Late Famennian gastropoda from south-west England

The gastropod fauna of the Upper Devonian Baggy and Pilton formations in south‐west England is revised and includes some 30 taxa. The topmost part of the Upper Famennian succession in Devon is represented by clastic near‐shore and shallow shelf sediments, indicating a short‐term transgressive phase (‘Strunian Transgression’). The sequence yields a highly diverse fauna dominated by brachiopods and ostracodes, locally supplemented by crinoids, bryozoans, trilobites and molluscs. The taxa ‘Patellostium’britannicum sp. nov., Angyomphalus (Angyomphalus) junius sp. nov. and Dictyotomaria eurocapillaria sp. nov. are erected; a junior homonym is replaced by Macrochilina? piltonensis nom. nov. The gastropod fauna displays an independent character, where latest Devonian faunal elements overlap with Late Palaeozoic taxa expressing a transition similar to that of the bivalves, brachiopods, echinoderms and corals, without a sharp faunal break at the Devonian/Carboniferous boundary. Apart from the Caenogastropoda, all subclasses of gastropods are represented. Members of the bellerophontoids, pleurotomarioids and loxonematoids are most abundant, followed by murchisonioids, naticimorphs, euomphalomorphs and platyceratoids. The various gastropod groups represent different ecological demands and trophic categories, and together with the accompanying fauna indicate that nearly all habitats and niches were occupied in the shallow South Laurussian Shelf.     

Carboniferous reef succession of the Panthalassan open-ocean setting: example from Omi Limestone, central Japan

Summary The Carboniferous-Permian (Visean-Midian) Omi Limestone in the Akiyoshi Terrane, central Japan is a large carbonate unit developed on a seamount in the Panthalassa Ocean. As the seamount subsided during Carboniferous and Permian time, the carbonate deposition at the top of a seamount was almost continous. Terrigenous siliciclastic sediments are absent, because the seamount was situated in an open-ocean setting. The lower part of this seamount-type limestone records a nearly continuous Carboniferous reef succession. Sedimentary facies in the Carboniferous part of the Omi Limestone are generally highly diverse, but their diversity varies in each age. The Upper Carboniferous part consists of highly diversified facies including fore reef, reef front, reef crest, sand shoal, and lagoon facies, while a simple facies assemblage, composed only of fore reef, reef front, and sand shoal facies, occurs in the Lower Carboniferous. The Carboniferous reef succession consists of four phases characterized, in ascending order, by the coralbryozoan-crinoid community, problematic skeletal organism-microencruster community, chaetetid-microencruster community, and calcareous algal community. The first phase, comprising the coral-bryozoan-crinoid community, occurs in theEndothyra spp. Zone to theEostaffella kanmerai Zone (Visean to Serpukhovian). This community acted only as sediment-bafflers and/or contributors. The second phase, represented by the problematic skeletal organism-microencruster community, is developed in theMillerella sp. Zone to theAkiyoshiella ozawai Zone (Bashkirian to lowermost Moscovian), and the third phase, comprising the chaetetid-microencruster community, occurs in the overlyingFusulinella biconica Zone (Lower Moscovian). These two communities are characterized by highly diversified reef-building organisms that had the ability to build rigid frameworks. Calcareous algae and incertae sedis such asHikorocodium, solenoporaceans and phylloid algae characterize the fourth phase, which occurs in theBeedeina sp. Zone (Upper Moscovian). The changes of the reef communities were sucessive for a long period of more than 40 m.y., and each community was distributed in various environments. In addition, the continuous subsidence of the isolated seamount resulted in environmental stability. These properties indicate that this succession represents the biotic evolution of reef-building organisms. The problematic skeletal organism-microencruster community and chaetetid-microencruster community of the Late Carboniferous formed wave-resistant and rigid frameworks along with abundant submarine cements. The growth of these reef frameworks resulted in the formation of highly diversified sedimentary facies comparable to those of a modern reef complex. Such reefs are also recognized in the seamount-type Akiyoshi Limestone, but rare on Carboniferous Pangean shelves. Therefore, the formation of these types of reefs appear to be characteristic of open-ocean seamount settings, which differed from epicontinental shelf settings in having no siliciclastic input, being exposed to relatively strong openocean waves and swells, and probably more environmental stability resulting from the relatively continuous subsidence of the seamount.     

