Early Cretaceous Angiosperms of the Yanji Basin,Jilin Province

An assemblage of fossil plants was discovered in the Yanji Basin, Jitin Province, consisting mainly of pterid0Phytes, gymnosperms and a few angiosperms. The present paper deals with the angiosperms only; They are: Rogersia angunifolia, Saliciphyllum longifoliurn, Sapindopsis magnifolia, Sterculophyllurn eleganurn, ,Ficophyllum, "Sassafras", Ranunculophyllum pinnatisectum sp. nov., Clernatites lanceolatus sp. nov., and the fruits Carpolithus brookensis, Carpolithus sp. gymnosperm Sequoia as well, all angiosperms having the morphological features of early angiosperms. Most of them are similar to the elements of the Potomac Group in North America and to some extent approach the fossil plants of Neocomian in Mongolia. This assemblage is manifestly different from the Albian flora of Kolyma River (URSS) and Portugal of Europe because of belonging to different stages. Thus, the age of the Dalazi Formation of Yanji Basin is tentatively ascribed to Aptian. The characteristics of this assemblage indicate that the floras of Eurasia and North America had been closely related during the early Mid-Cretaceous and that the early angiosperms were widely distributed in the North Hemisphere. Judging from the characteristics of this assemblage and the deposition, the authors speculate that in Northeast China the climate was warm and humid during the early Mid-Cretaceous.     

Two Angiosperm Reproductive Organs from the Early Cretaceous of China

Two fossil reproductive organs of early angiosperms were collected from the Yanji Basin, Jilin Province of China. The assemblage of fossil plants consist mainly of pteridophytes, gymnosperms and a few angiospoermms. The present paper only reports the two reproductive organs of angiosperms. They are Archimagnolia rostrato-stylosa gen.et sp. nov., Eucommioites orientalis sp.nov. The first is a slightly elongated floral axis(receptacle), with about 20 carpels helically arranged. The carpels are free from each other and attenuated into a beak-like structure at the apex, with the base inserted into the receptacle. A comparison with living plants indicated its close relationship with some members of the Magnoliaceae. The second is a samara, similar to a fruit of the genus Eucommia, narrow-oblong, 2-lobed at the apex with the lobes stigmatic on theinner side. The seed is situated at the middle of fruit, oblong in shape.     

Fossil evidence of insect pathogens

The present report describes fossil evidence of insect pathogens, heretofore, almost non-existent, from six samples of amber ranging in age from 15 to 100 million years. They include a cytoplasmic polyhedrosis virus and trypanosomatid infection in an adult biting midge (Diptera: Ceratopogonidae), and a nuclear polyhedrosis virus in an adult sand fly (Diptera: Phlebotomidae), both from Early Cretaceous Burmese amber, several types of fungal thalli on the cuticle of an adult mosquito (Culicidae: Diptera), as well as a fungal growth on the prothorax of a fungus gnat (Mycetophilidae: Diptera) in Dominican amber and large tumors in the body cavity of a caterpillar (Lepidoptera) in Mexican amber. These discoveries suggest that insect polyhedrosis viruses were present 100 million years ago and present the possibility that vertebrate arboviruses (especially those in the family Reoviridae) could have evolved from cytoplasmic polyhedrosis viruses infecting biting insects. The flagellates in the Early Cretaceous biting midge represent the first fossil record of monogenetic trypanosomatid infections of arthropods.     

被子植物的花化石研究

五十多年前胡骕在研究山东临朐县山旺组的植物化石中,发现有花的化石,仅保存了5个花瓣或仅5个萼片,均难给予确切的分类位置;六十年代我们两次去山旺野外工作,发现为数较多,同样仅保存花瓣或萼片的化石。本文研究的是80年代发现并保存较为完好的花化石。新近李凤麟详细论述了各门类化石,均认为山旺组的地质时代属中中新世。近十余年来,国际上被子植物的花化石的研究进展较快。每次花化石的发现,对研究被子植物种系发生、系统位置及在地史中的演化及演变速率等均是极重要     

