Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian.

In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters.

The visual surface, that contains the calcite lenses is surrounded by fracture lines (or circumocular sutures), so that it has most often broken away from the rest of the cephalon.

The hypostomes of redlichiids have narrow borders, are not split into backward pointing forks, and have only small muscle attachment areas (or maculae).

To each side of the central axis, the third segment from the front may have an exta large and wide rib (a state called macropleural).

The absence in the fossil record of the earliest larval stage, the protaspid, suggests that it may have been uncalcified, which would be a second unique character that distinguishes the Olenellina from all other trilobites.