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Soft anatomy of the Early Cambrian arthropod Isoxys curvirostratus from the Chengjiang biota of South China with a discussion on the origination of great appendages

100%

Fu D.-J. , Zhang X.-L. , Shu D.-G.

Acta Palaeontologica Polonica

2011

tom 56

nr 4

An updated reconstruction of the body plan, functional morphology and lifestyle of the arthropod Isoxys curvirostratusis proposed, based on new fossil specimens with preserved soft anatomy found in several localities of the Lower Cambrian Chengjiang Lagerstätte. The animal was 2–4 cm long and mostly encased in a single carapace which is folded dorsally without an articulated hinge. The attachment of the body to the exoskeleton was probably cephalic and apparently lacked any well−developed adductor muscle system. Large stalked eyes with the eye sphere consisting of two layers (as corneal and rhabdomeric structures) protrude beyond the anterior margin of the carapace. This feature, together with a pair of frontal appendages with five podomeres that each bear a stout spiny outgrowth, suggests it was raptorial. The following 14 pairs of limbs are biramous and uniform in shape. The slim endopod is composed of more than 7 podomeres without terminal claw and the paddle shaped exopod is fringed with at least 17 imbricated gill lamellae along its posterior margin. The design of exopod in association with the inner vascular (respiratory) surface of the carapace indicates I. curvirostratus was an active swimmer. Morphological comparisons demonstrate that species of Isoxys were diverse in feeding habits and occupied a very broad morphospace, i.e., carapace bivalved or a single shield, the pre−oral limbs antenniform or modified into great appendages, the succeeding endopods slim or stout. This casts doubt on the current taxonomy that assigns all species to a single genus, and on any presumed lifestyle of Isoxys extrapolated to the generic level. Finally, since I. curvirostratus and I. acutangulus carry a pair of great appendages, Isoxys has recently been placed into the great appendage arthropods. Such placement might be inadequate because the homology of the great appendages can not be established.

Multi-index classification model for loess deposits based on rough set and BP neural network

75%

Zhang X.-L. , Xue Y.-G. , Qiu D.-H. , Yang W.-M. , Su M.-X. , Li Z.-Q. , Zhou B.-H.

Polish Journal of Environmental Studies

2019

tom 28

nr 2

Classifying loess deposits is an important process for selecting support form and construction methods for tunnels. An accurate evaluation of loess deposits is a necessary prerequisite to control deformation, save cost, and improve construction efficiency. In this paper, a neural network model with an evaluation system consisting of physical and mechanical indices of loess is proposed to realize intelligent classification of loess deposits for tunneling. The influence of water content, natural density, cohesion, internal friction angle, elastic modulus, and Poisson ratio on stability level of loess is analyzed by rough set theory based on statistical data of borehole samples. Results show that the affect of natural density is negligible. Then other indicators such as input nodes and the BP neural network model are formed after learning statistical samples and being applied to the project for testing. Finally, the output of the model is consistent with the actual. This study provides a multi-index model for evaluating loess deposits surrounding tunnels and provides a reference for future research.