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Visnyk of Dnipropetrovsk University. Biology, ecology     Open Access   (Followers: 2)
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Journal Cover Memoirs of the Association of Australasian Palaeontologists
  [SJR: 0.462]   [H-I: 6]   [2 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0810-8889
   Published by RMIT Publishing Homepage  [403 journals]
  • Issue 44 - Morphology and taxonomy of the late Silurian rhynchonellide
           brachiopod 'Notoconchidium'
    • Abstract: Wright, Anthony J; Garratt, Michael J
      The distinctive brachiopod genus Notoconchidium is known from late Silurian, mostly sandy, shallow marine strata in Tasmania, Victoria and New Zealand. Material from the Zeehan and Wynyard areas (Tasmania), the Whittlesea-Wallan and Heathcote areas (Victoria), and the Wangapeka River area (New Zealand), permits further insight into detailed aspects of morphology and relationships between the previously named species N. tasmaniense, N. florencense and N. thomasi. We conclude that N. thomasi is a junior synonym of N. tasmaniense, but N. florencense is retained as a separate species. New species described are N. talenti and N. argentium. The diamond-shaped septalium of Notoconchidium exhibits, depending on the degree of calcification, either an anteriorly located perforation interpreted as the surface end of a tube extending to the dorsal umbo, or a deep, anteriorly located notch, both presumably housing dorsal adjustor muscles. Bifurcation of costellae is irregularly developed and is considered taxonomically insignificant. Possible brood pouches are noted in some dorsal valves.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - The Silurian of central Kentucky, U.S.A.: Stratigraphy,
           palaeoenvironments and palaeoecology
    • Abstract: Ettensohn, Frank R; Lierman, RThomas; Mason, Charles E; Andrews, William M; Hendricks, RTodd; Phelps, Daniel J; Gordon, Lawrence A
      Silurian rocks in Kentucky are exposed on the eastern and western flanks of the Cincinnati Arch, a large-wavelength cratonic structure separating the Appalachian foreland basin from the intracratonic Illinois Basin. The Cincinnati Arch area experienced uplift during latest Ordovician-early Silurian time, so that the exposed Silurian section is relatively thin due to onlap and post-Silurian erosional truncation on the arch. On both flanks of the arch, dolomitic carbonates predominate, but the section on the eastern side reflects a more shale-rich ramp that faced eastern Appalachian source areas. In the Silurian section on the western side of the arch, which apparently developed across a platform-like isolation-accommodation zone, shales are rare except dur ing some highstand episodes, and rocks in the area reflect deposition across a broad, low-gradient shelf area, interrupted by structurally controlled topographic breaks. Using the progression of interpreted depositional environments and nearshore faunal communities, a relative sea-level curve, which parallels those of previous workers, was generated for the section in Kentucky. While the curve clearly shows the influence of glacial eustasy, distinct indications of the far-field, flexural influence of Taconian and Salinic tectonism are also present. In fact, at times, regional tectonic subsidence seems to have overwhelmed the effects of glacio-eustasy. Regional angular truncations in the section, as well as overlying bentonitic shales and a dysaerobic fauna in the deepest-water part of the section (Estill Shale), are best explained in terms of far-field tectonic subsidence accompanying the first tectophase of the Salinic Orogeny in the Appalachian area.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Late Devonian (Frasnian) trilobites and brachiopods from the
           Soh area, Central Iran
    • Abstract: Pour, Mansoureh Ghobadi; Popov, Leonid E; Hosseini, Mehri; Adhamian, Artabaz; Yazdi, Mehdi
      An asteropygine trilobite and brachiopod association, including new species Heliopyge sohensis and Leptagonia' lakhalensis, is described from the Soh area, north of Esfahan, Iran. The co-occurrence of Douvillina and Neocalmonia aff. quadricosta Pillet indicates a Frasnian age for the trilobite-bearing horizon. The underlying units of limestone (Bahram Formation equivalent) contain a diverse conodont assemblage characteristic of the upper Givetian hemiansatus to ansatus biozones. The faunal assemblage from Soh has an affinity to the contemporaneous faunas of Afghanistan, Chitral in Northern Pakistan and the eastern Pamir.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - First occurrence and biogeographical significance of the
           operculate tetracoral 'Goniophyllum' from the Wenlock (Silurian) of
           Baillie-Hamilton Island, Canadian Arctic
    • Abstract: Wright, Anthony J
      Opercula of the Silurian tetracoral genera Goniophyllum and Rhizophyllum are described from early Wenlock (Sheinwoodian) strata of the Cape Phillips Formation, Baillie-Hamilton Island, Canadian Arctic. This is the first record of Goniophyllum in northern Laurentia, emphasising previously recognised faunal connections of this region with Baltica and Avalonia. As the opercula of Goniophyllum belong mostly to very early juveniles, which have not previously been documented, specific identification is impossible.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Amid Telychian (Llandovery) graptolite fauna from Mojiang,
           Yunnan province, southwestern China
    • Abstract: Zhang, Yuandong; Fan, Junxuan; Wang, Yi; Song, Yanyan; Cheng, Junfeng
      A mid Telychian (Llandovery, Silurian) graptolite fauna is described from the Manbo Formation at Keman, Mojiang County, central Yunnan Province, SW China, a region widely regarded as belonging to the Indochina Block in the early Palaeozoic. The fauna includes abundant Oktavites kemanensis sp. nov., O. aff. spiralis (Geinitz), Retiolites geinitzianus (Barrande) and R. australis McCoy, together with less abundant Monoclimacis crenulata (Elles and Wood), M. directa' Zalasiewicz et al., Monograptus priodon (Bronn), M. sp., Stimulograptus clintonensis (Hall), Diversograptus' pergracilis (Bouček), Pristiograptus sp., Oktavites sp. and Stomatograptus' sp. Of these, thirteen species belonging to seven genera are described in the present paper. Comparison with similar faunas from other regions suggests that the fauna is indicative of the Monoclimacis crenulata Zone of the middle Telychian. This is the first account of Telychian graptolites from Indochina, and may serve as a reference for the palaeontology and stratigraphy of coeval intervals within and outside the block.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - New palynological information from the subsurface Copo, Cabure
           and Rincon formations (upper Lochkovian - Emsian), Salta Province,
           Argentina
    • Abstract: Noetinger, Sol; di Pasquo, Mercedes
      New palynological information recovered from cutting and core samples from the Puesto El Tigre x-1 well in northwestern Argentina is presented. The studied interval corresponds to the Copo, Cabure and Rinc n formations. The assemblage comprises 41 spore and cryptospore species, 27 species of acritarchs together with prasinophycean and chlorophycean algae, and 12 chitinozoan species. The stratigraphic distribution of these taxa allow the definition of five associations, ranging in age from late Lochkovian to latest Emsian. These associations reflect palaeoenvironmental changes related to transgressive-regressive cycles occurring during this time span, which corroborates previous interpretations.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Coral-stromatoporoid faunas from the shores of a late Silurian
           island, Inner Mongolia, North China
    • Abstract: Jiayu, Rong; Johnson, Markes E; Zhanqiu, Deng; Deyuan, Dong; Xue, Yaosong; Baarli, BGudveig; Wang, Guangxu
      Previous research on a small continental island called Bater Island in south-central Inner Mongolia focused on palaeogeographic relationships in the context of the North China Block, and on the prevailing pattern of atmospheric and oceanic circulation interpreted from Ludlow (upper Silurian) strata surrounding an Ordovician diorite inlier. Preliminary information initially available regarding the palaeontology of a rare rocky-shore environment preserved around this ancient island is revised and expanded based on study of the dominant fossil fauna of corals and stromatoporoid sponges. The fauna, here described and illustrated for the first time, includes seven genera of tabulate corals (Mesoculipora, Thamnopora, Striatopora, Cladopora, Taxopora, Planocoenites and Okopites) and two genera of stromatoporoids (Clathrodictyon and Actinostromella). Compared to other rocky-shore faunas from North America, the diversity of the tabulate corals from the more sheltered, leeward side of Bater Island is high (AFR19), whereas no tabulates have been discovered on the windward, rough-water side of the island where only stromatoporoids were found. Bater Island is the only known locality worldwide to feature stromatoporoids in a rocky-shore setting.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Notes on the early Devonian brachiopod 'Leptaena ouralensis' de
           Verneuil, 1845
    • Abstract: Wright, Anthony J
      On the basis of the type material, an attempt is made to review the widely reported brachiopod Leptaena ouralensis de Verneuil, 1845, much more commonly known as Megastrophia uralensis (de Verneuil, 1845). Assignment of this species to Megastrophia is still tentative, and many reports of the species, especially those based on crack-out material, must remain doubtful. The species has an established narrow geographic and stratigraphic range to the upper Emsian (upper Lower Devonian) of mostly Siberia, Mongolia and China.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Morphological plasticity in the forgotten brachiopod
           'Dicoelosia acutiloba' (Ringueberg) from the lower Silurian Rochester
           Formation of New York
    • Abstract: Jin, Jisuo; Chen, Pengfei
      Multivariate analyses of biometric measurements of 200 well preserved shells of the largely forgotten orthide brachiopod Dicoelosia acutiloba (Ringueberg) from the lower Rochester Formation (Wenlock, Silurian) reveal a very wide range of infraspecific variations, with seven morphotypes (A-F) recognised. Study of a large sample of 5375 specimens confirms that D. acutiloba is not synonymous with D. biloba or D. verneuiliana as previously thought. The greatest degree of morphological overlap with D. acutiloba is found in D. parvifrons, D. bilobella and D. alticavata. Dicoelosia parvifrons is most likely a junior synonym of D. acutiloba, and D. bilobella a subspecies of D. acutiloba. Among Silurian species, D. acutiloba belongs to a groups of Dicoelosia species with a moderate emargination index (EI 0.3-0.4), intermediate between relatively shallow-water forms with short and fat lobes (e.g. D. bilobella and D. paralata, EI 0.2-0.3; BA3) and deep-water species with long and slender lobes (e.g. D. diversifrons, EI > 0.4; BA5 or deeper). Dicoelosia acutiloba was an opportunistic species that thrived in relatively deep and cool waters (BA4) of outer shelf or equivalent depositional environments during the Sheinwoodian glaciation.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - 'Sapelnikoviella santuccii', a new gypidulinid brachiopod genus
           and species from the upper Silurian of Glacier bay national park and
           preserve, Southeast Alaska
    • Abstract: Blodgett, Robert B; Boucot, Arthur J; Baranov, Valeryi V; Rohr, David M
      A new late Silurian (Ludlow) gypidulinid genus and species, Sapelnikoviella santuccii, is established from carbonate mudstone interbeds within an algal reef tract in shoreline exposures of the Willoughby Limestone on the southwest side of Drake Island in Glacier Bay, Southeast Alaska. The new brachiopod co-occurs with smooth atrypid brachiopods (Septatrypa) and less abundant high-spired gastropods (murchisoniids and less common Coelocaulus) in small nest-like accumulations between the algal buildups. Recent field work in Glacier Bay indicates that the Tidal Formation, formerly considered to overlie the shallow-water platform carbonates of the Willoughby Limestone, is now recognised as a laterally equivalent, deeper water basinal unit. A similar platform to basin transition is recognised to the immediate south on the northeastern part of Chichagof Island.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - The trilobite 'Cirriticeps gen.' nov. (Proetida,
           Tropidocoryphidae) from the Silurian of New South Wales
    • Abstract: Holloway, David J
      The new tropidocoryphid genus Cirriticeps is represented in the Silurian of New South Wales by two species - C. auranticum sp. nov., the type species, from the Wenlock to Ludlow of the Orange district, and C. rattei (Etheridge and Mitchell, 1891) from the upper Ludlow of the Yass Basin. The genus probably arose from a species of Decoroproetus and was ancestral to Tropidocoryphe, which is known from the Lower and Middle Devonian of Europe and North Africa. In both Cirriticeps and Tropidocoryphe the anterior and lateral cephalic borders are very broad, poorly differentiated from the genal field, and carry an epiborder furrow The structure of the borders has been misinterpreted previously in Tropidocoryphe, the epiborder furrow having been regarded as the border furrow, and the inner part of the border as part of the genal field.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Evolution, migration and biogeography of the plicathyridine
           brachiopods with a revision of Devonian faunas from the Kuznetsk Basin,
           Russia
    • Abstract: Modzalevskaya, Tatyana L; Alvarez, Fernando; Rzhonsnitskaya, Maria A
      Plicathyridine brachiopods from the Middle to Upper Devonian of the Altai-Sayan area, Kuznetsk Basin (Russia) include at least two species referred to Plicathyris, 17 to Anathyris and four to Anathyrella. Generic and familial diagnoses are emended, and eight existing species are revised, re-described and their diagnoses emended. Seven lectotypes are selected and four illustrated. Two new species Anathyris helmersenioides (lower-middle Frasnian, Vassino Horizon) and Anathyris strelnaensis (upper Frasnian, Solomino Horizon) are described. The origin and dispersal of the plicathyridines is discussed.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Conodont evidence for a latest Emsian to early Eifelian
           (Devonian) age for the phacopid trilobite 'Plagiolaria kitabi' from
           Uzbekistan
    • Abstract: Klapper, Gilbert; Cronier, Catherine; Vodrazkova, Stanislava
      The Devonian phacopid trilobite Plagiolaria kitabi Cronier and Tsmeyrek was described from a part of the Akbasai Formation in Uzbekistan that had been considered tentatively to be of late Famennian age based on the misidentification of Polygnathus inornatus Branson, a late Famennian' - Tournaisian conodont species. The revised identification herein of the associated conodont as Polygnathus serotinus Telford, in the unit containing Plagiolaria kitabi, supports the uppermost Emsian to lower Eifelian range of the trilobite genus Plagiolaria. Two new conodont specimens represent an early ontogenetic stage of Polygnathus serotinus in which there is a flat, asymmetrically curved area to the outer side of the growth center of the pit.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Upper Homerian and Gorstian (Silurian) Retiolitidae
           (Graptolithina) from Lithuania and Latvia
    • Abstract: Kozlowska, Anna; Radzevicius, Sigitas
      A well preserved retiolitid fauna isolated from upper Homerian and Gorstian (Silurian) strata is documented for the first time from boreholes in Lithuania and Latvia. The faunal assemblage corresponds very closely to species of retiolitoids recovered from the Polish part of the East European Platform. The retiolitoids described provide new data on biostratigraphic ranges as well as on some aspects of morphology. Rudimentary transverse rods in Spinograptus spinosus, S. clathrospinosus and Neogothograptus balticus are described for the first time in post-lundgreni retiolitoids. The described material includes ten species belonging to five genera: Gothograptus nassa, Papiliograptus papilio, Spinograptus spinosus, S. clathrospinosus, S. munchi, Neogothograptus purus purus, N. balticus, N. alatiformis, Plectograptus toernquisti and Pl. mobergi.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 44 - Latest Early to early Middle Devonian acastid trilobites from
           the eastern part of the Dinant Synclinorium, Belgium (Rhenohercynian Zone)
           
