part of overlaps develops from prothoracic episternum leg joint prothoracic leg prothoracic coxa proximal joint of prothoracic coxa FBbt:00007660 The joint between the proximal end of the prothoracic coxa and the body of the prothoracic segment. The fossa (socket) of this joint is part of the coxa. The condyle (ball) is part of the body. GTh fly_anatomy.ontology body-coxa joint presumptive prothoracic structures from prothoracic leg disc