山西永济白草坪组具刺疑源类的发现及其地质意义

该文着重报道了山西永济白草坪组(一般认为系中元古界上部相当于蓟县系的层位),以具刺疑源类为主的微化石群,计有4类6属15种,其中包括1新属,4新种,1新组合,1亲近种,2未定种,新属是具细网状纹饰的复杂具刺疑源类Shuiyousphaeridium Yan gen.nov.,4新种是Shuiyousphaeridium membraniferum Yan sp.nov.,Dictyosphaera incrassate Yan sp.nov.,Foliomorpha stipuliferaYan sp.nov.,Manicosiphoninema shuiyouense Yan sp.nov.。本微化石群以球形疑源类为主体,以具刺疑源类的大量发育为特征,并伴生有推测是绿藻和褐藻的化石,其组合面貌与蓟县上前寒武系各组皆有明显区别,具有更高的进化程度,从生物地层标志推测白草坪组所在的汝阳群应归入震旦系。白草坪组具刺疑源类可能是横裂甲藻的原始分子,它在地层对比和藻类进化方面皆具有重要意义。     

松辽盆地阿尔必期微体浮游植物新属种

该文描述了松辽盆地中白垩世阿尔必期泉头组三段的微体浮游植物化石1新属7新种,隶属于微咸水沟鞭藻类2属5新种(含4新亚种),淡水绿藻1属1种和疑源类1新属1新种。并对沟鞭藻 Ngktericysta Bint,1986进行了修订。     

Cryptospore Assemblages from the Ordovician/silurian Boundary in the Puna Region, North-west Argentina

Palynomorph assemblages have been recovered from deposits believed to straddle the Ordovician/Silurian boundary, from the upper member of the Salar del Rincón Formation, in the Puna region of north-west Argentina. The palynomorph assemblages are dominated by terrestrial cryptospores, but also contain marine elements (acritarchs, prasinophycean algae and chitinozoans). The cryptospore assemblages are similar in composition to those described from coeval deposits worldwide, suggesting that the producers were cosmopolitan and tolerated a wide range of climatic conditions. They are correlated with the Imperfectotriletes spp. Interval Biozone (sub-biozone α) of the Imperfectotriletes spp.- Laevolancis divellomedia Assemblage Biozone, indicating a Hirnantian (latest Ordovician) age. Acritarchs include late Ordovician species such as Eupoikilosusa striata and Villosacapsula cf. setosapellicula , that coexist with the Llandovery species Dactylofusa estillis. Based on lithological and palynological evidence, an early Llandovery, or a late Hirnantian (post-glacial) age is proposed for the basal part of the upper member of the Salar del Rincón Formation.     

Chemico-structure of the organophosphatic shells of siphonotretide brachiopods

The organophosphatic shell of siphonotretide brachiopods is stratiform with orthodoxly secreted primary and secondary layers. The dominant apatitic constituents of the secondary layer are prismatic laths and rods arranged in monolayers (occasionally in cross-bladed successions), normally recrystallized as platy laminae. Sporadically distributed, interlaminar, lenticular chambers, containing apatitic meshes of laths and aggregates of plates and spherulites, probably represent degraded, localized exudations of glycosaminoglycans (GAGs) with dispersed apatite.
The shells of Helmersenia and Gorchakovia are perforated by canals with external depressions (antechambers) that possibly contained chitinous tubercles in vivo . The immature shell of Siphonotreta and most other siphonotretids is similarly perforated and pitted; but the mature part bears recumbent, rheomorphic, hollow spines that grew forward out of pits. Internally, spines pierce the shell as independent structures to terminate as pillars in GAGs chambers. Spines and pillars were probably secreted by collectives of specialized cells (acanthoblasts) within the mantle.
The shell of the oldest siphonotretide, Schizambon , is imperforate but the ventral valve has a pedicle foramen that lies forward of the posterior margin of the juvenile valve. This relationship characterizes all siphonotretides, suggesting that the pedicle, in vivo , originated within the ventral outer epithelium and not from the posterior body wall as in lingulides.     

Fluorescence intensity studies of Triassic acritarchs from the Yanchang Formation in Ordos basin, northwestern China

Fluorescence properties of Early Cambrian acritarchs were investigated using Leica das Mikroskop (DM) microscopy with a mercury lamp. Well-preserved autoflurescence properties show a correlation between acritarchs morphology and the intensity of emitted fluorescence. In accordance with the fluorescence intensity of organic cell walls, two groups of microfossils were distinguished. Results of observation in this study, which are consistent with those of the previous foreign studies, are in good agreement with regular difference in autofluorescence intensity among palynomorphs reported by McPhilemy (1998). Spores and algae, including Botryococcus, have very bright fluorescence while acritarchs often show less intense fluorescence. Dark brown microfossils have been reworked, and have little or no fluorescence. __________ Translated from Acta Micropalaeontologica Sinica, 2006, 23(3): 309–312 [译自: 微体古生物学报]     

Fluorescence intensity studies of Triassic acritarchs from the Yanchang Formation in Ordos basin,northwestern China

Fluorescence properties of Early Cambrian acritarchs were investigated using Leica das Mikroskop (DM)microscopy with a mercury lamp.Well-preserved autoflurescence properties show a correlation between acritarchs morphology and the intensity of emitted fluorescence.In accordance with the fluorescence intensity of organic cell walls,two groups ofmicrofossils were distinguished.Results of observation in this study,which are consistent with those of the previous foreign studies,are in good agreement with regular difference in autofluorescence intensity among palynomorphs reported by McPhilemy (1998).Spores and algae,including Botryococcus,have very bright fluorescence while acritarchs often show less intense fluorescence.Dark brown microfossils have been reworked,and have little or no fluorescence.     

