Redescription of Parexus recurvus,an Early Devonian acanthodian from the Midland Valley of Scotland

Parexus Agassiz was one of the first Early Devonian ‘spiny sharks’ to be described. The genus is readily recognized by the large size and ornament of its anterior dorsal fin spine. Although two species were erected, reappraisal of all known specimens indicate they should be synonymized in the type species Parexus recurvus. Farnellia tuberculata Traquair, originally described as a vertebral column, is actually tooth rows of jaw dentition, and is also now considered to be a junior synonym of P. recurvus. Parexus has a perichondrally ossified scapulocoracoid of typical acanthodian shape, and diagnostic features of the family Climatiidae, but has distinctive scales comprising appositional growth zones that closely resemble those of the putative stem chondrichthyan Seretolepis elegans Karatajute-Talimaa.