Late Devonian Brachiopods Research Articles

Malformations in Late Devonian brachiopods from the western Junggar, NW China and their potential causes.

Although malformations are found in both extant organisms and the fossil record, they are more rarely reported in the fossil record than in living organisms, and the environmental factors causing the malformations are much more difficult to identify for the fossil record. Two athyrid brachiopod taxa from the Upper Devonian Hongguleleng Formation in western Junggar (Xinjiang, NW China) show distinctive shell malformation. Of 198 Cleiothyridina and 405 Crinisarina specimens, 18 and 39 individuals were malformed, respectively; an abnormality ratio of nearly 10%. Considering the preservation status and buried environment of the abnormal specimens, and analysis of trace elements and rare earth elements from whole-rock and brachiopod shells, we conclude that the appearance of malformed athyrids is likely related to epi/endoparasites, or less likely the slightly higher content of heavy metal in the sea.

Calcium stable isotopes place Devonian conodonts as first level consumers

Conodont animals are an extinct group of jawless vertebrates whose hard parts, also known as conodont elements, represent the earliest evidence of a mineralised skeleton in the vertebrate lineage. Conodont elements are interpreted as parts of a feeding apparatus, which together with the presence of eyes and microwear patterns, support the controversial hypothesis that conodont animals were macrophagous predators and/or scavengers. Here, we explore the trophic position of five conodont genera (Palmatolepis, Polygnathus, Ancyrodella, Ancyrognathus and Icriodus) from five contemporary Late Devonian sites distributed worldwide (France, Morocco, Vietnam and Australia) by means of calcium (Ca) stable isotope compositions. The seawater Ca isotope composition was calibrated using contemporary Late Devonian brachiopod isotopic values. By comparison with extant marine trophic chain composed of cartilaginous fish, conodont Ca isotope compositions are indicative of a zooplanktivore-primary piscivore niche, with no genus-specific trophic pattern. The question of active predation or scavenging cannot be resolved definitively but our results strongly suggest that Late Devonian conodonts were first level consumers.

Late Devonian Brachiopods from Choanji, South Kitakami Belt, Japan, and Their Stratigraphic Significance

Late Devonian brachiopods from Choanji, South Kitakami Belt, northeastern Japan, are re-examined to determine their age. Two brachiopod assemblages are recognized in the Choanji area. The assemblage from locality CHJ2 in the middle part of the Choanji Formation consists of one species, Desquamatia (Seratrypa) sp., which indicates a Frasnian age. The assemblage from locality CHJ1 in the upper part of the Choanji Formation consists of 13 species in 10 genera, including a new species, Parallelora minatoi sp. nov., and is of late Famennian age. Thus, the Choanji Formation is correlated with the Upper Devonian (Frasnian–upper Famennian), although until quite recently it was considered to be the lowest Carboniferous (Tournaisian) in Japan.

Patterns of cornulitid encrustation on the Late Devonian brachiopod shells from Russia

Upper Devonian brachiopods from the Central Devonian Field, Russia have been investigated with respect to encrustation patterns of cornulitids. These Palaeozoic encrusters were very characteristic component of shelly substrates during the Devonian and may serve as valuable objects for palaeoecological studies, especially those concerning the encrusters-host relationships. On the basis of rich material, it has been shown that cornulitid abundance significantly increased in the lower Famennian. Their disparity also increased from one morphotype (robust) present in the upper Frasnian to two distinct morphotypes (robust and slender, presumably representing two different species) in the lower Famennian. The analysis of the spatial occurrence of cornulitids on two dominant lower Famennian brachiopod species (Cyrtospirifer zadonicus and Ripidiorhynchus huotinus) showed, that these encrusters preferred the marginal parts of the shells. This, together with a dominant directional growth of cornulitids toward the commissure, indicates that cornulitids benefited from food brought by feeding currents produced by the brachiopod’s lophophore. The unequivocal evidence for syn vivo association of the cornulitids and their brachiopod hosts is the presence of distinct shell malformations caused by cornulitid growth affecting the host’s shell-secreting epithelium, preserved on some lower Famennian specimens. Interestingly, these malformations were caused by a slender cornulitid morphotype only. Thus, it is evident that during food gathering from the inhalant currents, this cornulitid species exerted a distinct, negative effect on the brachiopod – a deviation of its shell growth. In this case, we may consider this particular cornulitid species as ectoparasite rather than commensal with respect to its host.

