首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
A lower molar of a haramiyoid mammal is described from the Toutunhe Formation of Liuhuanggou near Urumqi in the southern Junggar Basin, Xinjiang, China. It is referred to Eleutherodon sp., otherwise exclusively known from the Upper Bathonian of England. It is the first record of the order Haramiyida from Asia and the first Mesozoic mammal described from the southern Junggar Basin. Apart from the English specimens of Eleutherodon and Staffia from the Upper Jurassic of East Africa, it is the geologically youngest haramiyoid known. It is the first vertebrate taxon from the Toutunhe Formation that is probably not endemic and lends some support to the dating of the Formation as late Middle Jurassic, probably Bathonian.
Michael W. MaischEmail:
  相似文献   

2.
In 2008, a new basal neoceratopsian was discovered in the Tando beds (Albian) of Tando Basin in South Korea. It represents the first ceratopsian dinosaur in the Korean peninsula and is assigned to Koreaceratops hwaseongensis gen. et sp. nov. Autapomorphies of Koreaceratops include very tall neural spines over five times higher than the associated centra in the distal caudals, and a unique astragalus divided into two fossae by a prominent craniocaudal ridge on the proximal surface. A phylogenetic analysis indicates that Koreaceratops is positioned between Archaeoceratops and all more derived neoceratopsians, and the elongation of caudal neural spines was an important derived character in non-ceratopsid neoceratopsians. The very tall caudal neural spines in Koreaceratops, Montanoceratops, Udanoceratops, Protoceratops, and Bagaceratops appear to be homoplasious, suggesting an independent adaptation, possibly for swimming. Skeletal evidence suggests that obligate quadrupedalism occurred gradually in neoceratopsians progressing from bipedal through facultative quadrupedalism, to complete quadrupedalism in Coronosauria.  相似文献   

3.
Sauropoda is one of the most diverse and geographically widespread clades of herbivorous dinosaurs, and until now, their remains have now been recovered from all continental landmasses except Antarctica. We report the first record of a sauropod dinosaur from Antarctica, represented by an incomplete caudal vertebra from the Late Cretaceous of James Ross Island. The size and morphology of the specimen allows its identification as a lithostrotian titanosaur. Our finding indicates that advanced titanosaurs achieved a global distribution at least by the Late Cretaceous.  相似文献   

4.
5.
Described here is a sauropod tooth from the Early Cretaceous of South Korea, similar to Brachiosaurus. The crown of the tooth is beveled off lingually so that when worn it presents a chisel-like edge. This find confirms the presence of a brachiosaurid in East Asia during the Early Cretaceous.  相似文献   

6.
7.
8.
Yearlong hibernation in a marsupial mammal   总被引:1,自引:3,他引:1  
Many mammals hibernate each year for about 6 months in autumn and winter and reproduce during spring and summer when they are generally not in torpor. I tested the hypothesis that the marsupial pygmy-possum (Cercartetus nanus), an opportunistic nonseasonal hibernator with a capacity for substantial fattening, would continue to hibernate well beyond winter. I also quantified how long they were able to hibernate without access to food before their body fat stores were depleted. Pygmy-possums exhibited a prolonged hibernation season lasting on average for 310 days. The longest hibernation season in one individual lasted for 367 days. For much of this time, despite periodic arousals after torpor bouts of ∼12.5 days, energy expenditure was reduced to only ∼2.5% of that predicted for active individuals. These observations represent the first report on body-fat-fuelled hibernation of up to an entire year and provide new evidence that prolonged hibernation is not restricted to placental mammals living in the cold.  相似文献   

9.
10.
11.
12.
A simple method for obtaining prometaphase chromosomes from cultured first trimester cells involves the addition of BrdU and FdU 11 h before harvest and ethidium bromide 1.5 h before harvest. High resolution R-banding is obtained by acridine orange staining.  相似文献   

13.
14.
随着城乡一体化建设的推进,人们搬进了一幢幢楼房,孩子的活动区域小了。为了让孩子能和人们从前一样,尽情地玩,享受童年幸福,健康快乐地成长,根据孩子们的情况确立了以人为本、安全第一、自主锻炼、整合适用的原则,通过巧妙借用民间游戏、灵活渗透乒乓资源、扎实开展课程内容来丰富、夯实幼儿的健康活动内容,帮助孩子树立健康第一的思想,为之后的和谐发展奠定基础。  相似文献   

