A devonian tetrapod from north america

An early tetrapod fossil from the Upper Devonian of Pennsylvania (Catskill Formation) extends the temporal range of tetrapods in North America and suggests that they attained a virtually global equatorial distribution by the end of the Devonian. Derived features of the shoulder girdle indicate that appendicular mechanisms of support and propulsion were well developed even in the earliest phases of tetrapod history. The specialized morphology of the pectoral skeleton implies that the diversity of early tetrapods was great and is suggestive of innovative locomotor patterns in the first tetrapods.     

Ascent of dinosaurs linked to an iridium anomaly at the Triassic-Jurassic boundary

Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years.     

Hind limbs of eocene basilosaurus: evidence of feet in whales

New specimens of middle Eocene Basilosaurus isis from Egypt include the first functional pelvic limb and foot bones known in Cetacea. These are important in corroborating the intermediate evolutionary position of archaeocetes between generalized Paleocene land mammals that used hind limbs in locomotion and Oligocene-to- Recent whales that lack functional pelvic limbs. The foot is paraxonic, consistent with derivation from mesonychid Condylarthra. Hind limbs of Basilosaurus are interpreted as copulatory guides.     

A devonian spinneret: early evidence of spiders and silk use

A nearly complete spider spinneret was found in Middle Devonian rocks (about 385 to 380 million years old) near Gilboa, New York. This is the earliest evidence yet discovered for silk production from opisthosomal spigots, and therefore for spiders. Two previously known Devonian fossils described as spiders lack any apomorphies of the order Araneae and are probably not spiders. The spigots of the Devonian spinneret resemble those of members of the living suborder Mesothelae, but the number of spigots and their distribution are like those of members of the suborder Opisthothelae, infraorder Mygalomorphae. The Devonian spider belonged to a clade that may be the sister group of all other spiders, of Mesothelae, or of Opisthothelae.     

The Ischigualasto Tetrapod Assemblage (Late Triassic, Argentina) and 40Ar/39Ar Dating of Dinosaur Origins

(40)Ar/(39)Ar dating of sanidine from a bentonite interbedded in the Ischigualasto Formation of northwestern Argentina yielded a plateau age of 227.8 +/- 0.3 million years ago. This middle Carnian age is a direct calibration of the Ischigualasto tetrapod assemblage, which includes some of the best known early dinosaurs. This age shifts last appearances of Ischigualasto taxa back into the middle Carnian, diminishing the magnitude of the proposed late Carnian tetrapod extinction event. By 228 million years ago, the major dinosaurian lineages were established, and theropods were already important constituents of the carnivorous tetrapod guild in the Ischigualasto-Villa Unión Basin. Dinosaurs as a whole remained minor components of tetrapod faunas for at least another 10 million years.     

Origin of the Tetrapod Limb

The paired fins of fishes were first used as props and supports for resting on the bottom; these were later used in a clumsy, walking manner, and this behavior perforce began first in the water, because the weak props could not support the animals without the water bouyancy; increased perfection of the mechanics of walking took place in the shallows; which was a refuge from the chief predators; the land was also attractive as a haven and as a source of food; the first vertebrate invaders of land probably had fins, and these became legs by enlargement of the fin base and loss of fin rays; these original limbs and girdles were weak and probably underwent a considerable period of evolution in swampy country; later they were perfected by further selection when it became necessary for early amphibians to move across dry land because of a failing local water supply. This syllogism conforms to the known behavior and capabilities of fishes and amphibians and to the general facts of zoology and paleontology. It suggests that common, continuous activities and stresses-escape from enemies and food getting-led to the origin of the tetrapod limb. This obviates the necessity for explaining how discontinuous and somewhat catastrophic events, such as the drying up of water bodies, could have led to the origin of limbs, which at the very outset had to be fairly strong. The general theory stated here is fairly clearly implied by Berry (8), who said, "Those fishy pioneers with air-bladders -and paired fins-which, after ages of using their fins for pushing and paddling themselves over mud flats, gradually ventured onto drier and drier ground-where they avoided the competition for food-and the dangers of swarming hordes of ganoid pirates of the waters, were the ancestors of the amphibians."     