Reconstructing a complex early Neoproterozoic eukaryote, Wynniatt Formation, arctic Canada

Flanged filamentous microfossils from two geographically separated assemblages in the early Neoproterozoic Wynniatt Formation, arctic Canada, co-occur with flanged Clavitrichoides -type filaments, flanged Osculosphaera-type vesicles and wrinkled, bi-layered vesicles assigned to a new acritarch form-taxon Plicatosphaeridium impostor n. gen., n. sp. Marked similarities in morphological and microstructural detail identify most, if not all, of these forms as components of a single, relatively complex, multicellular eukaryote, Cheilofilum hysteriopsis n. gen., n. sp. The filamentous, occasionally branched thallus was composed of large cylindrical cells, and extended via rupture of cell termini. Filaments originated from Clavitrichoides -type or Osculosphaera -type vesicles via a similar process of rupture, flange formation and apical extension. Presence of a distinctively mottled wall texture supports the ontogenetic relationship of Wynniatt Cheilofilum, 'Clavitrichoides' and 'Osculosphaera,' and provides circumstantial evidence for including a Plicatosphaeridium phase. Despite superficial similarities, Cheilofilum cannot be interpreted as a filamentous cyanobacterium, strobilating scyphozoan or polychaete worm tube. The distinctive cytokinesis of the filamentous component has close analogues among the annellophores and/or phialides (conidiophores) of various hyphomycetous fungi, though its large size and absence of an associated mycelium argue against its placement within the Fungi. Unambiguous fungal synapomorphies are expressed in co-occurring Tappania, however, and both Cheilofilum and Tappania include a closely comparable Clavitrichoides -type phase in their life cycle.     

Proterozoic phytoplankton and timing of Chlorophyte algae origins

Abstract: Morphological and reproductive features and cell wall ultrastructure and biochemistry of Proterozoic acritarchs are used to determine their affinity to modern algae. The first appearance datum of these microbiota is traced to infer a minimum age of the divergence of the algal classes to which they may belong. The chronological appearance of microfossils that represent phycoma‐like and zygotic cysts and vegetative cells and/or aplanospores, respectively, interpreted as prasinophyceaen and chlorophyceaen microalgae is related to the Viridiplantae phylogeny. An inferred minimum age of the Chlorophyte origin is before c. 1800 Ma, the Prasinophyceae at c. 1650 Ma and the Chlorophyceae at c. 1450 Ma. These divergence times differ from molecular clock estimates, and the palaeontological evidence suggests that they are older.     

Microfossils from the Krol ‘A’ of the Lesser Himalaya,India: Additional supporting data for its early Ediacaran age

An assemblage of microfossils of moderate diversity, with the remarkable occurrence of ECAP acritarchs, is reported from the Ediacaran Krol ‘A’ (= the Mahi Formation) succession of Lesser Himalaya, India. Microfossils occur in the chert nodules exposed in Solan district, Himachal Pradesh. Two microfossils, Barogophycus symmetricus n. gen. n. sp. and Botominella lineata are new to the well-established Krol assemblage. The paper concentrates predominantly on fossil eukaryotic filamentous and coccoidal micro-organism of simple morphology. The assemblage is dominated by remains of prokaryotic cyanobacteria and demonstrates the diversity achieved by microorganisms at the beginning of the Ediacaran Period in the aftermath of the Marinoan glaciation. Filamentous and coccoidal microorganisms differ in taxonomic composition from the Mesoproterozoic microbiotas. The Krol microfossils assemblage has biostratigraphic potential and usefulness in broadly demarcating the different levels of the Ediacaran strata. Because of the presence of ECAP acritarchs, along with the appearance of other eukaryotic microorganisms of filamentous and coccoidal morphology, the general level of the Krol ‘A’ assemblage is considered as Ediacaran.     

The development of growth lines on articulate brachiopods

Three types of growth lines are recognised on articulate brachiopod shells: (1) very fine diurnal growth lines formed by calcite increments at the shell margin, (2) seasonal growth lines, formed by inward reflection (doubling back) of the mantle edge, seen as concentric steps on the shell surface and marked by re-orientation of growth vectors evidenced by secondary shell fibres, (3) disturbance lines, formed by abrupt regression of the mantle edge, also seen as concentric steps on the shell surface, but indicated by a dislocation in the shell fabric. Lamellose and spinose ornaments of the sort seen in Tegulorhynchia are essentially genetically controlled. Periodic outgrowths from the outer mantle lobe secrete frills of primary shell that project from the shell surface and form short hollow spines where they cross the radial ornament. In longitudinal section spine formation is seen to involve gradual increase in the rate of secretion of primary shell followed by retraction, and often collapse, of the mantle outgrowth, accompanied by regression. Reflection of the mantle edge usually follows spine formation.