Cephalon: with opisthoparian sutures, anterior sutures generally subparallel; glabella long, subparallel, or expanding anteriorly; eyes typically elongate, narrow;  hypostome typically fused with rostral plate (conterminant); genal spines often present.
Thorax: 2-12 or rarely up to 18 segments (typically 7-8), pleurae typically spine-tipped.
Pygidium: variable, typically large and spinose, some with smooth border.