New early Jurassic tetrapod assemblages constrain Triassic-Jurassic tetrapod extinction event

The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all "typical Triassic" forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.     

Hormones and endocrine glands of fishes. Studies of fish endocrinology reveal major physiologic and evolutionary problems

The structures discussed above illustrate some of the evolutionary knowledge to be obtained from studies of the comparative biology of the endocrine system among the fishes (see also 17, 78). The interrenal (adrenocortical) gland is an example of an endocrine structure which shows great morphologic variation in the vertebrate series, and among the fishes themselves. The structural variability implies little selective value for any particular pattern, and, in fact, biochemically the interrenal tissue would seem to be involved in much the same kind of steroidogenesis in the vertebrates generally. However, the hormone aldosterone may be a tetrapod novelty. The caudal neurosecretory system is a good example of a ubiquitous endocrine apparatus, among at least teleostean and elasmo-branch fishes, for which a function has yet to be elucidated and which continues to challenge the comparative physiologist. This system, along with the Stannius corpuscles, is lacking in the tetrapods. The existence of these structures makes it clear that the endocrine biology of fishes cannot be tacitly summarized as being essentially similar to that of the tetrapods, only less well developed. The prolactin situation illustrates the existence of a gland-the pituitary-present among fishes as among tetrapods, which secretes a product only partly related to the tetrapod hormone and having a very different functional significance. In this case it is clear that "the hormone and the uses to which it is put" have undergone evolutionary change during vertebrate phylogeny.     

Glassy microspherules (microtektites) from an upper devonian limestone

The properties of microspherules recovered from an Upper Devonian marine limestone immediately overlain by a geochemical anomaly of siderophile and chalcophile elements are similar to those of impact-derived microtektites. These microspherules are glass, have splash-form shapes, contain spherical vesicles and lechatelierite inclusions, and show oxide compositional variations similar to those in known microtektites. These characteristics suggest that these Upper Devonian microspherules have an impact origin. A bolide impact may have occurred about 365 million years ago on the South China Plate and caused a faunal extinction on eastern Gondwana.     

Early Forest Soils and Their Role in Devonian Global Change

A paleosol in the Middle Devonian Aztec Siltstone of Victoria Land, Antarctica, is the most ancient known soil of well-drained forest ecosystems. Clay enrichment and chemical weathering of subsurface horizons in this and other Devonian forested paleosols culminate a long-term increase initiated during the Silurian. From Silurian into Devonian time, red clayey calcareous paleosols show a greater volume of roots and a concomitant decline in the density of animal burrows. These trends parallel the decline in atmospheric carbon dioxide determined from isotopic records of pedogenic carbonate in these same paleosols. The drawdown of carbon dioxide began well before the Devonian appearance of coals, large logs, and diverse terrestrial plants and animals, and it did not correlate with temporal variation in volcanic or metamorphic activity. The early Paleozoic greenhouse may have been curbed by the evolution of rhizospheres with an increased ratio of primary to secondary production and by more effective silicate weathering during Silurian time.     

海口市城市森林结构及植物多样性指标相关性分析

选取海口市主建成区随机建立的235个植物样方进行调查,评价其结构特征,分析其植物多样性指数相关性。结果表明:①主建成区常见植物共283种隶属于72科218属,其中,本地种114种,外来种169种;②优势植物主要有椰子Cocos nucifera、印度紫檀Pterocarpus indicus、王棕Roystonea regia、垂叶榕Ficus benjamina等;③树木径级结构呈现"整体偏小"的分布格局,整体立木层次较低,平均树高仅6.8 m;④物种多样性指数与功能多样性指数之间多数存在显著相关（P < 0.05）;⑤谱系多样性指数（PD）与乔木层、草木层中各物种多样性指数多数存在显著相关（P < 0.05）;谱系变异性指数（PSV）与多数物种多样性指数、功能多样性指数均不相关,但谱系均匀度指数（PSE）与多数物种多样性指数、功能多样性指数显著相关（P < 0.05）。为避免物种同质化现象,提倡运用乡土物种进行城市森林建设,同时选择多层次且具有针对性的多样性指数和功能性状参数,以保证对城市森林植物多样性评估的全面性和准确性。     

