Eurynotus, Platysomus and Cheirodus

Bobasatrania canadensis (White 1932; Permian–Triassic, 255–237mya) This discoidal fish from Madagascar nests with Cheirodus in the LRT. It is the latest known placoderm.

Amphicentrum granulosus = Cheirodus granulosus (McCoy 1848, 1855 20cm; Carboniferous) is a disc-shaped fish lacking pelvic fins, covered in large rectangular ganoid scales. The postparietals are absent. The intertemporal rims the posterior orbit. The jugal is convergent with the operculum. The pelvic fins are missing. Teeth are absent from the upper jaws. Note the heterocercal tail.

Platysomus parvulus (Agassiz 1843, Carboniferous Cheirodus to Permian; 18cm long) is a taller, more disc-like fish transitional from Campbellodus and. Note the reduction of the mandible. Probably a plankton eater.

Agassiz JLR 1835. On the fossil fishes of Scotland. Report of the British Association for the Advancement of Science, British Association for the Advancement of Science, Edinburgh.

Friedman M, Pierce SE, Coates M and Giles S 2018. Feeding structures in the ray-finned fish Eurynotus crenatus (Actinopterygii: Eurynotiformes) implicationsfor trophic diversification among Carboniferous actiniopterygians. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 109, 33–47.

McCoy F 1855. A synopsis of the classification of the British Palaeozoic rocks, with a systematic description of the British Palaeozoic fossils. Fasciculus 3, Mollusca and Palaeozoic fishes. British Palaeozoic Fossils, Part II. Palaeontology 407-666.

Ørvig T 1975. Description, with special reference to the dermal skeleton, of a new radotinid arthodire from the Gedinnian of Arctic Canada. Colloque International due CNRS 218:41–71.

Trinajstic K, Long JA, Johanson Z, Young G and Senden T 2012. New morphological information on the ptyctodontid fishes (Placodermi, Ptyctodontida) from Western Australia. Journal of Vertebrate Paleontology 32(4):757–780.

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