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prosoma

prosomaThe prosoma is the anterior short, and flat region of the body. It is formed by the merger of head and thorax. It is made up of six segments, each of which bears a pair of appendages on the ventral side. Dorsally the prosoma is covered by a single, thick and square-shaped cephalothoracic shield or dorsal carapace. The dorsal carapace is formed by fusion of terga of this region. The anterior margin of the dorsal carapace has a deep notch forming right and left frontal lobes. The carapace bears a pair of median eyes in the middle and two to five pairs of smaller lateral eyes on the anterolateral margins. On the ventral surface of the prosoma there is a single median, small triangular plate, the sternum, lying between the coxae of third and fourth pairs of legs. The sternum is greatly reduced due to the enormous development of the coxae of thoracic appendages.