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1.
辽宁西部早白垩世义县组一新驰龙类   总被引:2,自引:0,他引:2  
我国辽西早白垩世义县组底部陆家屯层近年来产出大量恐龙和其他脊椎动物化石 ,其中包括兽脚类恐龙当中的伤齿龙类和窃蛋龙类 (Xu ,2 0 0 2 )。本文报道该层位产出的一件驰龙类化石标本。通过对比研究 ,我们确认这一标本不同于热河群已知的其他 3种驰龙类 ,并建立了驰龙类的一个新属种 :陆家屯纤细盗龙 (Graciliraptorlujiatunensisgen .etsp .nov .)。驰龙类最初发现于北美晚白垩世地层中 (MatthewandBrown ,1 92 2 ) ,随后在蒙古晚白垩世地层中也有发现 (Osborn ,1 92 4 ) ;现在已知驰龙类的化石记录主要集中在北美和中亚地区的白垩纪地层中 (Xu ,2 0 0 2 )。千禧中国鸟龙 (Sinornithosaurusmillenii)曾代表最早的确定无疑的驰龙属种 (Xuetal.,1 999) ,其生存时代大约为 1 2 5Ma (Swisheretal.,1 999)。陆家屯纤细盗龙正型标本产于义县组底部陆家屯层 ,其上覆和下伏岩层的同位素年代分别为 1 2 8Ma和 1 39Ma (Swisheretal.,2 0 0 1 )。因此 ,陆家屯纤细盗龙代表已知最早的驰龙属种。陆家屯纤细盗龙和其他驰龙类共享以下近裔特征 :尾椎前关节突和脉弧极度加长、上颌齿后缘锯齿明显大于前缘锯齿和指节III- 2明显缩短。陆家屯纤细盗龙的以下近裔特征区别于其他驰龙类 :中部尾椎有一板状结构连接左右后关节  相似文献   

2.
Theropod teeth from the Bajo Barreal Formation (Upper Cretaceous: Cenomanian-Turonian) at the “estancia Ocho Hermanos”, Chubut Province are described. Most of them show features of Abelisauroidea, a clade already represented in the Bajo Barreal Formation by Xenotarsosaurus bonapartei and other isolated remains including a left maxilla. Dromaeosauridae and Carcharodontosauridae represent the first record of these taxa for the Bajo Barreal Formation. Besides this, at least three theropod clades (Abelisauroidea, Carcharodontosauridae, and Dromaeosauridae) coexisted in central Patagonia during the Cenomanian-Turonian along with other theropods as Aniksosaurus darwini and Megaraptor sp.  相似文献   

3.
Abstract: Isolated pterosaur and dinosaur teeth and a sauropod metatarsal I and manual phalanx V-1 from the Middle Jurassic (Callovian) Balabansai Svita in the northern Fergana Valley, Kyrgyzstan, are described and attributed to the pterosaur taxon Rhamphorhynchinae indet., a theropod Tetanurae indet., a sauropod Neosauropoda indet., and a new pachycephalosaurid Ferganocephale adenticulatum gen. et sp. nov. The Balabansai theropod is possibly a stem-lineage representative of Dromaeosauridae. The new pachycephalosaurid is the oldest representative of the group and extends its known history by 10–20 myr. The Balabansai vertebrate assemblage is most similar to the Callovian assemblages from the Qigu and Upper Shaximiao formations in China, and intermediate in the evolutionary level of the taxa present between the Bathonian assemblages from Wucaiwan and the Lower Shaximiao formations (China) and the Late Jurassic Shar Teg fauna from Mongolia.  相似文献   

4.
The dinosaur fauna of the palynologically dated lower Berriasian Skyttegård Member of the Rabekke Formation on the Baltic island of Bornholm, Denmark, is represented by isolated tooth crowns. The assemblage is restricted to small maniraptoran theropods, assigned to the Dromaeosauridae incertae sedis and Maniraptora incertae sedis. The dromaeosaurid teeth are characterized by their labiolingually compressed and distally curved crowns that are each equipped with a lingually flexed mesial carina and a distinctly denticulated distal cutting edge. A morphologically aberrant tooth crown (referred to as Maniraptora incertae sedis) has triangular denticles of uneven width, a feature occasionally found in Upper Cretaceous hesperornithiform toothed diving birds, but also in premaxillary teeth of the velociraptorine Nuthetes from the Lower Cretaceous of England.  相似文献   

