anteroaxis noun1 •The anterior section of the central axial lobe on the pygidium of an agnostoid trilobite.[…] but retention of a cephalothoracic aperture (Rushton, 1979, p.45), and presence always of three segments in the anteroaxis of the pygidium serve to differentiate Condylopygoidea from Agnostoidea. — 1990 formsanteroaxes
