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870 results for “Ordovician”
Data from: Phylogeny and morphologic evolution of the Ordovician Camerata (Class Crinoidea, Phylum Echinodermata)
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Original dataset, coded matrix, and Bayesian phylogenetic trees of three Late Ordovician brachiopod genera (Atrypida: Anazygidae)
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Data from: Trilobites of Thailand’s Cambrian-Ordovician Tarutao Group
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Did hard substrate taxa diversify prior to the Great Ordovician Biodiversification Event?
<p>The Great Ordovician Biodiversification Event (GOBE) refers to one of the greatest increases in biodiversity during the Phanerozoic. Recent studies have shown that this taxonomic increase can be attributed to elevated origination rates around the Dapingian-Darriwilian boundary in the Middle Ordovician, while extinction rates stayed relatively constant throughout the Ordovician. Even though this global pattern of origination and extinction appears similar across diverse groups and geographic areas, earlier studies suggested that hard substrate taxa may have diversified prior to the GOBE, during the Early Ordovician. Here, we quantify Ordovician diversification dynamics of hard substrate taxa while simultaneously accounting for temporally varying sampling probabilities. Diversification rates of hard substrate taxa, both as a whole and when analysed as separate groups, appear to be very similar to those of free-living benthic taxa. The observation that the diversification dynamics of many different taxonomic and ecological groups show the same temporal pattern, suggests a common-cause to Ordovician diversification dynamics.</p>
Data from: Evenness and diversity in Upper Cambrian – Lower Ordovician trilobite communities from the Central Andean Basin (Cordillera Oriental, Argentina)
Community evenness has recently received much attention, either because it is related to ecosystem functioning or because it may affect estimation of diversity. Temporal and environmental trends in diversity and evenness of trilobite communities during the Late Cambrian – Early Ordovician of the Cordillera Oriental (north-western Argentina) are here analysed. Richness and evenness increase through time in both deep subtidal (between fair-weather and storm wave base) and offshore (below storm wave base) communities. Two significant patterns are superimposed on this general trend: (1) the magnitude of the increase in evenness is much more pronounced in deep than in shallower settings, and (2) richness and evenness trajectories are decoupled (while a significant rise in evenness is recorded in the middle Tremadocian (Tr2), an increase in richness is delayed until the late Tremadocian (Tr3)). In contrast to expectations, a single family (Olenidae) is dominant in samples associated with this earlier rise in evenness relative to richness. Hence, this trend is explained neither by the number of families present in the communities nor by the familial identity of the most abundant taxon. Large-scale comparisons of the timing and geographical components of these trends are restricted to the patterns recognized in Laurentian North American studies. Results from the Cordillera Oriental mirror those of Laurentia regarding the rise in both metrics in deep marine settings. Nevertheless, the timing of this increase in richness and evenness is delayed in the Cordillera Oriental, supporting the idea that palaeogeographical regions differed in the nature and timing of ecological changes. Finally, the rise in trilobite alpha-diversity through the Late Cambrian – Early Ordovician of the Cordillera Oriental supports the idea that trilobite alpha-diversity did not decline worldwide, suggesting that the relative decline in trilobite alpha-diversity is most probably caused by the dilution effect.
Data from: Ecology, biofacies, biogeography and systematics of micromorphic lingulate brachiopods from the Ordovician (Darriwilian–Sandbian) of south-central China
Ordovician (Darriwilian to Sandbian) micromorphic linguliform lingulate brachiopods are described from the Guniutan Formation at the Fenxiang section in Hubei province, and the Maocaopu and Cili sections in Hunan province of south-central China, situated on the Yangtze Platform. A total of 7560 specimens from 155 limestone samples (within the interval of Lenodus variabilis – Pygodus anserinus biozones) are assigned to 22 species, representing a low taxonomic diversity and low abundance fauna. The fauna is dominated by the Acrotretoidea, mainly species of the Torynelasmatidae, with Torynelasma the most abundant (more than 40% of total number of specimens), along with the Eoconulidae and Eoconulus (18% of total) representing the second most common forms. Species of the Ephippelasmatidae are also common (16% of total) diverse, and include representatives of Myotreta and Numericoma, as well as Ephippelasma, whereas species of the Scaphelasmatidae are somewhat less common (13% of total). All three investigated sections represent outer shelf environments, but the Maocaopu section is situated in a relatively deeper position, in proximity of the south-eastern outer margin of the Upper Yangtze Platform, close to its boundary with the Jiangnan Slope. A quantitative analysis of the relative abundance data was carried out in order to investigate the biofacies distribution of the micromorphic brachiopod communities across the Yangtze Platform, something that has not been attempted before with Palaeozoic linguliforms. Six lingulate microbrachiopod communities could be recognized in the sections. The major biofacies shift, which occurred in the Cili section in the upper part of the Microzarkodina ozarkodella Zone, at the time of the onset and initial rise of the Mid Darriwilian Carbon Isotope Excursion (MDICE) suggests that these biofacies may have been depth controlled.
