Ischyodus (from , 'power' and 'tooth') is an extinct genus of chimaera. It is the most diverse and long-lived chimaera genus, with over 39 species found worldwide spanning over 140 million years from the Middle Jurassic to the Miocene. Complete specimens of I. quenstedti from the Late Jurassic of Germany most closely resemble the genus Callorhinchus amongst living chimaera genera. It is sometimes placed in the "Edaphodontidae" a unclearly defined group of chimaera with an uncertain position within the clade. While other authors place it into Callorhinchidae along with Callorhinchus. Based on complete specimen, total length is 21 times larger than mesiodistal length of mandibular tooth plate. For example, I. bifurcatus with mandibular plate length of possibly belongs long specimen. References External links Image of a ratfish, Ischyodus rayhaasi, mandible Prehistoric cartilaginous fish genera Jurassic cartilaginous fish Cretaceous cartilaginous fish Paleocene fish Prehistoric fish of Europe Prehistoric fish of Australia Prehistoric fish of North America Mooreville Chalk Chimaeriformes