[3] Some scholars do not consider the Agnostina true trilobites, and consequently rejected the idea that they were related to the Eodiscina.

[1][4] Consequently, these scientists have proposed to elevate the group to ordinal level, which would thus be called Eodiscida Kobayashi, 1939.

This is because of the dominant palpebroocular ridges, extremely long librigenae, and free pleural tips on the pygidium of variable numbers of segments.

Many characters that are divergent from other trilobites may be explained by paedomorphosis, such as the small number of thorax segments and proparian facial sutures, that occur in all trilobites during larval development, while the Eodiscoid abatochroal eye is not unlike early development stages of the holochroal eye, where lenses are also separated.

And finally the Hebediscidae, that themselves gave rise to the Weymouthiidae, which contain Tannudiscus, the probable ancestor of the peronopsid genus Archaeagnostus,[6] the earliest of the Agnostina.

This seals the opening in the axis between cephalon and the anterior thorax segment that is created when the animal was enrolled.

Agnostida do not have an articulating half-ring, resulting in an opening between the thorax and the cephalon when enrolled, called cephalothoracic aperture.

[8] Like all Agnostida, members of the Eodiscina are relatively small and isopygous with the cephalon and pygidium of approximately similar size and outline.

[9] Many later Eodiscina however, lost their visual organs altogether, and this may have resulted from living in an environment with very low visibility.