15.
The available data on the syntheses of critically important precursor molecules for chemical evolution are reviewed and problems of rates of production versus rates of destruction in the primitive ocean are discussed. It is concluded that many global chemical syntheses would have been improbable in the Earth's oceans and that more attention should be paid to specific environments which would have favored such syntheses. The recent discovery of an accelerating effect of formaldehyde on the oligomerization of HCN as well as the eutectic-concentration mechanism are discussed in relation to a new scenario for chemical evolution on the primitive Earth.  相似文献   

16.
17.
18.
Small mammal communities were snaptrapped for six years in agricultural landscapes to establish their relationship to various crop habitats in southern Moravia, Czech Republic. The presence of 14 small mammals was documented; 77% of the community found in crops consisted of three rodents, namely Microtus arvalis, Apodemus microps and A. sylvaticus, whereas in woody habitats, 89% of the community was represented by Clethrionomys glareolus, Apodemus flavicollis and A. sylvaticus. In permanent habitats (windbreaks, small woods and fallow land), the community was more abundant and diversified. Among the crop fields, the lowest abundance was found in cereal fields whereas the lowest diversity was observed in alfalfa. Soil-cultivating practices affected abundances especially in sugar beat and maize. Seasonal variation in numbers was lowest in forest and fallow land. Species richness decreased from spring and summer to autumn and winter in annual crops (cereal, maize, sugar beet and other crops), increased in alfalfa and fallow land, and remained relatively stable in windbreaks and forests. Based on similarity indices, two groups of small mammal communities were identified: one for field crops and another for permanent habitats. The fallow land assemblages in spring and summer were more similar to field crop species assemblages and in autumn and winter to permanent habitats one. Trophic requirements of small mammals and the food supply available in the various habitats are discussed.  相似文献   

19.
Spinosaurids are among the largest and most specialized carnivorous dinosaurs. The morphology of their crocodile-like skull, stomach contents, and oxygen isotopic composition of the bones suggest they had a predominantly piscivorous diet. Even if close relationships between spinosaurids and Middle Jurassic megalosaurs seem well established, very little is known about the transition from a generalized large basal tetanuran to the specialized morphology of spinosaurids. Spinosaurid remains were previously known from the Early to Late Cretaceous of North Africa, Europe, and South America. Here, we report the discovery of a new spinosaurid theropod from the late Early Cretaceous Savannakhet Basin in Laos, which is distinguished by an autapomorphic sinusoidal dorsosacral sail. This new taxon, Ichthyovenator laosensis gen. et sp. nov., includes well-preserved and partially articulated postcranial remains. Although possible spinosaurid teeth have been reported from various Early Cretaceous localities in Asia, the new taxon I. laosensis is the first definite record of Spinosauridae from Asia. Cladistic analysis identifies Ichthyovenator as a member of the sub-clade Baryonychinae and suggests a widespread distribution of this clade at the end of the Early Cretaceous. Chilantaisaurus tashouikensis from the Cretaceous of Inner Mongolia, and an ungual phalanx from the Upper Jurassic of Colorado are also referred to spinosaurids, extending both the stratigraphical and geographical range of this clade.  相似文献   

20.
Little is known about the evolution of large-bodied theropod dinosaurs during the Early to mid Cretaceous in Asia. Prior to this time, Asia was home to an endemic fauna of basal tetanurans, whereas terminal Cretaceous ecosystems were dominated by tyrannosaurids, but the intervening 60 million years left a sparse fossil record. Here, we redescribe the enigmatic large-bodied Chilantaisaurus maortuensis from the Turonian of Inner Mongolia, China. We refer this species to a new genus, Shaochilong, and analyze its systematic affinities. Although Shaochilong has previously been allied with several disparate theropod groups (Megalosauridae, Allosauridae, Tyrannosauroidea, Maniraptora), we find strong support for a derived carcharodontosaurid placement. As such, Shaochilong is the first unequivocal Asian member of Carcharodontosauridae, which was once thought to be restricted to Gondwana. The discovery of an Asian carcharodontosaurid indicates that this clade was cosmopolitan in the Early to mid Cretaceous and that Asian large-bodied theropod faunas were no longer endemic at this time. It may also suggest that the ascent of tyrannosaurids into the large-bodied dinosaurian predator niche was a late event that occurred towards the end of the Cretaceous, between the Turonian and the Campanian. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号