 All Olenellina lack facial sutures (see below), and this is thought to represent the original state.The earliest sutured trilobite found so far ("Lemdadella"), occurs almost at the same time as the earliest Olenellina, suggesting the trilobites origin lies before the start of the Atdabanian, but without leaving fossils.Other groups show secondary lost facial sutures, such as all Agnostina and some Phacopina.