    • Abstract: van Viersen, Allart P
      Several species of acastid trilobites are recorded from shallow-water deposits at two localities in the eastern part of the Dinant Synclinorium, Ardennes, Belgium. The species are Acastava' lerougei sp. nov., Treveropyge sp. and Delocare sp. in the Hierges Formation (upper Emsian) near Marche-en-Famenne, and Jaylopygiella debruni sp. nov. in the Riviere Formation (Eifelian to lower Givetian) at Kin. Previous reports of Proetidae, Phacopidae and Odontopleuridae from the Hierges Formation in the southern part of the Dinant Synclinorium are corroborated. Saharops Morzadec and Wiltzops Basse are considered to be junior subjective synonyms of Delocare Struve. The lectotype and several topotype specimens of Acastava' schmidti (Richter) from the Gladbach Formation (lower Emsian) in the Eifel are refigured.

      PubDate: Mon, 3 Jun 2013 09:38:40 GMT
       
  • Issue 43 - Revision of New Zealand Cenozoic fossil Mollusca described by
           Zittel (1865) based on Hochstetter's collections from the Novara
           Expedition
    • Abstract: Beu, Alan G.; Nolden, Sascha; Darragh, Thomas A.
      New Zealand Cenozoic molluscs described by Zittel in 'Pal ontologie von Neu-Seeland' (1865) are revised, the plates republished, and most type specimens reillustrated, along with comparative specimens. Hochstetter's fossil localities are clarified, based on diary entries and published descriptions, and Zittel's introduction and figure captions are translated. The locality 'several miles north of Raglan Harbour' is Te Hara Point, 6.5 km north of Raglan.

      PubDate: Fri, 28 Sep 2012 09:51:22 GMT
       
  • Issue 42 - Cambrian and Ordovician stratigraphy and biostratigraphy of the
           Arafura Basin, offshore Northern Territory
    • Abstract: Zhen, Yong Yi; Laurie, John R; Nicoll, Robert S
      Recovery of conodonts and other fossils from four petroleum exploration wells (Esso Tasman 1 and Torres 1; Petrofina Goulburn 1 and Arafura 1), drilled in the Goulburn Graben of the Arafura Basin off the northern coast of Australia, have extended the known distribution of both Ordovician and Cambrian sediments across part of the northern Australian continental margin. The Cambrian and Ordovician sediments in the Arafura Basin comprise the four formations of the Goulburn Group. The recovered fossils indicate that in the offshore, the Jigaimara Formation is most likely of middle to late Templetonian age, the Naningbura Dolomite is Furongian to early Tremadocian, the Milingimbi Formation is middle Tremadocian, and the Mooroongga Formation is of late Tremadocian to middle Floian age.

