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1.
Marin B  Palm A  Klingberg M  Melkonian M 《Protist》2003,154(1):99-145
Sequence comparisons and a revised classification of the Euglenophyceae were based on 92 new SSU rDNA sequences obtained from strains of Euglena, Astasia, Phacus, Trachelomonas, Colacium, Cryptoglena, Lepocinclis, Eutreptia, Eutreptiella and Tetreutreptia. Sequence data also provided molecular signatures for taxa from genus to class level in the SSU rRNA secondary structure, revealed by a novel approach (search for non-homoplasious synapomorphies) and used for taxonomic diagnoses. Photosynthetic euglenoids and secondary heterotrophs formed a clade, designated as Euglenophyceae (emend.) with two orders: Euglenales and Eutreptiales. The mostly marine Eutreptiales (Eutreptia, Eutreptiella; not Distigma) comprised taxa with two or four emergent flagella (the quadriflagellate Tetreutreptia was integrated within Eutreptiella). The Euglenales (freshwater genera with < or = one emergent flagellum) formed nine clades and two individual branches (single strains); however, only two clades were congruent with traditional genera: Trachelomonas (incl. Strombomonas) and Colacium. Euglena was polyphyletic and diverged into four independent clades (intermixed with Astasia, Khawkinea and Lepocinclis) and two individual branches (e.g. E. polymorpha). Phacus was also subdivided into Phacus s. str. and two combined lineages (mixed with Lepocinclis spp. or Cryptoglena). In consequence, Euglena (s. str.), Phacus and other genera were emended and one lineage (mixed Phacus/Lepocinclis-clade) was recognized as the previously neglected genus Monomorphina Mereschkowsky (1877). The sister clade of Phacus s. str. (mixed Euglena/Lepocinclis-clade) was identified as Lepocinclis Perty (emended).  相似文献
2.
The morphology of the erythrosuchid ankle joint is reassessed. Two specimens, recently thought to have been incorrectly referred to Erythrosuchus africanus , are shown without doubt to belong to this taxon. Furthermore, the morphology is essentially similar to that of other early archosaurs. The tarsus of Erythrosuchus is poorly ossified and consists of a calcaneum, astragalus, and two distal tarsals. The calcanea of Erythrosuchus, Vjushkovia triplicostata , and Shansisuchus shansisuchus are all similar in being dorsoventrally compressed, possessing a lateral tuber, and lacking a perforating foramen. The astragalus of V. triplicostata is currently unknown. The astragalus of Shansisuchus is apparently unique in form. The erythrosuchid pes is therefore more derived than has been recently proposed. The tarsal morphology of several other archosauromorph taxa is reviewed and many details are found to be at variance with the literature. The plesiomorphic condition for the Archosauromorpha consists of four distal tarsals and a proximal row of three elements; two of which articulate with the tibia. These proximal elements are interpreted as the astragalus, calcaneum, and a centrale, and the same pattern is retained in the earliest archosaurs. This reassessed tarsal morphology has implications for the homology of the centrale and reconstruction of early diapsid phylogeny.  相似文献
3.
Newly emerging molecular phylogenetic hypotheses involving the sponge Order Haplosclerida (Class Demospongiae) are far removed from traditional views on their classification using morphology. In the new grouping of marine haplosclerid taxa by molecular data all members of one highly supported clade were found to have three large indels in the 18S rRNA gene. These indels were not found in this gene in other marine haplosclerids or in any other demosponges analysed. These indels were found in the variable V4 and V7 region of the gene, had high GC contents and formed stable double stranded helices in the 18S rRNA secondary structure. These indels are very important synapomorphies, provide high support for an alternative taxonomic scheme and could help resolve the phylogeny of this order in conjunction with other phylogenetically informative characters.  相似文献
4.
We investigated evolutionary relationships among orders in phylum Rotifera and among species in genus Notholca (Rotifera) by computing parsimonious cladograms. All of the most-parsimonious cladograms generated for the ordinal level confirm the view that class Monogononta, superclass Eurotatoria, and phylum Rotifera are monophyletic. Species within the genus Notholca were separated into six groups (clades), but some species have been defined based on highly variable characters not reliably studied using cladistics. Therefore, phenetic studies are warranted, especially for species possessing caudal processes.  相似文献
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6.