Age and distribution of the Late Devonian brachiopod genus Dzieduszyckia Siemiradzki, 1909 in southern China

Conodont biostratigraphical work was done at four sections recently found with occurrence of the rhynchonellide brachiopod genus, Dzieduszyckia Siemiradzki, in southern Guangxi and in the border area between Dushan County of Guizhou and Nandan County of Guangxi, South China. These sections represent two different types of facies, i.e., carbonate platform and intraplatform basin. The conodont analysis reveals that this genus occurs in the Upper triangularis Zone and the Middle crepida Zone at the Dazhai Section, through the Lower to Upper crepida zones at Dalong, and is restricted within the Upper rhomboidea Zone at the two intraplatform basin sections (Changtang and Duli). This result demonstrates that the occurrence of these peculiar rhynchonellide brachiopods in South China, regardless of the depositional environments, is within the Lower Famennian instead of the previously suggested Upper Famennian. Furthermore, this brachiopod genus in South China began to inhabit on the carbonate platform almost since the beginning of the Famennian and did not extend to the intraplatform basin facies until the late Early Famennian.Available biostratigraphic data indicate that during the Early and Middle Famennian, Dzieduszyckia is widely distributed not only in South China, but also throughout the world, such as Morocco and southern Ural.Observation on the new collections from the four studied sections reveals that the peculiar rhynchonellide brachiopods have a great morphological variation within each section. Significant differences existed among the collections from different sedimentary settings and localities, probably reflecting the environmental and geographic constraint on the morphology of Dzieduszyckia. Samples from different layers in the same section have nearly identical morphological variation, suggesting the temporal inheritance in morphology of the rhynchonellide brachiopod.

Middle and Late Devonian brachiopod assemblages, sea level change and paleogeography of Hunan, China

Givetian through middle Famennian brachiopods of Hunan are used to define five biozones, comprising, in ascending order, the Stringocephalus Abundance Zone, the Ambocoeliid-Leiorhynchid Assemblage Zone, the Cyrtospiriferid Assemblage Zone, the Yunnanellina-Sinospirifer Assemblage Zone, and the Yunnanella-Hunanospirifer Assemblage Zone. They correspond approximately to the Po. hemiansatus Zone to Po. varcus Zone, S. hermanni Zone to Pa. punctata Zone, Pa. hassi Zone to Pa. linguiformis Zone, Pa. triangularis Zone to Upper Pa. crepida Zone, and Uppermost Pa. crepida Zone to Pa. marginifera Zone, respectively. Intensified rifting activity in South China during the Devonian began in the middle of the Lower Po. varcus Zone (a level marked by the first appearance of Po. rhenanus), which is consistent with the Lower-Middle Givetian substage boundary suggested by the International Subcommission on Devonian Stratigraphy (SDS). This assumed that rifting activity in the Lower Po. varcus Zone was signified by the deposition of the Baqi Formation in Guangxi and was marked largely by the extensive deposition of the Qiziqiao Formation in central Hunan, which probably led to an opposite pattern of relative sea level change-rising in deeper water trough areas and lowering in carbonate platform areas. The previously recognized S. hermanni Zone sea level rise in platform margin areas of Guangxi can be identified not only in the trough areas but also in platform areas, which probably indicates an overall marine transgression at this time, rather than tectonically induced sea level change. Similarly, this level coincides with the Middle-Upper Givetian substage boundary suggested by the SDS. Although the sea level rise may have occurred in the deeper water trough areas of South China towards the end of the Givetian, platformal areas experienced uplifting at various degrees, especially in the central and northern regions of Hunan where Early Frasnian deposits were apparently absent in many places. Similarly, the end-Frasnian regression led to exposure of many places and absence of early Famennian deposits, which probably accounts for the restricted distribution of the Yunnanellina brachiopod fauna.

