AbstractSiren intermediais peculiar in that the lateral‐line system is retained throughout life, even though the animal is forced into terrestrial situations during aestivation. The lateral‐line system is constructed of neuromasts arranged in pit fields instead of pit lines as in most amphibians. The neuromasts are unusual, because the sense cells are arranged in a single row through the long axis of the organ and a few of the sustentacular cells contain “orange granules.”During aestivation, the neuromasts are either shielded by a secreted cocoon, or occluded by proliferated skin epithelium. Those organs occluded by epithelium undergo dedifferentiation which continues through postaestivation.Loss of the lateral‐line system by amphibians was apparently late in amphibian evolution. Gradual loss of the system suggests that retention and/or protection of the lateral‐line system proved maladaptive and physiologically too expensive. Thus the system was abandoned by most amphibian taxa at me