Data from: Morphometrics and paleoecology of Catenipora (Tabulata) from the Xiazhen Formation (Upper Ordovician), Zhuzhai, South China
Catenipora is one of the most common tabulate coral genera occurring in various lithofacies in the Upper Ordovician Xiazhen Formation at Zhuzhai in South China. A combination of traditional multivariate analysis and geometric morphometrics is applied to a large number of specimens to distinguish and identify species. Based on three major principal components extracted from 11 morphological characters, three major groups as determined by the cluster-analysis dendrogram are considered to be morphospecies. Their validity and distinctiveness are confirmed by discriminant analysis, descriptive statistics, and bivariate plots. Tabularium area and common wall thickness are the most meaningful characters to distinguish the three morphospecies. Geometric morphometrics is adopted to compare the morphospecies with types and/or figured specimens of species previously reported from the vicinity of Zhuzhai. Despite discrepancies in corallite size, principal component analysis and discriminant analysis, as well as consideration of overall morphological characteristics, indicate that the morphospecies represent C. zhejiangensis Yu in Yu et al., 1963, C. shiyangensis Lin and Chow, 1977, and C. dianbiancunensis Lin and Chow, 1977. Catenipora occurs in seven stratigraphic intervals in the Xiazhen Formation at Zhuzhai, representing a variety of heterogeneous environments. The coralla preservation is variable due to differential compaction; coralla preserved in limestones are commonly intact and in growth position, whereas those in shales are mostly crushed or fragmentary. The size and shape of corallites are considered primarily to be species-specific characters, but are also related to the depositional environments. In all species, morphological characters, including corallite size, septal development, and shape and size of lacunae, show high variability in accordance with lithofacies and stratigraphic position. The intraspecific differences in corallite size at various localities in the Zhuzhai area may indicate responses to local environmental factors, but may also reflect genetic differences if there was limited connection among populations.
Data from: Controls on niche stability in geologic time Congruent responses to biotic and abiotic environmental changes among Cincinnatian (Late Ordovician) marine invertebrates
The set of environmental conditions under which a taxon can survive and maintain viable populations, known as the ecological niche, is a fundamental determinant of a taxon's distribution. Because of the central importance of ecological niches, they have been assumed to remain relatively stable during intervals of morphological stasis. However, the assumption of niche stability has rarely been tested directly with fossil data spanning multiple temporal intervals. Thus, the conditions under which this assumption is likely to be accurate are not well understood. In this study, we use ecological niche modeling (ENM) to reconstruct the ecological niche for 11 genera of marine benthos (crinoids, trilobites, molluscs, bryozoans, and corals) from the Type Cincinnatian Series (Late Ordovician, Katian Stage) across nine temporal intervals spanning approximately three million years. This interval includes both abiotic environmental change (gradual sea-level fall) and biotic change (rapid pulses of the Richmondian Invasion), thus allowing the relative effect of different environmental perturbations to be constrained. A previous symmetrical analysis of niche stability of brachiopod species recovered an increase in niche evolution following the Richmondian Invasion. Herein we test the generality of the brachiopod pattern within the community. Niche stability was evaluated in geographic space, ecological space, and niche parameter space. Niche stability varied through time; during the Pre-Invasion interval, taxa exhibited niche stability during gradual shallowing of sea level in the basin, whereas niche evolution became more common during the Richmondian Invasion. Taxa adjusted to the increased competition by altering aspects of their niche. Notably, surviving taxa contracted their niche into a subset of their previous niche parameters. This represents an adaptive response to increased competition for resources with the newly established invader taxa, and it was employed most successfully by generalist taxa. Patterns of niche evolution were congruent between clades, among feeding styles, and across taxonomic levels.
