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a part of the middle germ layer, or mesoderm, in the early stages of embryonic development in chordates (including man). The somatopleure consists of an external (parietal) layer of the lateral plate, or splanchnotome. The lining of the abdominal cavity and the skeleton of the extremities are formed from the somatopleure. In higher vertebrates (including man) the somatopleure also participates in the formation of the amnion and chorion, two embryonic membranes.