Published justifications for weighting characters in parsimony analyses vary tremendously. Some authors argue for weighting a posteriori, some for a priori, and especially those authors that rely on a falsificationist approach to systematics argue for non-weighting. To find a decision, while following the falsificationist approach, one first has to investigate the necessary conditions for the possibility of phylogenetic research to establish an empirical science sensu Popper. A concept of phylogenetic homology together with the criterion of identity is proposed, which refers to the genealogical relations between individual organisms. From this concept a differentiation of the terms character and character state is proposed, defining each character as a single epistemological argument for the reconstruction of a unique transformation event. Synapomorphy is distinguished from homology by referring to the relationship between species instead of individual organisms, thus the set of all synapomorphies constitutes a subset of the set of all homologies. By examining the structure of characteristics during character analysis and hypothesizing specific types of transformations responsible for having caused them, a specific degree of severity is assigned to each identity test. It thus provides a specific degree of corroboration for every hypothesis that successfully passed this test. Since the congruence criterion tests hypotheses of synapomorphy against each other on grounds of their degree of corroboration gained from the identity test, these different degrees of corroboration determine the specific weights given to characters and character state transformations before the cladistic analysis. This provides a reasonable justification for an a priori weighting scheme within a falsificationist approach to phylogeny. It also demonstrates the indispensable necessity of its application.  相似文献
7.
The cephalic and pectoral girdle structures of the erethistid Erethistes pusillus (Erethistinae) are described and compared with those of another species of the subfamily Erethistinae, namely Hara filamentosa , and of the single species of the subfamily Continae, Conta conta , as well as of several other catfishes, as the foundation for a discussion on the synapomorphies and phylogenetic position of the Erethistidae. The observations and comparisons support de Pinna's phylogenetic hypothesis, according to which the Erethistidae is the sister‐group of the Aspredinidae, with the clade formed by these two families being the sister‐group of the Sisoridae sensu stricto . In addition, the observations and comparisons pointed out a new, additional character to diagnose the family Erethistidae, namely: mesocoracoid arch deeply bifurcated dorsally.  相似文献
8.
A statistical test has been developed to ascertain whether a given number of presumptive synapomorphies between one pair of taxa is significantly greater than the number between another pair of taxa. This is shown to be a form of testing the significance of a difference between two proportions. It is necessary first to adjust for common patterns of synapomorphy that raise or lower both numbers. The method has been checked by simulation, and is illustrated by data on the relationships of tetrapods. It proves that Hennigian cladistics has statistical constraints.  相似文献
9.
本文研究了半翅目长蝽科盐长蝽亚科(Henestarinae)的外部形态,希图为长蝽总科复合体的系统发育研究提供资料。材料选用盐长蝽HenestarisoschaniniBergroth1919和卤长蝽EngistussalinusJakovlev1874,分别作为该亚科3个成员属中两个属(即盐长蝽属HenestarisSpinola1839和卤长蝽属EngistusFieber1864)的代表。文章还初步提出了该亚科的一些共有新征,并作了有关讨论,认为此分类单元为一单系群。  相似文献
10.
The phylogenetic relationships among two Paracyprichromis and five Cyprichromis species, included in the Tanganyikan cichlid tribe Cyprichromini, were investigated using morphological features. The previously proposed diagnostic characters of Paracyprichromis are not synapomorphies, because the nonelongated swim bladder is plesiomorphic, the numbers of dorsal and anal fin rays and scales on longitudinal line and around the caudal peduncle overlap with those of Cyprichromis, and these counts and number of vertebrae are all included within the ranges of other Tanganyikan cichlids. The monophyly of Paracyprichromis is supported by a unique condition of infraorbitals to this genus. Additionally, the monophyly of Cyprichromis was reconfirmed by one of the previously proposed diagnostic characters, the presence of an elongated swim bladder.  相似文献
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