      PubDate: Thu, 8 Mar 2012 14:26:30 GMT
       
  • Issue 42 - Middle Ordovician linguliformean brachiopods from the
           Maruia-Springs Junction area, New Zealand
    • Abstract: Percival, Ian G; Simes, John E; Cooper, Roger A; Zhen, Yong Yi
      The Sluice Box Formation, exposed in the Maruia-Lake Daniels-Springs Junction area at the southernmost extension of the Takaka Terrane, west of the Alpine Fault in New Zealand's South Island, ranges in age from late Cambrian (Furongian) to Middle Ordovician (late Darriwilian). Linguliformean brachiopods described from the upper part of the Sluice Box Formation include species previously documented from the Thompson Creek area in the northern Takaka Terrane, such as Scaphelasma paturauensis, Torynelasma takakaea and Hyperobolus' thompsonensis (herein assigned to the new genus Thomsonobolus), together with representatives of Apatobolus, Elliptoglossa, Paterula, Schizotreta, Acrosaccus', Cyrtonotreta, Physotreta' and Undiferina. The new species Multispinula pustulosa, Hisingerella potistra, Numericoma magnaspina and Biernatia maruiaensis are described from the upper Sluice Box Formation. An unnamed zhanatellid and an enigmatic form with scaphelasmatid affinities, neither of which can be confidently attributed to known genera, are also documented. Differences in the faunal composition compared with the Thompson Creek assemblage probably reflect the slightly older age (early to middle Darriwilian, Da2-3) of that fauna, whereas the brachiopods described in this report extend over the Eoplacognathus suecicus and lower Pygodus serra zones of the mid to late Darriwilian (late Da3), based on the age of associated conodonts.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - New symphysurinid trilobites from the Cambrian-Ordovician
           boundary interval in the western United States
    • Abstract: Loch, James D; Taylor, John F
      The Ibexian (Lower Ordovician) Symphysurina Zone has been subdivided into three subzones (in ascending order): the Symphysurina brevispicata, Symphysurina bulbosa and Symphysurina woosteri subzones. During deliberations over the selection of the GSSP for the base of the Ordovician System the base of the S. bulbosa Subzone was believed to closely approximate the First Appearance Datum (FAD) of the conodont Iapetognathus fluctivagus and the associated restricted occurrence of the cosmopolitan trilobite Jujuyaspsis. This correspondence allowed the approximate position of the Cambrian-Ordovician boundary in platform sequences of Laurentia to be determined on the basis of the endemic trilobite faunas. However, recent work has shown the tripartite division of the Symphysurina Zone to be untenable and, in particular, raised doubt regarding the suitability of the base of the S. bulbosa Subzone as a proxy for the base of the Ordovician System. This study describes four new species from the Cambrian-Ordovician boundary interval that are assigned to the Family Symphysurinidae. Symphysurina ethingtoni sp. nov. and Symphysurina straatmannae sp. nov. are recovered from the uppermost Cambrian. The genus Chasbellus gen. nov. is erected to include punctate symphysurinids that exhibit a concave pygidial border that extends posteriorly as a flat shelf. Two species are formally described: C. milleri (the type species) and C. repetskii, while a third is left in open nomenclature. All species of Chasbellus are restricted to the lowest Ordovician. Collectively, these species allow more confident distinction of the lower (Cambrian) from upper (Ordovician) portions of the Symphysurina Zone than was previously possible.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Systematics and affinity of the Lower Ordovician (Tulean; lower
           Floian) trilobite 'Psalikilopsis'
    • Abstract: Adrain, Jonathan M; McAdams, Neo EB; Westrop, Stephen R; Karim, Talia S
      Psalikilopsis Ross, 1953, has been known from a single species and interpreted as a "hystricurine" ancestral to some, but not all, "bathyurids". Comprehensive revision of the type species and the description of three new species demonstrate that the taxon is ingroup Bathyuridae. The unusual morphology of its more derived species is associated with a change from normal bathyurid sphaeroidal enrolment to spiral enrolment, with part of the pygidium tucked inside the cephalon, stopped medially by a pygidial spine docking against a medially modified anterior border. The oldest and apparently basal species lacks these modifications and is of "normal" bathyurid morphology. The genus occurs in lower Floian (Tulean) Psalikilus spinosum, Hintzeia celsaora, and Psalikilopsis cuspidicauda zones in Idaho, Utah, and Nevada, and its striking morphology and common occurrence make it biostratigraphically significant. A pygidium from the Fort Cassin Formation of New York, and two species illustrated in open nomenclature from the Shallow Bay Formation of Newfoundland demonstrate the occurrence of Psalikilopsis in eastern Laurentia. The eastern Laurentian species appear to be younger than those from western Laurentia. New species are Psalikilopsis paracuspidicauda (Psalikilopsis cuspidicauda Zone), P. redfordi (H. celsaora Zone), and P. newmani (Psalikilus spinosum Zone).

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Affinities of the Lower Ordovician (Tulean; lower Floian)
           trilobite 'Gladiatoria', with species from the Great Basin, western United
           States
    • Abstract: Adrain, Jonathan M; McAdams, Neo EB; Westrop, Stephen R
      Macropyge gladiator Ross, 1951a, is the type species of the previously monotypic Gladiatoria Hupe, 1955. It has been regarded as the only known post-Tremadocian macropygine ceratopygid, and the only known ceratopygid from the Ordovician of Laurentia. Well preserved new material from western Utah and southern Idaho includes the first positively identified cephalic sclerites and demonstrates that Gladiatoria is a component of Bathyuridae, a family common in shallow water Lower Ordovician assemblages from Laurentia. Gladiatoria is closely related to and regarded as the sister taxon of Bathyurellus Billings, 1865, to which it is nearly identical in cephalic morphology. In addition to an extended revision of the type species, which is from the lower Psalikilopsis cuspidicauda Zone, new species described include G. phoenixi (Hintzeia celsaora Zone), G. nielsenae (Psalikilopsis cuspidicauda Zone and Psalikilus typicum Zone), G. harrisi (upper Psalikilopsis cuspidicauda Zone), G. reedi (Psalikilus typicum Zone and Psalikilus hestoni Zone) and G. crowei (Protopliomerella contracta Zone). All are from the Tulean Stage (lower Floian).

