Ischyodus dolloi
Ischyodus dolloi
Common name
Chimaeroid
Fossil group
Sharks & Rays
Order
Chimaeriformes
Family
Ischyodontidae
Genus
Ischyodus
Taxonomic status
Accepted
Geological age
Thanetian
Summary
Ischyodus dolloi was an extinct chimaeroid known mainly from specialised dental plates. Like other holocephalans it lacked replaceable shark-like tooth rows and instead used persistent plates that grew continuously and contained hard tritor tissues.
The plate system was suited to crushing and shearing resistant food.
Quick Identification
Look for: a chimaeroid dental plate with a recognisable plate margin and organised tritors; determine whether it is palatine, mandibular or vomerine before comparing it with Ischyodus.
Diagnostic Features
- Dentition consists of persistent tooth plates rather than individual replaceable teeth.
- Dense tritor tissues form organised crushing surfaces within the plate.
- Plate outline differs strongly between jaw positions.
- The relationship of tritors to the plate margins is a primary identification character.
- Species-level identification requires a sufficiently complete plate to distinguish Ischyodus from Edaphodon and other chimaeroids.
Fossil Details
Typical size
Dental plates are centimetre-scale, with dimensions varying strongly between jaw positions and growth stages.
Fossil material
Tooth Plate
Preservation
Small tritor-bearing chips can be difficult to separate from other chimaeroids. Complete margins or enough plate architecture to establish position should be present before assigning the species.
Similar Species
Recorded Fossil Sites
Beltinge Fish Bed
Upnor Formation
Confirmed
References
- Dineley, D. & Metcalf, S. (1999). Fossil Fishes of Great Britain. Geological Conservation Review Series, 675 pp.. Joint Nature Conservation Committee, Peterborough View reference
- Ward, D.J. (1973). The English Palaeogene Chimaeroid fishes. Proceedings of the Geologists' Association, 84(3), 315–330 View reference
- Ward, D.J. (1978). The Lower London Tertiary (Palaeocene) succession of Herne Bay, Kent. Report of the Institute of Geological Sciences. Institute of Geological Sciences View reference
- Ward, D.J. (1980). The distribution of sharks, rays and chimaeroids in the English Palaeogene. Tertiary Research, 3(1), 13–19 View reference
Last Reviewed
15 August 2026
Reviewed by
Sam Harris