Distribution of pedicle boring traces and the life habit of Late Paleozoic leiorhynchid brachiopods fiom dysoxic habitats

Alexander, R.R. 1994 10 15: Distribution of pedicle boring traces and the life habit of Late Paleozoic leiorhynchid brachiopods from dysoxic habitats.
Pedicle boring traces, Podichnus isp., are concentrated on the anterolateral commissure of both valves of Leiorhynchoidea carboniferum and L. weeksi from the black ferruginous micrites of the Chainman Formation (Upper Carboniferous; west-central Utah, USA) and black phosphatic ('False Cap') limestone of the Phosphoria Formation (southeastern Idaho, USA), respectively. The absence of Podichnus isp. from the posterior of shells of both species indicates that the beak of the shell was buried in the mud, inaccessible to colonization by conspecific larvae. The concentration of pedicle boring traces near the anterolateral incurrent regions of leiorhynchid shells with a well-developed central fold further suggests that settling conspecific larvae behaved rheotaxically. Larvae were induced to metamorphose near the commissure of the host shell, where suspended food was drawn to the incurrents of the host. The piggybacked mode of life on the anterior of conspecific hosts provided a refuge for juveniles above the dysoxic black sediments. In contrast, modem brachiopods that live as epibionts on skeletal substrates display either a random or posteriorly concentrated distribution of pedicle boring traces. Permian, Carboniferous, brachiopods, leiorhynchids, Podichnus, dysoxic, rheotaxis .     

Large extinctions of articulate brachiopods in the paleozoic and their ecological and evolutionary consequences

The largest Paleozoic extinctions of articulate brachiopods occurred at the Frasnian—Famennian boundary in the Late Devonian and at the Permian—Triassic boundary. Both extinctions affected taxa of all levels, including orders, but differed in scale, course, and ecological and evolutionary consequences. The Frasnian—Famennian extinction event was selective and evolutionary activity after the crisis varied in different orders. However, in the Early Carboniferous, the brachiopod diversity was mostly restored in comparison with the Devonian maximum. In particular groups, preadaptation played a role in changes in diversity and reconstruction of communities. The brachiopod composition at this boundary changed sharply. The extinction event at the end of Permian was global and accompanied by changes in the biota. Later, in the Meso-Cenozoic, the brachiopod diversity was not restored, and bivalves acquired primary importance in various bottom communities of different sea zones where Paleozoic brachiopods previously dominated. Extinction of brachiopods at this boundary was long and gradual. The symptoms of the ecological crisis in the development of Permian brachiopods are recognized beginning from the Roadian Age, which was probably the onset of this crisis.     

Late Devonian benthic marine communities of the central Appalachian Allegheny Front

Four benthic marine communities occur in the clastic facies of the prograding Upper Frasnian-Lower Famennian (Upper Devonian) Foreknobs Formation in the Central Appalachians along the Allegheny Front in Maryland, West Virginia, and Virginia. Deep-water, rapidly prograding environments were inhabited by the Ambocoelia-Chonetes Community, dominated by an epifauna of unattached brachiopods. Offshore bar environments were inhabited by the Cyrtospirifer-Camarotoechia Community, exhibiting adaptations to shallow-water, high-energy conditions and probably lowered salinities. Shallow-water, sublittoral environments were inhabited by the Atrypa-Cypricardella Community, a community in which existed a variety of life habitats and a diverse epifaunal and infaunal association of brachiopods and bivalve molluscs. The Leptodesma-Tylothyris Community flourished in nearshore bar-protected environments in the southern region of the study area, whereas in the north the Cyrtospirifer-Camarotoechia Community inhabited nearshore environments in conjunction with the onshore development of a large fluviodeltaic system.     

