Yukoniidae are typically isopygous, belonging to the Superfamily Eodiscoidea. The narrow glabella is usually parallel sided, anteriorly rounded and separated from smoothanterior border by broad 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 has three thoracic segments, the anterior of which has strong backwardly directed pleural spines. Pygidium of Yukoniidae has an axis of three to seven rings.