The morphological characters given below are the ones standardly used to diagnose the salamander family Hyobiidae and to assess its phylogenetic relationships to other salamanders. The individual characteristics in most cases are shared with other salamanders and should not be interpreted as synapomorphies of the Hynobiidae. The premaxilla may consist of separated, paired bones, or these bones may be fused to form a single premaxillary bone. Maxillary bones are present and usually well developed. Bilaterally paired septomaxillary bones are present.
Lacrimal bone is present.
Quadratojugal bone is absent. Pterygoid bone is absent. Internal carotid foramina are absent from parasphenoid bones. The angular bone is separated from the mandible. The columella and operculum appear as separate ear bones detached from the otic capsule in some species, whereas others lack the operculum.