorans took place with a paleogeographic dispersion essentially limited to the periphery of Gondwana. In the Late Ordovician, stylophorans steadily extended toward lower paleolatitudes, and new environmental conditions, where some of them radiated, and finally survived the end-Ordovician mass extinction (e.g., anomalocystitids). This pattern of paleobiogeographic dispersion is comparable to that of other examples of Paleozoic groups of marine invertebrates, such as bivalve mollusks.
Palaeogeography Palaeoclimatology Palaeoecology, 2007
This paper reviews the global biogeography and affinities of the Bradoriida, a group of Cambrian-early Ordovician arthropods. Bradoriida appear in the fossil record during the early Cambrian, just prior to the earliest trilobite faunas. Seven families may form a natural (monophyletic) group of Bradoriida sensu stricto, comprising Cambriidae, Kunmingellidae, Comptalutidae, Bradoriidae, Hipponicharionidae, Beyrichonidae and Svealutidae. Amongst the Bradoriida sensu lato, some forms that lie outside these families have carapace designs that suggest an ostracod affinity, particularly Altajanella and Vojbokalina. Bradoriida formed a major element of the 'Cambrian evolutionary fauna' and are components of the Chengjiang, Burgess Shale, and Buen Formation Lagerstätten. Bradoriida achieved global distribution from the Atdabanian (early Cambrian). Their diversity peaked during the early and middle Cambrian, with highest diversity at the species and genus level amongst the palaeo-tropical faunas of the South China (17 genera) and east Gondwana palaeocontinental regions (23 genera). By contrast Laurentian faunas were of much lower diversity (10 genera for the whole Cambrian). Bradoriid diversity declined rapidly from the latest middle Cambrian, a trend that may be related to the major extinction of trilobites at the base of the late Cambrian. The youngest Bradoriida comprise a few, rare Ordovician forms. Bradoriids appear to have occupied well-oxygenated marine shelf facies. The biogeographical patterns of early and middle Cambrian Bradoriida suggest climatic control on their distribution (temperate and tropical faunas), together with palaeogeographical constraints that also reflect trilobite provinciality. Kunmingellids and comptalutids were restricted to palaeo-tropical/subtropical sites, but migrated between South China, Siberia and eastern Gondwana palaeocontinents. They are absent from the mid-and high latitude faunas of the western Gondwana, Avalonia and Baltica palaeocontinental areas that were dominated by hipponicharionids, beyrichonids and Bradoriidae. The Laurentia palaeocontinent was isolated from the main zones of bradoriid diversity, but its faunas include a number of early and middle Cambrian Bradoriidae (Indota, Bradoria, Walcottella), and the region was colonised by cosmopolitan cambriids during the early Cambrian and by supposed pelagic svealutids (Liangshanella and Anabarochilina) during the middle Cambrian. The genera Walcottella, Dielymella and Bullaluta were endemic to Laurentia. One species of Anabarochilina that possibly dwelt near the sea-surface achieved an equatorial to high southern latitude (70°S) distribution during the late middle Cambrian (Lejopyge laevigata Biozone), perhaps reflecting a reduced latitudinal temperature gradient for near surface ocean waters.