Ontogenetic variation is documented within many dinosaur species, but extreme ontogenetic changes are rare among dinosaurs, particularly among theropods. Here, we analyze 19 specimens of the Jurassic ceratosaurian theropod Limusaurus inextricabilis, representing six ontogenetic stages based on body size and histological data. Among 78 ontogenetic changes we identify in these specimens, the most unexpected one is the change from fully toothed jaws in the hatchling and juvenile individuals to a completely toothless beaked jaw in the more mature individuals, representing the first fossil record of ontogenetic edentulism among the jawed vertebrates. Jaw morphological data, including those derived from Mi-CT and SR-μCT scanning of Limusaurus specimens, reveal dental alveolar vestiges and indicate that ontogenetic tooth loss in Limusaurus is a gradual, complex process. Our discovery has significant implications for understanding the evolution of the beak, an important feeding structure present in several tetrapod clades, including modern birds. This radical morphological change suggests a dietary shift, probably from omnivory for juvenile Limusaurus to herbivory for adult Limusaurus, which is also supported by additional evidence from gastroliths and stable isotopes. Incorporating new ontogenetic information from Limusaurus into phylogenetic analyses demonstrates surprisingly little effect on its placement when data from different stages are used exclusively, in contrast to previous analyses of tyrannosaurids, but produces subtle differences extending beyond the placement of Limusaurus.
Canine influenza virus (CIV) is an emerging pathogen that causes severe and acute respiratory disease in dogs. In 2006, the H3N2 canine influenza virus was first identified in dogs from Guangdong province in China. Up to now, nine CIVs have been isolated from different populations in Guangdong. The nine isolates were grouped together with the canine H3N2 viruses isolated from dogs and felines in Korea, when the eight phylogenetic trees constructed were compared. These findings emphasize the importance of CIV surveillance in this region for understanding the genesis of this virus, and it is important to remain aware of the potential of H3N2 CIV to be transmitted from dogs to the human population.
As a strong tool for the study of nanoscience, the synchrotron hard X‐ray nanoprobe technique enables researchers to investigate complex samples with many advantages, such as in situ setup, high sensitivity and the integration of various experimental methods. In recent years, an important goal has been to push the focusing spot size to the diffraction limit of ∼10 nm. The multilayer‐based Kirkpatrick–Baez (KB) mirror system is one of the most important methods used to achieve this goal. This method was chosen by the nanoprobe beamline of the Phase‐II project at the Shanghai Synchrotron Radiation Facility. To overcome the limitations of current polishing technologies, the use of an additional phase compensator was necessary to decrease the wavefront distortions. In this experiment, a prototype phase compensator has been created to show how to obtain precise wavefront compensation. With the use of finite‐element analysis and Fizeau interferometer measurements, some important factors such as the piezoresponse, different actuator distributions, stability and hysteresis were investigated. A global optimization method based on the measured piezoresponse has also been developed. This method overcame the limitations of the previous local algorithm related to the adjustment of every single actuator for compact piezoelectric layouts. The mirror figure can approach a target figure after several iterations. The figure difference can be reduced to several nanometres, which is far better than the mirror figure errors. The prototype was also used to successfully compensate for the real wavefront errors from upstream and for its own figure errors, measured using the speckle scanning technique. The residual figure error was reduced to a root‐mean‐square value of 0.7 nm.
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