5.
Accounts are given of the structure and some aspects of the biology of three commensal crustaceans from Singapore. One of these represents a new genus of prawns of the subfamily Pontoniinae; the others are little known members of the family Porcellanidae.
It is suggested that the apparent rarity of these and other tropical commensal decapods is probably a spurious phenomenon resulting from inadequate collecting methods.
The functional taxonomy of these commensals is discussed and it is suggested that many of their structural peculiarities can be interpreted as adaptations to their mode of life.  相似文献   

6.
Some isolated teeth of theropod and sauropod dinosaurs from the Cenomanian (Late Cretaceous) of Charentes are described. Two new teeth of Troodontidae confirm the presence of this theropod family, previously based on a single specimen. New dental morphotypes are recognized within Dromaeosauridae and Brachiosauridae in comparison with those already known from Charentes. Lastly, a very small tooth is tentatively assigned to an embryonic or neonatal sauropod. The palaeobiogeographical history of European hadrosauroids is briefly discussed. This history was probably more complex than it appears, involving exchanges with both North America and Asia as early as the mid-Cretaceous (Albian–Cenomanian).  相似文献   

7.
Most non-avian theropod dinosaurs are characterized by fearsome serrated teeth and sharp recurved claws. Interpretation of theropod predatory ecology is typically based on functional morphological analysis of these and other physical features. The notorious hypertrophied 'killing claw' on pedal digit (D) II of the maniraptoran theropod Deinonychus (Paraves: Dromaeosauridae) is hypothesized to have been a predatory adaptation for slashing or climbing, leading to the suggestion that Deinonychus and other dromaeosaurids were cursorial predators specialized for actively attacking and killing prey several times larger than themselves. However, this hypothesis is problematic as extant animals that possess similarly hypertrophied claws do not use them to slash or climb up prey. Here we offer an alternative interpretation: that the hypertrophied D-II claw of dromaeosaurids was functionally analogous to the enlarged talon also found on D-II of extant Accipitridae (hawks and eagles; one family of the birds commonly known as "raptors"). Here, the talon is used to maintain grip on prey of subequal body size to the predator, while the victim is pinned down by the body weight of the raptor and dismembered by the beak. The foot of Deinonychus exhibits morphology consistent with a grasping function, supportive of the prey immobilisation behavior model. Opposite morphological trends within Deinonychosauria (Dromaeosauridae + Troodontidae) are indicative of ecological separation. Placed in context of avian evolution, the grasping foot of Deinonychus and other terrestrial predatory paravians is hypothesized to have been an exaptation for the grasping foot of arboreal perching birds. Here we also describe "stability flapping", a novel behaviour executed for positioning and stability during the initial stages of prey immobilisation, which may have been pivotal to the evolution of the flapping stroke. These findings overhaul our perception of predatory dinosaurs and highlight the role of exaptation in the evolution of novel structures and behaviours.  相似文献   

8.
9.
《Journal of Zoology》1968,154(1):1-8
The external structure of the cleaning organ or brush situated on the tarsus of the pedipalp in the Amblypygi has been examined in the following six species from tropical and southern Africa: Damon variegatus (Perty) Damon medius (Herbst), Titanodamon johnstoni Pocock, Phrynichus scullyi Purcell, Phrynichus bacillifer (Gerst.) and Hemiphrynus machadoi Fage.
In all except one of these species the organ consists of two approximately parallel rows of modified setae; in Hemiphrynus machadoi there is only one. When both rows are present the constituent setae of each are quite different in appearance and structure.
It is probable that the variations in number, size and shape of the setae in these forms furnish specific characters; further indirect support for this is afforded by the marked difference in the structure of the organ in Hemiphrynus as compared with the other five species; taxonomically Hemiphrynus belongs to the subfamily Tarantulinae while all the others are accommodated in the Phrynicinae or Damoninae.
A brush-like cleaning organ of some kind is found on the pedipalp-tarsus of both old and new world Amblypygi and most probably in all members of the order.  相似文献   

