Holocephali Bonaparte 1832
Sometimes their tooth plates are intact enough to be identifiable.
Some holocephalian's (vomerine?) dental plate
stereopair
Piece of mandibular? Vomerine?
Notice wear of pleromin on the convex side.
Ischyodus Egerton, 1843
Right palatine plate. Notice 2 outer tritors.
Specimens with 4 ones are also found.
Similar, but 4 times smaller one.
8 mm in length.
Links:
Ward, D. J. and Grande, L., 1991. Chimaeroid fish remains from Seymour Island, Antarctic Peninsula. Antarctic Science 3(3): 323-330.
(Review of Edaphodontidae and Chimaeridae dental plates structure (and how to differentiate some genera))
Duffin, C.J, 2001. A chimaerid (Holocephali, Chimaeriformes) vomerine toothplate from the Upper Cretaceous of Belgium. Palaeontology, Vol. 44, Part 6, 2001, pp. 1179-1188
(An information about stratigraphic ranges of chimaeroid genera and some data on vomerine toothplates)
Popov, E.V., Ward, D. J., Lepage, G. The diversity and nomenclatural revision of the holocephalian fishes (Chimaeriformes) from the Kimmeridgian (Late Jurassic) of Western Europe.
(A paper with good photos of Ischyodus and others' dental plates.)
A short review of ratfish dentition on www.chalk.discoveringfossils.co.uk
The closest living relative of Ischyodus — Callorhinchus on floridamuseum.ufl.edu
Ghost shark's smile on fishbase.mnhn.fr