Middle Ordovician Brachiopods Research Articles

Lower–Middle Ordovician brachiopods from the Eastern Cordillera of Peru: evidence of active faunal dispersal across Rheic and Iapetus oceans

AbstractNew Floian and early middle Darriwilian brachiopod assemblages of the San José Formation of the Eastern Cordillera of Peru are presented. A new genus and species, Apurimella santiagoi, and two new species, Phragmorthis henrylunae and Nocturnellia ashaninka, are described. The assemblages also contain additional characteristic taxa demonstrating links with other proto‐Andean localities (Peruvian Altiplano, Argentinian Eastern Cordillera, Famatina) as well as with some localities of Baltica (Estonia, Ingria, Norway), Ganderia (Anglesey, Tramore, Indian Bay, Summerford, Miramichi), peri‐Laurentia (Mayo, Svalbard) and Laurentia (Klamath Mountains). Those shared genera indicate dynamic faunal exchanges between the Peruvian Eastern Cordillera and these terranes during the Early–Middle Ordovician transition, suggesting active brachiopod dispersal mechanisms across the Rheic and Iapetus oceans. These connections seem to have still been active by the middle Darriwilian, as suggested by the presence of Phragmorthis in the Darriwilian assemblages of Cuyania and Laurentia. Similarly, the new Peruvian Nocturnellia species is of particular interest, given that this genus is likely to have originated in South China during the Floian, but extended its distribution to Avalonia and to high‐latitude peri‐Gondwana by the Dapingian. It thrived there until the middle Darriwilian, but by that time had also reached the proto‐Andean margin either via Avalonia across the Rheic Ocean or along the Gondwanan coast from high‐latitude settings. All of these occurrences improve our knowledge of Early–Middle Ordovician brachiopod faunas of the northern Central Andean Basin and their relationships with contemporaneous faunas worldwide.

Middle Ordovician brachiopods from Tagoat, Co. Wexford, SE Ireland: Dapingian diversity drivers

The Dapingian (Arenig) siltstones and sandstones of the Tagoat Group, County Wexford, SE Ireland, contain a well-preserved and diverse brachiopod fauna including a new genus of alimbellid, Palaeotagoatia (type species: Orthis Bailyana Davidson) together with the plectorthid Ffynnonia costata (Bates) hibernica nov. subsp. Of the 13 forms documented, at least six are conspecific with brachiopods from the upper Arenig (Dapingian-lowest Darriwilian) Treiorwerth Formation on Anglesey and a further two are identified with species occurring in the older Dapingian Carmel Formation. The faunal province affinities of the fauna are with those assemblages assigned to the peri-insular and marginal Celtic province and which occupied positions within the Middle Ordovician Iapetus Ocean between the Laurentian and Baltic platform provinces. More precise correlation of Middle Ordovician units suggests a significant species richness during the Dapingian-earliest Darriwilian and signalling also an early development of the Celtic province. But the shallow-water siliciclastic facies associated with these islands may also have influenced the distribution of some elements of the Celtic brachiopods and promoted the prevalence of coarse-ribbed orthides, such as Paralenorthis.

Lower–Middle Ordovician brachiopods from the Eastern Cordillera of Peru: biostratigraphical and palaeobiogeographical significance

Lower–Middle Ordovician brachiopods from the Eastern Cordillera of Peru: biostratigraphical and palaeobiogeographical significance

Early–Middle Ordovician brachiopod diversification in the middle Yangtze region of South China

The evolution of the Early–Middle Ordovician brachiopod diversity in the middle Yangtze region of South China has been analyzed. The brachiopods in this region originated in the early Tremadocian and radiated from the late Floian to the late Dapingian. The composition of rhynchonelliformean brachiopods underwent major changes in the late Floian, and endemic genera migrated from the upper Yangtze region to replace the cosmopolitan genera. A global comparison of the brachiopod diversity curves of South China, Laurentia, and Baltica reveals that (1) the processes and scales of brachiopod radiation in different paleocontinents were distinct; (2) unlike the global evolution of graptolites and chitinozoans, the correlation between brachiopod diversification and regional habitat change was more obvious, and the impact of habitat heterogeneity was reflected not only between plates but also in the interior of the plates, such as the closely connected middle and upper Yangtze regions of South China; and (3) geographical isolation was a key factor in the differential radiation on different paleocontinents.

The glacially induced Middle Ordovician rise of the Plectambonitoidea (Brachiopoda) and the phylogenetic placement of the Baltic genus Ukoa

