 the posterior antenniform cerci preserved only in "Olenoides serratus") remain difficult to assess in the wider picture.Trilobites had a single pair of preoral antennae and otherwise undifferentiated biramous limbs (2, 3 or 4 cephalic pairs, followed by one pair per thoracic segment and some pygidium pairs).Each endopodite (walking leg) had 6 or 7 segments, homologous to other early arthropods.