10.
This investigation has as its object the elucidation of the mode of action of dithiocarbamic acid derivatives as fungicides, with die help of the theory of variability, heavy metal salts being dealt with separately.
The experiments were carried out using Macrospcrium sarcinaeforme as the test organism; the chemical materials used are listed.
Deviations from the experimental and mathematical techniques described in previous papers of this series are explained.
From the results it is inferred that: ( a ) dithiocarbamates are decomposed by the spores to a greater or lesser degree into amine and carbon disulphide, both being toxic; ( b ) the amines can be absorbed only in a combined form, which may be the dithiccarbamate itself but is more probably a derivative, possibly an ester; ( c ) the carbon disulphide probably acts through the mediation of a thiocarbonate; ( d ) thiuramsulphides act through being decomposed to dithiocarbamates (or their derivatives mentioned above). The monosulphides are largely, and the disulphides slightly, decomposed; in the latter case with reduction.
It is suggested that the greater toxicity of the methyl-derivatives over all others tested is due to the shortness of the hydrocarbon chain.
It is concluded that the role of the carbon disulphide is chiefly that of a chemical carrier of the amino group, but that, owing to the negative index of variation of the spores to the latter, the carbon disulphide must play an essential part in completing the toxicity.
It is suggested that heavy-metal dimemyldithiocarbamates may show promise against M. sarcinaeforme, but that others may be effective against other fungi.  相似文献   

11.
Abstract— An exhaustive parsimony analysis of amniote phylogeny using 97 characters has substantiated the hypothesis that mammals and birds are sister groups. This deduction is further supported by parasitological and molecular evidence.
The presumed importance of "synapsid" fossils in amniote phylogeny is questioned and it is concluded that they represent a transformation series which when broken down into constit uent, monophyletic groups does not support the separation of the Mammalia from the remainder of the amniotes.
Fossil members of the Haematothermia include pterosaurs and "dinosaurs" (both stem-group birds) and Dinocephalia, Dicynodontia, Gorgonopsida and Therocephalia (all stem-group mammals). The Dromaeosauridae are the most crownward stem-group birds and the Morganucodontidae the most crownward stem-group mammals.
"Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problem which we are trying to solve." (K. R. Popper, 1972)  相似文献   

12.
The phylogeny of the Rosaceae   总被引:1,自引:0,他引:1  
KALKMAN, C., 1988. The phylogemy of the Rosaceae. A phylogenetic (cladistic) analysis of Rosaceae (excluding Chrysobalanaceae and Neuradaceae) is presented, based on the postulated direction of evolution in 14 morphological characters. Tribes or smaller groups, considered to be holophyletic, are taken as operational units. Three possible cladograms, made by hand, are presented and discussed. One of them is, within the limits of the method, selected as the most plausible image of real history, but this cladogram is not fully resolved and contains much homoplasy. Also presented is a fourth cladogram, produced by computer (CAFCA program); it is of about the same quality.
It is not justified to base drastic alterations in current classification on the weak phylogenetic hypothesis. For the time being it seems better not to recognize any subfamilies, but only a number of tribes.
It is hypothesized that the family originated in West Gondwana. A diagram is presented in which the most plausible cladogram is combined with the present distribution, clarifying the postulated routes of migration.
The sistergroup of Rosaceae is far from evident. The Cunoniaceae are considered to be the most plausible choice.  相似文献   

13.
The ecology and distribution of papyrus swamps are briefly reviewed together with the ecology, distribution structure and growth characteristics of Cyperus papyrus.
Three age-classes of culm are recognized and girth and density of each are recorded along transects through mree swamps in the Upemba Basin of Zaïre. A regression of culm-unit biomass on culm girth, developed for Ugandan swamps, is used to convert Upemba measurements into biomasses. It is shown that simple measurements, taken at only a single point in time, yield much information on both the structure and the dynamics of papyrus populations.
It is suggested that the standing-crops of such populations are determined by available light, and by local temperature regimes, and are therefore constant, irrespective of site quality (nutrient status), for any particular climatic zone. Culm-duration (life-time) is not significantly influenced by climate and the ratio culms/rhizomes provides a useful indicator of comparative productivity. Unlike community biomass, productivity can be limited by site quality.  相似文献   

