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The spread of marine anoxia is believed to have played a key role in the development of the SPICE (Steptoean Positive Carbon Isotope Excursion) event and the end-Marjuman extinction in the late Cambrian (∼497.5 m.y. ago), but their cause-and-effect relationship is poorly constrained. Here we present an integrated analysis of carbonate δ13C, cerium anomalies (Ce/Ce*), and genus-level diversity data of trilobites from the North China Platform. Our results show tightly coupled changes between the SPICE, an increase in Ce/Ce*, and a trilobite turnover event, which we interpret as indicating enhanced productivity and organic remineralization, leading to the development of low-oxygen conditions in shallowwater settings. This study therefore establishes a direct link between local ecological stress and trilobite turnover during the global SPICE event. Furthermore, the presence of low-oxygen rather than fully anoxic conditions during the peak of the SPICE event could explain the nature of the end-Marjuman crisis, which was characterized by the replacement of shallowwater fauna by deeper-water counterparts that were potentially more tolerant of hypoxia. [ABSTRACT FROM AUTHOR]

Trilobites achieved their maximum generic diversity in the Cambrian, but the peak of morphological disparity of their cranidia occurred in the Middle to Late Ordovician. Early to middle Cambrian trilobites with a specialized cephalon are rare, especially among the ptychoparioids, a group of libristomates featuring the so-called "generalized" bauplan. Here we describe an unusual ptychopariid trilobite Phantaspis auritus gen. et sp. nov. from the middle Cambrian (Miaolingian, Wuliuan) Mantou Formation in the Shandong Province, North China. This new taxon is characterized by a cephalon with an extended anterior area of double-lobate shape resembling a pair of rabbit ears in later ontogenetic stages; a unique type of cephalic specialization that has not been reported from other trilobites. Such a peculiar cephalon as in Phantaspis provides new insights into the variations of cephalic morphology in middle Cambrian trilobites, and may represent a heuristic example of ecological specialization to predation or an improved discoidal enrollment. [ABSTRACT FROM AUTHOR]

The preservation of digestive structures of trilobites is not unique but recognition and reporting about these remains are rare. Here we describe a specimen of Lioparia bassleri Resser & Endo, 1937, recently collected from the Weifang Biota in the Manto Formation (Cambrian, Miaolingian, Shandong, North China). This exceptionally preserved specimen displays the remains of the digestive system in the cephalon as well as in thoracic and pygidial parts of the body. The morphology of the remains of soft parts preserved in the specimen agrees with a simple digestive tract which included a simple gut tube in the thorax and pygidium associated with four pairs of cephalic gut diverticulae in the glabella. The morphology of the digestive tract of L. bassleri compares favourably with earlier observations on trilobites that had gut diverticulae. The preservation of the digestive system in the studied trilobite confirms that the depositional environment of the Manto Formation was favourable to soft-tissue preservation. Earlier papers on trilobites with preserved soft parts from China are summarized. Exceptional preservation of sponges, palaeoscolecids, radiodonts, bivalved arthropods, trilobites, and echinoderms in the Manto Formation is briefly discussed. [ABSTRACT FROM AUTHOR]

Searchable encryption mechanism and attribute-based encryption (ABE) are two effective tools for providing fine-grained data access control in the cloud. Researchers have also taken their advantages to present searchable encryption schemes based on ABE and have achieved significant results. However, most of the existing key word search schemes based on ABE lack the properties of key exposure protection and highly efficient key updating when key leakage happens. To better tackle these problems, we present a key insulated attribute-based data retrieval scheme with key word search (KI-ABDR-KS) for multi-tenant architecture. In our scheme, a data owner can make a self-centric access policy of the encrypted data. Only when the possessing attributes match with the policy can a receiver generate a valid trapdoor and search the ciphertext. The proposed KI-ABDR-KS also provides full security protection when key exposure happens, which can minimize the damage brought by key exposure. Furthermore, the system public parameters remain unchanged during the process of key updating; this will reduce the considerable overheads brought by parameters synchronization. Finally, our KI-ABDR-KS is proven to be secure under chosen-keyword attack and achieves better efficiency compared to existing works. [ABSTRACT FROM AUTHOR]