 However, they began to differentiate themselves by the late Early Cambrian period, and by the late Cambrian period had diversified into numerous varieties and reach 2 to 5 cm in width.Specimens from the late Cambrian to the earliest Ordovician exhibit shells with rounded and pointed pedicle valves, with sharp to obtuse extremities and ridges that are fine to course.Punctate shells appear during the mid-Ordovician, which establish the suborder Dalmanellidina.