An association between the stromatoporoid Diplostroma yavorskyi Nestor and calcareous algae from the Much Wenlock Limestone, England

Intergrowths of the stromatoporoid Diplostroma yavorskyi Nestor with calcareous algae are described for the first time from the Much Wenlock Limestone of Wenlock Edge, England. The intergrowth developed as irregular. nodular growth-forms which initiated around a nucleus of biomicrite sediment or skeletal clasts. The paired stromatoporoid laminae characteristic of this species form regular alternations throughout substantial portions of the skeleton with the calcareous algae Girvanella sp., Rothpletzella sp., Wetheredella sp. and Rhabdoporella sp., and micrite. Nodular growths developed as a result of intermittent rolling on the sea floor. The nature of the periodic intergrowth of different taxa suggests that the stromatoporoid grew on firm substrates by lateral growth at an edge zone. Epiphytes encrusted areas of the stromatoporoid skeleton devoid of soft tissue. □ Stromatoporoid. calcareous algae. epiphyte. intergrowth. Wenlock.     

A Wenlock ancestor of the micropoma phylogenetic lineage

A new graptolite species, Monoclimacis praemicropoma , from the Upper Wenlock of Poland is described. It is an ancestor of the Lower Ludlow M. micropoma (Jaeckel). The phytogeny of the praemicropoma-micropoma lineage is discussed. M. micropoma nannopoma (Jaeger) has been assigned to a separate evolutionary lineage. Graptolites, Wenlock, phytogeny .     

Graptolite extinction at the Llandovery—Wenlock boundary

Combined graptolite range data through the late Llandovery and early Wenlock of the Canadian Arctic Islands, the British Isles, and Lithuania reveal that survivorship rates from one zone to the next are between 56 and 85%, except at the Llandovery—Wenlock boundary, where only 19% (8 of 42) of the taxa of the upper sakmaricus—crenulata Zone survive into the centrifugus Zone. The high rate of graptolite extinction appears to coincide with glacioeustatic sea-level fall and may be attributed to changing oceanic temperatures, salinity, circulation patterns, oxygenation, and/or productivity associated with the onset of a glacial maximum event. □ Graptolite, extinction, Silurian, Llandovery, Wenlock.     

Silurian Chitinozoa from the type Wenlock and Ludlow of Shropshire,England

Chitinozoa recorded from the Wenlock and Ludlow from the type areas in Shropshire and other localities in the Welsh Basin are listed, and the ranges of 35 taxa of stratigraphic value plotted.     

Distinguishing between the Wenlock graptolite biozonal indicesCyrtograptus centrifugus andCyrtograptus murchisoni

The lower Wenlock biozonal indicesCyrtograptus centrifugus andCyrtograptus murchisoni, although easily separated as entire mature rhabdosomes, by the former’s tighter rhabdosome curvature proximally and the latter’s secondary cladia, are very similar proximally, the position of the sicular apex offering the most satisfactory basis for distinction. InC. centrifugus the apex reaches only to the aperture of th1, whilst inC. murchisoni it reaches to above the top of th1.     

A critique of diachronism, community distribution and correlation at the Wenlock-Ludlow boundary

This paper reviews conclusions reached by J. M. Hurst in a recent paper in Lethaia regarding abrupt, widespread deepening close to the Wenlock-Ludlow boundary as a result of possible eustatic or epeirogenically controlled transgression, and use of such an event as a means of stratigraphical correlation. Much of the benthic community evidence on which these conclusions are based is shown to be conflictory and the resulting correlations to be imprecise. Undoubted diachronism of the Much Wenlock Limestone Formation and overlying Lower Elton Beds is evident only between Dudley and Shropshire. Gradual deepening at this level in the Welsh Borderland appears to be a local reflection of tectonic movement. Wider regional evidence, from North America to the Anglo-Baltic area, rejects the view of a synchronous eustatic or epeirogenic transgression.     