The Upper Carboniferous Hamilton Fossil-Lagerstätte in Kansas: a valley-fill, tidally influenced deposit

A diverse assemblage of unusually well-preserved marine, euryhaline, freshwater, and terrestrial fossils (invertebrates, vertebrates, and plants) occurs within an Upper Carboniferous (Stephanian) Konservat Fossil-Lagerstätte near Hamilton, Kansas, USA. The Lagerstätte occurs within a paleovalley that was incised into the surrounding Carboniferous cyclothemic sequence during a time of low sea level, and was then filled-in during a subsequent transgression. The stratigraphically lowest and most voluminous facies within the valley is a cross-bedded, polymictic limestone conglomerate that contains caliche clasts and charcoal fragments as well as some normal-marine fossils apparently in situ. The origin of the conglomerate is enigmatic, but it was probably deposited by a migrating tidal channel. Overlying and interbedded with the conglomerate is an ostracode wackestone that contains plants (primarily seed ferns and ferns), eurypterids, shrimp, brachiopods, bivalves, and rare fish. The ostracode wackestone was deposited in a low-energy, marginal-marine environment. A thin sequence (<1 m thick) of interbedded laminated limestone and mudstone overlies the conglomerate in a small area. This facies contains a well-preserved mixed assemblage of terrestrial (conifers, insects, myriapods, reptile), freshwater (ostracodes), aquatic (amphibians, reptile), brackish or euryhaline (ostracodes, eurypterids, spirorbids, fish), and marine (brachiopods, echinoderms) fossils. Many of the vertebrates are articulated and show no evidence of preburial decay, scavenging, or predation. A few vertebrates exhibit signs of flotation. Most articulated vertebrate specimens exhibit soft-tissue preservation in the form of dark-brown to black early-diagenetic microbialite body outlines (‘skin preservation’) containing fossil bacteria. Rhythmic patterns of lamination thickness variation in the limestones and mudstones indicate that this facies was deposited in a tidal environment. High sedimentation rate and variable salinity (and therefore exclusion of bioturbators and invertebrate scavengers) are interpreted as key elements that led to the excellent preservation of the fossils in this ancient estuarine environment. □Lagerstätte, taphonomy, estuarine, tidal bedding, paleovalley, Carboniferous, Kansas.     

Marine benthic communities in the Upper Devonian of New York

Four distinctive benthic communities occur in the mid-shelf deltaic deposits of the Upper Devonian Sonyea Group: the Bellerophon Community, dominated by herbivorous gastropods and deposit-feeding bivalves; the Prodrtctella Community, dominated by brachiopods with adaptations for life on muddy substrata; the Cypricardella Community, dominated by bivalves and brachiopods with a variety of adaptations; and the Rhipidomella Community, dominated by brachiopods adapted for life on sandy substrata. The geographic and stratigraphic occurrence of the communities suggest that their distribution was controlled by two principal sets of environmental variables: (1) onshore to offshore gradients in salinity, dissolved oxygen concentrations, and sedimentary substrata, and (2) rate of delta progradation. A change in the rate of delta build-out during mid-Sonyea time led to a dramatic change in onshore to offshore community patterns. The change suggests that great care must be used in constructing generalized community models for longer intervals of Paleozoic time.     

黔南独山地区泥盆系法门阶–石炭系杜内阶革老河组和汤粑沟组长身贝类新认知

本文描述了在黔南独山县其林寨剖面和黎家寨剖面上泥盆统革老河组和下石炭统汤粑沟组中发现的长身贝类化石共8属10种(含未定种)。其中,在革老河组中发现有3属4种:Productella? sp.、Yanguania dushanensis、Xinshaoproductusxinshaoensis和X.quadrata;汤粑沟组中有8属9种:Productella?sp.、Hunanoproductushunanensis、Spinocarinifera qilinzhaiensis sp. nov.、Yanguania dushanensis、Y.? sp.、Xinshaoproductus xinshaoensis、Tomiproductussp.、Ozora?sp.和Ericiatiakiangsuensis。总体而言,革老河组和汤粑沟组中的长身贝类在组成上主要以Productoidea超科中Productidae科的分子为主,Productellidae科和Echinoconchoidea超科中Sentosiidae科的分子各有1种。本文记述的Hunanoproductus和Xins...     