Diversity in obscurity: fossil flowers and the early history of angiosperms

In the second half of the nineteenth century, pioneering discoveries of rich assemblages of fossil plants from the Cretaceous resulted in considerable interest in the first appearance of angiosperms in the geological record. Darwin''s famous comment, which labelled the ‘rapid development’ of angiosperms an ‘abominable mystery’, dates from this time. Darwin and his contemporaries were puzzled by the relatively late, seemingly sudden and geographically widespread appearance of modern-looking angiosperms in Late Cretaceous floras. Today, the early diversification of angiosperms seems much less ‘rapid’. Angiosperms were clearly present in the Early Cretaceous, 20–30 Myr before they attained the level of ecological dominance reflected in some mid-Cretaceous floras, and angiosperm leaves and pollen show a distinct pattern of steadily increasing diversity and complexity through this interval. Early angiosperm fossil flowers show a similar orderly diversification and also provide detailed insights into the changing reproductive biology and phylogenetic diversity of angiosperms from the Early Cretaceous. In addition, newly discovered fossil flowers indicate considerable, previously unrecognized, cryptic diversity among the earliest angiosperms known from the fossil record. Lineages that today have an herbaceous or shrubby habit were well represented. Monocotyledons, which have previously been difficult to recognize among assemblages of early fossil angiosperms, were also diverse and prominent in many Early Cretaceous ecosystems.     

A whole-plant monocot from the Lower Cretaceous

The Yixian Formation (the Lower Cretaceous) of China is world famous for its fossils of early angiosperms. Despite their great diversity, few of these fossils are preserved as whole plants, making our understanding of early angiosperms incomplete. Here, we report a fossil angiosperm, Sinoherba ningchengensis n. gen. n. sp. (Sinoherbaceae n. fam.), from the Yixian Formation of China. The fossil is of a whole plant, including physically connected root with fibrous rootlets, a stem with branches and nodes, leaves with parallel-reticulate veins, and a panicle of female flowers with an ovary surrounded by perianth. Morphological and phylogenetic analyses reveal that Sinoherba is an herbaceous monocot. This fossil underscores the great diversity of angiosperms in the Lower Cretaceous Yixian Formation and an earlier, pre-Cretaceous origin of angiosperms.     

<Emphasis Type="Italic">Schmeissneria</Emphasis>: A missing link to angiosperms?

Background  

The origin of angiosperms has been under debate since the time of Darwin. While there has been much speculation in past decades about pre-Cretaceous angiosperms, including Archaefructus, these reports are controversial. The earliest reliable fossil record of angiosperms remains restricted to the Cretaceous, even though recent molecular phylogenetic studies suggest an origin for angiosperms much earlier than the current fossil record.     

Cretaceous diversification of angiosperms in the western part of the Iberian Peninsula

The classic leaf fossil floras from the Cretaceous of the Lusitanian Basin, Portugal, which were first described more than one hundred years ago, have played an important role in the development of ideas on the early evolution of angiosperms. Insights into the nature of vegetational change in the Lusitanian Basin through the Cretaceous have also come from studies of fossil pollen and spores, but the discovery of a series of mesofossil floras containing well-preserved angiosperm reproductive structures has provided a new basis for understanding the systematic relationships and biology of angiosperms at several stratigraphic levels through the Cretaceous. In the earliest mesofossil floras from the Torres Vedras locality, which are of probable Late Barremian-Early Aptian age, angiosperms are surprisingly diverse with about 50 different taxa. In slightly later mesofossil floras, which are of probable Late Aptian-Early Albian age, the diversity of angiosperms is still more substantial with more than hundred different kinds of angiosperm reproductive structures recognized from the Famalicão locality alone. However, this early diversity is largely among angiosperm lineages that produced monoaperturate pollen (e.g., Chloranthaceae, Nymphaeales) and early diverging monocots (Alismatales). Eudicots are rare in these Early Cretaceous mesofossil floras, but already by the Late Cenomanian the vegetation of the western Iberian Peninsula is dominated by angiosperms belonging to various groups of core eudicots. The Normapolles complex is a particularly conspicuous element in both mesofossil floras and in palynological assemblages. In the Late Cretaceous mesofossil floras from Esgueira and Mira, which are of Campanian-Maastrichtian age, core eudicots are also floristically dominant and flowers show great organisational similarity to fossil flowers from other Late Cretaceous floras described from other localities in Asia, Europe and North America.     