Data from: Linguliform brachiopods across a Cambrian–Ordovician (Furongian–Early Ordovician) biomere boundary: the Sunwaptan/Skullrockian North American stage boundary in the Wilberns and Tanyard Formations of central Texas
The Cambrian-Ordovician Diversity Plateau, between the Cambrian Explosion and the Ordovician Radiation, is punctuated by a series of well-documented Laurentian trilobite extinction events. These events define the bounding surfaces of trilobite "biomeres" that correspond to North American stages, including those of the Sunwaptan and Skullrockian. Trilobites show a consistent pattern of recovery across these boundaries, and commonly each extinction and replacement of taxa is interpreted as a single event as changing environmental conditions spurred shoreward migration of shelf or oceanic faunas that displaced established cratonic faunas. Linguliform brachiopods are also abundant in strata of this interval, and we investigate their stratigraphic distribution across the Sunwaptan–Skullrockian Stage boundary in Texas through high-resolution stratigraphic sampling of subtidal sediments. We document complete genus- and species-level turnover of the linguliform brachiopod fauna coincident with trilobite extinction events, suggesting that these brachiopods were affected by the same factors that affected trilobites. The Skullrockian replacement fauna was cosmopolitan, with ties to Gondwana and Kazakhstan and to the Laurentian shelf environment. The timing of appearances of taxa suggests that the faunal migration onto the Laurentian shelf came from elsewhere during a transgression. The disappearance of the Sunwaptan fauna and the arrival of the Skullrockian fauna are distinct events. We suggest that "biomere" events may be complex, and the cause of the extinction is not necessarily the same event that facilitates the appearance of a replacement fauna. We describe one new species, Schizambon langei.
Data from: A combined morphometric and phylogenetic revision of the late Ordovician brachiopod genera Eochonetes and Thaerodonta
Systematic revision of the Late Ordovician brachiopod genera Eochonetes Reed, 1917 and Thaerodonta Wang, 1949 was conducted utilizing specimen-based morphometric and species-level phylogenetic analyses. Previous studies had recognized Thaerodonta and Eochonetes as either distinct taxonomic entities or synonyms. New multivariate and phylogenetic analyses confirm the synonymy of Thaerodonta with Eochonetes and provide a framework to assess evolutionary and ecological patterns within the clade. Multivariate analyses were employed to delineate species in morphospace and provided information on potential species relationships. Phylogenetic analysis was used to produce an evolutionary framework for taxonomic revision and identify character evolution within the clade. Most species previously assigned to Thaerodonta are transferred to Eochonetes, and three others are excluded from Eochonetes and provisionally referred to other sowerbyellid genera. Three new species (Eochonetes maearum new species, E. voldemortus new species, E. minerva new species) are described, one species (Leptaena saxea Sardeson, 1892) is synonymized with E. recedens Sardeson, 1892, and one subspecies (Thaerodonta mucronata scabra Howe, 1965) is rejected. This study demonstrates that a combination of complementary approaches and data types has the potential to advance interpretations beyond analyses confined to single analytical tools. Specifically, multivariate analyses provide constraints on species boundaries, whereas species-level phylogenetic analyses provide frameworks to examine morphological, ecological, and biogeographic evolution within a clade.
Data from: Trepostomate bryozoans from the upper Katian (Upper Ordovician) of Morocco: gigantism in high latitude Gondwana platforms
A study of the Upper Ordovician trepostomate bryozoans belonging to the families Amplexoporidae and Monticuliporidae, from the eastern Anti-Atlas of Morocco, is presented here. They occur in the marly to fine-grained limestone, intermediate unit of the Khabt-el-Hajar Formation, late Katian in age, representing outer-ramp depositional environments. They inhabited the highest paleolatitude known for a bryozoan fauna during the Ordovician, estimated at more than 65–70ºS. A total of 11 species of the genera Anaphragma, Atactoporella, Homotrypa, Monotrypa, Monticulipora, and Prasopora are described. Three species are already known from the equatorial-tropical paleocontinents of Baltica, Laurentia, and Siberia: Anaphragma mirabile, Monotrypa jewensis, and Prasopora falesi. Four new taxa are described:Anaphragma undulata, Atactoporella moroccoensis, Monticulipora globulata, and Monticulipora irregularis. The two species of Anaphragma and the one of Atactoporella display significantly larger zoarial sizes than congeneric species, representing gigantism among bryozoans. Polar gigantism is rejected for the two species of Anaphragma as is gigantism related to photosynthetic endosymbionts. An alternative proposal for their giant size is their long zoarial life span due to their well-balanced, robust branching form, with a relatively wide basal supporting surface, adapted to unconsolidated substrates in environments below wave base. Their great stability in outer-ramp environments, with infrequent storms, would allow the zoaria to grow for an extended time and reach large sizes before being overturned and buried. Atactoporella moroccoensis, has both zoaria and zooecia gigantic, suggesting a hypothesis of polar gigantism.
