The Upper Jurassic actinopterygian fish Gyrodus dichactinius Winkler 1862 (Gyrodus hexagonus [Blainville 1818]) from Solnhofen, Bavaria and anatomy of the genus Gyrodus Agassiz

Abstract

Quantitative analysis of morphometric data of the small Jurassic "species" of Gyrodus shows that they represent one species, viz. G. hexagonus, and allows for a differentation in two morphotypes, representing forms usually called G. hexagonus (including G. frontatus) and forms which were usually called G. macrophtalmus (including G. dichactinius) . An analysis of the anatomy of the well preserved type specimen of G. dichactinius of Teylers Museum and other material of the genus Gyrodus necessitates to review earlier classifications of the Pycnodontiformes .