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751.
The origin and early evolution of birds: discoveries,disputes, and perspectives from fossil evidence 总被引:1,自引:0,他引:1
Zhou Z 《Die Naturwissenschaften》2004,91(10):455-471
The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries. 相似文献
752.
The recently reported Jeholornis represents the only known bird with a complete long skeletal tail except for Archaeopteryx. Two newly discovered specimens referable to Jeholornis provide some important new information about its anatomy. The tail of Jeholornis is much longer than that of Archaeopteryx and comprises a maximum of 27 caudal vertebrae compared with only 23 in Archaeopteryx. More interestingly, the tail feathers are shaped more like those of dromaeosaurs than those of Archaeopteryx. We conclude that the common ancestor of birds must have a more primitive tail than that in Archaeopteryx, confirming the side branch position of Archaeopteryx in the early avian evolution. The synsacrum is composed of six sacrals, representing a transitional stage between Archaeopteryx and more advanced birds. The scapula of Jeholornis has a dorso-laterally exposed glenoid facet, and the coracoid has a supracoracoid foramen. The presence of a pair of fenestrae
in the sternum of Jeholornis has further implications for the air-sac system in early birds.
Electronic Supplementary Material The online version of this article (doi: contains supplementary material, which is available to authorized users. 相似文献
753.
Apesteguía S 《Die Naturwissenschaften》2004,91(10):493-497
Ornithischian and theropod dinosaurs were morphologically diverse during the Cretaceous. In contrast, sauropods were relatively more conservative. The anatomy of Bonitasaura salgadoi, a new 9-m titanosaurian sauropod from Upper Cretaceous beds of Patagonia, suggests that sauropod anatomical diversity would have included unexpected items. Its unusual, rectangular lower jaw possesses narrow, anteriorly restricted teeth and shows evidence of a sharp keratinous sheath over the non-dentigerous region that probably worked to guillotine plant material. This discovery definitely demonstrates that titanosaurs acquired a mandibular configuration similar to that of some basal diplodocoids, as had already been suggested by the lower jaw of the controversial genus Antarctosaurus. This oral configuration, plus the beak-like structure and the skull shape, resemble some traits more commonly seen in Laurasian ornithischians, mostly unexpressed in southern continents. A high sauropod morphological diversity seems to be in agreement with the poorly represented ornithischian clades of the southern hemisphere.Communicated by G. Mayr 相似文献
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Animals assess the fighting ability of conspecifics either by engaging in aggressive interactions or observing contests between others. However, whether individuals assess physical prowess outside the context of aggressive interactions remains unknown. We examined whether male green swordtails (Xiphophorus helleri) extract information about the fighting ability of solitary individuals via observation and whether acquiring such information elicits behavioral modifications. Contests preceded by mutual visual assessment were significantly shorter than fights where only one or neither of the two individuals was informed in advance. Focal animals initiated aggressive behavior more often against larger opponents only after previewing their adversary, indicating that swordtails can extract information about relative body size from watching solitary conspecifics. When a fighting disadvantage is perceived, observers adopt tactics that increase their probability of winning the contest. 相似文献
756.
Unai?IriarteEmail author Jon?I?aki?álvarez-Uriarte Rubén?López-Fonseca Juan?Ramón?González-Velasco 《Environmental Chemistry Letters》2003,1(1):57-61
The relatively recent discovery of disinfection by-products has driven the main regulatory organisms to set maximum contaminant
levels for certain substances in drinking water. Trihalomethanes can be deemed as the most important group of by-products
in chlorinated surface waters. The present work has focused on trihalomethane formation in a full-scale water treatment plant.
We studied the effect of several factors, including ozonation, on trihalomethane levels in chlorinated treated water. The
treatment scheme also includes an ozonation step.
Electronic Publication 相似文献
757.
Jeroen van der Heijden James Patterson Sirkku Juhola Marc Wolfram 《Journal of Environmental Planning and Management》2019,62(3):365-373
This special issue contributes to scholarly debates about the role of cities in global climate governance, reflecting on the promise, limits, and politics of cities as agents of change. It takes an empirically-informed approach drawing on multiple diverse geographical and political contexts. Overall, the special issue aims to stimulate reflection and debate about where understanding and practice needs improvement to advance the role of cities in global climate governance. Key questions that are addressed in the special issue include: To what extent do real world experiences confirm or disconfirm the high expectations of cities as agents and sites of change in addressing global climate change as expressed in urban climate governance literature? In what ways do internal political dynamics of cities enable or constrain urban climate governance? How is climate governance in cities enabled and constrained by interactions with broader governance levels? In what ways can climate governance in cities be advanced through critical attention to the previous issues? 相似文献
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