14.
By means of the analysis of probabilistic ethological structures of the intraspecies rats behaviour in the test "stranger-resident" and by the method of isolated destruction of the frontal cortex or the left and right hemispheres,--it is established that the frontal cortex of the left hemisphere regulates the intraspecies sociability and keeps it on a certain level, because the change (increase) of the intraspecies sociability is observed only at the unilateral destruction of the left frontal cortex. Isolation from the relatives in early ontogenesis leads to the loss of regulating influence of the left frontal cortex on the intraspecies sociability. In isolated animals the frontal cortex of the left hemisphere regulates the level and probability of the appearance of aggression. The right hemisphere ensures the adequate inclusion of the aggression in the probabilistic ethological structure of the total intraspecies behaviour; at its damage the forms appear of an adequate pathological aggression, and connection is lost between the elements of aggressive behaviour and the acts of intraspecies sociability.  相似文献   

15.
The basicranial region is examined in detail in didelphids, dasyurids, thylacinids, borhyaenids, myrmecobiids, and comparisons are made with notoryctids and peramelids. Three dasyurid genera ( Sminthopsis, Antechinus and Planigale ) were doubly injected with latex and basicranial foramina identified partly on the basis of the vessels which they transmit. The resulting terminology differs in several significant ways from terminologies currently in use. A basic terminology for sinuses, recesses, foramina and other structures in the basicranial region is developed from this new information combined with existing systems used for eutherian mammals and mammal-like reptiles.
It is concluded that on the basis of basicranial structure didelphids are structurally ancestral to all other marsupicarnivores, directly or indirectly. They are directly ancestral to thylacinids, borhyaenids, dasyurids and peramelids. Myrmecobiids are structural descendents of dasyurids. Notoryctids are not marsupicarnivores and may be diprotodonts. No special relationships exist between thylacinids and dasyurids or between dasyurids and peramelids. All groups except didelphids show unique specializations in some members and several show evidence of convergence in sinus development and structure of the foramen ovale.  相似文献   

16.
The toxicity as contact insecticides of the esters of (±)-3-methyl-2-allyl-cycfopent-3-en-4-ol-i-one with the natural (+ )-trans and with synthetic (±) -cis-trans-chrysaii- themum monocarboxylic acids has been compared with that of the natural pyrethrins. The comparison was carried out on five species of test-insects.
It was found that the figure for both the absolute and the relative toxicities of these compounds varied with the species used as test-subject.
The factors involved in this variation are discussed. The extremes of variation of relative toxicity for the compounds with the natural acid were from about one-eighth as toxic as the pyrethrum standard when the aphid Macrosiphum solanifolii was used as test subject to nearly four times as toxic as the standard with the larvae of the moth Plutella maculipennis. The fully synthetic material varied from about one-sixteenth as toxic as the standard to Macrosiphum solanifolii to nearly twice as toxic to the larvae of Plutella maculipennis. The compound with the natural acid was approximately twice as toxic as the fully synthetic material to three of the insect species, but the fully synthetic material was considerably more than half as toxic as the partially synthetic to the fourth test-species. It is pointed out that while it is widely recognized that large differences in relative toxicity may occur when the effect of chemicals of widely different structure and mechanism of action are compared on a number of different test-species, the fact that these differences may also occur with related chemicals with, presumably, a similar mechanism of action, has not been clearly stated.
Even when the differences in relative toxicity are taken into account, the two synthetic pyrethrin-like esters still show high insecticidal activity.
It seems reasonable to suppose from the results that economic commercial synthesis of pyrethrin-like insecticides is not impossible.  相似文献   

17.
A quantitative assessment of the frontal bone morphology of a sample of Middle Pleistocene hominins was undertaken in order to address questions regarding their population structure and evolutionary history. Outline tracings of the frontal bones of forty-seven fossil crania were obtained, and size-standardized measurements were then computed using an Elliptical Fourier analysis of these tracings. Principal component scores of the Fourier harmonic amplitudes were derived and served as a quantitative representation of the morphology of the frontal bone. Morphological, geographical, and temporal distance matrices were then constructed between each pair of fossils. A partial Mantel matrix correlation test was performed between morphological and geographical distance matrices, controlling for temporal distance, in order to determine if the pattern of geographical differentiation in features of the frontal bone of mid-Pleistocene Homo followed that of an isolation-by-distance model of population structure. The results of the partial Mantel tests indicate that the overall patterning of differentiation in the features of the frontal bone cannot best be explained by a population structure shaped by isolation-by-distance. Additionally, various aspects of the frontal bone quantified here follow different patterns of geographical differentiation, suggesting that a mosaic pattern of evolution holds true for characters within one cranial region and not just for those between regions.  相似文献   