Data from: Disparid and hybocrinid crinoids (Echinodermata) from the Upper Ordovician (lower Katian) Brechin Lagerstätte of Ontario
The Brechin Lagerstätte (Katian, Ordovician) from the Lake Simcoe region of Ontario, Canada, contains a diverse array of echinoderms. Here, we describe seven disparid and two hybocrinid crinoids (Subclass Pentacrinoidea, Infraclass Inadunata), including a new disparid species belonging to the Anomalocrinidae (Order Homocrinida). In total, the disparids include Anomalocrinus astrictus n. sp.; Cremacrinus guttenbergensis Kolata, 1975; Cremacrinus inaequalis Billings, E., 1859; Daedalocrinus bellevillensis Billings, W.R., 1883; Eustenocrinus springeri Ulrich, 1925; Iocrinus trentonensis Walcott, 1883; and Isotomocrinus tenuis Billings, E., 1857b; and the hybocrinids include Hybocrinus tumidus Billings, E., 1857a and Hybocystites problematicus Wetherby, 1880. Previously known from only the holotype, three additional specimens of E. springeri expand our understanding of this unusual crinoid. Nomenclatural acts include the following: the recommendation of Warn and Strimple (1977), who designated Daedalocrinus kirki as a junior synonym of Daedalocrinus bellevillensis is followed; Hybocrinus pristinus Billings, E., 1858 is designated a junior synonym of Hybocrinus tumidus; and previous decisions are followed herein to retain Hybocystites eldonensis (Parks, 1908) as a junior synonym of Hybocystites problematicus. Although probably assignable to Anomalocrinus, the aberrant crinoid Glaucocrinus falconeri is designated a nomen dubium. Iocrinus similis (Billings, E., 1857a) is also designated a nomen dubium.
Data from: New crinoids from the Baltic region (Estonia): fossil tip-dating phylogenetics constrains the origin and Ordovician–Silurian diversification of the Flexibilia (Echinodermata)
This study documents previously unknown taxonomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end-Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high-resolution temporal, taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end-Ordovician mass extinction. A Bayesian 'fossil tip-dating' analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via 'budding' cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from 'taxocrinid' grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post-Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeographical regions for clade-based phylogenetic studies and improving estimates of global biodiversity through geological time.
Data from: Katian (Upper Ordovician) conodonts from Wales
Middle and Upper Katian conodonts are previously known in the British Isles from relatively small collections obtained from a few localities. The present study is mainly based on 17 samples containing more than 17,000 conodont elements from an approximately 14 m thick succession of the Sholeshook Limestone in a road cut near Whitland, South Wales that yielded a diverse fauna of more than 40 taxa. It is dominated by representatives of Amorphognathus, Aphelognathus/Plectodina, and Eocarniodus along with several coniform taxa. Representatives of Decoriconus, Istorinus and Sagittodontina are reported from the Ordovician of UK for the first time. The fauna is a typical representative of the British Province of the Atlantic Realm and includes a mixture of taxa of North American, Baltoscandic, and Mediterranean affinities along with pandemic species. Based on the presence of many elements of Amorphognathus ordovicicus and some morphologically advanced specimens of A. superbus, the Sholeshook Limestone is referred to the lower A. ordovicicus Zone. Most of the unit is also coeval with Zone 2 of the Cautleyan Stage in the British regional stage classification, and Stage Slice Ka3 of the middle Katian Stage in the global stratigraphical classification, an age assignment consistent with data from trilobites, graptolites, and chitinozoans. The unusually large collection of M elements of Amorphognathus provides insight into the complex morphological variation of this element of some Katian species of this genus. The Sholeshook conodont fauna is similar to those of the Crûg and Birdshill limestones but differs in several respects from the slightly older ones from the Caradocian type area in the Welsh Borderland. Although having some species in common, the Sholeshook conodont fauna clearly differs from coeval Baltoscandic faunas, and is even more different in composition compared with equivalent North American Midcontinent faunas.