The rare Middle Ordovician brachiopod genus Ukoa has remained unassigned to any existing family. The original description by Öpik in 1932 was based primarily on the external morphology; all later revisions of the genus also lack information regarding the interior of the dorsal valve, as well as information on the shell ultrastructure. As these are critical morphological features for designating a placement within the superfamily Plectambonitoidea – or indeed the order Strophomenida – not even a higher-level taxonomical determination has hitherto been attempted for Ukoa. The current study has examined new material, as well as museum specimens, that allowed for an analysis of the shell ultrastructure confirming the genus placement within the plectambonitoids. Moreover, as dorsal cardinalia are preserved in one of the new specimens, we further place Ukoa within the family Taffiidae Schuchert and Cooper, 1931, assigned to a new subfamily, the Ukoainae n. subfam. This corresponds well with the stratigraphic range of the Taffiidae, and as such, Ukoa, therefore represents yet another short-ranged plectambonitoid genus that originated during the Middle Ordovician Darriwilian Stage. As this coincides with both the onset of the main phase of the Great Ordovician Biodiversification Event (GOBE) and suddenly cooling climate, the current study also reviews the early diversification of the Plectambonitoidea within that context. Based on a specific focus on Baltica, we suggest that the unusual morphology that characterizes the plectambonitoids could be a particularly successful functional morphological adaptation to the unfolding Darriwilian ice age. As sea level dropped – possibly in the same order of magnitude as that experienced during the Quaternary glaciations – increased siliciclastic input washed onto the epicontinental seas globally providing muddy substrates, and thus new ecospace for the plectambonitoids to exploit and utilize during the early Darriwilian sea-level lowstands. The millennial glacioeustatic oscillations further accelerated plectambonitoid diversity through multiple allopatric speciation events, contributing to the overall accumulation of biodiversity that characterises the GOBE.

Early–Middle Ordovician brachiopod dispersal patterns in South China

Paleobiogeographic patterns of the brachiopod faunas before and during the first radiation of the Great Ordovician Biodiversification Event (GOBE) in South China at 6 different localities from the upper Jiangnan Slope to the vast area of the Upper Yangtze Platform show several interesting features. First, the initial brachiopod diversity acme was accompanied by both high origination and extinction rates. Second, no significant changes took place in the taxonomic composition and paleobiogeographic pattern of the brachiopod fauna during the radiation at 5 of the 6 localities studied except the near shore locality, where the first brachiopod radiation was much later than at other localities and was marked by a dramatic increase in endemic constituents. Third, orthides were the predominant brachiopod group during the radiation, and regional brachiopod taxa played a significant role in defining the paleobiogeographic pattern of the radiation. Fourth, the first brachiopod radiation was associated with 3 major pulses of onshore migration from the upper Jiangnan Slope through the central Upper Yangtze Platform to the near shore settings of the platform, with the middle pulse being the most significant. Finally, paleogeographic dispersal took place in both onshore and offshore directions, although the onshore expansion was more prominent; several key brachiopods, such as Paralenorthis, Nocturnellia, Protoskenidioides, Nereidella, Euorthisina and Yangtzeella, first appeared on the upper Jiangnan Slope and later formed distinct, and taxonomically diverse, communities on the Upper Yangtze Platform. The paleogeographic dispersal of brachiopods is considered to be closely related to the tectonic evolution of the Qianzhong Arch.

Middle Ordovician brachiopods from the Stairway Sandstone, Amadeus Basin, central Australia

Jakobsen, K.G., Brock, G.A, Nielsen, A.T., Topper, T.P. & Harper, D.A.T., 2013. Middle Ordovician brachiopods from the Stairway Sandstone, Amadeus Basin, central Australia. Alcheringa. ISSN 0311–5518.Middle Ordovician brachiopod faunas from the Amadeus Basin, central Australia are poorly known. The Darriwilian Stairway Sandstone was sampled stratigraphically for macrofossils in order to provide new information on marine benthic diversity in this clastic-dominated, shallow-water palaeoenvironment along the margin of northeastern Gondwana. The brachiopods from the Stairway Sandstone are of low diversity and represent ca 9% of the entire shelly fauna. Five brachiopod taxa are described from the Stairway Sandstone; all are endemic to the Amadeus Basin at species level. Two new species, Amadeuphyla joanae gen. et sp. nov. and Paralenorthis luritjaorum sp. nov., are described. Unweighted cladistic analysis based on 20 characters places the new genus Amadeuphyla within the Taffinae.Kristian G. Jakobsen [kgjakobsen@snm.ku.dk] Geological Museum, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen, Denmark & Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia. Glenn A. Brock [glenn.brock@mq.edu.au] Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia. Arne T. Nielsen [arnet@snm.ku.dk] Geological Museum, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen, Denmark. Timothy P. Topper [timothy.topper@snm.ku.dk] Geological Museum, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen, Denmark. David A. T. Harper [david.harper@durham.ac.uk] Geological Museum, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen, Denmark & Department of Earth Sciences, Durham University, Durham, UK. Received 14.6.2013; revised 25.9.2013; accepted 8.10.2013.

