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.     

西昆仑地区志留系温泉沟群的疑源类和几丁虫

西昆仑地区处于中亚腹地的高寒缺氧地带,区域地质研究程度较低。下志留统温泉沟群中-下部轻变质的碎屑岩中一直未发现可靠的化石证据。最近,在温泉沟地区志留纪地层中发现较丰富的Leiosphaeridia,Flo-risphaeridium,Conochitina,Ancyrochitina,Desmochitina,Eisenackitina,Rhabdochitina,Cyathochitina,Lag-enochitina和?Eremochitina属等疑源类和几丁虫化石分子,为温泉沟群中-下部轻变质碎屑岩的时代确定提供了重要的微体化石方面依据。     

甘肃灵台文王沟晚中新世一早更新世小哺乳动物

根据大量小哺乳动物化石在地层中的分布,将文王沟剖面２３层划分出５个生物地层带： Ｉ带相当于榆社马会组;ＩＩ带与Ⅲ带相当于高庄组; ＩＶ带相当于麻则沟组; Ｖ带为午城黄土底部。根据牛物属种转达换判定出 ４个主要生物事件发生时期,分别在 ５．８、３６、３．０、２．４Ｍａ左右。每一个生物事件集中发生的时期指示生态环境的一次显著向干冷方向变化。     

THE GEOLOGICAL SIGNIFICANCE OF SINACANTHUS FROM TARIM, CHINA

TheSinacanthusfossiIlocalitieswererestrictedtotheYangtzeregionbeforethediscoveryoftheTarimfossils.TheyusedtobereferredtoasDevonianorEarlyDevonianinage,butlaterdiscoverieshavedemostratedthattheageofSinacanthus-bearingbedsshou1dbeSilurian(Li,198O).In1988,fiveSinacanthusfossill,edswerefoundintheTataertagPormationofKalping,NWTarimandtheageoftheTataertagFormationwasconsideredMiddle-LateSilurian(Table2).Inthesummerofl992,WangJunqing,ZhuMinandtheauthorofthispaperfoundalotoffossilfinspinesi…     

Fragmentary non-vascular plant microfossils from the late Silurian of Wales

A wide variety of cuticles and tubular elements is described from a late Silurian (Ludlow Series) locality in Wales which has already yielded a macroflora containing Cooksonia Lang, Steganotheca Edwards and vascularized axes. These microfossils are compared with Lang's Downtonian .Nematothallus complex and Silurian assemblages of similar composition from north America. It is concluded that the majority of these microfossils derive from non-vascular plants of uncertain affinity which lived on land.     

Late Ordovician-Early Silurian fluctuations in sea level from eastern Anticosti Island, Quebec

Over 1,000 m of Upper Ordovician to Lower Silurian mixed carbonate and clastic strata on Anticosti Island are nearly tectonically undisturbed, despite their proximity to the Northern Appalachians fronting Quebec's Gulf of St. Lawrence. Natural cliffs exposed along the coast and rivers in the eastern part of the island make a relatively conformable sequence belonging to the Ashgill and Llandovery Series. Fossil communities interpreted as depth-associated in life are especially repetitious in the Becscie, Gun River, Jupiter, and Chicotte Formations (Llandovery Series), and to a lesser degree in the Upper Vaureal and Ellis Bay Formations (Ashgill Series). Preliminary study of the pattern of changeovers in Eocoelia, Pentamerus and Stricklandia communities suggests that Anticosti seas deepened and shallowed three and a half times during the Early Silurian. High water peaks were reached during B₁-B₂, C₁-C₂ and C₄-C₅ times, with a final deepening trend beginning in late C₅ time. Age determinations of these events are based on the occurrence of graptolites (with some new records from Anticosti) keyed to the standard graptolite zones, and species of the Eocoelia lineage are also useful for correlation. The profile of the Anticosti sea-level curve compares well with other curves reconstructed from the Lower Silurian of New York, Michigan, and Iowa. Widespread synchronism in sea-level changes on the North American platform is thus corroborated.     

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.     

Some Silurian Brachiopods from Lithuania and Their Palaeobiogeographical Significance

Silurian brachiopods are described from 21 boreholes in Lithuania. Nine genera are recognized and represented by one or two species, including the atrypids Atrypoidea, Cromatrypa, Lissatrypa and Septatrypa, athyridids Collarothyris, Nucleospira, Meristina and Pseudoprotathyris, and rhynchonellids Ancillotoechia and Plagiorhyncha. Two new species, Cromatrypa? pubes and Lissatrypa lithuanica, are described. The same taxa are reported from England, Gotland, Belarus and Podolia in Wenlock and Ludlow strata, and from Podolia, Urals, the Canadian Arctic archipelago and Russian Arctic islands in Prídolí strata.     

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.     

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.