地下煤火不同燃烧阶段上覆土壤微生物群落功能多样性

[目的]了解不同燃烧阶段地下煤火上覆土壤微生物群落功能多样性.[方法]利用BIOLOG指纹图谱方法,分析新疆吉木萨尔县境内不同燃烧阶段地下煤火风化期、氧化期、自燃期、全面燃烧期、硫磺析出期、芒硝析出期和熄灭期的上覆土壤微生物功能多样性.[结果]地下煤火不同燃烧阶段上覆土壤理化性质差异显著,自燃期硝态氮含量最高,熄灭期有机质含量最低;不同时期微生物群落碳源利用能力及多样性均低于对照;主成分分析表明,土壤微生物在31种碳源构建的二维体系分布差异明显,微生物群落结构在地下煤火发生发展过程中呈现动态变化;相关性分析显示,土壤pH是影响地下煤火上覆土壤微生物群落利用碳源差异的显著因素.[结论]地下煤火降低上覆土壤微生物群落功能多样性,不同燃烧阶段微生物群落功能多样性差异显著,这对地下煤火区生态恢复具有一定参考利用价值.     

Triassic vertebrates of gondwanan aspect from the richmond basin of virginia

A new locality of early Late Triassic age in the Richmond basin of east-central Virginia has yielded abundant remains of a diversified assemblage of small to medium-sized tetrapods that closely resembles Southern Hemisphere (Gondwanan) assemblages in the predominance of certain synapsids. Associated palynomorphs indicate an early middle Carnian age for the fossiliferous strata. The discovery suggests that previously recognized differences between tetrapod assemblages of early Late Triassic age from Gondwana and Laurasia at least in part reflect differences in stratigraphic age, rather than geographic separation.     

Genetic diversity and elite gene introgression reveal the japonica rice breeding in northern China

Abundant genetic diversity and rational population structure of germplasm benefit crop breeding greatly.To investigate genetic variation among geographically diverse set of japonica germplasm,we analyzed 233 japonica rice cultivars collected from Liaoning,Jilin and Heilongjiang provinces of China,which were released from 1970 to 2011 by using 62 simple sequence repeat(SSR) markers and 8 functional gene tags related to yield.A total of 195 alleles(N_a) were detected with an average of 3.61 per locus,indicating a low level of genetic diversity level among all individuals.The genetic diversity of the cultivars from Jilin Province was the highest among the three geographic distribution zones.Moreover,the genetic diversity was increased slightly with the released period of cultivars from 1970 to 2011.The analysis of molecular variance(AMOVA) revealed that genetic differentiation was more diverse within the populations than that among the populations.The neighbor-joining(NJ) tree indicated that cultivar clusters based on geographic distribution represented three independent groups,among which the cluster of cultivars from Heilongjiang is distinctly different to the cluster of cultivars from Liaoning.For the examined functional genes,two or three allelic variations for each were detected,except for IPA1 and GW2,and most of elite genes had been introgressed in modem japonica rice varieties.These results provide a valuable evaluation for genetic backgrounds of current japonica rice and will be used directly for japonica rice breeding in future.     

A giant sauropod dinosaur from an Upper Cretaceous mangrove deposit in Egypt

We describe a giant titanosaurid sauropod dinosaur discovered in coastal deposits in the Upper Cretaceous Bahariya Formation of Egypt, a unit that has produced three Tyrannosaurus-sized theropods and numerous other vertebrate taxa. Paralititan stromeri is the first tetrapod reported from Bahariya since 1935. Its 1.69-meter-long humerus is longer than that of any known Cretaceous sauropod. The autochthonous scavenged skeleton was preserved in mangrove deposits, raising the possibility that titanosaurids and their predators habitually entered such environments.     

