The middle of the three main parts of the body (cephalon, thorax, and abdomen). It is formed by the seventh to fourteenth somites ( = thoracic somites one to eight) and bears the thoracopods. The somites of the thorax are fused with those of the cephalon and so form the cephalothorax. Dorsally and laterally, the lines between the thoracic somites are not noticeable; ventrally, however, they may show as transverse grooves on the sternum.