Catchment-scale biogeography of riverine bacterioplankton

Lotic ecosystems such as rivers and streams are unique in that they represent a continuum of both space and time during the transition from headwaters to the river mouth. As microbes have very different controls over their ecology, distribution and dispersion compared with macrobiota, we wished to explore biogeographical patterns within a river catchment and uncover the major drivers structuring bacterioplankton communities. Water samples collected across the River Thames Basin, UK, covering the transition from headwater tributaries to the lower reaches of the main river channel were characterised using 16S rRNA gene pyrosequencing. This approach revealed an ecological succession in the bacterial community composition along the river continuum, moving from a community dominated by Bacteroidetes in the headwaters to Actinobacteria-dominated downstream. Location of the sampling point in the river network (measured as the cumulative water channel distance upstream) was found to be the most predictive spatial feature; inferring that ecological processes pertaining to temporal community succession are of prime importance in driving the assemblages of riverine bacterioplankton communities. A decrease in bacterial activity rates and an increase in the abundance of low nucleic acid bacteria relative to high nucleic acid bacteria were found to correspond with these downstream changes in community structure, suggesting corresponding functional changes. Our findings show that bacterial communities across the Thames basin exhibit an ecological succession along the river continuum, and that this is primarily driven by water residence time rather than the physico-chemical status of the river.     

Paleoecology of some Carboniferous Pectinacea

Pectinacean bivalves in the Carboniferous of northern California, USA, occur in all observed biotic communities except bioherms of corals and productoid brachiopods. They show equal abundance in offshore, brachiopod-dominated habitats and nearshore, bivalve-dominated habitats, and are among the only common invertebrates in a 'black shale', restricted marine community. Different morphologic forms of the superfamily show little ecologic division. Pectinacea are least abundant in limestone, and most abundant in terrigenous beds, and bottom type was more important in controlling their distribution than water depth, current activity, or salinity.     

Mechanisms of ecological succession: insights from plant functional strategies

Successions are a central issue of ecological theory. They are governed by changes in community assembly processes that can be tracked by species’ traits. While single‐trait‐based approaches have been mostly promoted to address community assembly, ecological strategies actually encompass tradeoffs between multiple traits that are relevant to succession theory. We analyzed plant ecological strategies along a 140‐year‐long succession primary succession of 52 vertical outcrop communities after roadwork. We performed a RLQ analysis to relate six functional traits, associated with resource acquisition, competition, colonization ability and phenology, to the age of the outcrops. We found the prominence of two main axes of specialization, one related to resource acquisition and the other to reproduction and regeneration. We further examined the community‐level variation in ecological strategies to assess the abiotic and biotic drivers of community assembly. Using trait‐based statistics of functional richness, regularity and divergence, we found that different processes drove the variation in ecological strategies along the axes of specialization. In late succession, functional convergence was detected for the traits related to resource acquisition as a signature of habitat filtering, while the coexistence of contrasted strategies was found for the traits related to reproduction and regeneration as a result of spatial micro‐heterogeneity. We observed a lack of niche differentiation along the succession, revealing a weak importance of biotic interactions for the regulation of community assembly in the outcrops. Overall, we highlight a prominent role of habitat filtering and spatial micro‐heterogeneity in driving the primary succession governed by water and nutrient limitation.     

Biostratigraphic control of the latest-Ordovician glaciogenic unconformity in Alnif (Eastern Anti-Atlas, Morocco), based on brachiopods

In the Alnif region of the Eastern Atlas (Morocco), seven fossiliferous horizons within the Lower-Ktaoua and Upper-Tiouririne formations (Ktaoua Group), as well as in the glaciomarine microconglomeratic shales of the Upper Formation of the Second-Bani Group have yielded biostratigraphically significant brachiopods and other taxa, such as trilobites and echinoderms. Several brachiopod species with short stratigraphic ranges, well-known in south-western Europe, allow a precise chronostratigraphic control of a succession that displays important lateral lithological and facies changes, when compared with the type sections in the Central Anti-Atlas. They have also permitted a better consensus between the macrofauna-determined age and that based on micropaleontological analyses. For the first time, the occurrence of a Hirnantia Fauna within the microconglomeratic shales of the Upper Formation of the Second Bani Group is reported. The biostratigraphic conclusions restrict the age of the Latest Ordovician glaciation to the early Hirnantian.     