Extinction and opportunistic evolution among late Wenlock graptolites

The late Homerian was a time of profound importance to graptolites. Following the complete extinction of Cyrtograptus and the near extinction of Monograptus (s.s.)at the end of the lundgrenitestis Zone(lower Homerian, upper Wenlock), the morphologically simple and long-ranging Pristiograptus dubius lineage underwent rapid (opportunistic) cladogenesis during the succeeding upper Homerian. Two clades, each with novel and sometimes complex sicular and thecal structures, appeared. One clade, the 'Pristiograptus' praedeubeli group, gave rise to similar but more complex species, such as ' P.' ludensis and 'P.' deubeli , which in turn gave rise to Ludlow taxa, including Saetograptus (s.l.) and Pseudomonclimacis. The other clade, the Lobograptus group, gave rise to Ludlow taxa Lobograptus, Neolobograptus, Bohemograptus , and Neocucullograptus some with very complex thecal structures. Ludlow and younger monograptid faunas therefore comprise at least three separate lineages: Monograptus (s.s.), the Lobograptus group (clade), and the 'Pristiograptus' praedeubeli group (clade). Cladogenesis, evolution, extinction, Homerian, PRISTIOGRAPTUS, LOBOGRAPTUS     

Silurian acritarchs from the type Wenlock and Ludlow of Shropshire,England

Acritarch taxa are recorded and listed from the Wenlock and Ludlow from the type areas in Shropshire, England, and other localities in the Welsh Basin of South Wales and the Welsh Borderland of England. The ranges of 141 taxa of stratigraphic value are plotted. Five new genera are described: Hogklintia, Lepto brachion, Rhaco brachion, Salopidium and Wrensnestia. 36 new species are described, and 32 new combinations proposed. Seven acritarch zones are recognised in the Wenlock and Ludlow.     

The root of the problem: palaeoecology of distinctive crinoid attachment structures from the Silurian (Wenlock) of Gotland

The holdfast (attachment structure) is the most understudied aspect of the palaeoecology of the endoskeleton of fossil crinoids. A new collection of well-preserved holdfasts from a recently reopened quarry at Hunninge, Gotland, in Homerian (upper Wenlock) strata includes several morphologies. The most common are terminal dendritic radicular holdfasts (TDRHs) that may be derived from the cladid Ennallocrinus d'Orbigny. These have a consistent morphology of five, equally spaced, long radices that spread across the sea floor. These crinoids were gregarious, and TDRHs in a group commonly show the same radice orientations. The radices have a large axial canal compared with those of modern crinoids; each included, at least, nervous tissues. Taken together, these features suggest that, apart from attachment, these distinctive TDRHs may have served a sensory function. Other holdfasts in this assemblage also show monospecific aggregations, perhaps suggesting biochemical attraction such as that shown by certain other sessile invertebrates such as barnacles.     

A late Wenlock flora from Co. Tipperary, Ireland

An assemblage of macroplants preserved as highly coalified compressions which lack anatomy is described from a Wenlock locality in County Tipperary, Ireland. Most of the fertile specimens are assigned to Cooksonia Lang. The taxonomic status of this genus is discussed. Some poorly preserved palynomorphs, including miospores, acritarchs, chitinozoans and a variety of tubes, have been isolated from associated sediments, but the age of the flora is based on graptolites. Sedimentological and palaeontological studies of the region are summarized. They provide little direct evidence for the habitats of the plants which are considered to have been terrestrial. The relevance of this flora to the current debate on the colonization of the land is evaluated and it is concluded that these plants provide the earliest record of erect fertile land plants of possible pteridophyte affinity.     

