First documentation of Llandovery (Silurian) conodont genus Astropentagnathus in China (Langao,Shaanxi Province) and the age of Baiyaya Formation

Age of the Baiyaya Formation in the Ziyang-Langao region of Shaanxi Province remains debatable. Ten samples were taken for conodont biostratigraphical studies from the Tianwancun section. The first discovery of Astropentagnathus in China indicates that the genus has a wider geographical distribution than previously known. Conodont fauna from the Baiyaya Formation suggests that the lower part of the unit corresponds to the Pterospathodus eopennatus Superbiozone, and its upper part to the lower Wenlock (probably mainly to the Kockelella ranuliformis Superbiozone). Diachroneity of the Baiyaya Formation in the region is confirmed by conodont studies from the Tianwancun and Qiaoxi sections. Further studies are required to find out age-variation of the formation more precisely.     

Silurian (Wenlock–ludlow) Graptolites from Bolivia

Well preserved middle to upper Silurian (Wenlock–Ludlow) graptolites from Bolivia are described for the first time. Generally monospecific graptolite faunas, of species largely endemic to South America, are found in a few levels in the lower part of the Kirusillas, Rio Carrasco and Uncía formations. The oldest identified level yields specimens of Pristiograptus praedeubeli (Jaeger) and is referred to the upper Wenlock. Younger faunas belong to the Ludlow and include Saetograptus , Monograptus and Neodiversograptus specimens. These may be referred to the Gorstian (lower Ludlow). The fauna includes Saetograptus argentinus robustus ssp. nov. and Monograptus bolivianus sp. nov.     

Llandovery sporomorphs and graptolites from the Manbo Formation,the Mojiang County,Yunnan, China

Llandovery sporomorphs and graptolites have been recovered from the Manbo Formation, Mojiang area, western Yunnan, China, which belonged to the Indo-China Palaeoplate in the Palaeozoic. The graptolite fauna, including 8 genera and 12 species, is considered Mid Telychian, Llandovery in geological age, confirming the existence of Llandovery rocks in this region. The Silurian stratigraphical sequence of this area is reconsidered as in the ascending order: Manbo Formation (Llandovery–early Wenlock), Shuiqing Formation (late Wenlock–Ludlow) and unnamed formation (Pridoli?). The sporomorph assemblage from the Manbo Formation includes seven species in five genera. The dominant members of this assemblage are Tetrahedraletes medinensis and Laevolancis chibrikovae. Based on the low diversity and low abundance, the geological age of this assemblage is considered to be approximately the Telychian, Llandovery. The parent plants of sporomorphs probably inhabited the landmass near Mojiang area, these sporomorph-producing plants probably included bryophyte-like land plants and primitive vascular land plants. The sporomorph evidence shows that the South China and Indo-China palaeoplates may have been in close proximity (maybe with some continental bridges linking them) to each other at least in the Llandovery. They were also closely related with Gondwanaland in the Llandovery.     

Chitinozoan biostratigraphy of the basal Wenlock Series (Silurian) Global Stratotype Section and Point

Diverse and abundant assemblages of chitinozoans allow the recognition of the upper part of the Margachitina margaritana Biozone in the uppermost Llandovery and lowermost Wenlock series of the Hughley Brook section. The Cingulochitina bouniensis and Salopochitina bella biozones are identified in the lower part of the Buildwas Formation, Wenlock Series. The chitinozoan data indicate that the base of the Wenlock Series most probably correlates with a level in the upper centrifugus or lower murchisoni graptolite biozones. Chitinozoans also indicate that the base of the riccartonensis graptolite Biozone may occur within the Buildwas Formation and not the overlying Coalbrookdale Formation.     

Recognition of a probable secundo–primo event in the Early Silurian

The early Telychian graptolite extinctions discussed by Loydell in the Stimulograptus utilis Sub-zone agree completely with the predicted consequences of a secundo–primo event, the first to be identified. The event would have included brief inhibitions in vertical circulation, causing a drop in primary planktic productivity from an already low level and causing extinctions; less well-oxygenated deep waters would enhance preservation of organic-walled fossils. The succeeding primo episode would instigate more vigorous vertical circulation with increased primary planktic productivity and higher downward transport of oxygen.     

