Palaeospondylus gunni
Devonian
Old Red Sandstone
Achanarras, Scotland

Enigmatic 15mm fish on 97mm matrix.

Palaeospondylus gunni has been a riddle to paleontologists since its description in 1890.  It has been assigned to various fish groups and it’s been considered a larval and adult form by different researchers.  Recently, it was concluded that it belonged to a group ancestral to hagfishes but it has been reinterpreted as being a member of the group ancestral to cartilaginous fishes.

Some collectors like it because it has been called an early shark; others want it just because it is weird.

Links to the research:
It is a hagfish (2016): Palaeospondylus as a primitive hagfish

It is not a hagfish (2017): Questioning hagfish affinities of the enigmatic Devonian vertebrate Palaeospondylus

Latest interpretation as a bizarre Sarcopterygian fish (2022): Palaeospondylus Was Bizarre Lobe-Finned Fish