The dynamic reef and shelly communities of the Paleozoic / La nature dynamique des communautés récifales et coquillières du Paléozoïque

Shelly communities and reef ecosystems represent the pinnacle of generic diversity and organizational complexity in marine environments. These systems are sensitive to climatic, tectonic, eustatic, and catastrophic changes, and their evolution and extinctions help reveal the regional and global dynamics of the Paleozoic Earth. It is, therefore, not surprising that the fossil record of these ecosystems has commanded the attention of generations of researchers (e.g., Billings 1862; Ziegler 1965; Osgood 1970; and a large compendium of papers in Boucot and Lawson 1999 on paleocommunities and Kiessling et al. 2002 on reef ecosystems, such as Copper 2002 and Kiessling 2002), each with their own perspective on the dynamics of shallow-marine ecosystems. With a system approach to understanding these ancient environments in mind, it was our intention to bring together researchers of various disciplines — paleobiology, paleoecology, carbonate sedimentology, taphonomy — to present a broad yet integrated perspective on recent advances in the field of shelly communities and reef ecosystems. This special issue is a collection of papers presented at Topical Session 114 convened at the 2006 Annual Meeting of the Geological Society of America (GSA) in Philadelphia, held in honour of Dr. Paul Copper’s retirement as Professor at Laurentian University (Sudbury, Ontario, Canada). The session included researchers working on a variety of deposits, addressing different questions, but with a unified theme to explore the temporal and spatial patterns and evolution of Paleozoic shallow-marine benthic shelly and reef communities. The theme of the topic session, as well as the proceedings papers in this special issue, is very much in keeping with Paul Copper’s research career, almost equally divided between Paleozoic brachiopods and reef communities. The contributors to this volume all feel some close connection to Paul’s academic activities, either as his former graduate students, research associates, or colleagues; some of us have benefited greatly from both scientific discussions with him or from his enormous fossil collections. The articles in this issue (cited in bold) cover various aspects of Paleozoic level-bottom shelly communities and reef paleoecology. Ma et al. give a detailed account of the internal structures in the well-known and widespread Late Devonian brachiopod genus Desquamatia from Bergisches Land of Germany. This fundamental morphological study is crucial for understanding the autecology and synecology of this extremely common atrypid genus and its abrupt extinction near the end of the Devonian. Hollis and Ausich study the functional morphology of a top-tier crinoid and reinterpret its anchoring mechanism as a distal coil capable of wrapping around other crinoid columns. Zhan and Jin document a case of brachiopod migration from an upper slope setting to the Yangtze Platform in South China during the Early Ordovician. The upslope dispersal subsequently led to the development of distinct brachiopod communities and faunas of the Yangtze Platform. This study shows a relatively deepwater origin of some common brachiopod communities of the Yangtze Platform, as well as the pioneer stage of brachiopod community organization during the Early Ordovician. Jin discusses the temporal and spatial differentiation of Early Silurian pentameride brachiopod communities of Anticosti Island using multivariate analyses, and demonstrates that the Pentamerus and stricklandiid communities had largely overlapping overall ranges in terms of their water depth and water turbulence level, but stratigraphically, the two groups of communities were rather clearly segregated — a paleoecological pattern probably controlled by fluctuating oceanic water temperature. Continuing the theme on Anticosti paleontology, Li and Allen use a unique approach to explore the relationships between orthide brachiopod associations and their living environments in the Anticosti Basin during the Early Silurian, and Tapanila and Ebbestad explore a miniature island community, hosted on a large gastropod shell. Analysis of the overlapping relations of encrusters, borers, and symbiotic embedders provides a remarkable example of the spatial forcing that may have played an important evolutionary role in muddy-bottom environments. Daley provides a broad survey of the boring patterns in various types of brachiopod shells from the Late Ordovician to the Early Devonian. She uses a series of techniques to differentiate post-mortem Received 27 November 2007. Accepted 13 December 2007. Published on the NRC Research Press Web site at cjes.nrc.ca on 4 March 2008.

Carbon, oxygen and strontium isotope records of Devonian brachiopod shell calcite

