Proteids of the European genus Proteus are cave dwellers with depigmented skin and degenerate eyes. The morphological characters given below are the ones standardly used to diagnose the salamander family Proteidae and to assess its phylogenetic relationships to other salamanders. The individual characteristics are in most cases shared with other salamanders and should not be interpreted as synapomorphies of the Proteidae. Metamorphosis is absent in the Proteidae, leading to a number of paedomorphic features in adults. The premaxilla consists of separated, paired bones.
Maxillary bones are absent.
Bilaterally paired septomaxillary bones are absent. Lacrimal bone is absent. Quadratojugal bone is absent. Pterygoid bones are present. An internal carotid foramen is present in the parasphenoid bone.