Palaeospondylus
Palaeospondylus gunni is a mysterious, fish-like fossil vertebrate. Its fossils are described from Achanarras slate quarry in Caithness, Scotland.
The fossil as preserved is carbonized, and indicates an eel-shaped animal up to in length. The skull, which must have consisted of hardened cartilage, exhibits pairs of nasal and auditory capsules, with a gill apparatus below its hinder part, and ambiguous indications of ordinary jaws.
The phylogeny of this bizarre fossil has puzzled scientists since its discovery in 1890, and many taxonomies have been suggested. In 2004, researchers proposed that Palaeospondylus was a larval lungfish. Previously, it had been classified as a larval tetrapod, unarmored placoderm, an agnathan, an early stem hagfish, and a chimera. The most recent suggestion is that it is a stem chondrichthyan.