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Darriwilian (Middle Ordovician) conodonts from the Maruia-
           Springs Junction area, New Zealand
    • Abstract: Zhen, Yong Yi; Cooper, Roger A; Simes, John E; Percival, Ian G
      A diverse conodont fauna of 28 species has been recovered from the Sluice Box Formation, exposed in the Maruia-Lake Daniels-Springs Junction area at the southernmost extension of the fossiliferous Lower Palaeozoic terranes in the south west Nelson region of New Zealand's South Island. The fauna is characterised by several zonal index species including important age-diagnostic pectiniform taxa such as Pygodus serra, P. anitae, Eoplacognathus suecicus, Yangtzeplacognathus foliaceus, Histiodella kristinae, Dzikodus tablepointensis, Polonodus newfoundlandensis and P. clivosus. All except P. serra are reported for the first time from New Zealand, and indicate a middle to late Darriwilian age (from the E. suecicus Zone to the Y. foliaceus Subzone of the basal P. serra Zone) for the assemblage. Biostratigraphically the Maruia conodont fauna is the most well constrained known from this time interval in eastern Australia and New Zealand, and is comparable with contemporaneous offshore shelf-edge to slope assemblages previously documented from Thompson Creek in NW Nelson and from central New South Wales.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Middle Ordovician (Darriwilian) brachiopods associated with the
           'Neseuretus' biofacies, eastern Alborz Mountains, Iran
    • Abstract: Pour, Mansoureh Ghobadi; Popov, Leonid E; Kebria-Ee Zadeh, Mohammad Reza; Baars, Christian
      Five rhynchonelliform brachiopod taxa, including Bastamorthis multicostata n. gen., n. sp., Saucrorthis obtusus n. sp. and Semnanostrophia lata n. gen., n. sp., are described from the lower part of the Lashkarak Formation at Deh-Molla and Simeh-Kuh, eastern Alborz Mountains, northern Iran. Associated conodonts indicate an early to middle Darriwilian (Lenodus variabilis to Lenodus pseudoplanus biozones) age for the fauna. The Early to Middle Ordovician benthic faunas of the Alborz Region show closest affinity to South China, which is accentuated by the occurrence of brachiopod genera such as Martellia, Saucrorthis and Yangtzeella in the Darriwilian. In the Alborz Region, Yangtzeella is already present in the late Floian-early Dapingian where it is represented by Y. longiseptata n. sp. However, the early Darriwilian brachiopod fauna shows an increased degree of endemicity, which coincides with invasion of the cold water Neseuretus trilobite biofacies and may be a reflection of cooler climate at that time. It is demonstrated that in the Alborz Region, the base of the Lashkarak Formation (as originally defined) coincides with a widespread unconformity at the beginning of the Darriwilian, and its extension to the Lower Ordovician and Dapingian sediments within the Alborz Region is not justified.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Lower Cambrian (Branchian) eodiscoid trilobites from the lower
           Brigus formation, Avalon Peninsula, Newfoundland, Canada
    • Abstract: Westrop, Stephen R; Landing, Ed
      Eodiscoids form a significant component of the Lower Cambrian (Branchian) trilobite fauna of the St. Mary's and lower Jigging Cove members of the Brigus Formation exposed along Conception and Trinity bays, northern Avalon Peninsula, Newfoundland. Two species of Serrodiscus Richter and Richter, four species of Hebediscus Whitehouse, and rare sclerites of Meniscuchus' pik and Calodiscus Howell are documented; type material of M.' helena (Walcott) is reillustrated. Hebediscus attleborensis (Shaler and Foerste) is restricted to the types, and H. williamsi is new. A parsimony analysis indicates that Serrodiscus is paraphyletic but supports monophyly of Acidiscus Rasetti, Bolboparia Rasetti and Stigmadiscus Rasetti. Above a sparsely fossiliferous interval in the lowest part of the Brigus, three eodiscoid faunas can be identified in the upper St. Mary's and lower Jigging Cove members, in ascending order, the Hebediscus planus, H. williamsi and Calodiscus cf. C. lobatus faunas. The lower two faunas correspond to part of the traditional "Callavia Zone" of previous workers.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - First record of silicified Cambrian (Furongian)
           rhynchonelliform brachiopods from the Mila Formation, Alborz Range, Iran
    • Abstract: Popov, Leonid E; Pour, Mansoureh Ghobadi; Kebria-Ee Zadeh, Mohammad Reza; Shahbeik, Saeid
      The discovery of a small rhynchonelliform brachiopod fauna of late Cambrian (Furongian) age, dominated by early pentamerids, is reported from the Mila Formation (Member 4) in the eastern Alborz Range of Iran. Two brachiopod associations are recognised. The first, dominated by the eostrophiid Syntrophioides tersus n. sp. in association with Billingsella aff. seletensis Nikitin as a minor component, occurs in characteristic shell beds composed primarily of disarticulated pentameride shells. The second association is characterised by Billingsella' uniplicata n. sp., Palaeostrophia shahrudensis n. sp. and Plectotrophia tenuis n. sp. and also dominated by early syntrophioids. The late Furongian age of the fauna is confirmed by the occurrence of trilobites characteristic of the Alborsella Biozone. Most of the genera in the assemblage had a pantropical distribution during the Furongian, except Syntrophioides, which was previously known only from the middle Cambrian of Laurentia.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - The Cambrian trilobite 'Rhyssometopus', with taxonomic revision
           of Guzhangian species from Queensland, Australia
    • Abstract: Lee, Ann Hally
      A morphometric (bivariate) analysis of middle Cambrian (Series 3; Guzhangian) species of the trilobite Rhyssometopus from northwestern Queensland is conducted. Results show that the species Rhyssometopus rhyssometopus Opik, 1967, R. princeps Opik, 1967, R. rugiceps Opik, 1967, and R. neuter Opik, 1967 cannot be differentiated on the basis of linear dimensions previously used by Opik (1967) as diagnostic characters. Nonlinear characters are found to be more reliable for differentiating the species of Rhyssometopus. The type species, R. rhyssometopus, is herein considered a senior subjective synonym of R. princeps and R. rugiceps. The erection of the subgenus Rostrifinis is also found to be unwarranted. The occurrence of all Rhyssometopus species from Australia, Antarctica and China is reviewed, and a taxonomic revision provides emended diagnoses for the following valid species: R. rhyssometopus Opik, 1967, R. neuter Opik, 1967, R. nitidus Duan, 2004, R. rostrifinis Opik, 1967, R. thielei (Chapman, 1911), and R. zhongguoensis Zhou, 1977. The family Rhyssometopidae is also discussed, with membership consisting of the following genera: Rhyssometopus, Plectrifer, Qiandongaspis and Tasmana.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - First skeletal microfauna from the Cambrian Series 3 of the
           Jordan Rift Valley (Middle East)
    • Abstract: Elicki, Olaf
      For the first time, a Cambrian microfauna is reported from the Jordan Rift Valley. The fauna comes from low-latitude carbonates of the Numayri Member (Burj Formation, Jordan) and to a lesser degree the equivalent Nimra Member (Timna Formation, Israel). Co-occuring with trilobite, brachiopod and hyolith macrofossils, the microfauna is represented mostly by disarticulated poriferid (mostly hexactinellids) and echinoderm remains (eocrinoids and edrioasteroids). Among the hexactinellids, Rigbyella sp., many isolated triactins and tetractins, as well as a few pentactins and rare hexactins occur. Additional poriferid spicules come from heteractinids (Eiffelia araniformis [Missarzhevsky, 1981]) and polyactinellids ('Praephobetractinia). Chancelloriids (Archiasterella cf. hirundo Bengtson, 1990, Allonnia sp., Chancelloria sp., 'Ginospina sp.) are a rather rare faunal element. Micromolluscs are represented mainly by an indeterminable helcionellid. The probable octocoral spicule Microcoryne cephalata (Bengtson, 1990), torellellid and hyolithellid hyolithelminths, and a bradoriid arthropod occur as very few or single specimens. The same is the case with a probable siphogonuchitid. The occurrence of a cornulitid related microfossil may extend the stratigraphic range of this fossil group significantly. The rather low-diversity microfauna is overwhelmingly dominated by sessile epibenthic biota. The preferred feeding habit seems to have been suspension feeding and minor deposit feeding. The microfauna from the Jordan Rift Valley is typical for low-latitude carbonate environments of Cambrian Series 3 age that corresponds to the traditional late early to middle Cambrian. Some taxa indicate a closer relation to the equatorial Gondwanan Iran and Australia. Some connection to the European shelf of Perigondwana may also have existed.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Exceptionally preserved biota from a carbonate lithofacies,
           Huaqiao Formation (Cambrian: Drumian Stage), Hunan, China
    • Abstract: Babcock, Loren E; Peng, Shanchi; Wasserman, Gregory J; Robison, Richard A
      Thinly laminated, dark lime mudstones (calcilutites and calcisiltites) of the Huaqiao Formation (Cambrian: Series 3, Drumian Stage) near Paibi, Hunan Province, China, yield remains of exceptionally preserved fossils of organisms inferred to be cyanobacteria (Eubacteria), phaeophyte and chlorophyte algae (Protoctista or Chromista), and a possible hydrozoan cnidarian (Animalia). In addition, the strata yield a problematic fossil that may represent a fecal string. The putative cyanobacterium Morania fragmenta Walcott, which was widespread in South China and Laurentia during the Cambrian, is present in the Huaqiao biota. A brown alga, Padina corrugata sp. nov., is the first putative calcifying dictyotacean to be reported from the fossil record, and the earliest known brown alga to show inferred light calcification of the blades. Padina may have contributed to the production of lime mud from the Cambrian Period onwards by means of minute aragonite needles coating the blades. A presumed chlorophyte alga present in the Huaqiao Formation, Yuknessia simplex Walcott, was widespread in the Cambrian of South China and Laurentia. Archaeocryptolaria furongguoia sp. nov. is a possible cnidarian, and the first hydrozoan to be reported from the Cambrian of China. A fossil provisionally regarded as a fecal string, Megaspirellus', is known only from South China.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Late middle Cambrian trilobites from El Totoral, Mendoza,
           Argentina
    • Abstract: Tortello, MFranco
      Late middle Cambrian trilobites from open-shelf lithofacies of El Totoral, Precordillera of Mendoza, western Argentina, are described. The material belongs to the ngel Borrello collections in the Museum of Natural Sciences of La Plata, Argentina. In addition, type specimens of the Carlos Rusconi collections in the Museum J.C. Moyano, Mendoza, are reillustrated. Biostratigraphically important agnostoids of the Lejopyge laevigata Zone [Agnostus microcephalus (Rusconi), Ammagnostus beltensis (Lochman), Kormagnostus seclusus Walcott, Clavagnostus calensis Rusconi, Tomagnostella nepos (Br gger), Lejopyge sp.] are described from this locality for the first time, and the polymeroid faunas are fully revised. The latter include Asaphiscus cf. lasherensis (Rusconi), Blountia socorrensis Rusconi, Elrathia oscelata (Rusconi), Talbotinella communis Poulsen, Modocia sp., Olenoides faldeanus Rusconi and Hysteropleura (Verditerrina) totoralensis (Rusconi). As previously suggested by Borrello and Rusconi, the polymeroids have their closest affinities with faunas of North America (lower Cedaria Zone and equivalents).

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Revised stratigraphic nomenclature for parts of the
           Ediacaran-Cambrian Series 2 succession in the southern Great Basin, USA
    • Abstract: Ahn, Soo Yeun; Babcock, Loren E; Hollingsworth, JStewart
      Mixed carbonates and siliciclastics assigned to the Reed, Deep Spring, Campito, Poleta and Harkless formations of eastern California and western Nevada, USA, comprise one of the most complete stratigraphic successions across the Ediacaran-Cambrian Series 2 interval known in North America. Distinctive, widely mappable members, mostly informal, have long been recognised for each of the formations. New, formal lithostratigraphic names are proposed for members of the Deep Spring Formation (Dunfee, Esmeralda and Gold Point members) and the Harkless Formation (Weepah and Alkali members).

