Newly collected graptolites from the Co To Formation, Co To archipelago, NE Vietnam, comprise assemblages indicative of two biostratigraphical levels within the lower Silurian, Llandovery Series, Telychian Stage: the co-occurrence of Spirograptus turriculatus and Torquigraptus proteus? suggests an interval most likely within the upper part of the Spirograptus turriculatus Biozone or ‘Monograptus’ crispus Biozone, whilst Oktavites spiralis and Monoclimacis cf. subgeinitzi identify the Oktavites spiralis Biozone. The graptolites provide important biostratigraphical evidence for the age of the upper part of the lower Co To Formation, biostratigraphical ties between the NE Vietnamese succession of the Bac Bo Region and graptolite assemblages of the Long Dai Formation in the Viet-Lao Region of central Vietnam, and include the new species Monograptus hamulus sp. nov. co-occurring with S. turriculatus, which is perhaps an ancestral form to the later Telychian species Monograptus drepanoformis. We also report the first chitinozoans, including Belonechitina, from the Co To Formation.
Recent paleobotanical investigations in Vietnam provide a good opportunity to improve our understanding of the biodiversity and paleoclimatic conditions in the geological past of Southeast Asia. Palms (Arecaceae) are a diverse family of typical thermophilous plants with a relatively low tolerance for freezing. In this study, we describe well-preserved fossil palm leaves from the Oligocene Dong Ho Formation of Hoanh Bo Basin, northern Vietnam. Characters of the fossil leaves, such as a fan-shaped costapalmate lamina, an unarmed petiole, a costa slightly enlarged at the base that then tapers distally into the blade, and well-preserved amphistomatic leaves with cuticles, suggest that they represent a new fossil species, which we herein designate Sabalites colaniae A. Song, T. Su, T. V. Do et Z.K. Zhou sp. nov. Together with other paleontological and palaeoclimatic evidence, we conclude that a warm climate prevailed in northern Vietnam and nearby areas during the Oligocene.
Abstract. In this study, we investigated ostracod assemblages from the Co To Islands in northeastern Vietnam. We identified 77 ostracod species belonging to 46 genera in nine surface sediment samples and recognized three biofacies (I, II, and III) based on Q-mode cluster analysis. The dominant species of biofacies I and II were Aurila hataii, Loxoconcha japonica, and Xestoleberis hanaii, which commonly occur in seaweed beds from southern China to Japan. This is the first report on the ostracod assemblage from the open-sea area in northeastern Vietnam. We clarified that the ostracod assemblages in the Gulf of Tongking, including northern Vietnam, have a strong biogeographical relationship with East Asia seas. A new species, Loxoconcha cotoensis sp. nov., was described herein from the Co To Islands (http://www.zoobank.org/NomenclaturalActs/41d3fb9f-ae17-4215-82c1-0874a8bf1a30, last access: 3 June 2019).
The imbalanced dataset is a crucial problem found in many real-world applications. Classifiers trained on these datasets tend to overfit toward the majority class, and this problem severely affects classifier accuracy. This ultimately triggers a large cost to cover the error in terms of misclassifying the minority class especially in credit-granting decision when the minority class is the bad loan applications. By comparing the industry standard with well-known machine learning and ensemble models under imbalance treatment approaches, this study shows the potential performance of these models towards the industry standard in credit scoring. More importantly, diverse performance measurements reveal different weaknesses in various aspects of a scoring model. Employing class balancing strategies can mitigate classifier errors, and both homogeneous and heterogeneous ensemble approaches yield the best significant improvement on credit scoring.