广西兴安早石炭世晚期三叶虫新资料

记述了产于广西兴安早石炭世晚期大塘阶双切尾虫亚科的１新亚属－Ｐａｌａｄｉｎｓｕｂｇｅｎ．ｎｏｖ．及其３新种：Ｐ．（Ｓ．）ｇｕｉｂｅｉｅｎｓｉｓｓｐ．ｎｏｗ．．Ｐ．（Ｓ．）ｘｉｎｇａｎｅｎｓｉｓｓｐ．ｎｏｖ。     

海南岛昌江地区石炭纪牙形刺化石

海南岛昌江地区前人所称南好组第四段及第三段分别发现的牙形刺Siphonodella isosticha-S.cooperi组合及Mesogondolella clarki组合,表明该组包括了早石炭早期及晚石炭世早中期,而不是传统的认为的属早石炭世并可能包括中－晚泥盆世,同时还证实原南好组第三段层位远远高于第四段,而不是位于其下,从而纠正了前人长期沿用的该地区石炭系层序的错误,并指出昌江地区石炭纪牙形刺属华南古生物地理系。     

Biophysical Controls on Community Succession in Stream Biofilms

Biofilm formation is controlled by an array of coupled physical, chemical, and biotic processes. Despite the ecological relevance of microbial biofilms, their community formation and succession remain poorly understood. We investigated the effect of flow velocity, as the major physical force in stream ecosystems, on biofilm community succession (as continuous shifts in community composition) in microcosms under laminar, intermediate, and turbulent flow. Flow clearly shaped the development of biofilm architecture and community composition, as revealed by microscopic investigation, denaturing gradient gel electrophoresis (DGGE) analysis, and sequencing. While biofilm growth patterns were undirected under laminar flow, they were clearly directed into ridges and conspicuous streamers under turbulent flow. A total of 51 biofilm DGGE bands were detected; the average number ranged from 13 to 16. Successional trajectories diverged from an initial community that was common in all flow treatments and increasingly converged as biofilms matured. We suggest that this developmental pattern was primarily driven by algae, which, as “ecosystem engineers,” modulate their microenvironment to create similar architectures and flow conditions in all treatments and thereby reduce the physical effect of flow on biofilms. Our results thus suggest a shift from a predominantly physical control to coupled biophysical controls on bacterial community succession in stream biofilms.     

Biophysical controls on community succession in stream biofilms

Biofilm formation is controlled by an array of coupled physical, chemical, and biotic processes. Despite the ecological relevance of microbial biofilms, their community formation and succession remain poorly understood. We investigated the effect of flow velocity, as the major physical force in stream ecosystems, on biofilm community succession (as continuous shifts in community composition) in microcosms under laminar, intermediate, and turbulent flow. Flow clearly shaped the development of biofilm architecture and community composition, as revealed by microscopic investigation, denaturing gradient gel electrophoresis (DGGE) analysis, and sequencing. While biofilm growth patterns were undirected under laminar flow, they were clearly directed into ridges and conspicuous streamers under turbulent flow. A total of 51 biofilm DGGE bands were detected; the average number ranged from 13 to 16. Successional trajectories diverged from an initial community that was common in all flow treatments and increasingly converged as biofilms matured. We suggest that this developmental pattern was primarily driven by algae, which, as "ecosystem engineers," modulate their microenvironment to create similar architectures and flow conditions in all treatments and thereby reduce the physical effect of flow on biofilms. Our results thus suggest a shift from a predominantly physical control to coupled biophysical controls on bacterial community succession in stream biofilms.     

