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Temporal range: 176–23 Ma
Middle Jurassic to Miocene
Ischyodus avitus.jpg
Ischyodus avitus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: Chimaeriformes
Family: Callorhynchidae
Genus: Ischyodus
  • Ischyodus bifurcatus
  • Ischyodus brevirostris
  • Ischyodus dolloi
  • Ischyodus gubkini
  • Ischyodus incisus
  • Ischyodus latus
  • Ischyodus lonzeensis
  • Ischyodus minor
  • Ischyodus mortoni
  • Ischyodus planus
  • Ischyodus rayhaasi
  • Ischyodus thurmanni
  • Ischyodus townsendi
  • Ischyodus williamsae
  • Ischyodus yanshini
  • Ischyodus zinsmeisteri

Ischyodus is an extinct genus of cartilaginous fish belonging to the subclass Holocephali, which includes the modern-day chimaeras. Fossils are known from Europe (including Russia), North America, and New Zealand.

Ischyodus was rather similar to the present-day chimaera Chimaera monstrosa, which is found in the Atlantic Ocean and Mediterranean Sea. Just like C. monstrosa, Ischyodus had large eyes, a long whip-like tail, small lips, large pectoral fins and dorsal fin, and a dorsal spike attached to the front of the dorsal fin. The spike probably served as a method of protection against predators, and may have been venomous, as it is in modern chimaeras.[1]

Dental plates of at least two species, Ischyodus rayhaasi and Ischyodus dolloi, have been found at several sites in North Dakota.[2]


  1. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 29. ISBN 1-84028-152-9. 
  2. ^ Hoganson, J. W. and J. M. Erickson. 2005. A new species of Ischyodus (Chondrichthyes: Holocephali: Callorhynchidae) from Upper Maastrichtian shallow marine facies of the Fox Hills and Hell Creek formations, Williston Basin, North Dakota, USA. Palaeontology 48: 709-721. doi:10.1111/j.1475-4983.2005.00475.x

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