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - The mid-Cambrian (Drumian) centropleurid trilobite 'Luhops' and
           its relatives from the Abbey Shale formation near Nuneaton, central
           England
    • Abstract: Rushton, Adrian WA
      Mature and juvenile specimens of Luhops expectans (Barrande) are described from strata in the English Midlands lying near the boundary between the agnostoid zones of Tomagnostus fissus and Hypagnostus parvifrons. Clarella groenwalli Howell and Poulsen is probably a synonym of L. expectans. Other centropleurid trilobites from the same strata include Clarella impar (Hicks) and Luhops coquus sp. nov. Centropleura pugnax Illing, formerly assigned to Clarella and Luhops, is returned to Centropleura; an elongated thorax is tentatively assigned to the species.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Late Ordovician (Hirnantian) 'Mucronaspis (Songxites')-dominant
           trilobite fauna from northwestern Zhejiang, China
    • Abstract: Zhou, Zhiqiang; Zhou, Zhiyi; Yuan, Wenwei
      Hirnantian (Late Ordovician) trilobites Mucronaspis (Songxites) mucronata (Brongniart), Platycoryphe songtaoensis Lu and Wu and Eoleonaspis sp. are described from the Yankou and Anji formations at Sanqiaopu, Deqing, northwestern Zhejiang, China. The species mucronata previously referred to Mucronaspis Destombes, 1963, is reassigned to Mucronaspis (Songxites) (Lin, 1981) on the basis of a close comparison with the type species Dalmanitina (Songxites) wuningensis (Lin), the type material of which is refigured and restudied. Similar trilobites widely recorded from other areas of China in the same stage are listed and revised. Mucronaspis (Songxites) mucronata was extensively distributed in Europe, Asia and central North America, suggesting a close biogeographic link between those areas during the Hirnantian.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Lingulate brachiopods from the upper Cambrian (Sunwaptan)
           Hellnmaria member of the Notch Peak formation, Western Utah, USA
    • Abstract: Freeman, Rebecca L; Miller, James F
      Bulk samples collected from the Hellnmaria Member of the Notch Peak Formation of western Utah, USA have yielded a lingulate brachiopod fauna with many new taxa. Two new lingulid genera are named, Stittia and Tuleobolus. Seven new species are described, the lingulid species Stittia ornata, Tuleobolus cretatus and Discotreta' arcana, and the acrotretid species Quadrisonia congerensis, Q. rattlesnakensis, Q. sawtoothensis and Q. swaseyensis. The genus Quadrisonia Rowell and Henderson, 1978 is emended. The species Obolus (Westonia) notchensis Walcott, 1908 is assigned to the new genus Stittia. Zhanatella rotunda Koneva, 1986 is documented from the lower beds of the Hellnmaria Member, establishing it as coeval with strata in Kazakhstan and southern France, from where this species was described previously. These collections extend downward the range of Quadrisonia lavadamensis Popov et al., 2002, Zhanatella utahensis Popov et al., 2002 and Wahwahlingula sp., which were described previously from Utah.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - A Cambrian series 3 (Guzhangian) fauna with 'Centropleura' from
           Northern Victoria Land, Antarctica
    • Abstract: Jago, James B; Bentley, Christopher J; Cooper, Roger A
      A Cambrian Series 3 (Guzhangian, probably lower Lejopyge laevigata Zone) trilobite assemblage is described from the northern Bowers Mountains, Northern Victoria Land, Antarctica. This is the oldest known fossil assemblage from the northern Bowers Mountains. There are ten agnostoid taxa including the widespread species Lejopyge armata, L. calva, Onymagnostus hybridus, Acidusus aculeatus and Goniagnostus nathorsti. The nine polymerid taxa include the cosmopolitan genus Centropleura plus the widespread genera Fuchouia, Pianaspis and Acontheus. Acontheus is recorded from Antarctica for the first time. A revised diagnosis of Acontheus is given. The fossils occur within a succession of mudstone with thin layers of calcareous mudstone and concretionary bands that are more resistant than the mudstone; an outer shelf to upper slope depositional environment is proposed.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - Exceptionally preserved 'Conchopeltis' (Cnidaria) from the
           Ordovician of New York, USA: Taphonomic inferences
    • Abstract: Babcock, Loren E
      Two specimens of the medusoid cnidarian Conchopeltis alternata Walcott from the Trenton Group of New York, USA, provide further information on the taphonomic history of this rare taxon. The specimens are unusual in that they represent exceptional preservation in a non-concretionary limestone. Umbrella-like tests were probably transported and rapidly buried by storm currents. Three-dimensional preservation of non-biomineralising umbrella-like tests or periderms is inferred to have resulted from early replication of structures related to bacterially mediated mineral precipitation. Tentacles are known from only two specimens of C. alternata, and they seem to have separated quickly from the umbrellas. When preserved, tentacles apparently have been carbonised.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 42 - The first known complete Lichakephalid trilobite, lower
           Ordovician of Morocco
    • Abstract: Fortey, Richard A
      The trilobite Family Lichakephalidae has hitherto only been known from incomplete material. A new discovery of a complete exoskeleton of a giant species of Lichakephalus, L. stubbsi sp. nov., from the Fezouata Formation of Morocco (Tremadocian) allows a more thorough understanding of the morphology of these early lichoid trilobites. The similarity to more advanced Lichidae is confirmed, and suggested that the Family Lichakephalidae may be a paraphyletic group comprising a collection of primitive taxa. Lichakephalus is strikingly convergent upon other large, benthic trilobites in the Fezouata Formation, which may be a consequence of having shared similar predator/scavenger life habits.

