Palaeospondylus gunni Traquair, 1890
What is Palaeospondylus? That is a question that remains unanswered since its description more than a century ago by Traquair. The anatomy of this little fish is such that it cannot be readily placed in any particular group of fishes. It has been suggested to be associated with hagfishes, lampreys, placoderms, chondrichthyans, actinopterygians, acanthodians, lungfishes, and even as a larval tetrapod. In other words, it has been assigned to nearly every major group of early fishes. Most recently it has been proposed to show an affinity to hagfishes by Hirasawa et al. (2016) and to chrondrichthyans by Johanson et al. (2017). This fish occurs at several localities in Caithness and Orkney. Specimens range in size from approximately 5mm to nearly 70mm.