An updated Telychian (Late Llandovery, Silurian) conodont zonation based on Baltic faunas

Five conodont zones, Pterospathodus eopennatus ssp. n. 1, P. eopennatus ssp. n. 2, P. amorphognathoides angulatus , P. a. lennarti and P. a. lithuanicus , are described in the interval previously known as the P. celloni Zone. The new zones are grouped into two superzones: the first two form the P. eopennatus Superzone and the other three the P. celloni Superzone. All zones correspond to the intervals of the total ranges of the nominal taxa and to the boundaries between the zones to the levels at which one taxon was evolutionally replaced by another. The lower boundary of the P. a. amorphognathoides Zone is redefined. The P. eopennatus ssp. n. 2, P. a. angulatus and P. a. amorphognathoides zones are further subdivided into the Lower and Upper subzones. Although the zones described are mainly based on data from Estonia, they can be recognized all over the world, in most sections containing Telychian strata and from where adequate data are available. Most of the subzones can so far be applied only in a limited area.     

Integrated Telychian (Silurian) K-bentonite chemostratigraphy and biostratigraphy in Estonia and Latvia

Kiipli, T., Kallaste, T., Nestor, V. & Loydell, D.K. 2010: Integrated Telychian (Silurian) K-bentonite chemostratigraphy and biostratigraphy in Estonia and Latvia. Lethaia , Vol. 43, pp. 32–44.
The distribution of altered volcanic ash layers (K-bentonites) and Telychian chitinozoans in four East Baltic drill core sections are compared. This information is integrated with graptolite and conodont biozonations to give a precise correlation chart using four different stratigraphical tools: K-bentonite-based chemostratigraphy; chitinozoan biostratigraphy; graptolite biostratigraphy; and, conodont biostratigraphy. Thickness variations in the K-bentonites suggest that the source of the volcanic ash was to the west and north-west.     

Sea level and faunal changes during the latest Llandovery and earliest Ludlow (Silurian)

It is now recognized that the late Telychian and early Gorstian sea level changes are, like many others in the Silurian, of world‐wide extent. The 30–50 m deepening events at these times were between 1 and 2 Ma in duration, so melting continental ice caps appear to be the most probable cause. The faunal changes associated with the two events are respectively very close to the base and the top of the Wenlock Series and thus segregate many of the faunas diagnostic of the Llandovery, Wenlock, and Ludlow series. Permanent extinctions (often followed by radiations) are more prevalent in the graptolites, conodonts, and acritarchs, while benthic faunas are more affected by regional shifts in community distributions. This means that, in the benthos, slowly evolving lineages are the only reliable guides to time. Such phyletic evolution, however, appears to have been unaffected by sea‐level events.     

Proetid trilobites from the middle Telychian (Llandovery,Silurian) Ningqiang Formation,Shaanxi, China

Four proetid trilobite species, Chuanqianoproetus guizhouensis Yin in Yin and Li, 1978, C. shuangheensis Wu, 1977, C. sp., and Latiproetus guizhouensis Yin in Yin and Li, 1978, are described from the Ningqiang Formation in Ningqiang County, Shaanxi, China. They are middle Telychian (Llandovery, Silurian) in age. Chuanqianoproetus and Latiproetus are both regarded as members of the subfamily Warburgellinae; the former has been considered to be a junior subjective synonym of Astroproetus, but on the basis of its morphology we argue here that they represent two independent genera. The poorly sorted bioclastic grainstones containing trilobite sclerites may indicate their deposition in turbulent conditions on an open marine platform.     