      PubDate: Thu, 8 Mar 2012 09:12:47 GMT
       
  • Issue 41 - Nanostructures in Palaeozoic linguloid brachiopods
    • Abstract: Lang, Liisa; Uibopuu, Ethel; Puura, Ivar
      SEM studies of untreated and uncoated fracture sections of the linguloid brachiopods Obolus ruchini Khazanovitch and Popov and Bicarinatina bicarinata Kutorga from the Cambrian of NW Russia and Devonian of Estonia, respectively, revealed fibril-like nanostructures, less than 200 nm in diameter. These structures are interpreted here as phosphatised biopolymers that were not mineralised in vivo and may have supported the apatite mineralisation from the early stages of the formation of bacula. Previous documentation of nanostructures in Palaeozoic fossils is quite rare.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Reassessment of the Ordovician brachiopod Poramborthis and
           Poramborthidae
    • Abstract: Mergl, Michal
      The history, morphology and distribution of the genus Poramborthis and the family Poramborthidae are reviewed. Although the rectimarginate commissure and presence of a low notothyrial platform are suggestive of an orthid affinity, other features - especially the digitate mantle canal system, costellate ornament with subcircular pits in the interspaces and the sessile spondylium - argue for a syntrophiidine affinity. The associated brachiopod fauna, with dominant eoorthids, early plectorthoideans and tritoechiids, indicate communication with Laurentia and various low-latitude Gondwana microcontinents, representing a high-latitude counterpart of the orthide-syntrophioidean association. The uniqueness of the Mediterranean province in the late Cambrian and Tremadocian is thus challenged.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - The Cisuralian faunal succession in Patagonia (Tepuel-Genoa
           Basin, Argentina): An updated brachiopod biostratigraphic scheme
    • Abstract: Pagani, MAlejandra; Taboada, Arturo C
      The Tepuel-Genoa Basin, located in the Patagonian region (Chubut Province) of southern Argentina, was a wide embayment open to the Panthalassic Ocean at the southwestern border of Gondwana; it was infilled by nearly 7000 m of a continuous succession (Tepuel Group), from the early Carboniferous (late Tournaisian) to the early Permian (Artinskian). Lowermost Permian faunas were recognised in the upper part of the Pampa de Tepuel Formation, but the first record of a Costatumulus-like faunal assemblage starts in the lower part of the overlying Moj n de Hierro Formation and ends in the upper part of the Rio Genoa Formation. Recently, refined proposals on the stratigraphic arrangement of the Moj n de Hierro and Rio Genoa formations, and discrimination of faunal assemblages throughout these units, allowed us to identify a wide spatial and temporal distribution for Costatumulus Waterhouse within the basin. New material collected from different localities and fossiliferous horizons throughout the Tepuel-Genoa Basin suggests a greater number of species than the previously recorded single occurrence of Costatumulus, and also the presence of its allied genus Magniplicatina Waterhouse. Such adjustment in the taxonomic composition of the former Costatumulus Biozone allows the recognition of six different and successive faunal assemblages; and also three potentially new species of Costatumulus, as follows. The Cimmeriella Fauna ( late Asselian-Sakmarian) recorded with Costatumulus sp. 1 (formerly Cancrinella cf. C. farleyensis), and the Kochiproductus-Costatumulus Fauna ( latest Sakmarian-earliest Artinskian) bearing Costatumulus sp. 2, are both recorded in the upper section of the Moj n de Hierro Formation. The younger Costatumulus-Tivertonia Fauna ( early Artinskian) yields Costatumulus sp. 3 in the lower part of the Rio Genoa Formation, whilst the Jakutoproductus ( late early Artinskian), Piatnitzkya ( late early -middle Artinskian) and the youngest Magniplicatina sp. ( middle Artinskian) faunas characterise the uppermost section of the Rio Genoa Formation. The taxonomic composition of the Costatumulus Biozone faunal succession in Patagonia initially suggests strong but temporally varied faunal links with western Australia and the Cimmerian regions in south and southeast Asia, as well as moderate but significant links with the Siberian Arctic region and, to a lesser extent, with eastern Australia.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Endolithic algae, fungi and bacterial activity in Holocene and
           Cretaceous brachiopod shells - diagenetic consequences
    • Abstract: Gaspard, Daniele
      Most published reports of perforations in brachiopod shells concern predatory drill holes. There has been little attention on borings produced by endolithic organisms, which use the brachiopod shells as substrates. Using the calcitic shells of both Holocene rhynchonelliform brachiopods and Cretaceous fossil representatives, from a range of different locations and environments, this study shows that many brachiopod shells are perforated by the activities of endoliths including brachiopod pedicle rootlets and other micro-endoliths like micro sponges, filamentous algae, fungi and bacteria. Despite brachiopods' natural protection (periostracum and punctae, when present), they are vulnerable to the attacks of endolithic organisms which live either in direct association with the brachiopods (e.g., the association between the living brachiopod Gryphus vitreus (Born) and the green algae Ostreobium queketti Bornet & Flahault, in the Mediterranean Sea), or attack the brachiopods as invaders into the brachiopod shells, the latter leading to early diagenetic modifications in the fine structure of the shells to form secondary calcite and/or shell silicification (e.g., in the form of amorphous silica). A precise knowledge of water depth of a sampling site is important in ascertaining the origin and nature (type) of the endoliths, which may include algae, cyanobacteria, sulfate reducing bacteria or fungi. Sulfate reducing bacteria (SRB), which are in need of organic supply, are often located in the organic matrix. A parallel is drawn with Cretaceous brachiopod shells where comparable endolithic microorganisms were revealed.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Morphology and systematics of late Palaeozoic syringothyrid
           brachiopods from West-Central Argentina
    • Abstract: Cisterna, Gabriela A
      Late Palaeozoic syringothyrid brachiopods from the central western Argentinian basins, have been studied for the small changes in the ventral interior features (i.e. syrinx, delthyrial plate, median septum), considered critical for the generic diagnoses of this group. Argentinian species previously described are also reviewed and, with the new collections obtained for the present study, some are considered synonyms. Three time intervals are studied. Early Carboniferous (Tournaisian-Visean) syringothyrids are not abundant and are characterised by the presence of a delthyrial plate, an incomplete wedge-shaped syrinx and a median septum, the latter suggesting a possible new (') Septosyringothyridine genus. Late Carboniferous (late Serpukhovian-Bashkirian) syringothyrids have a delthyrial plate, syrinx and median septum, all typical of Septosyringothyris Vandercammen. This genus is well known in the Argentine Precordillera with two species: Septosyringothyris keideli (Harrington) and Septosyringothyris sp. aff. S. keideli. These species are found in the Levispustula fauna that is usually associated with glaciomarine deposits related to the late Carboniferous glacial events in southwestern Gondwana. Early Permian syringothyrids (Asselian-Sakmarian) are very abundant and are characterised by a large syrinx (which is partially enclosed by the delthyrial plate unlike the genus Septosyringothyris), a very short delthyrial plate and a distinctive median septum. These features suggest that species previously described as Septosyringothyris jaguelensis Lech, Septosyringothyris sp. aff. S. jaguelensis, Septosyringothyris globosa Lech, Septosyringothyris feruglioi (Amos) and Septosyringothyris sp. aff. S. feruglioi (Amos), can be included in a new subgenus of Septosyringothyris Vandercammen, here named Septosyringothyris (Precosyringothyris) subgen. nov. The new subgenus and its constituent species appear in the Tivertonia jachalensis-Streptorhynchus inaequiornatus and Costatumulus amosi faunas, of basal Permian age, and are associated with an important climatic amelioration recorded in the central western Argentinian basins.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Late Eocene (Priabonian) micromorphic brachiopods from the
           Upper Austrian Molasse Zone
    • Abstract: Dulai, Alfred
      Until now, Eocene brachiopods were unknown in Austria. Thirty-five upper Eocene samples from two boreholes (Helmberg-1, Perwang-1) in the Upper Austrian Molasse Zone yielded more than 2000 micromorphic brachiopod specimens, representing nine species of seven genera. Some of them (Terebratulina tenuistriata, Megathiris detruncata) are widely distributed in the European Eocene, while others (Orthothyris pectinoides, Argyrotheca batalleri, Platidia anomioides, Terebratulida gen. indet. A. [="Terebratula" italica]) are known only from a few other Eocene localities. Two species are described as new (Terebratulina johansenae n. sp., Rugia zagorseki n. sp.). Previously, Rugia was known only from the Cretaceous and early Palaeocene, making this is the first record of the genus from the Eocene. The taxonomic composition of the faunas (very limited occurrence of Megathyridoidea and dominance of Cancellothyridoidea) indicates a deep water environment. The ecological composition of the brachiopods suggests a more (Perwang) or less (Helmberg) soft sediment substrate with an abundance of small hard objects for the attachment of micromorphic, pedunculate species. Orthothyris and Terebratulina alternate with each other at the lithological change in Helmberg-1, but occur within the same lithology in Perwang-1. This suggests that they do not occupy different bottom types, but are probably competitors for the same ecological niches.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - An early Cambrian chileate brachiopod from South Australia and
           its phylogenetic significance
    • Abstract: Holmer, Lars E; Skovsted, Christian B; Brock, Glenn A; Popov, Leonid
      The first record of a chileate (Rhynchonelliformea, Chileata, Chileida) brachiopod, Chile' sp. in South Australia is described based on a well preserved, phosphatised ventral valve from the early Cambrian (lower-mid Botoman; Pararaia tatei trilobite Zone) Parara Limestone exposed in Horse Gully, Yorke Peninsula. The ventral valve of Chile' sp. is the only known record of a phosphatised chileate and provides the first critical insight into the ontogeny of the poorly understood Cambrian Chileata. The early ontogeny of Chile' sp. closely parallels that of the aberrant early Cambrian paterinate-like phosphatic-shelled Salanygolina from Mongolia. In both Salanygolina and Chile' sp., the anterior margin of the well defined ventral larval shell is indented by an unrestricted notch that, through later ontogeny, develops into a foramen, directly anterior to the umbo. In subsequent ontogenetic development, this subtriangular foramen is enlarged by resorption and covered posteriorly by the colleplax - a triangular plate - in the umbonal foramen. The ontogeny of Chile' sp. further supports the notion that the umbonal foramens and colleplax of Chileata and Salanygolina are homologous and they belong in the stem of the Rhynchonelliformea.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Brachiopod biogeographic change during the Early to Middle
           Ordovician in South China
    • Abstract: Zhan, Renbin; Li, Rongyu; Percival, Ian G; Liang, Yan
