• 1
    Diademodus hydei, a new genus and species of shark from the Cleveland Shale, is described and figured from the holotype in the Cleveland Museum of Natural History.
  • 2
    About 40 centimetres in length, the fish is an adult male with well-developed claspers; it shows a combination of hybodont and cladoselachian characteristics.
  • 3
    The teeth are many-cusped and bilaterally symmetrical, with the outer cusps longer than the inner; they approach more closely to the sculpturing of the scale pattern than in orther primitive sharks.
  • 4
    A comparison with the contemporaneous Cladoselache and Ctenacanthus clarki suggests that Diademdus is an early and not distant offshoot from the primitive chondrichthyan stock, the main line of which led through Ctenacanthus and the hybodonts to the modern elamobranchs; Cladoselache is a specialized side line of this main stock and is not an appropriate ancestral type for the Chondrichthyes.