A late Rhuddanian (early Llandovery,Silurian) trilobite association from South China and its implications

A recovery trilobite association after the end-Ordovician mass extinction, the ‘Encrinuroides’ Association, is documented from the lower Niuchang Formation (upper Rhuddanian, lower Llandovery, Silurian) of Gaojiang, Meitan, northern Guizhou, South China paleoplate, including 10 genera of eight families. Three subassociations of this association could be differentiated, i.e., ascendingly the ‘Encrinuroides’-Eoleonaspis Subassociation, the ‘Encrinuroides’-Aulacopleura (Paraaulacopleura) Subassociation, and the ‘Encrinuroides’-Meitanillaenus Subassociation. The succession of these subassociations in the section indicates a shallowing upward trend of the environment as a result of regional tectonic activities (i.e., the Qianzhong Uplift) against the background of the Rhuddanian global transgression. A relatively complete trilobite succession in South China across the Ordovician–Silurian transition has been summarized and its implications for the trilobite macroevolution of this particular time interval are discussed in detail.     

Aeronian (Llandovery, Lower Silurian) palynomorphs and graptolites from the Lipeón Formation, Eastern Cordillera, north-west Argentina

The lower levels of the Lipeón Formation, in the Eastern Cordillera, north-west Argentina, yield a marine-dominated palynomorph assemblage, together with graptolites of mid to late mid Llandovery age (Demirastrites convolutus and probably Stimulograptus sedgwickii zones). The palynomorph assemblage is dominated by acritarchs, but also contains algae and terrestrial cryptospores. Crassiangulina variacornuta, considered a potentially good global biostratigraphical marker for the Upper Llandovery is recovered for the first time from the Silurian of Argentina. The occurrence of this species in strata not younger than late Aeronian, and independently dated by graptolites, indicates an early first appearance for Crassiangulina variacornuta, in the Lipeón Formation, below the Aeronian/Telychian boundary. The lower part of the unit corresponds to a quiet marine environment; thus supporting that Crassiangulina variacornuta is a facies-sensitive acritarch.     

New species of stromatoporoidea from the Upper Ordovician and Silurian of the Subpolar Urals

Stromatoporoidea are widespread in the Upper Ordovician and Silurian beds of the Kozhim River (western slope of the Subpolar Urals). Five new species Cystostroma prodigiosum sp. nov., Stylostroma flabellatum sp. nov., Labechiina arguta sp. nov., Ecclimadictyon faveolatum sp. nov., and Araneosustroma astroplexum sp. nov. are described.     

Integrated Silurian Chitinozoan and Graptolite Biostratigraphy of the Banwy River Section, Wales

The succession of 38 upper Llandovery–lower Wenlock chitinozoan taxa from graptolitic horizons in the Banwy River section (Powys, Wales) is described. Five new species are named: Bursachitina nestorae Conochitina leviscapulae Conochitina mathrafalensis Belonechitina cavei Belonechitina meifodensis . A further ten taxa are described under open nomenclature. Seven chitinozoan biozones are recognized in the Banwy River section, three of which ( Cingulochitina bouniensis Conochitina acuminata Salopochitina bella ) are new. The base of each biozone is correlated with the graptolite biostratigraphical scheme as follows: Angochitina longicollis Biozone — upper spiralis Biozone; Conochitina acuminata Biozone — lowermost lapworthi Biozone; Margachitina banwyensis Biozone — upper lapworthi Biozone; Margachitina margaritana Biozone — lowermost insectus Biozone; Cingulochitina bouniensis Biozone — upper murchisoni Biozone; Salopochitina bella Biozone — upper firmus Biozone. The succession of chitinozoan biozones in the Banwy River section is compared with that in other sections which have graptolite biostratigraphical control. This has highlighted the following: (1) the correlation of the base of the dolioliformis Biozone with the graptolite biozonation is imprecise; (2) E. dolioliformis is recorded only from levels after the first A. longicollis in Sweden (although this may reflect previously unrecognized synonymies); (3) the longicollis Biozone may be diachronous, its base correlating with levels low in the Telychian in Sweden, Norway and Estonia and with the upper Telychian spiralis Biozone in Wales and the Prague Basin; (4) data herein and from the Prague Basin indicate that the base of the margaritana Biozone correlates with a level low in the insectus Biozone.     

