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
ABSTRACT. This paper describes the methodology for a nutrient balance to evaluate the sources and distribution of nutrients in a small river basin. Loadings for total nitrogen and phosphorus are calculated from measured nutrient concentration and river discharge data. Using a special retrieval program and a data storage and processing system, loadings are accumulated over a given time period to allow for time of passage through the basin and seasonal changes in nutrient distribution. Nutrient balances are made with the accumulated loadings to obtain the relative contribution of each nutrient source and the retention of nutrients within the basin through sedimentation and aquatic growth. The methodology has been used to study nutrients in the Qu'Appelle River Basin, Saskatchewan, Canada. 相似文献
The international minerals industry continues to have a substantial investment shortfall. The widening exploration and mineral development gaps, not only in the lesser developed countries but also in the developed nations, are sowing the seeds for future mineral supply disruptions and conflicts. Mutuality of interests demands concerted initiatives, individual as well as collective, to reverse the investment trends established by international mineral finance and the multinational corporations in order to pave the way for secure mineral supplies in the future at acceptable prices. 相似文献
ABSTRACT: At a time in history when water resource development in the United States is being condemned as both economically inefficient and an environmental disaster, perhaps economists need to look back at previous development to see what the fruits of water development (be they sweet or sour) have been. The Boise Project of south-western Idaho is 70 years old and to some people it represents a gross error in resource use, while to others it represents a means of livelihood and well being. A recent research project at the University of Idaho attempted to measure not only the direct economic income benefits of the project (from irrigation), but also the indirect or secondary income benefits (from the food processing industry). Periodic regional input-output tables were constructed to assess the income generated from irrigation and food processing over the period from 1946 to 1970. Input-output analysis allowed researchers to evaluate the direct and indirect impacts of both the irrigation sector and the food processing sector and to compare their growth over time. 相似文献
ABSTRACT: Hierarchical diversity analysis of data on fish and aquatic insects showed that the component of diversity contributed by the species level was generally very small compared with the component at the generic level or with the total diversity. Very high rank correlations between generic diversity, in which genera were discriminated but not identified, and species diversity suggested that the purposes of environmental monitoring might best be served by working at the generic level rather than the species level. This is particularly true when an index of diversity is to be used as the major comparative and communicative tool. The savings of time and money could be appreciable. 相似文献
Movement of nutrients from livestock manure handling sites has the potential to negatively impact the environment. This study was conducted using electromagnetic induction (EMI) measurements to develop apparent soil electrical conductivity (EC(a)) maps to identify regions of nutrient buildup beneath an abandoned compost site. A trailer-mounted EM-38 coupled with a global positioning satellite system was towed across an area used for composting of feedlot manure. The resulting EC(a) maps were compared with known locations of compost rows confirming the alignment of row locations with high EC(a) regions. The identified rows were cored and compared with the region between the rows. The identified rows with a compost history demonstrated significant (P < 0.05) increases in soluble salts (1.6 times greater), NO3 (6.0 times greater), and Cl (2.0 times greater) compared with the area between the rows at a 1.5-m depth. Image processing techniques were used to display yearly changes that were associated with nutrient movement and transformations in the soil beneath the site. Correlations between EMI measurements and soil core analyses for NO3-N, Cl, and EC provided ancillary support for the EMI methods. The use of EMI for mapping of sites having a history of livestock waste application was effective in delineating high nutrient buildup areas and for observing spatial EC(a) changes over time. 相似文献
Organochlorines, metals, and trace elements were measured in liver, kidney, or whole-body tissues of canvasbacks (Aythya valisineria), lesser scaups (A. affinis), and greater scaups (A. marila) collected from San Francisco Bay and three coastal areas of California during the winter of 1986–1987. Potentially toxic concentrations of mercury (mean 10.4 µg/g, dry weight) and selenium (mean 32.7 µg/g, dry weight) were found in livers of scaups and canvasbacks from several San Francisco Bay sites. These elements varied spatially, temporally, and between species, with the highest concentrations found in late winter. Mean concentrations of mercury, selenium, and cadmium were generally higher in scaups than in canvasbacks. Of all the organochlorines included in the analyses, only p,p'-DDE and total PCBs were detected in all samples in this study. Mean whole-body concentrations of DDE and PCBs from San Francisco Bay ducks collected in late winter varied spatially and between species, but the concentrations were not considered toxic. Causes for inter-specific differences are unclear, but may be attributable to differences in diet, movement, or physiology. 相似文献
ABSTRACT: Economic models sometimes indicate that irrigation water is misallocated in agriculture, especially when it appears that the marginal value product is higher in other uses (such as for hydro-power). Historically, trends tend to contradict this reasoning, however, especially since irrigation has grown from 20 million acres in 1940 to over 50 million acres in 1980. Results of this study tend to indicate that as agriculture becomes more and more intensive (in terms of inputs), irrigation is part of that long term trend. Further, major economic variables, such as output and investments in agriculture, appear to be more highly correlated with irrigated land than with dryland agriculture. Recent data indicate an upper limit of about 320 million acres for dryland farming in the United States, while no such constraint is apparent for irrigated agriculture. 相似文献