      Biogeographic analysis of the Early to Middle Ordovician brachiopod fauna of South China shows close linkages to that of Laurentia during the Tremadoc, but as the South China block drifted away from Gondwana its faunal affinity gradually shifted to closer relationships with the terranes of Baltica, Avalonia, Sibumasu and southern Kazakhstan during the Floian to Darriwilian interval. Palaeobiogeographically, a major change of brachiopod faunal affinities in South China happened at the beginning of the Floian in the Tetragraptus approximatus Biozone, which is earlier than trends in the alpha- and beta-diversity change. The first acme of brachiopod alpha-diversity change that occurred in the Didymograptellus eobifidus Biozone (middle Floian) in South China was manifested by modest increases of regionally distributed genera, together with expansion of cosmopolitan families, outweighing a decrease in endemic genera. It is postulated that South China served as a "cradle" for brachiopod biodiversification during the Early to Middle Ordovician, because there are more than 10 genera that had their earliest known occurrence in this region.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - The type specimens of the Holocene brachiopod Diestothyris
           frontalis (Middendorff, 1849)
    • Abstract: Pakhnevich, Alexey V
      Type material of Diestothyris frontalis (Middendorff, 1849) with the original label of A.F. Middendorff has been located. One specimen was confirmed as original and is nominated as the lectotype. Serial sections of the lectotype plus 3D dorsal valve interior views were obtained using x-ray microtomography. A mass sample from the lectotype locality was analysed and provides population data on size, age and shape. The size and age structures were bimodal in this population.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Brachiopod life histories from spiral deviations in shell shape
           and microstructural signature - preliminary report
    • Abstract: Aldridge, Anthony E; Gaspard, Daniele
      Preliminary investigation of valve shape and section microstructure has been made for individuals of the extant species Calloria inconspicua (Sowerby) and Terebratulina retusa (Linne). In each individual, valve shape closely followed that of a logarithmic spiral (r2 > 98%). Deviations from fitted spiral comprised periodic and aperiodic components that were matched to known life history and growth. One periodic component was proposed as signalling seasonal or annual growth. On a valve section, such annual changes were usually, but not always, matched to growth breaks that extended into the secondary shell layer. Although identified changes were not always clearly visible on a shell, they were located using spiral deviations. The proposed annual component of spiral deviations was distinguished from major disturbances and other, more numerous growth lines. Individual growth rates have been estimated up to four years of age. When these rates and a maximal length were included with a sigmoidal growth model, the age at death was predictable for each individual. For the individuals studied, we estimated adult ages of less than fifteen years, and around seven years as a typical life span. These results offered opportunities to develop brachiopod chronologies that could test links with environmental variables such as average water temperature, depth and salinity over long periods of time. Identifying components of deviations about spiral shape presented a nondestructive complement to conventional growth ring counting, sectioning and geochemical analysis. The starting requirement was an accurate and precise outline in the sagittal plane for either the ventral or dorsal valve. Digital photography of median longitudinal sections of valves and individual profiles provided the means for such outline processing. Further specimens and population studies are needed to confirm and extend our preliminary investigations.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Application of niche modelling to analyse biogeographic
           patterns in Palaeozoic brachiopods: Evaluating niche stability in deep
           time
    • Abstract: Stigall, Alycia L
      The ecological niche of a species can be estimated from a set of species occurrence points associated with data about the environmental conditions at those locations using a method known as ecological niche modelling (ENM). This technique has been widely employed with modern organisms, and great potential exists for ENM studies in the fossil record. By modelling a species' niche during multiple time slices, the relative degree of niche conservatism or niche evolution a species undergoes during intervals of biotic, environmental, or climatic change can be assessed. In this case study, the relative stability of ecological niches of eight Late Ordovician (Katian) brachiopods from the Cincinnati Arch of eastern North America is assessed across an extra-basinal immigration event, the Richmondian Invasion. This framework provides an opportunity to examine whether species altered the parameters of their ecological niches more in response to species invasions and ecosystem turnover or during gradual environmental changes preceding the invasion event. Niches were modelled for nine time slices spanning the interval before, during, and after the invasion using the Maxent program based on environmental parameters estimated from the sedimentary record including: inferred water depth, lithology, bedding thickness, bedding style and physical sedimentary structures. Niche stability was assessed through pairwise comparisons of the percent contribution of each environmental parameter to species' niche models between adjacent time slices. Bray-Curtis similarity among environmental contributions to species niche models through time varied. Species exhibited low similarity (niche evolution) prior to the onset of the Richmondian Invasion, but high similarity (niche stability) during the invasion interval. Similarity levels (niche stability) relax post-invasion, although similarity values still significantly exceed pre-invasion levels. Cincinnatian brachiopod species which successfully persist through the invasion, therefore, appear to have responded to invasion pressure through niche conservatism.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Origin and evolution of Permian brachiopods of Australia
    • Abstract: Waterhouse, JBruce
      Permian brachiopods of Australia fall into two major associations. Faunas of eastern Australia have a characteristic make-up, dominated by few families and strongly affected by cool to glacial conditions, interspersed with a few warmer-water faunas or terrestrial intervals, often containing coal measures. Brachiopods from Western Australia share some genera, but have much more in common with faunas of southeast Asia and the Himalayan region. They are of note because they later played a major role in stocking the Lopingian faunas of south Asia, especially the Himalayas. The concept that the faunas were displaced into Australia by the evolution of new taxa in the palaeotropics is dismissed: instead the faunas evolved from local forerunners and immigrants from high latitudes of Patagonia and the boreal Arctic, with some input from temperate latitudes. Rarely, Australian genera penetrated the tropics during the Guadalupian as "reciprocants". The faunas, together with Mollusca, fall in a succession of well defined biozones. As in other parts of the globe, they displayed accelerated evolution during Sakmarian time, and the greatest loss of genera in the Artinskian: otherwise gain and loss of genera proceeded erratically until the end of the period, with a last burst of new genera in the youngest known zone. However, not all parts of the earth conformed to this pattern, pointing to the need to avoid overreliance on few sample-points with unjustified extrapolation, or over-amalgamation of data that submerges unusual trends.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Ontogenetic discontinuities in brachiopod populations: Their
           detection and significance
    • Abstract: Aldridge, Anthony E
      While measurements of shell length, width, and thickness are included in taxonomic studies, they seldom refer to population discontinuities in shape. Is this because such discontinuities are rare, or because we lack the methods to detect them' Piecewise regression fits two connected, bent lines instead of a single line to every bivariate plot of width vs length and thickness vs length. Piecewise regression is used to detect and estimate shape discontinuities as line breakpoints in six Holocene species (Calloria inconspicua, Macandrevia africana, M. cranium, Terebratella sanguinea, T. dorsata and Magellania venosa). Previously published studies and new measurements are investigated using piecewise regression on shell length, width and thickness. That is, the traditional measurements of shell shape are treated in a way to highlight additional population features. A population shape breakpoint and its size related confidence limits are estimated then corroborated through changes in valve shape with seven large individuals of the abyssal brachiopod M. africana. Breakpoints can occur at various sizes, and appear to be taxon specific. Shell and substrate relationships are the preferred, but not exclusive cause of discontinuities studied. Detail on the rotational mass of M. africana suggests an active function for the substrate plus shell shape that assists individual orientation and stability. Piecewise regression supports the hypothesis that substrate relationships and behaviour can be inferred from shell shape in articulate brachiopods. The method is suitable for both large and small samples. Spiral analysis on individual valves provides additional confirmation of breakpoints. Such confirmation is important for small samples (less than ten brachiopods), where piecewise regression itself might not be statistically valid.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Early Devonian diversification of athyridide brachiopods in the
           Cantabrian Zone (NW Spain) and their affinities, revisited
    • Abstract: Alvarez, Fernando; Modzalevskaya, Tatyana L; Brime, Covadonga
      New athyridide brachiopods collected from the Early Devonian of the Cantabrian Zone (NW Spain) include Protathyris praecursor Kozlowski, P. strelnikovi sp. nov., and Athyris butleri sp. nov. The species of Protathyis are the first of the genus to be described from northwestern Spain. Two species referred to Athyris from the Middle-Late Devonian are also described and discussed. These are: A. concentrica (von Buch) of Givetian age and A. howardi sp. nov. of Givetian-Frasnian age.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Mesozoic brachiopods of Misool Archipelago, eastern Indonesia
    • Abstract: MacFarlan, DAB; Hasibuan, F; Grant-Mackie, JA
      The Mesozoic brachiopod fauna of Misool is shown to consist of ten species, only one of which, the Rhaetian Misolia misolica, has previously been described. For it, a lectotype is selected. We record a further four species of Late Triassic age ('Piarorhynchiinae gen. et sp. indet., 'Cyclothyridinae gen. et sp. indet., Pentactinella pachycostata n.sp., Zugmayerella bogalica n. sp.), two of Jurassic age (Aucklandirhynchia yefbiensis n. sp., 'Terebratulina sp.) and three from Cretaceous strata (Ptilorhynchia pugnaciformis n. sp., Zeilleriinae 'n. gen. et n. sp., Prochlidonophora spinulifera n.sp.). All species, apart from M. misolica are new, although two rhynchonellides and two terebratulides are left in open nomenclature. Biogeographically the fauna is Perigondwanan (or Southern Tethyan), but Pentactinella pachycostata n. sp. is more generally Tethyan, Aucklandirhynchia yefbiensis n. sp. and Prochlidonophora spinulifera n. sp. are Austral in their affinities, and Ptilorhynchia pugnaciformis n. sp. belongs to a circum-Pacific or bipolar genus.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - There's no place like home: Cambrian to Devonian brachiopods
           critically useful for analysing palaeogeography
    • Abstract: Cocks, LRobin M
