Pattern of some Silurian bioevents

The best‐known Silurian bioevent occurred at the end of the Wenlock: the lundgreni event, together with the nassa‐ludensis crisis, was established among planktic graptolites. The East Baltic data show several peaks of high diversity (especially triangulatus, turriculatus, scanicus zones) and three levels of low diversity of graptolites (antennularius, radians, ludensis zones). These are more or less coincident with sea‐level changes. Energetic innovation of the shallow shelf corals started in the early Silurian. The late Wenlock regression seems not to affect them seriously but the late Silurian decline coincides with the aridization of the climate and a regression of the shelf seas. The Agnatha had strong radiations in the Wenlock (ludensis Zone) and Ludlow (leintwardinensis Zone), the fishes in the Pridoli. Many Silurian vertebrates were long‐ranging and extinction rate was relatively low; only at the late leintwardinensis level and in the latest Ludlow did considerable extinctions occur.     

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.     

西藏南部聂拉木志留纪笔石新材料*

聂拉木是西藏南部志留纪含笔石地层(石器坡组)的主要产地。近期在该地亚来村新发现一批笔石标本,包括Normalograptus sp.、Glyptograptus sp.、Campograptus lobiferus、C. cf. lobiferus、C. cf. obtusus、C.? circularis、Lituigraptus cf.convolutus、Rastrites cf.perfectus、Stimulograptussedgwickii、Streptograptus sp.和Torquigraptus decipiens。该组合面貌确定其属于志留系兰多维列统埃隆阶上部Lituigraptusconvolutus带至Stimulograptus sedgwickii带。这一新材料的发现,使西藏南部的志留纪地层得以作全球对比。     

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.     

Retiolitid graptolites from the collection of HermannJaeger in the Museum für Naturkunde, Berlin (Germany). I.Neogothograptus andHoloretiolites

Isolated material of Ludlow (Upper Silurian) retiolitid graptolites are described from isolated material in theJaeger collection of the Museum für Naturkunde (Humboldt Universität Berlin, Germany). This material from glacial erratic boulders of northern Germany has never been published, even though it yields important structural information for retiolitid taxonomy. The astogeny and formation of the clathrial and reticular lists ofNeogothograptus andHoloretiolites rhabdosomes is discussed in some detail. New species includeNeogothograptus ornatus n. sp. andNeogothograptus eximinassa n. sp. Hermann Jaeger recognized both species as new and named them in his collection, but not publish the material.Neogothograptus thorsteinssoni Lenz &;Kozlowska-Dawidziuk andNeogothograptus romani Koz?owska-Dawidziuk have been recognized for the first time in north German glacial erratic boulders.     

Genetically controlled cortical tissue deposition inNormalograptus scalaris (Hisinger, 1837)

A specimen ofNormalograptus scalaris (Hisinger) from the Llandovery of Dalarna, Sweden, shows a highly asymmetrical rhabdosome in which one stipe was abandoned at an early stage in the growth of the colony. The surface of the rhabdosome is thickly covered by cortical tissue, but the remaining dorsal side of the second stipe is left free. Even though the symmetry of the colony is strongly distorted, it survived for a considerable time. It is suggested that this unusual development involved genetic control of cortical tissue deposition in the graptolite colony.      

鄂西志留纪早期三叶虫Latiproetus Lu,1962的新材料

本文描述湖北宜昌、兴山志留纪兰多维列世艾隆期蚜头虫类三叶虫Latiproetus latilimbatus(Grabau,1925)和Latiproetus tenuis Chang,1974的新材料.Latiproetus Lu,1962的有效性长期多有争论,通过新材料研究确认,该属和Prantlia P(r)ibyl,1946的区别在于其较短的鞍前区,向前收缩较少的头鞍,较微弱的尾肋沟和间肋沟,并不具鞍前区横脊.该属和Astroproetus Begg,1939的区别在于其较深的S1,清晰的S2,较小的活动颊刺,及宽而清晰的尾边缘.因此,笔者认为Latiproetus应为有效属.     

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.     

Trilobites from the Silurian “Lower Red Beds” of Wuhan,South China: stratigraphic and paleogeographic implications

The age of the Silurian “Lower Red Beds” (LRBs), which occur widely in South China, has long been controversial because of the scarcity of index fossils. Here, we report a fauna with abundant trilobites from the LRBs in Wuhan, Middle Yangtze region, consisting of Aulacopleura (Paraaulacopleura) pijiazhaiensis, ‘Encrinuroides’ yichangensis, Gaotania hubeiensis, Hyrokybe gaotanensis, Japonoscutellum yichangense, Latiproetus latilimbatus, and Ptilillaenus lojopingensis. These trilobites are common in the Leijiatun, upper Xiangshuyuan, Shihniulan, and Lojoping formations in the Upper Yangtze region, and belong to the middle to upper Aeronian Ptilillaenus or ‘Encrinuroides’–Ptilillaenus–Latiproetus assemblages. The discovery of this trilobite assemblage suggests that the LRBs are probably partly of middle–late Aeronian age in the Middle Yangtze region. Thus, the lower boundary of the LRBs is likely diachronous in the Yangtze region, ranging from the middle–late Aeronian to the early Telychian. The discovery of the Ptilillaenus assemblage in the Wuhan LRBs expands the paleogeographic distribution of this assemblage and provides evidence of deeper depositional environment of the LRBs in the study area versus shallow waters in other areas of the Yangtze region.