The age of the angiosperms: a molecular timescale without a clock

The age of the angiosperms has long been of interest to botanists and evolutionary biologists. Many early efforts to date the age of the angiosperms and evolutionary divergences within the angiosperm clade using a molecular clock have yielded age estimates that are grossly inconsistent with the fossil record. We investigated the age of angiosperms using Bayesian relaxed clock (BRC) and penalized likelihood (PL) approaches. Both of these methods allow the incorporation of multiple fossil constraints into the optimization procedure. The BRC method allows a range of values for among-lineage rate of substitution, from a nearly clocklike behavior to a condition in which each branch is allowed an optimal substitution rate, and also accounts for variation in molecular evolution across multiple genes. A topology derived from an analysis of genes from all three plant genomes for 71 taxa was used as a backbone. The effects on age estimates of different genes, single-gene versus concatenated datasets, and the inclusion and assumptions of fossils as age constraints were examined. In addition, the influence of prior distributions on estimates of divergence times was also explored. These results indicate that widely divergent age estimates can result from the different methods (198-139 million years ago), different sources of data (275-122 million years ago), and the inclusion of temporal constraints to topologies. Most dates, however, are between 180-140 million years ago, suggesting a Middle Jurassic-Early Cretaceous origin of flowering plants, predating the oldest unequivocal fossil angiosperms by about 45-5 million years. Nonetheless, these dates are consistent with other recent studies that have used methods that relax the assumption of a strict molecular clock and also agree with the hypothesis that the angiosperms may be somewhat older than the fossil record indicates.     

Heydenius dominicus n. sp. (Nematoda: Mermithidae), a Fossil Parasite from the Dominican Republic

Heydenius dominicus n. sp. is described as a new species of fossil mermithid nematode from Dominican Republic amber. The species is represented by two specimens of parasitic juveniles that left their insect host and became embedded in the resin. The nematodes are associated with an adult male limoniid (Diptera: Limoniidae) and an adult female mosquito (Diptera: Culicidae). The parasites are thought to have emerged from the mosquito host. This is the first report of a fossil mermithid from a Neotropical area.     

被子植物的起源-以喜花虻类化石为据

喜花昆虫在被子植物的起源和早期演化上起着决定性的作用。虻类化石中的许多类群都有访花习性,它们为研究被子植物的起源提供了独特材料。虽然最老的被子植物化石还没有发现,但是喜花虻类的爆发式出现,表示了被子植物出现的时间和地点。本文主要以欧亚大陆东部,特别是中国辽西的侏罗杨虻类化石为材料,在功能形态分析和与现代类群作对比的基础上,证证实了虻类是显花植物最原始的传粉类群之一。中国东北、哈萨克斯坦和西伯利来晚     

Approaches to the identification of angiosperm leaf remains

During the past 125 years the history of early angiosperms, interpreted through the fossil leaf record has been largely an exercise in paleofloristic studies, ignoring evolution. Imprecise identifications of ancient leaves “matched” to extant genera and families have been used as the basis for reconstructions of paleocommunities and paleoclimates. However, as the result of careful morphological studies of leaf form, venation and cuticular features new insights into the evolution of angiosperms are now available. In this paper considerations are given to the usefulness and shortcomings of leaf form, venation and cuticular analysis as diagnostic tools of plant identification. Many techniques for the study of the morphology of modern and fossil leaves are included in this paper as well as tables outlining features of leaf venation and the epidermis. Careful morphological studies of leaf form (such as the venation and epidermal characters emphasized in this paper) will provide better understanding of the relationships of living angiosperms and transform the fossil leaf record into useful data that can be used to study the evolution of the angiosperms.     

Sources of error and confidence intervals in estimating the age of angiosperms from rbcL and 18S rDNA data

Molecular estimates of the age of angiosperms have varied widely, and many greatly predate the Early Cretaceous appearance of angiosperms in the fossil record, but there have been few attempts to assess confidence limits on ages. Experiments with rbcL and 18S data using maximum likelihood suggest that previous angiosperm age estimates were too old because they assumed equal rates across sites-use of a gamma distribution of rates to correct for site-to-site variation gives 10-30 my (million years) younger ages-and relied on herbaceous angiosperm taxa with high rates of molecular evolution. Ages based on first and second codon positions of rbcL are markedly older than those based on third positions, which conflict with the fossil record in being too young, but all examined data partitions of rbcL and 18S depart substantially from a molecular clock. Age estimates are surprisingly insensitive to different views on seed-plant relationships. Randomization schemes were used to quantify confidence intervals due to phylogenetic uncertainty, substitutional noise, and lineage effects (deviations from a molecular clock). Estimates of the age of crown-group angiosperms range from 68 to 281 mya (million years ago), depending on data, tree, and assumptions, with most ～140-190 mya (Early Jurassic-earliest Cretaceous). Approximate 95% confidence intervals on ages are wider for rbcL than 18S, ranging up to 160 my for phylogenetic uncertainty, 90 my for substitutional noise, and 70 my for lineage effects. These intervals overlap the oldest occurrences of angiosperms in the fossil record, as well as some estimates from previous molecular studies.     

