The enigmatic Middle Devonian chordate Palaeospondylus gunni from the the Achannaras Slate Quarry, Caithness, Scotland, has recently been reinterpreted as a member of the Cyclostomata (the group that includes living jawless fishes). If this interpretation is correct, then Palaeospondylus either retains a vertebral column as a vestigial organ, or represents a remarkable case of skeletal homoplasy convergent on bony fishes. The ‘hard cartilage’ of Palaeospondylus may be a unique biomaterial restricted to the Devonian lifespan of this enigmatic genus.