Middle Telychian (upper Llandovery, Silurian) graptolites from boreholes of northwestern Libya: Their biostratigraphic significance and palaeogeographical implication

A low-diversity but stratigraphically and palaeobiogeographically important graptoloid association comprising Metaclimacograptus flamandi (Legrand), Parapetalolithus meridionalis (Legrand), and Torquigraptus australis Štorch was identified in the core samples of wells A1-66, F1-66 and A1-43 in the Ghadamis Basin of Libya. The former two species have been originally recovered from Algeria. All three taxa are common and widespread in the middle Telychian strata of Spain (Central Iberian Zone and western Iberian Cordillera) and France (Brittany). In European sections, the species are associated with other, moderately diverse graptoloid fauna, which enables a more precise and worldwide biostratigraphic correlation of Saharan boreholes and surface sections. The present faunal association indicates a middle Telychian age (upper crispus, griestoniensis and lowermost crenulata/tullbergi biozones) for the strata and suggests palaeobiogeographical links between North African pericratonic basins and Ibero-Armorican shelves. M. flamandi has not been found outside this NW-Gondwanan realm.     

The early Ludfordian leintwardinensis graptolite Event and the Gorstian–Ludfordian boundary in Bohemia (Silurian,Czech Republic)

The late Gorstian to early Ludfordian hemipelagic succession of the south‐eastern part of the Prague Synform preserves a rich fossil record dominated by 28 species of planktic graptoloids associated with pelagic myodocopid ostracods, pelagic and nektobenthic orthocerid cephalopods, epibyssate bivalves, nektonic phyllocarids, rare dendroid graptolites, brachiopods, crinoids, trilobites, sponges and macroalgae. Faunal dynamics have been studied with particular reference to graptolites. The early Ludfordian leintwardinensis graptolite extinction Event manifests itself as a stepwise turnover of a moderate diversity graptolite fauna rather than an abrupt destruction of a flourishing biota. The simultaneous extinction of the spinose saetograptids Saetograptus clavulus, Saetograptus leintwardinensis and the rare S. sp. B. at the top of the S. leintwardinensis Zone was preceded by a short‐term acme of S. clavulus. Cucullograptus cf. aversus and C. rostratus vanished from the fossil record in the lower part of the Bohemograptus tenuis Biozone. No mass proliferation of Bohemograptus has been observed in the postextinction interval. Limited indigenous speciation gave rise to Pseudomonoclimacis kosoviensis and Pseudomonoclimacis cf. dalejensis. Egregiograptus (the only novel element of cryptic origin) made its earliest occurrence in association with the latest cucullograptids. A postextinction graptolite assemblage of moderate diversity, composed for the most part of long‐ranging taxa, persisted through the middle and upper tenuis Biozone until new rediversification in the Neocucullograptus inexpectatus Biozone. Unlike the graptoloids, the planktic, epiplanktic, nektonic and nektobenthic shelly fauna did not suffer significant extinction in the early Ludfordian. The Gorstian–Ludfordian boundary is placed at the lowest occurrence of S. leintwardinensis in spite of the very modest graptolite record available from the Ludfordian GSSP where no graptolites occur below the basal bed of the Lower Leintwardine Formation. Elsewhere, the Gorstian–Ludfordian boundary has been placed at the base of the Saetograptus linearis Biozone which has been considered roughly correlative with the leintwardinensis Biozone. Indeed, our morphometric study places the worldwide biozonal index species S. linearis in synonymy with S. leintwardinensis and thus considerably enhances the biostratigraphical utility of the latter index species. Pseudomonoclimacis antiqua sp. nov. is described.     

Devonian antiarchs (Pisces,Antiarchi) from central and Southern European Russia

Antiarchi (Pisces, Placodermi) from the Devonian of central and southern European Russia (Central Devonian Field) are studied. Antiarchs belong to three families, the Asterolepididae, Remigolepididae (suborder Asterolepidoidei), and Bothriolepididae (suborder Bothriolepidoidei). The diagnoses of the order, two suborders, three families, and five genera (two of which are new) are given. Sixteen species, including one new, are described; ten taxa are determined in open nomenclature. Morphological structures of representatives of these families are considered in detail. Classifications of antiarchs and their position in the system of the lower vertebrates are discussed. Devonian vertebrate localities of central and southern European Russia that have yielded antiarchs are listed. Each locality is characterized by its ichthyoassemblage.     