The identification of fossil angiosperm pollen and its bearing on the time and place of the origin of angiosperms

Studies in the 1970's reporting the occurrence of fossil pollen types in the Cretaceous, coupled with surveys of extant pollen morphology of primitive flowering plants, laid the foundation for proposing a Lower Cretaceous origin of angiosperms. Over the last 30 years, morphological, ultrastructural, and ontogenetic studies of both extant and fossil pollen have provided an array of new characters, as well as greater resolution in defining character polarities. Moreover, a range of fossil pollen types exhibiting angiosperm characters occur in low frequency within Triassic and Jurassic sediments. The pollen data provide evidence of a pre-Cretaceous origin of angiosperms. Speciation and extinction rates were likely equal during the Triassic and Jurassic, resulting in the paucity of angiosperm pollen types from different geographic areas in the Atlantic – South American/African rift zone. It was not until the Lower Cretaceous that origination rates exceed extinction rates, resulting in the subsequent diversification of angiosperms and the origin of the eudicots.     

Fossil pollen records of extant angiosperms in China

About 250 fossil pollen types related to 113 extant angiospermous families from the Cretaceous and the Tertiary in China are discussed in the first part of this article. In the second part, comparisons of early records of fossil pollen in and outside China are made to trace the oldest fossil records. Based on these data, we conclude that many plants may have originated in China, a finding that may be important for the study of the origin and early development of angiosperms.     

First fossil record of transfer cells in angiosperms

Transfer cells are specialized plant cells that optimize short-distance transport by an extension of the interior surface of the cell walls. Using scanning electron microscopy (SEM), we found transfer cells in the fossil seed coat of Ehretia clausentia (Ehretiaceae, Boraginales) from the London Clay flora (Lower Eocene). This is the first fossil record of transfer cells in angiosperms.     

中国中生代昆虫化石研究新进展

回顾了1990年以来中国中生代昆虫化石研究的新进展,简述了我国学者在古昆虫分类学、昆虫内部形态学、昆虫系统学、古生态学、昆虫生物地层学、昆虫区系的历史演变、生物古地理学、昆虫与植物的关系等8个方面取得的突出贡献,并给出了我国发现的世界最低层位昆虫科级类群表。     

THE REPRODUCTIVE BIOLOGY OF A RELICT–ILLICIUM FLORIDANUM ELLIS

The flowers of Illicium floridanum are pollinated by a wide variety of insects, particularly Diptera that emerge from the litter and stream in early spring. Coleoptera rarely visit the flowers. It is suggested that the mode of pollination is ancient and may also exist in species of primitive angiosperms in the South Pacific. Illicium floridanum is self-incompatible and possesses features of a gametophytically controlled incompatibility system. As a result of asexual reproduction, a lack of long-distance dispersal of pollen and self-incompatibility, fruit production is very low. This pattern of reproduction is found in other species of primitive angiosperms; incompatibility mechanisms which undoubtedly aided the angiosperms to become dominant may now be one of the major factors responsible for their extinction.     

The origin of angiosperms

The claim of monophyletic origin of angiosperms arose from the confusion of phylogenetic and taxonomic concepts. Unpreconceived studies of extant angiosperms point to more than one archetype. Several lines of angiosperms have simultaneously entered the fossil record; the monocotyledons, proto-Hamamelidales, proto-Laurales and “proteophylls” (possibly ancestral to the Rosidae) are recognized among them. Three groups of Mesozoic seed plants — the Caytoniales, Czekanowskiales and Dirhopalostachyaceae — are distinguished as major sources of angiosperm characters (proangiosperms). Other Mesozoic lineages probably also contributed to the angiosperm character pool. Angiospermization is related to Mammalization and other processes involved in development of the Cenozoic lithosphere and biosphere.     

The early evolution of the angiosperm flower

An unexpected variety of new fossil flowers from the Lower and mid-Cretaceous and new results on the structure, development and biology of the flowers of extant primitive angiosperms are leading to modifications of earlier concepts of early flower evolution. Most fossil flowers conform best to those of the angiosperm subclass Magnoliidae, diverse though they may be. The unusual variety in organ number and organ arrangement patterns is a characteristic not only of the fossils but also of the extant Magnoliidae. It is a feature of the still 'open' organization of the flower (without intricate synorganization of parts) at this evolutionary level, and not an expression of only distant phylogenetic relationship. On the other hand, many other predominant features of modern angiosperms are lacking in both earliest fossils and most extant Magnoliidae.