黑土区不同林龄落叶松人工林土壤微生物群落功能多样性的对比研究

采用Biolog-ECO微平板检测法,以21、30、40和52年生落叶松人工林土壤为对象,研究了典型黑土区0～20 cm土层范围内土壤微生物群落碳源代谢的多样性变化特征。结果表明:1）在培养168 h时,落叶松人工林地上层（0～10 cm）和下层（10～20 cm）土壤的微生物碳源平均颜色变化率（AWCD）的变化范围分别为0.41～1.40和0.20～0.69,且均随林龄的增加而逐渐增大。2）落叶松人工林微生物群落功能多样性指数随林龄的增加呈逐渐升高的趋势,即52 a40 a30 a21 a,且上层土壤的微生物功能多样性高于下层。上层和下层土壤的丰富度指数、Shannon Weiner多样性指数、Simpson指数和McIntosh指数的变化范围分别为12～25和6～14、2.55～3.12和1.83～2.62、0.89～0.95和0.76～0.91、4.22～9.49和2.52～6.18。3）落叶松人工林土壤微生物群落对6类碳源的利用率均随林龄的增加而增大,且碳水类、多聚物类和胺类是导致上层土壤微生物代谢差异的敏感碳源,碳水类、羧酸类和胺类是导致下层土壤微生物代谢差异的敏感碳源。4）落叶松人工林土壤微生物多样性指标与土壤理化性质相关性极为密切。可以认为,随着林龄的增加,落叶松人工林微生物功能多样性逐渐提高,这为进一步揭示其林地土壤质量的演变提供了参考。      

旅游干扰对青海湖景区沙化草地生物多样性的影响研究

研究青海湖景区旅游干扰下沙化草地群落的植物多样性,利用主要物种重要值、α多样性、功能群重要值和β多样性比较分析不同干扰后群落植物多样性及结构功能的变化。结果表明：随着干扰强度的增加,群落物种组成从以不耐旅游干扰的物种为主逐渐发展到以耐旅游干扰的物种为主,群落的重要值有向少数物种集中的趋势;Pat-rick丰富度指数和Shannon-Wiener指数均随着干扰强度的增加而呈下降趋势,均匀度指数则在中度干扰下最大,生态优势度的变化与α多样性的变化存在一定的负关联;功能群丰富度在中度干扰下最高;中度-重度干扰阶段群落间的物种替代速率最快。青海湖景区沙化草地群落稳定与群落自身的物种多样性、功能群功能特性及结构特点密切相关。     

基于四针状ZnO 纳米结构的高灵敏紫外探测器件

首先采用化学气相沉积法合成出四针状ZnO纳米结构,并通过X射线衍射、扫描电镜、透射电镜等测试手段对其进行了表征和研究.进而采用一种简易的方法制备了ITO/ZnO/ITO结构的紫外探测原型器件,测试了器件的电学特性和紫外响应特性,并讨论了相应的物理机制.研究结果表明:基于四针状纳米ZnO的器件对紫外光(365nm)具有非常灵敏的响应特性,响应度约为0.8A/W,在1V的偏压下器件稳定的光电流与暗电流比高达104～105,光响应度峰值在372nm波长附近.     

Ginkgophyton (Psygmophyllum) with a Stem of Gymnospermic Structure

A specimen identified as Ginkgophyton (Psygmophyllum) with a structurally preserved stem of gymnospermic organization has been collected from a late Devonian stratum in New York.     

That's my hand! Activity in premotor cortex reflects feeling of ownership of a limb

When we look at our hands, we immediately know that they are part of our own body. This feeling of ownership of our limbs is a fundamental aspect of self-consciousness. We have studied the neuronal counterparts of this experience. A perceptual illusion was used to manipulate feelings of ownership of a rubber hand presented in front of healthy subjects while brain activity was measured by functional magnetic resonance imaging. The neural activity in the premotor cortex reflected the feeling of ownership of the hand. This suggests that multisensory integration in the premotor cortex provides a mechanism for bodily self-attribution.