Taxonomy and biostratigraphy of Ordovician brachiopods from northeastern Ny Friesland, Spitsbergen

We describe Early and Middle Ordovician brachiopod faunas from northeastern Spitsbergen and discuss their biostratigraphical and palaeoecological implications. We recognise 60 species and 41 genera representing both linguliform and rhynchonelliform brachiopods. These include one new genus, the obolid Lenticulella with the type species Lenticulella amphora (Krause & Rowell, 1975), and 23 new species: Ectenoglossa? oviforma, Elliptoglossa vulgaris, Rosobolus? elongatus, Broeggeria obscura, Mirilingula? svalbardensis, Schizotreta marginalis, Conotreta convexa, Cyrtonotreta profilbekkiensis, Cyrtonotreta spinosa, Eurytreta subtriangularis, Hisingerella maniformis, Semitreta basisslettaensis, Semitreta pustulosa, Semitreta spitsbergensis, Numericoma? proclina, Eoconulus subquadratus, Dictyonites mugilis, Pelonomia sulcata, Leptella (Leptella) inequicostellata, Protoskenidioides promontorium, Anomalorthis rossi, Nothorthis subpyramidalis and Phragmorthis noda. The Ordovician succession contains both intertidal and deep-sea deposits with brachiopod faunas from nearly the whole range of environments. The Tremadocian is represented by a succession of low-diversity, rhynchonelli-6 · Zootaxa 3076 © 2011 Magnolia Pressform-dominated assemblages occupying shallow-marine environments. With the abrupt and large-scale drowning during the Floian, these faunas were replaced by a sparse slope fauna of micromorphic linguliforms. The outer shelf environments established in the latest Floian were occupied by a highly diverse brachiopod fauna dominated by micromorphic linguliform taxa. As the environment shifted toward the mid-shelf during the Darriwilian, however, the composition of the fauna changed to an Orthidiella-dominated assemblage of mostly rhynchonelliform taxa. The very late occurrence of the Orthidiella assemblage suggests that the Dapingian Orthidiella Zone found in America is probably diachronic. Although it includes many endemic species, the Middle Ordovician fauna shows a strong resemblance to the brachiopod fauna of Nevada. This study is based on approximately 16 500 brachiopod specimens obtained from both crack-out samples and acetic-acid-treated bulk samples.

The earliest atrypides and athyridides (Brachiopoda) from the Ordovician of Kazakhstan

The middle Ordovician brachiopod faunas of Kazakhstan provide one of the most complete records of the evolution and radiation of some of the oldest known spire‐bearing brachiopods. By contrast with North American faunas, Kazakhstanian atrypide taxa mostly belong to the suborders Atrypidina and Lissatrypidina, whereas the suborder Anazygidina is completely absent. Kazakhstanian species referred previously to ZygospiraKuzgunia are reassigned to Sulcatospira, which appeared in the Caradoc Diplograptus multidensClimacograptus clingani biozones (Sulcatospira? praecursor and Sulcatospira prima sp. nov.). Primitive, and possibly the oldest known Athyridida also appeared in Kazakhstan sometime during the Caradoc (Kellerella misiusi sp. nov.) and became widespread in brachiopod assemblages developed in carbonate mud mounds. Phylogenetic analysis suggests the early divergence of the Anazygidina, Atrypidina and Athyridida, which probably evolved independently from various primitive smooth Lissatrypidina. The new atrypide subfamily Pectenospirinae and two new atrypide genera (Rozmanospira gen. nov. and Pectenospira gen. nov. with P. pectenata sp. nov. as type species) are erected.

Gradient Analysis of Middle Ordovician Brachiopod Biofacies: Biostratigraphic, Biogeographic, and Macroevolutionary Implications

Gradient Analysis of Middle Ordovician Brachiopod Biofacies: Biostratigraphic, Biogeographic, and Macroevolutionary Implications

Faunal Provinces in the Ordovician of North Atlantic Areas

WILLIAMS1 has recently pointed out a number of quantitatively significant relationships between Ordovician brachiopod faunas on both sides of the Atlantic. In the Early Ordovician and the early stages of the Middle Ordovician three brachiopod faunal provinces persisted in the area of the British Isles. The provinces occurred as belts in the NE–SW strike direction of the Caledonian geosyncline. Along the northern margin of the geosyncline, extending through NW Ireland and Scotland, there was a province with mainly North American faunal affinities (American Province). Williams suggests that the migration of the brachiopods in this province took place by a current transporting the brachiopod spat towards the NE. The central part of the geosyncline was occupied by anaerobic bottoms with graptolitic mud, devoid of significant brachiopod fauna. South of this belt there was a strip extending through SE Ireland and NW Wales (Anglesey), in which the Lower–Middle Ordovician brachiopod faunas are most closely related to stratigraphically equivalent faunas of the Baltic area (Baltic Province). Williams shows that these faunas probably spread with a current system flowing towards the SW. The same current system was responsible for the migration of the Anglo-Welsh fauna occupying the southern marginal area of the geosyncline.

Distribution of the Toquima-Table Head (Middle Ordovician Whiterock) Faunal Realm in the Northern Hemisphere

Discovery of a Whiterock trilobite assemblage in the Albany Mudstone, Girvan District, southwestern Scotland, led to an assessment of the distribution of Middle Ordovician brachiopod and trilobite faunas previously assigned to the White-rock Stage of Cooper (1956). These faunas lie within a belt designated as the Toquima-Table Head Faunal Realm. This realm is closely related to the position of the transition from miogeosynclmal to eugeosynclinal facies, presumed to indicate the position of Ordovician continental margins. In Middle Ordovician time North America, parts of Ireland, Scotland, Norway, Sweden, and northeastern Asia may have constituted a single continental mass.