Palaeospondylus was a mysterious worm-like fish which has been described as a larval tetrapod, lungfish, unarmored placoderm, and agnathan.
Palaeospondylus was discovered in Scotland and is 2" long. This image shows Coccosteus attacking four Palaeospondylus.
Palaeospondylus may have been a parasite or an early lungfish.
Palaeospondylus had a weird basket-like formation in the skull, but the use for this basket-like formation is unknown.