[4] Yukoniidae are typically isopygous, belonging to the Superfamily Eodiscoidea.

preglabellar field which occupies about 25% of cephalic length excluding occipital spine.

Posterior glabellar furrows are reduced to a pair of slits low on sides of glabella and directed backwards.

Occipital ring bears a strong backwardly directed spine.

Yukonia intermedia Palmer (1968) has three thoracic segments, the anterior of which has strong backwardly directed pleural spines.