The turtles of the Purbeck Limestone Group of Dorset, southern England

The turtles from the Purbeck Limestone are revised and it is concluded that there are four shell‐based cryptodire species present, namely Pleurosternon bullockii, ‘Glyptops’typocardium comb. nov., Helochelydra anglica comb. nov.,Hylaeochelys latiscutata. There is also one skull‐based species, Dorsetochelys delairi, which may prove to be the skull of ‘Glyptops’, Hylaeochelys or an unknown shell‐type. All other taxa are junior synonyms except ‘Chelone’obovata Owen, 1842 and Tretosternon punctatum Owen, 1842 which are nomina dubia, the material being unfigured and either lost or incorrectly associated. Other taxonomic conclusions are that (1) because Tretosternon is a nomen dubium, the next senior name for this Purbeck–Wealden genus is Helochelydra Nopcsa, 1928; (2) ‘Pleurosternon’typocardium and ‘Glyptops’ruetimeyeri are synonymous, the senior combination being ‘Glyptops’typocardium; (3) the Purbeck ‘Tretosternon’ material is combined with the holotype and only specimen of Platychelys? anglica as Helochelydra anglica comb. nov.; (4) Hylaeochelys emarginata and H. sollasi are junior synonyms of Hylaeochelys latiscutata; (5) one of Owen's ‘lost’ syntypes of ‘Tretosternon punctatum’ has been recognised and is a plastron of Hylaeochelys latiscutata.     

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.     

Wenlock carbonate,level bottom,brachiopod-dominated communities from Wales and the Welsh Borderland

Four marine level bottom communities are described from Wenlock carbonate rocks (i.e. the Wenlock and Woolhope limestones) of Wales and the Welsh Borderland. The communities are: (1) Sphaerirhynchia wilsoni, (2) Isorthis clivosa, (3) Eoplectodonta duvalii, and (4) Visbyella trewerna. The Sphaerirhynchia wilsoni community is divided into: (a) an argillaceous micrite phase, and (b) a biomicrite phase. The communities and the phases are defined on the basis of consistent and recurrent numerical species combinations.The community spectrum from Sphaerirhynchia wilsoni to Visbyella trewerna is broadly correlated with an increase in water depth. The communities show no correlation with major limestone facies types. It is suggested that turbulence, rates of sedimentation and substrate type are some of the environmental parameters, in the shallow near-shore regime, which determine the distribution of brachiopods.     

A high-precision global biostratigraphy of myodocope ostracods for the Silurian upper Wenlock Series and Ludlow Series

The wide, trans-oceanic geographical distribution of myodocope ostracods during the Silurian (especially during the Ludlow and Pridoli epochs), and their widespread preservation in rocks of that age, permits the establishment of a transcontinental biostratigraphy of comparable resolution to coeval graptolite/chitinozoan/conodont biozones. Seven myodocope biozones, extending from the Homerian Stage, upper Wenlock Series Cyrtograptus lundgreni graptolite biozone to the middle part of the Ludfordian Stage of the Ludlow Series, enable a time-resolution for each biozone of circa 1 million years. These biozones can provide high-resolution correlation across Europe into Arctic Russia and Central Asia. There is also the potential for a myodocope biostratigraphy applicable from the uppermost Silurian (Pridoli) to the Carboniferous.     

Reconstruction of the proximal ends of retiolitid rhabdosomes (Graptolithina) from the Upper Wenlock and the Lower Ludlow

Detailed study of the ultrastructures on the cortical lists of retiolitids occurring after the lundgreni event has been undertaken. The extremely well preserved material from the Go?dap borehole of Poland (Baltica) enables classification of clathrial lists into two types—with single and double seams. Significantly different seam development is observed between two groups of retiolitids occurring before and after the lundgreni event. The study of seams and increments on the lists enables reconstruction of the membrane arrangement of the rhabdosomes. Reconstruction of the proximal ends, the arrangement of the ancora umbrella, and the layout of the proximal ventral and lateral orifices of five genera, Neogothograptus, Holoretiolites, Plectograptus, Spinograptus, and Quattuorgraptus n. gen., is presented. The new genus Quattuorgraptus is separated from Spinograptus because of the different development of the ancora umbrella and the width of the lateral walls of the rhabdosome.     

