Compare the pictorial approach to the narrative equivalent below (salient features in color):
Cephalon: semicircular cephalon with long librigenal spine, glabella widens anteriorly to rounded or bluntly pointed LA (parallel in early forms), L1 - L4 equal or subequal, S1 generally transglabellar, but shallow medially, S2 long, may be transglabellar, S3 and S4 short (S4 strongly oblique in Centropleuridae, making large angle with S3), preglabellar field generally absent in adult, opisthoparian, anterior facial sutures divergent, transverse, to retrodivergent.
Thorax: with 14 - 21 segments, short to long pleural spines directed progressively more strongly backward from front to rear, sometimes tips bluntly truncated (Centropleuridae), 1st and 2nd segments may be macropleural.
Pygidium: generally small in Paradoxididae, but tending to medium sized in Centropleuridae.
Other: often large trilobites.
Walking Trilobite animation ©2000 by S. M. Gon III