Large dwellers of the Silurian Halysites biostrome: rhizosessile life strategies of cystiphyllid rugose corals from the Llandovery of Gotland

An exceptionally well‐preserved, unusual biostrome composed of the framebuilding cateniform tabulate coral Halysites catenularius (Linnaeus, 1767) bears an assemblage of the relatively large solitary cystiphyllid rugosan Cystiphyllum visbyense Wedekind, 1927. The corallites of solitary cystiphyllids are embedded within the ranks of the halysitid colonies, which developed on a soft, muddy substrate and in relatively turbid water. The cystiphyllid larvae successively settled mostly on the ranks of halysitid colonies and on colonies of the tiny phaceloid rugose coral Nanophyllum ramosum Johannessen, 1995, whereas calice‐in‐calice recruitment was not successful for these cystiphyllid corals. Further growth of C. visbyense was supported by rhizoid structures, which were most frequently developed on the cardinal (convex) side of the corallite. The process of formation of the rhizoid structures is here discussed and explained in detail, showing that they were formed by the extension of the basal ectodermal tissue of the polyp. The cystiphyllids, which settled on the walls of living corallites of halysitid colonies, used sweeper tentacles to kill the smaller polyps of the colony to maintain the space around them and expand. Hence, they ultimately used the halysitid colonies only as a hard substrate to stabilize their position on the soft muddy sediment.     

New and Rare Typhloplanoid Species (Turbellaria,Neorhabdocoela) for Fauna of the Urals and Russia

Morphological decriptions and information on the biology and distribution are given for the first time for fauna of the Urals turbellarians from the Neorhabdocoela order of the Typhloplanidae family: Strongylostoma simplex Meixner 1915, Typhloplanella halleziana (Vejdovsky 1880), Phaenocora rufodorsata (Sekera 1904). The species Typhloplanella halleziana was found the first time on the territory of Russia.     

Zooplankton of the Argazi reservoir (Southern Urals, Russia) and its long-term changes

The Argazi reservoir on the Miass River, the oldest reservoir in the Southern Urals, has been investigated. In total 49 species and forms of zooplankton are identified, including new and rare species for the fauna of the Urals. Throughout the reservoir zooplankton has high species diversity and considerable biomass (up to 11 g/m³). Rotifers are the leading group in the plankton of the reservoir. Compared to the early 1960s, the abundance and biomass of zooplankton has increased by 5–10 times. The disappearance of some plankton forms and the emergence of new ones, as well as an increased number of rotifers and some crustaceans by 1–2 orders of magnitude, are noted. The influence of three main factors that could lead to long-term changes in zooplankton—eutrophication, heavy metals pollution, and global warming—are considered. The last factor seems to be the most important.     

Sea level and faunal change during the late Wenlock and earliest Ludlow (Silurian): A point of view from the Algerian Sahara

A late Wenlock transgression (C. rigidus zone) affecting a large area of the Algerian Sahara has been known for the last thirty years; in this case there is no break at the Wenlock‐Ludlow boundary and the sedimentation is continuous to the earliest Ludlow. But in many other areas of Sahara a late Wenlock regression is observed. This regression may or may not be followed by a latest Wenlock or an early Ludlow transgression. A sedimentary model is proposed in despite of several problems. In order to compare what happens in each region a schematic diagram is used showing the tendencies to shallowing and deepening. Differences observed between the North Sahara basin and the other parts of the Algerian Sahara and comparison between local sea‐level curves and the global sea‐level curve proposed by Johnson et al. (1991) lead to reconsider the evidence of an eustatic early Ludlow event. To end the problem of the disappearance of nearly all graptolites at the end of Wenlock is discussed. The influence of land emergence in the evolution of marine fossil groups in the disturbance that it can bring to the development of the microplankton and the chemistry of the sea seems to have been too neglected.