中国西南部石灰岩地区受威胁动物的现状及保护

中国西南部石灰岩地区因其独特的喀斯特自然条件,是生物多样性极为丰富的地区,具有重要的保护和科研价值.通过实地调查以及查证文献,全面整理了该区受威胁的陆栖脊椎动物.中国西南部石灰岩地区现有陆栖脊椎动物37目143科1 297种,列入IUCN红色名录的全球受威胁的物种有133种,占该区动物总数的10.25%;列入<中国物种红色名录>的动物共有305种;占该区动物总数的23.52%.该区受威胁的物种种类多,一些物种仍然缺乏有效的保护,通过分析导致该区动物受威胁的主要原因,对今后该区的保护工作提出了建议.     

广东肇庆七星岩石灰岩的植物群落及其与风景区景观关系的研究

就肇庆七星岩石灰岩的自然环境、植被的主要特征和植物群落１１个类型作了论述，并对石灰岩植被的发展与风景区景观的关系作了探讨，提出加强保护、发展植被的建议     

The Effects of Doubling Limestone Sand Applications in Two Acidic Southwestern Pennsylvania Streams

We studied the effects of limestone sand additions in Bear and Rock runs, two chronically and episodically acidified streams in southwestern Pennsylvania, U.S.A. Linn Run, a nearby episodically acidified stream, served as a reference stream. Our objectives were to evaluate the effects of doubling recommended limestone sand amounts on water quality and macroinvertebrates on Bear and Rock runs and to assess substrate changes resulting from limestone sand inundation. Approximately 23 and 6 tonnes of limestone sand were added annually to the headwaters of Bear and Rock runs, respectively, from 1999 to 2001. In 2002, amounts were doubled. Macroinvertebrate communities were assessed from 1999 to 2003 at points above and below the sand additions on Bear Run and Rock Run. Small, plastic substrate samplers were used to assess sand substrate effects. Doubling annual limestone sand amounts resulted in significantly improved pH and acid‐neutralizing capacity; however, total dissolved aluminum increased significantly downstream (α≤ 0.05). Macroinvertebrate density and diversity were not significantly affected, but an increase in acid‐sensitive taxa was observed at a site 3,500 m downstream. Substrate sampler data indicated a significant negative relationship between amount of sand deposited and density of macroinvertebrates. The mixed water quality and benthic macroinvertebrate results were reasonably consistent with earlier work and call into question the use of limestone sand in the restoration of chronically and episodically acidified waters.     

Late Wenlock (Middle Silurian) global Bioevent: Possible chemical cause for mass graptolite mortalities

Graptolites nearly became extinct in the latest Wenlock in all preserved stratigraphic sequences of this age. Graptolite mortalities occurred along the western coast of Laurentia and at sites that surrounded the Proto‐Tethys. Graptolite mass mortalities took place among deep‐water, open ocean dwelling organisms. After the mass mortalities, only the Pristiograptus dubius group and retiolids surface or near‐surface dwellers, survived. For a period of time, little speciation or diversification occurred. The base of the Ludlow is marked by diversification, with appearances of S. colonus, M. nilssoni and other groups which occur in near surface waters. None of the extensive plate movements postulated for the Silurian readily explain the mass extinctions that occurred. During the Silurian, global temperatures were warmer than present and atmospheric oxygen concentrations were lower, creating extensive oceanic anoxia. Below the oxygenated surface layers of the ocean, was an anoxic, non‐sulfidic zone (i.e. nitrate‐reducing) above a sulfidic zone. Graptolites lived over a range of depth from the oxygenated zone to either near or in the nitrate‐reducing zones. As the oxygen concentration declined through the Silurian, the depth of the oxic zone would have become shoaler with expanding anoxia. Late Wenlock graptolites that were unable to migrate to shallower depths, living in borderline oxygen conditions, could have been killed, resulting in the mortalities of the late Wenlock. Only those graptolites that were surface dwellers survived, adapted and reradiated.