Middle Cambrian – Early Silurian
Asaphida is an extinct order of fast-moving, low-level epifaunal deposit feeder.
Characteristics of the Order
- A large, morphologically diverse order that contains six superfamilies.
- Cephalon and pygidium tend to me similar in size and smooth.
- Most species of Asphida exude a prominent medial ventral suture.
- Thorax segments normally numbering 5-12 segments, but may be as few as 2 and as many as 30.
Fortey and Chatterton (1988)