''Ischyodus'' (from el, ισχύς , 'power' and el, ὀδούς 'tooth') is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

chimaera Chimaeras are cartilaginous fish in the order Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively. A ...

. 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 The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations ...

to the

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

. Complete specimens of ''I. quenstedti'' from the Late Jurassic of Germany most closely resemble the genus ''

Callorhinchus ''Callorhinchus'', the plough-nosed chimaeras or elephantfish, are the only living genus in the family Callorhinchidae (sometimes spelled Callorhynchidae). A few extinct genera only known from fossil remains are recognized. ''Callorhinchus'' spp ...

'' 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.

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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 {{Jurassic-fish-stub