The term obsolete terminal filament refers to a strand of connective tissue identified by dissection in vertebrates. It extends from the end of the spinal cord to the coccyx of the vertebral column. Historically it was believed to be a nerve or intertwined pair of nerves, hence the obsolete synonym 'unpaired nerve' ( Swanson-2014 ). obsoleted because already in NeuroNames as Filum terminale...changed that to terminal filament