T. seeleyi is the type and only species of Tricleidus. The holotype specimen (NHMUK R.3539) consists of disarticulated elements including most of skull and half the postcranium, from the Kosmoceras jason – Peltoceras athleta zones of the lowest deposits of the Oxford Clay.
Skull of Tricleidus in lateral view. From Brown (1981).Palate of Tricleidus in lateral view. From Brown (1981).
