Article: The Scottish Lower Carboniferous shark Onychoselache traquairi

The discovery near Edinburgh of a second articulated specimen of a small Carboniferous hybodontiform shark has encouraged renewed anatomical study of the original Glencartholm specimen. This shark is not referable to Tristychius arcuatus Agassiz, 1837, as previous authors have suggested, but has recently been renamed Onychoselache traquairi Dick, 1978. Onychoselache has a tribasal pectoral fin similar to most hybodontiforms and neoselachians, not a dibasal fin as is often supposed. Furthermore, the structure of the head and tail are typically hybodontiform and, therefore, there is no justification for its subordinal separation from the hybodontids, as proposed by Moy-Thomas (1936).