Devonian brachiopod shells from North America, Spain, Morocco, Siberia, China and Germany were analysed for δ 13C, δ 18O and 87Sr/ 86Sr. The samples were screened for diagenetic alteration by means of cathodoluminescence, trace element chemistry (Sr, Mn, Fe) and scanning electron microscopy. 409 out of 1678 shells ranging from the middle Emsian to the middle Famennian were accepted as well-preserved. 87Sr/ 86Sr ratios start with values of 0.70860 in the Lochkovian and decline continuously to 0.70782 at the Emsian–Eifelian boundary. This decrease is attributed to a reduced riverine strontium flux caused by the termination of the Caledonian orogeny. For the Eifelian and Givetian, relatively uniform values between 0.70782 and 0.70784 are observed. 87Sr/ 86Sr ratios start to rise again in the late Givetian and reach a value of 0.70807 in the early Famennian. An enhanced continental delivery of strontium as consequence of tectonic uplift due to the Eovariscan orogeny, in combination with climatic warming, as suggested by the δ 18O record, is interpreted to be responsible for the shift to more radiogenic strontium isotope values. The carbon isotope curve shows four positive δ 13C excursions with amplitudes ranging from + 2.0‰ and + 3.5‰. The positive excursion observed in the australis Zone coincides with the deposition of the Bakoven black shale in New York state. The δ 13C excursion near the Eifelian–Givetian boundary is correlated with the Kacàk event while the two positive excursions in the late Frasnian and at the Frasnian–Fammenian transition are contemporaneous with the deposition of the Kellwasser horizons. All carbon isotope excursions are interpreted to be the result of increased burial of organic carbon. The oxygen isotope record reveals short-term excursions in the late Givetian, late Frasnian and at the Frasnian–Famennian transition which are interpreted to result from changes in surface water temperature. The long-term evolution in δ 18O shows values of − 2.8‰ to − 3.5‰ in the Early and Middle Devonian to generally lower δ 18O values between − 4.3‰ and − 6.1‰ in the latest Givetian and Late Devonian. Assuming a δ 18O of Devonian seawater of − 1‰ V-SMOW, Early and Middle Devonian δ 18O values translate into realistic palaeotemperatures (24 to 27 °C) for tropical to subtropical latitudes. In contrast, the δ 18O values of Late Devonian brachiopods indicate a shift to unrealistically warm palaeotemperatures (31 to 41 °C). The change in δ 18O of brachiopod calcite cannot be explained solely by a change in temperature, pH or by a secular decrease in δ 18O of seawater. A combination of climatic warming and a moderate decrease in δ 18O of seawater from the Middle to Late Devonian may account for the observed decrease in δ 18O of brachiopod calcite. However, this tentative interpretation is not confirmed by conodont apatite δ 18O data that translate into warm but realistic Late Devonian palaeotemperatures.

Systematic revision of the middle and late devonian brachiopods Schizophoria (Schizophoria) and ‘Schuchertella’ from North America

Synopsis Schizophoria and ’Schuchertella’, two common genera of Devonian brachiopods from North America, are systematically revised based on cladistic analysis. Several Early Devonian schizo‐phoriid species are placed within S. (Eoschuchertella), while all other North American Devonian and Mississippian species studied are placed within S. (Schizophoria). Schizophoria meeki Fenton & Fenton is synonymised with S. macfarlanii Meek. Ancestral forms of Schizophoria (Schizophoria) were present in Europe and the Appalachian basin and inhabited outer platform environments through the Frasnian. Several independent lineages of S. (Schizophoria) persisted through the Late Devonian biodiversity crisis and subsequently colonised nearshore environments. Most cladogenetic events within North American species of S. (Schizophoria) occurred via dispersal mechanisms, while vicariant speciation was rare. Cladistic analysis of North American species assigned to ’Schuchertella’ revealed that all species through the Frasnian belong to Floweria, an impunctate genus, while Famennian and later species belong to Schuchertella. The generic placement of the Devonian ‘schuchertellids’ is revised accordingly. Schuchertella and Floweria are superficially similar and exhibit an analagous (albeit temporally offset) evolutionary transition from free‐resting ancestors to descendants with attached pedicle valves. Floweria also exhibits reduced rates of vicariant speciation compared to speciation by dispersal. The relative reduction in vicariant speciation has been documented for other Devonian taxa (bivalves, phyllocarids and trilobites) and may be an important control on faunal dynamics in North America during the Late Devonian biodiversity crisis.

