Hapsidopareion was originally differentiated from other microsaurs by the large temporal emargination, which produced other variable morphology of the circum-emargination bones (e.g., postorbital). It is similar to the more recently described
Llistrofus pricei in this regard, but can be differentiated from
L. pricei by features such as the absence of a quadratojugal and a frontal excluded from the orbit. Because all specimens of
H. lepton are notably smaller than those of
L. pricei, and a number of anatomical differences are likely ontogenetically variable (e.g., contact between neural arch and centrum), some researchers considered that the former maybe represent a juvenile of the latter, but recent workers have maintained the separation of these taxa. Using high-resolution
micro-CT scans of three skulls of the coeval
Hapsidopareion, Jenkins et al. (2025) identified that many of the characters used to distinguish
Llistrofus from it are shared by both taxa, documenting the presence of a quadratojugal in
Hapsidopareion and demonstrating that the supposed exclusion of the frontal from the orbit was due to crushing in the holotype specimen. Due to its larger size, they identified
Llistrofus as representing a more mature
ontogenetic stage of
Hapsidopareion, and argued that the former should be regarded as a
junior synonym of the latter. == Relationships ==