      Brachiopods useful for assessing palaeogeography from the Cambrian to the Devonian are briefly reviewed, since they mostly occur in rocks deposited under the seas on the continental shelves. Comparison of the communities which were originally represented (especially when integrated with other phyla such as trilobites in the Cambrian and Ordovician) can help to distinguish between old continents, since different benthic faunas were often confined to the opposite sides of large oceans. Because there were fewer of them and they were largely confined to shallower-water environments, Cambrian articulated brachiopods are less useful than their descendants. However, from the Ordovician onwards the brachiopod community distributions characterise, for example among others, the Iapetus Ocean and its closure; and the Mediterranean Province, which was confined to the higher-latitude parts of Gondwana. During the Silurian, most faunas were less provincially distributed, apart from in the high southern palaeolatitudes where Clarkeia and others flourished in the Afro-South American Realm, and in the northern palaeolatitudes, only preserved in Siberia and Mongolia, which was colonised by the Tuvaella Fauna. There was marked provinciality of brachiopods in the Early Devonian, for example in the Malvinokaffric Province at high southern palaeolatitudes. However, the subsequent faunas became less provincial, since global temperatures were relatively high during the Middle and Late Devonian, and there were fewer notable endemic communities. The Carboniferous communities are less well known, but the Permian is well characterised, with a variety of different provincial brachiopod faunas. A systematic note is included on Pentamerus oblongus, the type species of the rock-forming early Silurian genus Pentamerus, which is also the type of its family, superfamily, suborder and order.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Preliminary data on shell cementation in fossil specimens of
           thecideide brachiopods
    • Abstract: Perez-Huerta, A; Harper, DAT; Jeffries, Teresa E
      Thecideide brachiopods have an uncommon mode of life as their substrate attachment is by cementation. The exact mechanisms of shell cementation, however, are currently not known for fossil and Holocene species. Analyses of fossil specimens of 'Thecidellina' reveal that there are protuberant regions at the tip of the ventral valve with differences in shell microstructure, including characteristic cavity structures. Additionally, there are differences in shell chemistry in these regions, especially enrichment in light rare earth elements (LREE), compared to the rest of the ventral valve. These results suggest that these cavities may be open after shell secretion, during the animal's life cycle, contributing to cementation processes. These observations are not conclusive but add new information that contributes to a better understanding of the life mode of thecideide brachiopods.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - The howellellid branches within the delthyridoid spiriferids
           (Brachiopoda, Silurian to Devonian)
    • Abstract: Schemm-Gregory, Mena
      Study of genera and species of the brachiopod superfamily Delthyridoidea has shown that the evolution of this group of spiriferids consists of independent branches developed from Howellella and characterised by unique morphological features. The phylogeny of the howellellid descendants is described by a short introduction to each of its branches and a phylogenetic tree is presented.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Taxonomic review and evolutionary trends of Levipustulini and
           Absenticostini (Brachiopoda) from Argentina: Palaeobiogeographic and
           palaeoclimatic implications
    • Abstract: Taboada, AC; Shi, Guang R
      The diagnosis and composition of the brachiopod Tribe Levipustulini Lazarev, 1985 is reviewed, leading to a detailed revision of the genera Levipustula Maxwell, 1951 and Lanipustula Klets, 1983, as well as a review of previous records of the species Levipustula levis Maxwell from Australia and Argentina. The presence of Lanipustula patagoniensis Simanauskas in Patagonia is confirmed with additional topotypic material described and illustrated. Based on this review, we reassign Levipustula levis from New South Wales, Australia to Lanipustula. Two new species, Lanipustula kletsi from the middle Pennsylvanian of Patagonia and the Absenticostinin Absenticosta bruntoneileenae from the latest Visean of western Argentina, are proposed. Abstenticosta bruntoneileenae is suggested as a possible ancestral stock of the Patagonian Levipustulini through the lineage Lanipustula-Verchojania-Jakutoproductus-Piatnitzkya (Serpukhovian-middle Artinskian). The development of similar phylogenetic lineages of Levipustulini in high latitude regions of both northern and southern hemispheres (such as Siberia in Northeast Asia and Patagonia in southwestern Gondwana) is here interpreted as a consequence of parallel evolution. The progressive palaeobiogeographic isolation of Patagonia from mainland South America, coupled with its southward drift under cold palaeoclimatic conditions during middle Carboniferous-earliest Permian times, is proposed to have triggered the Levipustulini vicariance.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Revision of Sowerby's species 'Spirifer bisulcatus, Spirifer
           pinguis and Spirifer rotundatus' from the late Tournaisian-Visean of Great
           Britain
    • Abstract: Angiolini, L; Long, S; Davies, L
      Sowerby's species 'Spirifer bisulcatus, Spirifer pinguis and Spirifer rotundatus' are here revised and their generic and suprageneric position assessed. The material on which the revision is based is housed at the Natural History Museum, London, and the provenance and history of the collections is also outlined. Spirifer bisulcatus Sowerby, 1825 is placed in the genus Angiospirifer Legrand-Blain based on its cancellate micrornamentation and occurrence of vascular markings. Spirifer pinguis Sowerby, 1821 and Spirifer rotundatus Sowerby, 1825 belong to Latibrachythyris n. gen. which is similar to Brachythyris M'Coy in its general shape, but differs in its wider hinge and presence of an apical median septum. Revision of the diagnosis of the superfamily Brachythyridoidea is thus required to include taxa with a wider hinge. During the Visean, the brachythyridoid families Brachythyridae and Skelidorygmidae show a tendency to increase the width of the hinge and to develop an apical septum or a myophragm.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Affinities and associations of new shallow-water brachiopods
           from the Late Cretaceous of New Zealand
    • Abstract: Hiller, Norton
      Four species of brachiopods are recorded from the Ostrea Bed at the top of the Broken River Formation (Haumurian; Late Cretaceous), North Canterbury, New Zealand. Two of these are indeterminate but the others are described as the new taxa Wekarhynchia cataracta gen. et sp. nov., a notosariid rhynchonellide, and Ostreathyris allani gen. et sp. nov., an unusual short-looped terebratulide of uncertain affinities. The brachiopods are interpreted to be members of a community of sessile suspension-feeding shelly invertebrates that occupied ecological niches in an oyster reef. In such a setting they lived in shallow water only a few metres deep with moderate to high energy levels; they may also have been tolerant of fluctuations in salinity.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - What do we really know about predation on modern
           rhynchonelliforms'
    • Abstract: Harper, Elizabeth M
      Although there is strong evidence that a range of predatory taxa do attack rhynchonelliform brachiopods in their natural environments, we currently lack sufficient data to establish how important such interactions might be. This contribution is an attempt to draw together and critically review the sparse and scattered data which exist, and to suggest areas for future collection of data.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Growth rates of Calloria inconspicua (Sowerby, 1846) from the
           upper intertidal zone of Portobello, New Zealand
    • Abstract: Schumann, Dietrich
      There are few studies dealing with the growth rates of articulate brachiopods. The most comprehensive studies interpreted major growth lines as possibly annual growth increments. By means of a simple marker method, the real growth rate (and the number of visible growth bands) per unit time were analysed in a gregarious community of Calloria inconspicua living in shallow water at Portobello, New Zealand. This study demonstrates that the number of the growth bands as well as the growth increments varied considerably.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Spine formation in 'Novocrania' and 'Danocrania' (Brachiopoda,
           Craniata)
    • Abstract: Robinson, Jeffrey H; Lee, Daphne E
      Spine formation in three species of 'Novocrania' and one species of 'Danocrania' is described and illustrated. These craniids display three methods of spine formation; tubular-hollow, sutured-hollow and, newly proposed herein, sutured-fold. Possible functions for craniid spines include extending sensory tissue beyond the valve margins, physically protecting the gape by creating a barrier, and discouraging settlement of epibionts.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - What is the ideal proxy of Palaeozoic seawater chemistry'
    • Abstract: Brand, Uwe; Logan, Alan; Bitner, Maria Aleksandra; Griesshaber, Erika; Azmy, Karem; Buhl, Dieter
      The chemistry of many biogenic allochems and whole rock is used as a proxy of original seawater chemistry during the geological past. Common Palaeozoic proxies are brachiopods, conodonts, and whole rocks. Brachiopods may secrete low-Mg calcite shells; conodonts consist of francolite, a carbonate fluorapatite; and whole rock is usually diagenetic low-Mg calcite altered from different original carbonate mineralogy. Stratigraphic uncertainty of specimens from isolated successions remains a serious impediment to accurate age assignment and in modelling events of the ancient hydrosphere. Furthermore, diagenesis is the great nemesis of these allochems and whole rocks, and in many instances they are not preserved in their original composition. Thus, the chemical composition of many of these proxies instead of being representative of the original and ambient seawater reflects the composition of the diagenetic fluid and character of the diagenetic microenvironment such as the water/rock ratio. Consequently, the best proxy is not necessarily the most abundant material, nor the most readily available (i.e. in outcrop or museums), nor the one supported exclusively by hypothetical concepts. Instead, the best proxy is the one that has passed the most screening tests, and in addition, is stratigraphically well constrained and provides results reflecting the natural variation of the ambient oceanographic environment.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
  • Issue 41 - Comparative experimental and simulation study on passive
           feeding flow generation in 'Cyrtospirifer'
    • Abstract: Shiino, Y; Kuwazuru, O
      As a preliminary step in clarifying the functional properties of the wing form of spiriferide brachiopod 'Cyrtospirifer' in terms of the generation of passive feeding flows, the flow structure around the shell of this species was analysed using both flow experiments and a computational fluid dynamics simulation of a hollow 'Cyrtospirifer' model. All passive flows in the model inevitably showed a gyrating behaviour around the sulcus, whereas the lateral space inside the shell exhibited a reversed vortex flow direction, which possibly resulted from wing form effects. Because outflows were intermittently generated at the lateral gapes in our experiments, they were used to describe the path of the wake flows in the simulation. Given the comparable results obtained from both our experiments and the simulation, this path generation is clearly related to the turbulent conditions along the spiriferide wing form. Our results suggest that wing form in spiriferids plays a role in intermittently generating both inflows and outflows through lateral gapes, making it possible to produce a high flow rate.

      PubDate: Tue, 3 Jan 2012 15:01:57 GMT
       
 
 
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