Using GIS to unlock the interactions between biogeography, environment, and evolution in Middle and Late Devonian brachiopods and bivalves

The Late Devonian was a time of profound evolutionary and environmental change associated with the Frasnian–Famennian biodiversity crisis. One way to unravel the faunal dynamics of this complex crisis is to document the spatial and temporal patterns associated with biodiversity decline. This analysis investigates the relationship between biogeography, relative sea level, and environmental changes in Laurentian brachiopod and bivalve species during the Givetian through Famennian Stages (upper Middle to terminal Devonian). Representatives from all major brachiopod and bivalve clades and paleocommunities were examined to provide a cross-faunal comparison. Species’ ranges were reconstructed both spatially and temporally (at the level of conodont zones) using GIS to understand the timing and extent of species invasions and the importance of geographic range during the crisis interval. Species’ geographic ranges were linked closely with both relative sea-level change and depositional environment and expanded as relative sea-level rose. In addition, times of interbasinal species invasions corresponded closely with sea-level rises that breached tectonic barriers. Species with larger geographic ranges were more resistant to extinction during the Late Devonian. This relationship is reflected partly in a general trend towards increased extinction resistance in taxa that are found farther offshore in environments that potentially included more area. For example, there is an increased survival advantage for species that inhabited the middle and outer platform environments, though not for species inhabiting the open shelf. Additionally, species whose Givetian to Frasnian history includes at least one interbasinal invasion event were more likely to survive the Late Devonian biodiversity crisis than noninvasive species; this may have relevance for our understanding of the current biodiversity crisis, given the role that invasive species are playing in mediating modern extinctions.

The Late Devonian brachiopodCyrtiopsis davidsoniGrabau, 1923, and related forms from central Hunan of South China

New specimens representing species ofCyrtiopsisGrabau, 1923, described by Grabau (1931a) were recovered in samples from the Late Devonian deposits of the Changlongjie Member of the Xikuangshan Formation in central Hunan Province of South China. Associated Famennian age conodonts and morphotypes of the rhynchonellid brachiopodYunnanellinalineage fix the ranges of species ofCyrtiopsisand related taxa in the Xikuangshan Formation within the interval of the MiddletriangularisZone through the LowercrepidaZone (early Famennian) in central Hunan Province.Detailed study and comparison of external and internal shell structures of the type species ofCyrtiopsisGrabau, 1923, and related species described in Grabau (1931a) shows thatCyrtiopsisfrom South China includes the type species,C. davidsoni(embodied by the holotype), andC graciosa.Both of these species are shown to lack a delthyrial plate. Grabau's paratypes ofC. davidsoniare considered to belong inCyrtiopsis intermediaGrabau, 1931. The speciesC. kayseriGrabau, 1931, andC. shensiensisGrabau, 1931, are also deemed synonyms ofC. davidsoniGrabau, 1923 (as restricted above).“Cyrtiopsis” intermediadiffers from other species ofCyrtiopsisby development of a short delthyrial plate and its systematic position remains uncertain.The genusPseudocyrtiopsisis proposed withCyrtiopsis spiriferoidesGrabau, 1931, as the type.Pseudocyrtiopsisnew genus is distinguished fromCyrtiopsisGrabau, 1923, by its alate hinge and development of a delthyrial plate. Comparisons of species ofCyrtiopsisfrom South China with cyrtospiriferid brachiopods identified asCyrtiopsisby Crickmay (1952) demonstrate that none of the early Famennian species from western Canada can be assigned to the genus as revised here, althoughC. mimetesCrickmay, 1952, is closely related to“C.” intermediaGrabau, 1931.

Intraspecific selective survival within variably uniplicate Late Devonian brachiopods

The central fold of the Late Devonian brachiopods Cyrtospirifer monticola, Cleiothyridina devonica, Rugaltorostrum madisonense, Sinotectirostrum banffense and Trifiodorostellum dunbarense (Three Forks Formation, Central Idaho) varies intraspecifically from nearly rectimarginate or weakly developed to chevron-shaped. Frequency of central fold morphotypes through succesSjve size classes indicates selective survival in favor of variants with a strongly developed central fold, although morphotypes with the most extremely developed central fold never numerically dominate the larger size classes of any species. Differential mortality among the morphotypes can be attributed to: (1) less resistance to shell fracture by morphotypes with weakly developed uniplicae which were preferentially culled out of the population by durophagous predators, (2) less efficiency of weakly uniplicate morphotypes in the generation of nutrient-bearing eddies against the downcurrent inhalant margins. Failure of the morphotypes with the most strongly developed uniplicae to numerically dominate adult (largest) size classes is attributed to the hydrodynamic instability of such shell geometries on current-scoured substrates.

Intraspecific selective survival within variably uniplicate Late Devonian brachiopods

Intraspecific selective survival within variably uniplicate Late Devonian brachiopods