Data from: The early record of halysitid tabulate corals, and morphometrics of Catenipora from the Ordovician of north-central China
Catenipora is one of the most common tabulate coral genera in the Upper Ordovician Jinghe and Beiguoshan formations on the southern margin of the Ordos Basin, north-central China. We distinguish and identify the species of Catenipora using multivariate morphometric procedures. Cluster analysis based on morphological characters of coralla yields a dendrogram showing five morphospecies. The validity and distinctiveness of the morphospecies are evaluated by discriminant analysis and non-metric multidimensional scaling. To identify the species represented by the morphospecies, type specimens of species that are morphologically similar from north-central China (Sino-Korean Block) and surrounding palaeocontinents are compared with the morphospecies by non-metric multidimensional scaling and descriptive statistics. The result indicates that one morphospecies represents C. daliangensis (Yu), another represents C. subovata Yu, and the others are considered to be new species named C. tongchuanensis, C. jingyangensis and C. tiewadianensis. Catenipora tongchuanensis from the middle of the Jinghe Formation (Sandbian; early Late Ordovician) is the earliest confirmed halysitid tabulate. Species of Catenipora in north-central China (Sino-Korean Block) show the highest morphological diversity (i.e. disparity) in terms of corallite size and shape, compared with other palaeocontinents in China. Species of Catenipora in North Qilian share more common components with those from north-central China than any other palaeocontinent in China. The different morphological characteristics in terms of corallite shape and ranks in some Katian species of Catenipora from East Junggar, Mongolia, South China and Estonia suggest that some species may have originated separately during the Great Ordovician Biodiversification Event, and Catenipora is possibly polyphyletic.
Data from: Continental-scale biogeographic variation: provinces versus gradients in the Upper Ordovician of Laurentia
Although provinces are widely used to delimit large-scale variations in biotic composition, it is unknown to what extent such variations simply reflect large-scale gradients, much as has been shown at smaller scales for communities. We examine here whether four previously described Middle and Late Ordovician provinces on Laurentia are best described as distinct provinces or as biotic gradients through a combination of the Paleobiology Database and new field data. Both data sets indicate considerable overlap in faunal composition, with spatial patterns in Jaccard similarity, quantified Jaccard similarity, and nonmetric multidimensional scaling ordination structure that correspond to variations in substrate type, specifically from carbonate-dominated strata in western Laurentia to mixed carbonate–siliciclastic strata in the midcontinent to siliciclastic-dominated rocks in easternmost Laurentia. Because sampling was limited to shallow-subtidal settings, this gradient cannot be attributed to variations in water depth. Likewise, geographic distance accounts for only a quarter of the variation in faunal composition. This cross-continent faunal gradient increases in strength into the early Late Ordovician, and appears to represent increased siliciclastic influx into eastern Laurentia during the Taconic orogeny. These results raise the question of whether biogeographic provinces may be in general better interpreted and analyzed as biotic gradients rather than as discrete entities.
Data from: Fusion or hypertrophy?: The unusual arms of the Petalocrinidae (Ordovician-Devonian; Crinoidea)
The large, triangular or cylindrical second brachial plate of the Petalocrinidae was formed through fusion of brachial plates along the distal margin of the growing arms. Based on the number of ambulacral bifurcations, brachials from the primibrachitaxis through at least the quintibrachitaxis may have been fused to form this large plate. In Petalocrinus, all calcite of fused second brachials assume the same crystallographic orientation, but in Spirocrinus more than one crystal comprises the second brachial plate.
FIGURE 2 in A new species of the Lower Ordovician pliomerid trilobite Pseudocybele and its biostratigraphic significance
FIGURE 2. Stratigraphic column of portion of Section H showing range of Pseudocybele paranasuta n. sp. and position of Hintze's (1951, 1953) original sampling horizons. Faunal zones (at left, lowest to highest; see Adrain et al., 2009) are Presbynileus ibexensis, Pseudocybele paranasuta, and "Pseudocybele nasuta".
FIGURE 1. 1 in A new species of the Lower Ordovician pliomerid trilobite Pseudocybele and its biostratigraphic significance
FIGURE 1. 1. Location of the Tule Valley in Millard County, western Utah. 2. Road map with black box indicating location of Section H in the southern Confusion Range. 3. Line of Hintze's (1951, 1953, 1973) Ibex Section H. Topographical map base from US Geological Survey 1: 24,000 Warm Point 7.5' provisional quadrangle map (1991).
FIGURE 2 in Systematics of the Lower Ordovician pliomerid trilobite Hintzeia, with species from the Great Basin, western USA
FIGURE 2. Section of stratigraphic column of Section G (see Adrain et al. [2009] for full columns of sections G and H) showing occurrence of species of Hintzeia in the Psalikilus spinosum and Hintzeia celsaora zones of the Tulean. This part of Section G is a succession of thin beds of intraclastic rudstone ("flat pebble conglomerate") and covered slopes. Note that the lithological symbol appears to the right of the beds because it is too large to fit inside them. Original sampling horizons of Hintze (1951, 1953) are indicated at the corresponding metreage of our (2009) remeasurement.
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