18.
Park, T.-Y. & Choi, D.K. 2010: Two middle Cambrian diceratocephalid trilobites, Cyclolorenzella convexa and Diceratocephalus cornutus , from Korea: development and functional morphology. Lethaia , Vol. 43, pp. 73–87.
Silicified sclerites of the latest middle Cambrian trilobites, Cyclolorenzella convexa and Diceratocephalus cornutus , have been recovered from the Sesong Formation, Korea. Their morphological similarity and stratigraphic occurrences suggest that D. cornutus is a descendant of C. convexa . The ontogenies of both trilobites demonstrate that a pair of long frontal horns in the cephalon of D. cornutus is an evolutionarily novel structure. It is inferred that redeployment of some pre-existing regulatory gene played a significant role in constructing the frontal horns of D. cornutus . The frontal horns may have been a defensive structure to deter predators. The facial suture of D. cornutus , which extends onto the frontal horns and splits them into the dorsal and ventral halves, was a solution to enable easier forward egression during ecdysis. □ Functional morphology, Korea, Middle Cambrian, ontogeny, trilobites .  相似文献   

19.
Aim To evaluate the relationship between marine fronts and (1) fish diversity patterns, (2) fish biomass distribution, and (3) fish assemblage structure. Location Patagonian Shelf, Southwestern Atlantic Ocean. Methods Three main frontal systems and eight nearby zones (frontal vs. non‐frontal areas) were compared. An extensive fishery database, obtained during an a priori sampling scheme (spatial resolution 1 × 1) from 1978 to 1979, was employed. Analyses of 248 trawling stations were performed using a combination of diversity measures (species richness, Shannon diversity and evenness), biomass analyses and multivariate analyses [nonparametric analysis of similarity (ANOSIM), non‐metric multidimensional scaling ordination (NMDS) and similarity percentages (SIMPER)] to evaluate the effect of fronts on fish communities. Results In total, 46 fish taxa were identified. Demersal fish diversity increased at the tidal front of Península Valdés but decreased in the frontal zones of the Southern Shelf‐Break and Magellan frontal systems. The richness and biomass of pelagic fish were higher at the Península Valdés Tidal Front, while the biomass of demersal fish was higher at its non‐frontal counterpart. Fish diversity did not differ consistently along the Northern Shelf‐Break Front. However, a higher fish biomass was registered at the non‐frontal zone. Demersal and pelagic fish assemblages differed between frontal and non‐frontal zones. Main conclusions The Patagonian Shelf Large Marine Ecosystem has diverse frontal types that appear to have different effects on fish diversity and assemblage structure. Seasonal (tidal) or permanent fronts have different effects on the parameters analysed, which could be due to productivity–diversity relationships. The Península Valdés Tidal Front, a relatively short temporal scale system, demonstrates a stronger influence on fish diversity, biomass and assemblage structure than the other frontal areas studied. The seasonality of nutrient input owing to frontogenesis, which begins during the austral spring, may play an important role in determining local diversity. At permanent frontal features, diversity decreases when the nutrient availability is high. This is potentially because, when food resources increase, a few species become dominant.  相似文献   

20.
The pangolin scale is a horny derivative of the epidermis. It is complex in structure and is divisible into three distinct regions. The dorsal plate forms approximately one-sixth of the scale thickness. It is composed of flattened solid keratinized cells without basophilic nuclear remnants. This region tends to fray easily. The dorsal plate contains bound phospholipids and sulphydryl groups but is weak in disulphide bonds.
The bulk of the scale is made up of the intermediate plate formed of less flattened cells without basophilic nuclei. This region is rich in disulphide bonds but contains no appreciable bound phospholipids or sulphydryl groups.
The ventral plate is only a few cells thick and is rich in bound phospholipids, which also occur in the underlying scale bed epidermis.
These three regions of the scale are formed from separate epidermal germinal areas which do not develop a granular layer. Keratohyalin granules are, however, formed in the epidermis between the scales.
It is suggested on the basis of histological structure and dishribution of chemical constituents that pangolin scales are probably homologous with primate nails.
Evidence against the views that they are homologous with reptilian scales or are derived from compressed hairs is presented.  相似文献   

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