Upper Cambrian-Ordovician successions overlying Timanian complexes: new evidence of acritarchs and brachiopods from Kolguev Island, Arctic Russia

Drillholes to several kilometres depth on Kolguev Island in the southern Barents Sea have sampled early Palaeozoic successions, known elsewhere in the Pechora Basin to overlie Neoproterozoic basement complexes. New studies on acritarch microfossils from the lowermost part of the Palaeozoic succession (c. 4500 m depth), reached by the Bugrino 1 and North-Western 202 boreholes, revealed diverse and biostratigraphically significant assemblages, which indicate the position of the Cambrian-Ordovician boundary in a sedimentologically continuous offshore marine succession. Upper Cambrian strata equivalent to the Peltura and Acerocare zones are distinguished on the basis of common taxa known from the neighbouring East European Platform and other areas in Baltica, Avalonia, and Gondwana. Invertebrate faunas, including brachiopods, problematic mollusc and phyllocarid arthropods, are revised taxonomically; they are indicative for the Tremadocian and Arenigian stages in the upper part of the succession. The Cambrian strata are insofar documented by fossil record only on the Kolguev Island, although their extension (of various series) in other areas of the Pechora Basin is claimed on the grounds of geophysical data and/or is inferred from geological successions. This new biostratigraphic evidence and facies development suggest that the Upper Cambrian-Tremadocian platformal deposits were likely widely distributed over the northeastern Baltica, as they were in the East European Platform and Baltoscandia. They were accumulated on a stable and passive margin of the craton with steady subsidence and a high rate of sedimentation.     

海南岛早志留世晚期腕足类Xinanospirifer的发现--兼论南好组

海南岛保亭县毛感乡南兵至南好公路边南好组以往被确认为下石炭统岩关阶 ,并认为与其下的上志留统足赛岭组呈角度不整合接触。著者最近在该剖面南好组中发现兰多维列世特里奇期晚期 (LateTelychian)Xi nanospirifer腕足动物群和三叶虫Latiproetuscf.latilimbatus,证明久归于下石炭统岩关阶南好组的地质时代应改归于早志留世 (Llandoverian) ;海南岛地区在早志留世明显属于扬子地台区的范畴 ;从地质时间上还暗示南好组与其下伏的足赛岭组不可能存在角度不整合接触 ;     

Middle Ordovician reefs of Norway

The Middle Ordovician reefs of Norway were the first to develop in the western part of the Balto-scandian epicontinental sea and are the earliest coral-stromatoporoid reefs so far reported in Europe. Small patch reefs in the Steinvika Limestone, Langesund-Skien district, consist mainly of algae, echinoderms, corals and stromatoporoids. Bryozoans, molluscs, arthropods and brachiopods are also present. The reefs developed on pelmatozoan-rich substrates and are organically zoned, consisting of a pioneer community of stemmed echinoderms and sheet algae, a high-diversity intermediate community dominated by fasciculate corals and a low diversity climax community of massive corals and stromatoporoids. These communities are interpreted as the seral stages of an autogenic ecological succession. Small patch reefs are also present in the laterally equivalent Mjøsa Limestone, Toten and Nes-Hamar districts. These are organically very similar to those in the Steinvika Limestone and developed in an identical way. A large complex, consisting of several reefs, is also present in the Mjøsa Limestone. Unlike the reefs elsewhere, which developed within shallow inshore areas, this complex developed at the outer edge of the inshore shelf. The outstanding feature of the complex is the main reef forming the offshore limit which is totally dominated by stromatoporoids and lacks a sequential development. This is due to the influence of the harsher environment at the shelf edge.     

Transgression, regression and fossil community succession

Recent paleoecological studies have emphasized the recognition of successional stages of level-bottom communities, but have neglected to point out techniques for distinguishing succession within a fossil community from the temporal and spatial replacement of one fossil community by another. The physical integrity of a marine level-bottom community is discernible, in most instances, through careful temporal and spatial study, and one community can be distinguished from another by judicious application of the 'end-member' concept. Community boundaries are only as distinct as the associated environmental stress gradient. Of first-order significance in understanding fossil community succession and replacement is appreciation of the basic asymmetry of the community dynamics involved in transgression-regression events. Of second-order importance is appreciation of the nature of the onshore-offshore environmental stress gradient, which, in turn, is controlled by the physical setting of transgression-regression (e.g. progradation versus eustatic control; high topographic relief versus low topographic relief, etc.). The application of the preceding concepts is shown by detailed study of community succession and replacement in the Cambridge Limestone (Upper Pennsylvanian), Guernsey County, Ohio.